network.c

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/*         SCIP --- Solving Constraint Integer Programs                      */
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/**@file   network.c
 * @ingroup OTHER_CFILES
 * @brief  Methods for detecting network (sub)matrices
 * @author Rolf van der Hulst
 *
 * Detecting if a matrix is a network matrix can be quite complex. Below is an introductory text, which may help with
 * navigating the functions and datastructures in this file by giving a general overview.
 * More details can be found in;
 * R.P. van der Hulst and M. Walter "A row-wise algorithm for graph realization"
 * and
 * R.E. Bixby and D.K. Wagner "An almost linear-time algorithm for graph realization"
 * for the column-wise algorithm.
 *
 * The main difficulty with detecting network matrices is that there may exist many pairs of a graph and a spanning tree
 * that realize a matrix. The ambiguity of these graphs may be characterized in terms of \f$k\f$-separations on the
 * graph associated to the network matrix. An edge partition \f$(E_1,E_2)\f$ is considered a \f$k\f$-separation if
 * \f$|E_i|\geq k \f$ holds for \f$i\in\{1,2\}\f$. The ambiguity of network matrices is completely given by all
 * the 1-separations and 2-separations of the associated graph(s). In particular, if the graph realizing a
 * network matrix is 3-connected, then it is unique, up to inverting all edges of the graph.
 *
 * A 1-separation given by edge sets \f$(E_1,E_2)\f$, which is given by a singular node that is referred to as an
 * articulation node, implies that no column of the network matrix contains edges in both \f$E_1\f$ and \f$E_2\f$.
 * Remember that each edge in a realizing graph is associated with a row or column of the network matrix. Then, we have
 * a 1-separation exactly when the network matrix contains two (or more) disconnected blocks, where the rows and columns
 * of each block are contained in either \f$E_1\f$ or \f$E_2\f$. To obtain a graph realizing our network matrix, we can
 * attach the graph realizing \f$E_2\f$ at any node of the graph realizing \f$E_1\f$.
 * Thus, we store the graphs corresponding to the connected blocks of the network matrix separately.
 * Each block has a 2-connected realization graph.
 *
 * If a graph \f$G\f$ realizing the network matrix has a 2-separation \f$(E_1,E_2)\f$ at vertices u and v, then we can
 * obtain another graph representing the network matrix, by inverting the direction of all edges in \f$E_2\f$ and
 * replacing u by v and vice-versa. One can also imagine
 * adding a virtual edge \f$e'=\{u,v\}\f$ to both E_1 and E_2. In the trivial realization, we simply map the head of
 * \f$e'\f$ in \f$E_1\f$ to the head of \f$e'\f$ in \f$E_2\f$ and remove \f$e'\f$ from both graphs. In the second
 * realization we do the same thing, but first invert all the edges in \f$E_2\f$, including \f$e'\f$.
 * An SPQR tree \f$\mathcal{T}=(\mathcal{V},\mathcal{E})\f$ is a tree data structure that represents the structure of
 * all 2-separations in a 2-connected graph. Each member \f$\nu\in\mathcal{V}\f$ has an associated skeleton graph that
 * has one of four different types:
 * - (S) The member's skeleton graph is a cycle with at least 3 edges (also referred to as series or polygon)
 * - (P) The member's skeleton graph consists of at least 3 parallel edges and 2 nodes (also referred to as bond)
 * - (Q) The member's skeleton graph consists of at most 2 edges connecting two nodes (also referred to as loop)
 * - (R) The member's skeleton graph is 3-connected and consists of at least 4 edges.
 *
 * An SPQR tree is considered minimal if it has no P-P or S-S connections. Each connected matrix has a unique minimal
 * SPQR tree. Each edge \f$\{\nu,\mu\}\in\mathcal{E}\f$ defines a 2-separation of the underlying graph. In particular,
 * each edge has one virtual edge in the member graph that it connects to the other member graph in the edge.
 *
 * We can obtain a realization of the graph underlying the network matrix by doing the following operations:
 * 1. Permute the edges of each (S)-member arbitrarily
 * 2. For each edge in \f$\mathcal{E}\f$, pick one of the two orientations of the virtual edges and merge the adjacent
 *    member graphs accordingly.
 *
 * In this way, all the graphs given by the network matrix are represented. In order to efficiently perform the merge
 * of two member graphs, the member and node labels are given by union-find datastructures. Additionally, we also
 * introduce a signed-union-find datastructure on the arcs of the graphs, so that we can efficiently invert the arcs
 * of one side of a 2-separation.
 * The 1-separations can be handled by storing an SPQR forest, with a (minimal) SPQR tree for every connected block
 * of the network matrix.
 *
 * For adding a column to the network matrix, one can show that one can add a column only if the nonzeros of the column
 * form a path with the correct signs in some graph represented by the network matrix. We solve the problem for each
 * graph represented by the network matrix simultaneously by decomposing over the SPQR tree. First, we compute the path
 * in each member. Then, we attempt to combine the paths by orienting the 2-separations so that the different member
 * paths form a path in the represented graph.
 * If some member has a set of edges that do not form a path, we can terminate.
 * An important step is 'propagation'; when we are in a leaf node of the sub-SPQR tree containing path edges and the
 * path in our leaf node forms a cycle with the virtual arc e connecting to the rest of the sub-tree, then we can
 * remove the leaf node from the SPQR tree and mark the virtual arc f that is paired with e.
 * After performing all such propagations, the sub-SPQR tree should form a path. Then, we merge these members into one,
 * forming a single path. By adding the new column edge to the end nodes of this path, we form a new member of type R.
 * Finally, we can easily join the paths of multiple SPQR trees using a series node to obtain the final path.
 *
 * The ideas for the row-wise algorithm have many parallels with the column-wise algorithm. One can add a row to a
 * network matrix if and only if a node is 'splittable' with respect to a certain auxiliary graph formed by the nonzero
 * columns indices of the row, for a graph represented by the network matrix. In particular, this auxiliary graph must
 * be a directed bipartite graph; then, the arcs incident to the given node can be reassigned to two new nodes, so that
 * the paths of the columns corresponding to the nonzeros of the row can be elongated to contain the new row, which is
 * placed between the two new nodes.
 * Similarly to the column-case, splittability of each graph represented by the network matrix can be computed at once
 * by computing the splittability (and the corresponding bipartition) of every member graph.
 * Similarly to the column algorithm, we can propagate; If a member is a leaf of the SPQR tree and both nodes of the
 * 2-separation connecting it to the rest of graph are splittable, then we can remove the leaf from the reduced
 * SPQR tree and mark the virtual edge connecting to the subtree.
 * Finally, we are left with some minimal subtree with splittable vertices for each member graph. If we can merge all
 * splittable vertices of the member graphs in the subtree into a single splittable vertex, then we perform this merge,
 * and split this vertex. This yields us a new, larger node of type R (rigid).
 *
 * Implementation notes:
 * 1. Quite a few algorithms used for network matrix detection are recursive in nature. However, recursive calls can
 *    cause stack overflows, particularly with large graphs. Quite frequently in the code, we need to allocate the
 *    call-data of these algorithms on the heap, instead, and use while loops to simulate the recursion.
 *
 * 2. In order to make the code fast in practice, a lot of emphasis is put on reusing allocated memory and avoiding
 *    allocations. In particular for the column-wise algorithm, even allocating and zeroing an array of size m+n for an
 *    m x n matrix can significantly slow down the code!
 *
 * 3. The graphs of the S, P and Q members do not need to be stored explicitly, as they always have the same structure.
 *    This also makes it easier to permute edges of S nodes on the fly.
 */
 
 /* TODO: fix tracking connectivity more cleanly, should not be left up to the algorithms ideally
 */
 
#include <assert.h>
 
#include "scip/misc.h"
#include "scip/pub_misc.h"
#include "scip/pub_network.h"
#include "scip/scip.h"
#include "blockmemshell/memory.h"
 
/* types which define matrix sizes */
typedef int spqr_matrix_size;
typedef spqr_matrix_size spqr_row;
typedef spqr_matrix_size spqr_col;
 
#define SPQR_INVALID INT_MAX
#define SPQR_INVALID_ROW SPQR_INVALID
#define SPQR_INVALID_COL SPQR_INVALID
 
 
/* Only check in debug mode if the used indices are valid */
#ifndef NDEBUG
 
/** Determine if the row index is invalid */
static
SCIP_Bool SPQRrowIsInvalid(
   spqr_row              row                 /**< The row to check */
   )
{
   return row == SPQR_INVALID_ROW;
}
 
/** Determine if the column index is invalid */
static
SCIP_Bool SPQRcolIsInvalid(
   spqr_col              col                 /**< The column to check */
   )
{
   return col == SPQR_INVALID_COL;
}
 
/** Determine if the row index is valid */
static
SCIP_Bool SPQRrowIsValid(
   spqr_row              row                 /**< The row to check */
   )
{
   return !SPQRrowIsInvalid(row);
}
 
/** Determine if the column index is valid */
static
SCIP_Bool SPQRcolIsValid(
   spqr_col              col                 /**< The column to check */
   )
{
   return !SPQRcolIsInvalid(col);
}
 
#endif
 
/** Columns 0..x correspond to elements 0..x and rows 0..y correspond to elements -1.. -y-1 */
#define MARKER_ROW_ELEMENT (INT_MIN)
#define MARKER_COLUMN_ELEMENT (INT_MAX)
typedef int spqr_element;
 
/** Checks if an element is a row */
static
SCIP_Bool SPQRelementIsRow(
   spqr_element          element             /**< The element to check */
   )
{
   return element < 0;
}
 
/** Checks if an element is a column */
static
SCIP_Bool SPQRelementIsColumn(
   spqr_element          element             /**< The element to check */
   )
{
   return !SPQRelementIsRow(element);
}
 
/** Convert an element to the corresponding row index */
static
spqr_row SPQRelementToRow(
   spqr_element          element             /**< The element to convert */
   )
{
   assert(SPQRelementIsRow(element));
   return (spqr_row) ( -element - 1 );
}
 
/** Convert a row to the corresponding element */
static
spqr_element SPQRrowToElement(
   spqr_row              row                 /**< The row to convert */
   )
{
   assert(SPQRrowIsValid(row));
   return (spqr_element) -row - 1;
}
 
/** Convert an element to the corresponding column index */
static
spqr_col SPQRelementToColumn(
   spqr_element          element             /**< The element to convert */
   )
{
   assert(SPQRelementIsColumn(element));
   return (spqr_col) element;
}
 
/** Convert a column to the corresponding element */
static
spqr_element SPQRcolumnToElement(
   spqr_col              column              /**< The column to convert */
   )
{
   assert(SPQRcolIsValid(column));
   return (spqr_element) column;
}
 
/** spqr_member is an index for the members of the SPQR decomposition
 *
 * The members are the nodes of the SPQR tree.
 * Each member has an associated subgraph, sometimes called a skeleton.
 * If two members are adjacent in the SPQR tree, the two corresponding subgraphs are connected by a 2-separation in any
 * graph represented by the matrix.
 * For members, we reserve all negative values as invalid. We use these negative values in union-find datastructure,
 * where we store the rank of the representative as a negative number.
 */
typedef int spqr_member;
#define SPQR_INVALID_MEMBER (-1)
 
/** Check if a member is invalid */
static
SCIP_Bool SPQRmemberIsInvalid(
   spqr_member           member              /**< The member to check */
   )
{
   return member < 0;
}
 
/** Check if a member is valid */
static SCIP_Bool SPQRmemberIsValid(
   spqr_member           member              /**< The member to check */
   )
{
   return !SPQRmemberIsInvalid(member);
}
 
/** spqr_node is an index for the nodes stored in the decomposition.
 *
 * The nodes are part of each member's skeleton.
 * Similar to spqr_member, we reserve all negative values as invalid and use these in union-find.
 */
typedef int spqr_node;
#define SPQR_INVALID_NODE (-1)
 
/** Check if a node is invalid */
static
SCIP_Bool SPQRnodeIsInvalid(
   spqr_node             node                /**< The node to check */
   )
{
   return node < 0;
}
 
/** Check if a node is valid */
static
SCIP_Bool SPQRnodeIsValid(
   spqr_node             node                /**< The node to check */
   )
{
   return !SPQRnodeIsInvalid(node);
}
 
/** spqr_arc is an index for the arcs stored in the decomposition.
 *
 * The arcs are part of each member's skeleton.
 * Similar to spqr_node and spqr_member, we reserve all negative values as invalid and use these in some union-find.
 * However, in contrast to spqr_node and spqr_member, the union-find data structure does not represent the arcs,
 * but rather if all arcs that have the same representative we know they are in the same member.
 */
typedef int spqr_arc;
#define SPQR_INVALID_ARC (-1)
 
/** Check if an arc is invalid */
static
SCIP_Bool SPQRarcIsInvalid(
   spqr_arc              arc                 /**< The arc to check */
   )
{
   return arc < 0;
}
 
/** Check if an arc is valid */
static
SCIP_Bool SPQRarcIsValid(
   spqr_arc              arc                 /**< The arc to check */
   )
{
   return !SPQRarcIsInvalid(arc);
}
 
/** The type of the member */
typedef enum
{
   SPQR_MEMBERTYPE_RIGID      = 0,           /**< The member's skeleton is 3-connected and has at least 4 edges */
   SPQR_MEMBERTYPE_PARALLEL   = 1,           /**< The member's skeleton consists of 2 nodes with at least 3 edges */
   SPQR_MEMBERTYPE_SERIES     = 2,           /**< The member's skeleton is a cycle with at least 3 edges */
   SPQR_MEMBERTYPE_LOOP       = 3,           /**< The member's skeleton consists of 2 nodes connected by 1 or 2 edges */
   SPQR_MEMBERTYPE_UNASSIGNED = 4            /**< To indicate that the member is not a representative member anymore */
} SPQRMemberType;
 
/** Represents a single node of cyclic doubly-linked list of arc edges*/
typedef struct
{
   spqr_arc previous;
   spqr_arc next;
} SPQRNetworkDecompositionArcListNode;
 
/** This structure stores the relevant data for a single node. */
typedef struct
{
   spqr_node representativeNode;             /**< Points to the next node in the union-find data structure.
                                              * Stores the rank as a negative number if this node represents itself */
   spqr_arc firstArc;                        /**< Points to the head node of the cyclic doubly linked list containing
                                              * the arcs that are adjacent to this node. */
   int numArcs;                              /**< The number of arcs adjacent to this node */
} SPQRNetworkDecompositionNode;
 
/** Structure that stores the relevant data for a single arc. */
typedef struct
{
   spqr_node head;                                      /**< The head node of the arc */
   spqr_node tail;                                      /**< The tail node of the arc */
   spqr_member member;                                  /**< The member that contains the arc */
   spqr_member childMember;                             /**< Stores the child member, if this arc points to one */
   SPQRNetworkDecompositionArcListNode headArcListNode; /**< Linked-list node for iterating over the head's arcs */
   SPQRNetworkDecompositionArcListNode tailArcListNode; /**< Linked-list node for iterating over the tail's arcs */
   SPQRNetworkDecompositionArcListNode arcListNode;     /**< Linked-list node for iterating over the member's arcs */
 
   spqr_element element;                                /**< The element associated to this arc */
 
   /** @name Signed union-find for arc directions.
    * @{
    *
    * If an arc is reversed, it's head becomes its tail and vice-versa.
    * For non-rigid members every arc is it's own representative, and the direction is simply given by the boolean.
    * For rigid members, every arc is represented by another arc in the member,
    * and the direction can be found by multiplying the signs along the union-find path
    * We use this data structure to efficiently reverse all arcs in a skeleton.
    */
   spqr_arc representative;                  /**< The representative of the arc */
   SCIP_Bool reversed;                       /**< Whether the arc's head and tail are reversed, or not */
   /** @} */
} SPQRNetworkDecompositionArc;
 
/** Structure that stores the relevant data for a single member */
typedef struct
{
   spqr_member representativeMember;         /**< The representative of this member (union-find) */
   SPQRMemberType type;                      /**< The type of this member */
 
   /** @name The SPQR tree is stored as an arborescence.
    * @{
    *
    * Each member stores its parents, and each edge of the member
    * pointing to a child member stores the associated member in childMember
    */
   spqr_member parentMember;                 /**< The parent of this member in the arborescence */
   spqr_arc markerToParent;                  /**< The arc pointing to the parent */
   spqr_arc markerOfParent;                  /**< The arc of the parent pointing to this member */
   /** @} */
 
   spqr_arc firstArc;                        /**< First arc of the linked list containing the member's arcs */
   int numArcs;                              /**< The number of arcs associated to the member */
} SPQRNetworkDecompositionMember;
 
/** Stores the SPQR forest data structure and its relevant data */
typedef struct
{
   int numArcs;                              /**< The number of slots used in the arc data array */
   int memArcs;                              /**< The amount of space allocated in the arc data array */
   SPQRNetworkDecompositionArc* arcs;        /**< Array of arcs of the SPQR forest, indexed by spqr_arc */
   spqr_arc firstFreeArc;                    /**< Points to the first unused slot in the arcs array */
 
   int memMembers;                           /**< The amount of space allocated in the member data array */
   int numMembers;                           /**< The number of slots used in the member data array */
   SPQRNetworkDecompositionMember* members;  /**< Array of members of the SPQR forest. Indexed by spqr_member */
 
   int memNodes;                             /**< The amount of space allocated in the node data array */
   int numNodes;                             /**< The number of slots used in the node data array */
   SPQRNetworkDecompositionNode* nodes;      /**< Array of nodes of the SPQR forest. Indexed by spqr_node */
 
   int memRows;                              /**< The (maximal) number of rows of the matrix */
   spqr_arc* rowArcs;                        /**< Maps the rows of the matrix to arcs in the decomposition */
 
   int memColumns;                           /**< The (maximal) number of columns of the matrix */
   spqr_arc* columnArcs;                     /**< Maps the columns of the matrix to arcs in the decomposition */
 
   BMS_BLKMEM * env;                         /**< used memory allocator */
 
   int numConnectedComponents;               /**< The number of disjoint SPQR trees in the SPQR forest */
} SCIP_NETMATDECDATA;
 
 
#ifndef NDEBUG
 
/** Check if a node is a representative in the union-find data structure for nodes */
static
SCIP_Bool nodeIsRepresentative(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_node             node                /**< The node to check if it is representative */
   )
{
   assert(dec);
   assert(node < dec->memNodes);
   assert(SPQRnodeIsValid(node));
 
   return SPQRnodeIsInvalid(dec->nodes[node].representativeNode);
}
 
#endif
 
/** Find the node its representative node in the union-find data structure */
static
spqr_node findNode(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_node             node                /**< The node to find the representative for */
   )
{
   assert(dec);
   assert(SPQRnodeIsValid(node));
   assert(node < dec->memNodes);
 
   spqr_node current = node;
   spqr_node next;
 
   //traverse down tree to find the root
   while( SPQRnodeIsValid(next = dec->nodes[current].representativeNode) )
   {
      current = next;
      assert(current < dec->memNodes);
   }
 
   spqr_node root = current;
   current = node;
 
   //update all pointers along path to point to root, flattening the tree
   while( SPQRnodeIsValid(next = dec->nodes[current].representativeNode) )
   {
      dec->nodes[current].representativeNode = root;
      current = next;
      assert(current < dec->memNodes);
   }
   return root;
}
 
/** Find the node its representative node in the union-find data structure, without compressing the union-find tree.
 *
 * Should only be used for debugging or asserts.
 */
static
spqr_node findNodeNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_node             node                /**< The node to find the representative for */
   )
{
   assert(dec);
   assert(SPQRnodeIsValid(node));
   assert(node < dec->memNodes);
 
   spqr_node current = node;
   spqr_node next;
 
   //traverse down tree to find the root
   while( SPQRnodeIsValid(next = dec->nodes[current].representativeNode) )
   {
      current = next;
      assert(current < dec->memNodes);
   }
   spqr_node root = current;
   return root;
}
 
/** Find the arc's tail node in the union find data structure of the nodes.
 *
 * Updates the arc's tail to point to the representative for faster future queries.
 */
static
spqr_node findArcTail(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc whose tail we want to find */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_node representative = findNode(dec, dec->arcs[arc].tail);
   dec->arcs[arc].tail = representative;//update the arc information
 
   return representative;
}
 
/** Find the arc's head node in the union find data structure of the nodes.
 *
 * Updates the arc's head to point to the representative for faster future queries.
 */
static
spqr_node findArcHead(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc whose head we want to find */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_node representative = findNode(dec, dec->arcs[arc].head);
   dec->arcs[arc].head = representative;//update the arc information
 
   return representative;
}
 
/** Find the arc's head node in the union find data structure of the nodes, without compressing the union-find tree.
 *
 * Should only be used in debugging statements or asserts.
 */
static
spqr_node findArcHeadNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc whose head we want to find */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_node representative = findNodeNoCompression(dec, dec->arcs[arc].head);
   return representative;
}
 
/** Find the arc's tail node in the union find data structure of the nodes, without compressing the union-find tree.
 *
 * Should only be used in debugging statements or asserts.
 */
static
spqr_node findArcTailNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc whose tail we want to find */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_node representative = findNodeNoCompression(dec, dec->arcs[arc].tail);
   return representative;
}
 
/** Find the first arc in the list of arcs that are adjacent to the given node.
 *
 * These arcs form a cyclic linked-list.
 */
static
spqr_arc getFirstNodeArc(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_node             node                /**< The node to find the arc for */
   )
{
   assert(dec);
   assert(SPQRnodeIsValid(node));
   assert(node < dec->memNodes);
 
   return dec->nodes[node].firstArc;
}
 
/** Given the current arc adjacent to this node, find the next arc in the cyclic linked list of adjacent arcs to the
 * given node.
 *
 * This function does not compress the union-find tree, and should only be used in debugging or asserts.
 */
static
spqr_arc getNextNodeArcNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc,                /**< The current arc that is adjacent to this node */
   spqr_node             node                /**< The node to which the arc is adjacent */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
   assert(nodeIsRepresentative(dec, node));
 
   if( findArcHeadNoCompression(dec, arc) == node )
   {
      arc = dec->arcs[arc].headArcListNode.next;
   }
   else
   {
      assert(findArcTailNoCompression(dec, arc) == node);
      arc = dec->arcs[arc].tailArcListNode.next;
   }
   return arc;
}
 
/** Given the current arc adjacent to this node, find the next arc in the cyclic linked list of adjacent arcs to the
 * given node.
 */
static
spqr_arc getNextNodeArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc,                /**< The current arc that is adjacent to this node */
   spqr_node             node                /**< The node to which the arc is adjacent */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
   assert(nodeIsRepresentative(dec, node));
 
   if( findArcHead(dec, arc) == node )
   {
      arc = dec->arcs[arc].headArcListNode.next;
   }
   else
   {
      assert(findArcTailNoCompression(dec, arc) == node);
      dec->arcs[arc].tail = node; //This assignment is not necessary but speeds up future queries.
      arc = dec->arcs[arc].tailArcListNode.next;
   }
   return arc;
}
 
/** Given the current arc adjacent to this node, find the previous arc in the cyclic linked list of adjacent arcs
 * to the given node.
 */
static
spqr_arc getPreviousNodeArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc,                /**< The current arc that is adjacent to this node */
   spqr_node             node                /**< The node to which the arc is adjacent */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
   assert(nodeIsRepresentative(dec, node));
 
   if( findArcHead(dec, arc) == node )
   {
      arc = dec->arcs[arc].headArcListNode.previous;
   }
   else
   {
      assert(findArcTailNoCompression(dec, arc) == node);
      dec->arcs[arc].tail = node;//This assignment is not necessary but speeds up future queries.
      arc = dec->arcs[arc].tailArcListNode.previous;
   }
   return arc;
}
 
/** Update the cyclic node-arc incidence data structure to move all arcs adjacent to one node to another node.
 *
 * We typically call this when two nodes are identified with one another, and we need to merge their adjacent arcs.
 */
static
void mergeNodeArcList(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_node             toMergeInto,        /**< The node that we want to give all the arcs of both nodes */
   spqr_node             toRemove            /**< The node whose arcs we want to remove */
   )
{
   spqr_arc firstIntoArc = getFirstNodeArc(dec, toMergeInto);
   spqr_arc firstFromArc = getFirstNodeArc(dec, toRemove);
   if( SPQRarcIsInvalid(firstIntoArc))
   {
      //new node has no arcs
      dec->nodes[toMergeInto].numArcs += dec->nodes[toRemove].numArcs;
      dec->nodes[toRemove].numArcs = 0;
 
      dec->nodes[toMergeInto].firstArc = dec->nodes[toRemove].firstArc;
      dec->nodes[toRemove].firstArc = SPQR_INVALID_ARC;
 
      return;
   }
   if( SPQRarcIsInvalid(firstFromArc))
   {
      //Old node has no arcs; we can just return
      return;
   }
 
   spqr_arc lastIntoArc = getPreviousNodeArc(dec, firstIntoArc, toMergeInto);
   assert(SPQRarcIsValid(lastIntoArc));
   spqr_arc lastFromArc = getPreviousNodeArc(dec, firstFromArc, toRemove);
   assert(SPQRarcIsValid(lastFromArc));
 
   SPQRNetworkDecompositionArcListNode* firstIntoNode =
      findArcHead(dec, firstIntoArc) == toMergeInto ? &dec->arcs[firstIntoArc].headArcListNode
                                                    : &dec->arcs[firstIntoArc].tailArcListNode;
   SPQRNetworkDecompositionArcListNode* lastIntoNode =
      findArcHead(dec, lastIntoArc) == toMergeInto ? &dec->arcs[lastIntoArc].headArcListNode
                                                   : &dec->arcs[lastIntoArc].tailArcListNode;
 
   SPQRNetworkDecompositionArcListNode* firstFromNode =
      findArcHead(dec, firstFromArc) == toRemove ? &dec->arcs[firstFromArc].headArcListNode
                                                 : &dec->arcs[firstFromArc].tailArcListNode;
   SPQRNetworkDecompositionArcListNode* lastFromNode =
      findArcHead(dec, lastFromArc) == toRemove ? &dec->arcs[lastFromArc].headArcListNode
                                                : &dec->arcs[lastFromArc].tailArcListNode;
 
   firstIntoNode->previous = lastFromArc;
   lastIntoNode->next = firstFromArc;
   firstFromNode->previous = lastIntoArc;
   lastFromNode->next = firstIntoArc;
 
   dec->nodes[toMergeInto].numArcs += dec->nodes[toRemove].numArcs;
   dec->nodes[toRemove].numArcs = 0;
   dec->nodes[toRemove].firstArc = SPQR_INVALID_ARC;
}
 
/** Flips the direction a given arc. */
static
void arcFlipReversed(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc that we want to flip */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   dec->arcs[arc].reversed = !dec->arcs[arc].reversed;
}
 
/** Sets the direction of a given arc */
static
void arcSetReversed(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc,                /**< The given arc */
   SCIP_Bool             reversed            /**< Are the head and tail reversed? */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   dec->arcs[arc].reversed = reversed;
}
 
 
/** Sets the representative of a given arc.
 *
 * The arcs reversed field is given with respect to the representative.
 * In particular, whether an arc is reversed or not is determined by the sign of the path in the signed union-find
 * data structure for arcs, which can be computed by multiplying the signs of the individual edges (xor over bools).
 */
static
void arcSetRepresentative(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc,                /**< The given arc */
   spqr_arc              representative      /**< The representative to set the arc to */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
   assert(representative == SPQR_INVALID_ARC || SPQRarcIsValid(representative));
 
   dec->arcs[arc].representative = representative;
}
 
/** Merge two representative nodes (Union operation) in the union-find data structure for nodes.
 *
 * Returns the id of the node that becomes representative for both.
 */
static
spqr_node mergeNodes(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_node             first,              /**< A node to merge */
   spqr_node             second              /**< A second node to merge */
   )
{
   assert(dec);
   assert(nodeIsRepresentative(dec, first));
   assert(nodeIsRepresentative(dec, second));
   assert(first != second);//We cannot merge a node into itself
   assert(first < dec->memNodes);
   assert(second < dec->memNodes);
 
   //The rank is stored as a negative number: we decrement it making the negative number larger.
   //We want the new root to be the one with 'largest' rank, so smallest number. If they are equal, we decrement.
   spqr_node firstRank = dec->nodes[first].representativeNode;
   spqr_node secondRank = dec->nodes[second].representativeNode;
   if( firstRank > secondRank )
   {
      SCIPswapInts(&first, &second);
   }
   //first becomes representative; we merge all of the arcs of second into first
   mergeNodeArcList(dec, first, second);
   dec->nodes[second].representativeNode = first;
   if( firstRank == secondRank )
   {
      --dec->nodes[first].representativeNode;
   }
   return first;
}
 
/** Check if a member is a representative in the union-find data structure for members. */
static
SCIP_Bool memberIsRepresentative(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_member           member              /**< The member to check */
   )
{
   assert(dec);
   assert(member < dec->memMembers);
   assert(SPQRmemberIsValid(member));
 
   return SPQRmemberIsInvalid(dec->members[member].representativeMember);
}
 
/** Find the member its representative member in the union-find data structure */
static
spqr_member findMember(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_member           member              /**< The member to find the representative for */
   )
{
   assert(dec);
   assert(member < dec->memMembers);
   assert(SPQRmemberIsValid(member));
 
   spqr_member current = member;
   spqr_member next;
 
   //traverse down tree to find the root
   while( SPQRmemberIsValid(next = dec->members[current].representativeMember) )
   {
      current = next;
      assert(current < dec->memMembers);
   }
 
   spqr_member root = current;
   current = member;
 
   //update all pointers along path to point to root, flattening the tree
   while( SPQRmemberIsValid(next = dec->members[current].representativeMember) )
   {
      dec->members[current].representativeMember = root;
      current = next;
      assert(current < dec->memMembers);
   }
   return root;
}
 
/** Find the member's representative member in the union-find data structure, without compressing the union-find tree.
 *
 * Should only be used for debugging or asserts.
 */
static
spqr_member findMemberNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_member           member              /**< The member to find the representative for */
   )
{
   assert(dec);
   assert(member < dec->memMembers);
   assert(SPQRmemberIsValid(member));
 
   spqr_member current = member;
   spqr_member next;
 
   //traverse down tree to find the root
   while( SPQRmemberIsValid(next = dec->members[current].representativeMember) )
   {
      current = next;
      assert(current < dec->memMembers);
   }
 
   spqr_member root = current;
   return root;
}
 
/** Merge two representative members (Union operation) in the union-find data structure.
 *
 * Returns the id of the member that becomes representative for both.
 */
static
spqr_member mergeMembers(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_member           first,              /**< The first member to merge */
   spqr_member           second              /**< The second member to merge */
   )
{
   assert(dec);
   assert(memberIsRepresentative(dec, first));
   assert(memberIsRepresentative(dec, second));
   assert(first != second);//We cannot merge a member into itself
   assert(first < dec->memMembers);
   assert(second < dec->memMembers);
 
   //The rank is stored as a negative number: we decrement it making the negative number larger.
   // We want the new root to be the one with 'largest' rank, so smallest number. If they are equal, we decrement.
   spqr_member firstRank = dec->members[first].representativeMember;
   spqr_member secondRank = dec->members[second].representativeMember;
   if( firstRank > secondRank )
   {
      SCIPswapInts(&first, &second);
   }
   dec->members[second].representativeMember = first;
   if( firstRank == secondRank )
   {
      --dec->members[first].representativeMember;
   }
   return first;
}
 
/** Finds the member in which the arc is located */
static
spqr_member findArcMember(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the member for */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_member representative = findMember(dec, dec->arcs[arc].member);
   dec->arcs[arc].member = representative;
   return representative;
}
 
/** Finds the member in which the arc is located, without compressing the member union-find tree */
static
spqr_member findArcMemberNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the member for */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_member representative = findMemberNoCompression(dec, dec->arcs[arc].member);
   return representative;
}
 
/** Find the representative parent member of the given member.
 *
 * Note the given member must be representative.
 */
static
spqr_member findMemberParent(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_member           member              /**< The member to find the parent for. Must be representative. */
   )
{
   assert(dec);
   assert(member < dec->memMembers);
   assert(SPQRmemberIsValid(member));
   assert(memberIsRepresentative(dec, member));
 
   if( SPQRmemberIsInvalid(dec->members[member].parentMember))
   {
      return dec->members[member].parentMember;
   }
   spqr_member parent_representative = findMember(dec, dec->members[member].parentMember);
   dec->members[member].parentMember = parent_representative;
 
   return parent_representative;
}
 
/** Find the representative parent member of the given member.
 *
 * Note the given member must be representative.
 * This version does not perform compression of the union-find tree, and should only be used in debug or asserts.
 */
static
spqr_member findMemberParentNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_member           member              /**< The member to find the parent for. Must be representative. */
   )
{
   assert(dec);
   assert(member < dec->memMembers);
   assert(SPQRmemberIsValid(member));
   assert(memberIsRepresentative(dec, member));
 
   if( SPQRmemberIsInvalid(dec->members[member].parentMember))
   {
      return dec->members[member].parentMember;
   }
   spqr_member parent_representative = findMemberNoCompression(dec, dec->members[member].parentMember);
   return parent_representative;
}
 
/** Find the child member associated to the given arc, which must be virtual. */
static
spqr_member findArcChildMember(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the child member for */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_member representative = findMember(dec, dec->arcs[arc].childMember);
   dec->arcs[arc].childMember = representative;
   return representative;
}
 
/** Find the child member associated to the given virtual arc.
 *
 * This version does not compress the union-find tree and should only be used for debugging and asserts.
 */
static
spqr_member findArcChildMemberNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the child member for */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   spqr_member representative = findMemberNoCompression(dec, dec->arcs[arc].childMember);
   return representative;
}
 
/** Checks if the arc has a child member */
static
SCIP_Bool arcIsChildMarker(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to check */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   return SPQRmemberIsValid(dec->arcs[arc].childMember);
}
 
/** Check whether the given arc is a tree arc or not, i.e. whether it belongs to a (virtual) row or column or not */
static
SCIP_Bool arcIsTree(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to check */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   return SPQRelementIsRow(dec->arcs[arc].element);
}
 
/** Output data structure that stores both the arc's sign and representative */
typedef struct
{
   spqr_arc representative;
   SCIP_Bool reversed;
} ArcSign;
 
#ifndef NDEBUG
 
/** Check if an arc is a representative in the signed union-find data structure for arc directions.
 *
 * In each member, exactly one arc is the representative.
 */
static
SCIP_Bool arcIsRepresentative(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to check */
   )
{
   assert(dec);
   assert(arc < dec->memArcs);
   assert(SPQRarcIsValid(arc));
 
   return SPQRarcIsInvalid(dec->arcs[arc].representative);
}
 
#endif
 
/** Find an arcs representative and its direction in the signed union-find data structure for arcs. */
static
ArcSign findArcSign(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the representative and direction for */
   )
{
   assert(dec);
   assert(arc < dec->memArcs);
   assert(SPQRarcIsValid(arc));
 
   spqr_arc current = arc;
   spqr_arc next;
 
   SCIP_Bool totalReversed = dec->arcs[current].reversed;
   //traverse down tree to find the root
   while( SPQRarcIsValid(next = dec->arcs[current].representative) )
   {
      current = next;
      assert(current < dec->memArcs);
      //swap boolean only if new arc is reversed
      totalReversed = ( totalReversed != dec->arcs[current].reversed );
   }
 
   spqr_arc root = current;
   current = arc;
 
   SCIP_Bool currentReversed = totalReversed != dec->arcs[root].reversed;
   //update all pointers along path to point to root, flattening the tree
 
   while( SPQRarcIsValid(next = dec->arcs[current].representative) )
   {
      SCIP_Bool wasReversed = dec->arcs[current].reversed;
 
      dec->arcs[current].reversed = currentReversed;
      currentReversed = ( currentReversed != wasReversed );
 
      dec->arcs[current].representative = root;
      current = next;
      assert(current < dec->memArcs);
   }
 
   ArcSign sign;
   sign.reversed = totalReversed;
   sign.representative = root;
   return sign;
}
 
/** Find an arcs representative and its direction in the signed union-find data structure for arcs.
 *
 * This version does not compress the union-find tree and should only be used in debug and asserts.
 */
static
ArcSign findArcSignNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the representative and direction for */
   )
{
   assert(dec);
   assert(arc < dec->memArcs);
   assert(SPQRarcIsValid(arc));
 
   spqr_arc current = arc;
   spqr_arc next;
 
   SCIP_Bool totalReversed = dec->arcs[current].reversed;
   //traverse down tree to find the root
   while( SPQRarcIsValid(next = dec->arcs[current].representative))
   {
      current = next;
      assert(current < dec->memArcs);
      //swap boolean only if new arc is reversed
      totalReversed = ( totalReversed != dec->arcs[current].reversed );
   }
   ArcSign sign;
   sign.reversed = totalReversed;
   sign.representative = current;
   return sign;
}
 
/** Finds the arcs head, taking into account whether it is reversed by the signed union-find data structure. */
static
spqr_node findEffectiveArcHead(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the head for */
   )
{
   assert(dec);
   if( findArcSign(dec, arc).reversed )
   {
      return findArcTail(dec, arc);
   }
   else
   {
      return findArcHead(dec, arc);
   }
}
 
/** Finds the arcs tail, taking into account whether it is reversed by the signed union-find data structure. */
static
spqr_node findEffectiveArcTail(
   SCIP_NETMATDECDATA*   dec,                /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the tail for */
   )
{
   assert(dec);
   if( findArcSign(dec, arc).reversed )
   {
      return findArcHead(dec, arc);
   }
   else
   {
      return findArcTail(dec, arc);
   }
}
 
/** Finds the arcs head, taking into account whether it is reversed by the signed union-find data structure.
 *
 * This version does not compress the union-find tree and should only be used in debug and asserts.
 */
static
spqr_node findEffectiveArcHeadNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the head for */
   )
{
   assert(dec);
 
   if( findArcSignNoCompression(dec, arc).reversed )
   {
      return findArcTailNoCompression(dec, arc);
   }
   else
   {
      return findArcHeadNoCompression(dec, arc);
   }
}
 
/** Finds the arcs tail, taking into account whether it is reversed by the signed union-find data structure.
 *
 * This version does not compress the union-find tree and should only be used in debug and asserts.
 */
static
spqr_node findEffectiveArcTailNoCompression(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to find the tail for */
   )
{
   assert(dec);
   if( findArcSignNoCompression(dec, arc).reversed )
   {
      return findArcHeadNoCompression(dec, arc);
   }
   else
   {
      return findArcTailNoCompression(dec, arc);
   }
}
 
/** Merges the sign union-find structures for two arc sets.
 *
 * If reflectRelative is set to true then all arcs of the represented by the second arc are reversed
 * w.r.t. their current orientation. Otherwise, all arcs keep the same
 * reversed status with respect to the root node of the union find tree.
 */
static
spqr_arc mergeArcSigns(
   SCIP_NETMATDECDATA*   dec,                /**< The decomposition data structure */
   spqr_arc              first,              /**< Representative arc of the first arc set */
   spqr_arc              second,             /**< Representative arc of the second arc set */
   SCIP_Bool             reflectRelative     /**< Should all arcs in the second arc set be reversed?*/
   )
{
   assert(dec);
   assert(arcIsRepresentative(dec, first));
   assert(arcIsRepresentative(dec, second));
   assert(first != second);//We cannot merge a member into itself
   assert(first < dec->memArcs);
   assert(second < dec->memArcs);
 
   //The rank is stored as a negative number: we decrement it making the negative number larger.
   //We want the new root to be the one with 'largest' rank, so smallest number. If they are equal, we decrement.
   spqr_member firstRank = dec->arcs[first].representative;
   spqr_member secondRank = dec->arcs[second].representative;
 
   if( firstRank > secondRank )
   {
      SCIPswapInts(&first, &second);
   }
   dec->arcs[second].representative = first;
   if( firstRank == secondRank )
   {
      --dec->arcs[first].representative;
   }
   //These boolean formula's cover all 16 possible cases, such that the relative orientation of the first is not changed
   //but the relative orientation of the second is changed based on whether we want to reflect.
   SCIP_Bool equal = dec->arcs[first].reversed == dec->arcs[second].reversed;
   dec->arcs[second].reversed = ( equal == reflectRelative );
   if( firstRank > secondRank )
   {
      dec->arcs[first].reversed = ( dec->arcs[first].reversed != reflectRelative );
   }
   return first;
}
 
/** Checks whether an arc is reversed for arcs in non-rigid members.
 *
 * For non-rigid members, we do not use the union-find datastructure, as we can get away without it.
 */
static
SCIP_Bool arcIsReversedNonRigid(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to check */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   return dec->arcs[arc].reversed;
}
 
/** Gets the element (row/column) associated to the given arc. */
static
spqr_element arcGetElement(
   const SCIP_NETMATDECDATA* dec,            /**< The network decomposition */
   spqr_arc              arc                 /**< The arc to get the element for */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   return dec->arcs[arc].element;
}
 
/** Check whether the network matrix decomposition contains an edge for the given row index. */
static
SCIP_Bool netMatDecDataContainsRow(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   int                   row                 /**< The row index that is checked */
   )
{
   assert(SPQRrowIsValid(row) && row < dec->memRows);
   assert(dec);
 
   return SPQRarcIsValid(dec->rowArcs[row]);
}
 
/** Check whether the network matrix decomposition contains an edge for the given column index. */
static
SCIP_Bool netMatDecDataContainsColumn(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   int                   column              /**< The column index that is checked */
   )
{
   assert(SPQRcolIsValid(column) && column < dec->memColumns);
   assert(dec);
 
   return SPQRarcIsValid(dec->columnArcs[column]);
}
 
/** Associate the given arc to the given column in the network matrix decomposition. */
static
void setDecompositionColumnArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_col              col,                /**< The column to associate */
   spqr_arc              arc                 /**< The arc to associate to the column */
   )
{
   assert(SPQRcolIsValid(col) && col < dec->memColumns);
   assert(dec);
   assert(SPQRarcIsValid(arc));
 
   dec->columnArcs[col] = arc;
}
 
/** Associate the given arc to the given row in the network matrix decomposition. */
static
void setDecompositionRowArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_row              row,                /**< The row to associate */
   spqr_arc              arc                 /**< The arc to associate to the row */
   )
{
   assert(SPQRrowIsValid(row) && row < dec->memRows);
   assert(dec);
   assert(SPQRarcIsValid(arc));
 
   dec->rowArcs[row] = arc;
}
 
/** Get the decomposition arc associated to the given column. */
static
spqr_arc getDecompositionColumnArc(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_col              col                 /**< The given column */
   )
{
   assert(SPQRcolIsValid(col) && col < dec->memColumns);
   assert(dec);
 
   return dec->columnArcs[col];
}
 
/** Get the decomposition arc associated to the given row. */
static
spqr_arc getDecompositionRowArc(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_row              row                 /**< The given row */
   )
{
   assert(SPQRrowIsValid(row) && row < dec->memRows);
   assert(dec);
 
   return dec->rowArcs[row];
}
 
/** Initialize the network matrix decomposition data structure. */
static
SCIP_RETCODE netMatDecDataCreate(
   BMS_BLKMEM*           blkmem,             /**< Block memory */
   SCIP_NETMATDECDATA**  pdec,               /**< buffer to store pointer to created decomposition */
   int                   nrows,              /**< The maximal number of rows that the decomposition can expect */
   int                   ncols               /**< The maximal number of columns that the decomposition can expect */
   )
{
   assert(blkmem);
   assert(pdec);
   assert(!*pdec);
 
   SCIP_ALLOC( BMSallocBlockMemory(blkmem, pdec) );
   SCIP_NETMATDECDATA* dec = *pdec;
   dec->env = blkmem;
 
   //Initialize arc array data
   int initialMemArcs = 8;
   {
      assert(initialMemArcs > 0);
      dec->memArcs = initialMemArcs;
      dec->numArcs = 0;
      SCIP_ALLOC( BMSallocBlockMemoryArray(blkmem, &dec->arcs, dec->memArcs) );
      for( spqr_arc i = 0; i < dec->memArcs; ++i )
      {
         dec->arcs[i].arcListNode.next = i + 1;
         dec->arcs[i].member = SPQR_INVALID_MEMBER;
      }
      dec->arcs[dec->memArcs - 1].arcListNode.next = SPQR_INVALID_ARC;
      dec->firstFreeArc = 0;
   }
 
   //Initialize member array data
   int initialMemMembers = 8;
   {
      assert(initialMemMembers > 0);
      dec->memMembers = initialMemMembers;
      dec->numMembers = 0;
      SCIP_ALLOC( BMSallocBlockMemoryArray(blkmem, &dec->members, dec->memMembers) );
   }
 
   //Initialize node array data
   int initialMemNodes = 8;
   {
      assert(initialMemNodes > 0);
      dec->memNodes = initialMemNodes;
      dec->numNodes = 0;
      SCIP_ALLOC( BMSallocBlockMemoryArray(blkmem, &dec->nodes, dec->memNodes) );
   }
 
   //Initialize mappings for rows
   {
      dec->memRows = nrows;
      SCIP_ALLOC( BMSallocBlockMemoryArray(blkmem, &dec->rowArcs, dec->memRows) );
      for( int i = 0; i < dec->memRows; ++i )
      {
         dec->rowArcs[i] = SPQR_INVALID_ARC;
      }
   }
   //Initialize mappings for columns
   {
      dec->memColumns = ncols;
      SCIP_ALLOC( BMSallocBlockMemoryArray(blkmem, &dec->columnArcs, dec->memColumns) );
      for( int i = 0; i < dec->memColumns; ++i )
      {
         dec->columnArcs[i] = SPQR_INVALID_ARC;
      }
   }
 
   dec->numConnectedComponents = 0;
   return SCIP_OKAY;
}
 
/** Free the network matrix decomposition data structure */
static
void netMatDecDataFree(
   SCIP_NETMATDECDATA**  pdec                /**< pointer to the network matrix decomposition to freed */
   )
{
   assert(pdec);
   assert(*pdec);
 
   SCIP_NETMATDECDATA* dec = *pdec;
   BMSfreeBlockMemoryArray(dec->env, &dec->columnArcs, dec->memColumns);
   BMSfreeBlockMemoryArray(dec->env, &dec->rowArcs, dec->memRows);
   BMSfreeBlockMemoryArray(dec->env, &dec->nodes, dec->memNodes);
   BMSfreeBlockMemoryArray(dec->env, &dec->members, dec->memMembers);
   BMSfreeBlockMemoryArray(dec->env, &dec->arcs, dec->memArcs);
 
   BMSfreeBlockMemory(dec->env, pdec);
}
 
/** Get the first arc of the linked list of arcs contained in the given member. */
static
spqr_arc getFirstMemberArc(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_member           member              /**< The given member */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
 
   return dec->members[member].firstArc;
}
 
/** Given the current arc, get the next arc of the linked list of arcs that are in the same member. */
static
spqr_arc getNextMemberArc(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_arc              arc                 /**< The current arc */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   arc = dec->arcs[arc].arcListNode.next;
   return arc;
}
 
/** Given the current arc, get the previous arc of the linked list of arcs that are in the same member. */
static
spqr_arc getPreviousMemberArc(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_arc              arc                 /**< The current arc */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
 
   arc = dec->arcs[arc].arcListNode.previous;
   return arc;
}
 
/** Adds an arc to the linked list of arcs of the given member. */
static
void addArcToMemberArcList(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The arc to add */
   spqr_member           member              /**< The member to add the arc to */
   )
{
   spqr_arc firstMemberArc = getFirstMemberArc(dec, member);
 
   if( SPQRarcIsValid(firstMemberArc))
   {
      spqr_arc lastMemberArc = getPreviousMemberArc(dec, firstMemberArc);
      dec->arcs[arc].arcListNode.next = firstMemberArc;
      dec->arcs[arc].arcListNode.previous = lastMemberArc;
      dec->arcs[firstMemberArc].arcListNode.previous = arc;
      dec->arcs[lastMemberArc].arcListNode.next = arc;
   }
   else
   {
      assert(dec->members[member].numArcs == 0);
      dec->arcs[arc].arcListNode.next = arc;
      dec->arcs[arc].arcListNode.previous = arc;
   }
   dec->members[member].firstArc = arc;
   ++( dec->members[member].numArcs );
}
 
/** Create a new arc in the network matrix decomposition. */
static
SCIP_RETCODE createArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member,             /**< The member that contains the arc */
   SCIP_Bool             reversed,           /**< Is the arc reversed or not? */
   spqr_arc*             pArc                /**< out-pointer to the id that is assigned to the arc. */
   )
{
   assert(dec);
   assert(pArc);
   assert(SPQRmemberIsInvalid(member) || memberIsRepresentative(dec, member));
 
   spqr_arc idx = dec->firstFreeArc;
   if( SPQRarcIsValid(idx))
   {
      dec->firstFreeArc = dec->arcs[idx].arcListNode.next;
   }
   else
   {
      //Enlarge array, no free nodes in arc list
      int newSize = 2 * dec->memArcs;
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &dec->arcs, dec->memArcs, newSize) );
      for( int i = dec->memArcs + 1; i < newSize; ++i )
      {
         dec->arcs[i].arcListNode.next = i + 1;
         dec->arcs[i].member = SPQR_INVALID_MEMBER;
      }
      dec->arcs[newSize - 1].arcListNode.next = SPQR_INVALID_ARC;
      dec->firstFreeArc = dec->memArcs + 1;
      idx = dec->memArcs;
      dec->memArcs = newSize;
   }
 
   dec->arcs[idx].tail = SPQR_INVALID_NODE;
   dec->arcs[idx].head = SPQR_INVALID_NODE;
   dec->arcs[idx].member = member;
   dec->arcs[idx].childMember = SPQR_INVALID_MEMBER;
   dec->arcs[idx].reversed = reversed;
 
   dec->arcs[idx].headArcListNode.next = SPQR_INVALID_ARC;
   dec->arcs[idx].headArcListNode.previous = SPQR_INVALID_ARC;
   dec->arcs[idx].tailArcListNode.next = SPQR_INVALID_ARC;
   dec->arcs[idx].tailArcListNode.previous = SPQR_INVALID_ARC;
 
   dec->numArcs++;
 
   *pArc = idx;
 
   return SCIP_OKAY;
}
 
/** Create a new arc in the network matrix decomposition that is associated to the given row. */
static
SCIP_RETCODE createRowArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member,             /**< The member that contains the arc */
   spqr_arc*             pArc,               /**< out-pointer to the id that is assigned to the arc. */
   spqr_row              row,                /**< The row associated to the arc */
   SCIP_Bool             reversed            /**< Is the arc reversed or not? */
   )
{
   SCIP_CALL( createArc(dec, member, reversed, pArc) );
   setDecompositionRowArc(dec, row, *pArc);
   addArcToMemberArcList(dec, *pArc, member);
   dec->arcs[*pArc].element = SPQRrowToElement(row);
 
   return SCIP_OKAY;
}
 
/** Create a new arc in the network matrix decomposition that is associated to the given column. */
static
SCIP_RETCODE createColumnArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member,             /**< The member that contains the arc */
   spqr_arc*             pArc,               /**< out-pointer to the id that is assigned to the arc. */
   spqr_col              column,             /**< The column associated to the arc */
   SCIP_Bool             reversed            /**< Is the arc reversed or not? */
   )
{
   SCIP_CALL( createArc(dec, member, reversed, pArc) );
   setDecompositionColumnArc(dec, column, *pArc);
   addArcToMemberArcList(dec, *pArc, member);
   dec->arcs[*pArc].element = SPQRcolumnToElement(column);
 
   return SCIP_OKAY;
}
 
/** Create a new member in the network matrix decomposition. */
static
SCIP_RETCODE createMember(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SPQRMemberType        type,               /**< The SPQR-type of the member */
   spqr_member*          pMember             /**< out-pointer to the id that is assigned to the member */
   )
{
   assert(dec);
   assert(pMember);
 
   if( dec->numMembers == dec->memMembers )
   {
      int newSize = dec->memMembers * 2;
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &dec->members, dec->memMembers, newSize) );
      dec->memMembers = newSize;
   }
   SPQRNetworkDecompositionMember* data = &dec->members[dec->numMembers];
   data->markerOfParent = SPQR_INVALID_ARC;
   data->markerToParent = SPQR_INVALID_ARC;
   data->firstArc = SPQR_INVALID_ARC;
   data->representativeMember = SPQR_INVALID_MEMBER;
   data->numArcs = 0;
   data->parentMember = SPQR_INVALID_MEMBER;
   data->type = type;
 
   *pMember = dec->numMembers;
 
   dec->numMembers++;
   return SCIP_OKAY;
}
 
/** Create a new node in the network matrix decomposition. */
static
SCIP_RETCODE createNode(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_node*            pNode               /**< out-pointer to the id that is assigned to the node */
   )
{
   if( dec->numNodes == dec->memNodes )
   {
      int newSize = dec->memNodes * 2;
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &dec->nodes, dec->memNodes, newSize) );
      dec->memNodes = newSize;
   }
   *pNode = dec->numNodes;
   dec->nodes[dec->numNodes].representativeNode = SPQR_INVALID_NODE;
   dec->nodes[dec->numNodes].firstArc = SPQR_INVALID_ARC;
   dec->nodes[dec->numNodes].numArcs = 0;
   dec->numNodes++;
 
   return SCIP_OKAY;
}
 
/** Remove an arc from the linked list of arcs that are adjacent to a given node. */
static
void removeArcFromNodeArcList(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The arc to remove */
   spqr_node             node,               /**< The node to remove the arc from */
   SCIP_Bool             nodeIsHead          /**< Indicates whether the node is the arcs head, or tail */
   )
{
   SPQRNetworkDecompositionArcListNode* arcListNode = nodeIsHead ? &dec->arcs[arc].headArcListNode
                                                                 : &dec->arcs[arc].tailArcListNode;
 
   if( dec->nodes[node].numArcs == 1 )
   {
      dec->nodes[node].firstArc = SPQR_INVALID_ARC;
   }
   else
   {
      spqr_arc next_arc = arcListNode->next;
      spqr_arc prev_arc = arcListNode->previous;
      SPQRNetworkDecompositionArcListNode* nextListNode =
         findArcHead(dec, next_arc) == node ? &dec->arcs[next_arc].headArcListNode
                                            : &dec->arcs[next_arc].tailArcListNode;
      SPQRNetworkDecompositionArcListNode* prevListNode =
         findArcHead(dec, prev_arc) == node ? &dec->arcs[prev_arc].headArcListNode
                                            : &dec->arcs[prev_arc].tailArcListNode;
 
      nextListNode->previous = prev_arc;
      prevListNode->next = next_arc;
 
      if( dec->nodes[node].firstArc == arc )
      {
         dec->nodes[node].firstArc = next_arc;
      }
   }
   --( dec->nodes[node].numArcs );
}
 
/** Add an arc to the linked list of arcs that are adjacent to a given node. */
static
void addArcToNodeArcList(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The arc to add */
   spqr_node             node,               /**< The node to add the arc to */
   SCIP_Bool             nodeIsHead          /**< Indicates whether the node is the arcs head, or tail */
   )
{
   assert(nodeIsRepresentative(dec, node));
 
   spqr_arc firstNodeArc = getFirstNodeArc(dec, node);
 
   SPQRNetworkDecompositionArcListNode* arcListNode = nodeIsHead ? &dec->arcs[arc].headArcListNode
                                                                 : &dec->arcs[arc].tailArcListNode;
   if( SPQRarcIsValid(firstNodeArc))
   {
      SCIP_Bool nextIsHead = findArcHead(dec, firstNodeArc) == node;
      SPQRNetworkDecompositionArcListNode* nextListNode = nextIsHead ? &dec->arcs[firstNodeArc].headArcListNode
                                                                     : &dec->arcs[firstNodeArc].tailArcListNode;
      spqr_arc lastNodeArc = nextListNode->previous;
 
      arcListNode->next = firstNodeArc;
      arcListNode->previous = lastNodeArc;
 
      SCIP_Bool previousIsHead = findArcHead(dec, lastNodeArc) == node;
      SPQRNetworkDecompositionArcListNode* previousListNode = previousIsHead ? &dec->arcs[lastNodeArc].headArcListNode
                                                                             : &dec->arcs[lastNodeArc].tailArcListNode;
      previousListNode->next = arc;
      nextListNode->previous = arc;
   }
   else
   {
      arcListNode->next = arc;
      arcListNode->previous = arc;
   }
   dec->nodes[node].firstArc = arc;
   ++dec->nodes[node].numArcs;
   if( nodeIsHead )
   {
      dec->arcs[arc].head = node;
   }
   else
   {
      dec->arcs[arc].tail = node;
   }
}
 
/** Initializes the data structures of the arcs head and tail nodes. */
static
void setArcHeadAndTail(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The arc to initialize */
   spqr_node             head,               /**< The arc its head node*/
   spqr_node             tail                /**< The arc its tail node*/
   )
{
   addArcToNodeArcList(dec, arc, head, TRUE);
   addArcToNodeArcList(dec, arc, tail, FALSE);
}
 
/** Deinitializes the data structures of the arcs head and tail nodes. */
static
void clearArcHeadAndTail(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc                 /**< The arc to deinitialize */
   )
{
   removeArcFromNodeArcList(dec, arc, findArcHead(dec, arc), TRUE);
   removeArcFromNodeArcList(dec, arc, findArcTail(dec, arc), FALSE);
   dec->arcs[arc].head = SPQR_INVALID_NODE;
   dec->arcs[arc].tail = SPQR_INVALID_NODE;
}
 
/** Change the arc's head node to a new node. */
static
void changeArcHead(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The given arc */
   spqr_node             oldHead,            /**< The current head node of the arc */
   spqr_node             newHead             /**< The new head node of the arc */
   )
{
   assert(nodeIsRepresentative(dec, oldHead));
   assert(nodeIsRepresentative(dec, newHead));
 
   removeArcFromNodeArcList(dec, arc, oldHead, TRUE);
   addArcToNodeArcList(dec, arc, newHead, TRUE);
}
 
/** Change the arc's head node to a new node. */
static
void changeArcTail(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The given arc */
   spqr_node             oldTail,            /**< The current tail node of the arc */
   spqr_node             newTail             /**< The new tail node of the arc */
   )
{
   assert(nodeIsRepresentative(dec, oldTail));
   assert(nodeIsRepresentative(dec, newTail));
 
   removeArcFromNodeArcList(dec, arc, oldTail, FALSE);
   addArcToNodeArcList(dec, arc, newTail, FALSE);
}
 
/** Returns the degree of the given node. */
static
int nodeDegree(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_node             node                /**< The given node */
   )
{
   assert(dec);
   assert(SPQRnodeIsValid(node));
   assert(node < dec->memNodes);
 
   return dec->nodes[node].numArcs;
}
 
/** Get the SPQR-type of the given member. */
static
SPQRMemberType getMemberType(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_member           member              /**< The given member */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
   assert(memberIsRepresentative(dec, member));
 
   return dec->members[member].type;
}
 
/** Update the SPQR-type of the given member. */
static
void updateMemberType(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_member           member,             /**< The member to update the type for */
   SPQRMemberType        type                /**< The new SPQR-type of the member */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
   assert(memberIsRepresentative(dec, member));
 
   dec->members[member].type = type;
}
 
/** Returns the virtual arc pointing to the parent member (in the arborescence) of the given member. */
static
spqr_arc markerToParent(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_member           member              /**< The given member */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
   assert(memberIsRepresentative(dec, member));
 
   return dec->members[member].markerToParent;
}
 
/** Updates the parent information of a member that is identified with another another member. */
static
void updateMemberParentInformation(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   const spqr_member     newMember,          /**< The new large member containing both members */
   const spqr_member     toRemove            /**< The member that was merged and removed */
   )
{
   assert(memberIsRepresentative(dec, newMember));
   assert(findMemberNoCompression(dec, toRemove) == newMember);
 
   dec->members[newMember].markerOfParent = dec->members[toRemove].markerOfParent;
   dec->members[newMember].markerToParent = dec->members[toRemove].markerToParent;
   dec->members[newMember].parentMember = dec->members[toRemove].parentMember;
 
   dec->members[toRemove].markerOfParent = SPQR_INVALID_ARC;
   dec->members[toRemove].markerToParent = SPQR_INVALID_ARC;
   dec->members[toRemove].parentMember = SPQR_INVALID_MEMBER;
}
 
/** Returns the virtual arc of the parent member that points to the given member. */
static
spqr_arc markerOfParent(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_member           member              /**< The given member */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
   assert(memberIsRepresentative(dec, member));
 
   return dec->members[member].markerOfParent;
}
 
/** Returns the number of arcs in the member. */
static
int getNumMemberArcs(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_member           member              /**< The member to get the number of arcs of */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
   assert(memberIsRepresentative(dec, member));
 
   return dec->members[member].numArcs;
}
 
/** Returns the number of nodes in complete network matrix decomposition. */
static
int getNumNodes(
   const SCIP_NETMATDECDATA* dec             /**< The network matrix decomposition */
   )
{
   assert(dec);
 
   return dec->numNodes;
}
 
/** Returns the number of members in complete network matrix decomposition. */
static
int getNumMembers(
   const SCIP_NETMATDECDATA* dec             /**< The network matrix decomposition */
   )
{
   assert(dec);
 
   return dec->numMembers;
}
 
/** Creates a standalone parallel member with the given row and columns that is not connected to other members of the
 * network matrix decomposition.
 *
 * New arcs are created for the given row and columns.
 */
static
SCIP_RETCODE createStandaloneParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_col*             columns,            /**< The columns in the parallel member */
   SCIP_Bool*            reversed,           /**< Array indicating the direction of each column edge */
   int                   num_columns,        /**< The number of columns in the parallel member */
   spqr_row              row,                /**< The row in the parallel member */
   spqr_member*          pMember             /**< out-pointer to the new parallel member id */
   )
{
   spqr_member member;
   SCIP_CALL( createMember(dec, num_columns <= 1 ? SPQR_MEMBERTYPE_LOOP : SPQR_MEMBERTYPE_PARALLEL, &member) );
 
   spqr_arc row_arc;
   SCIP_CALL( createRowArc(dec, member, &row_arc, row, num_columns <= 1) );
 
   spqr_arc col_arc;
   for( int i = 0; i < num_columns; ++i )
   {
      SCIP_CALL( createColumnArc(dec, member, &col_arc, columns[i], reversed[i]) );
   }
   *pMember = member;
 
   ++dec->numConnectedComponents;
 
   return SCIP_OKAY;
}
 
/** Creates a parallel member with the given row and columns is connected to other members of the
 * network matrix decomposition.
 *
 * New arcs are created for the given row and columns.
 */
static
SCIP_RETCODE createConnectedParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_col*             columns,            /**< The columns in the parallel member */
   SCIP_Bool*            reversed,           /**< Array indicating the direction of each column edge */
   int                   num_columns,        /**< The number of columns in the parallel member */
   spqr_row              row,                /**< The row in the parallel member */
   spqr_member*          pMember             /**< out-pointer to the new parallel member id */
   )
{
   spqr_member member;
   SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &member) );
 
   spqr_arc row_arc;
   SCIP_CALL( createRowArc(dec, member, &row_arc, row, FALSE) );
 
   spqr_arc col_arc;
   for( int i = 0; i < num_columns; ++i )
   {
      SCIP_CALL( createColumnArc(dec, member, &col_arc, columns[i], reversed[i]) );
   }
   *pMember = member;
 
   return SCIP_OKAY;
}
 
/** Creates a standalone series member with the given row and columns that is not connected to other members of the
 * network matrix decomposition.
 *
 * New arcs are created for the given rows and column.
 */
static
SCIP_RETCODE createStandaloneSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_row*             rows,               /**< The rows in the series member */
   SCIP_Bool*            reversed,           /**< Array indicating the direction of each row edge */
   int                   numRows,            /**< The number of rows in the parallel member */
   spqr_col              col,                /**< The column in the parallel member */
   spqr_member*          pMember             /**< out-pointer to the new series member id */
   )
{
   spqr_member member;
   SCIP_CALL( createMember(dec, numRows <= 1 ? SPQR_MEMBERTYPE_LOOP : SPQR_MEMBERTYPE_SERIES, &member) );
 
   spqr_arc colArc;
   SCIP_CALL( createColumnArc(dec, member, &colArc, col, FALSE) );
 
   spqr_arc rowArc;
   for( int i = 0; i < numRows; ++i )
   {
      SCIP_CALL( createRowArc(dec, member, &rowArc, rows[i], !reversed[i]) );
   }
   *pMember = member;
   ++dec->numConnectedComponents;
 
   return SCIP_OKAY;
}
 
/** Creates a series member with the given row and columns that is connected to some other member of the
 * network matrix decomposition.
 *
 * New arcs are created for the given rows and column.
 */
static
SCIP_RETCODE createConnectedSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_row*             rows,               /**< The rows in the series member */
   SCIP_Bool*            reversed,           /**< Array indicating the direction of each row edge */
   int                   numRows,            /**< The number of rows in the parallel member */
   spqr_col              col,                /**< The column in the parallel member */
   spqr_member*          pMember             /**< out-pointer to the new series member id */
   )
{
   spqr_member member;
   SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &member) );
 
   spqr_arc colArc;
   SCIP_CALL( createColumnArc(dec, member, &colArc, col, FALSE) );
 
   spqr_arc rowArc;
   for( int i = 0; i < numRows; ++i )
   {
      SCIP_CALL( createRowArc(dec, member, &rowArc, rows[i], !reversed[i]) );
   }
   *pMember = member;
 
   return SCIP_OKAY;
}
 
/** Remove an arc from the linked list containing all arcs of a single member. */
static
void removeArcFromMemberArcList(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The arc to remove */
   spqr_member           member              /**< The member to remove it from */
   )
{
   assert(findArcMemberNoCompression(dec, arc) == member);
   assert(memberIsRepresentative(dec, member));
 
   if( dec->members[member].numArcs == 1 )
   {
      dec->members[member].firstArc = SPQR_INVALID_ARC;
   }
   else
   {
      spqr_arc nextArc = dec->arcs[arc].arcListNode.next;
      spqr_arc prevArc = dec->arcs[arc].arcListNode.previous;
 
      dec->arcs[nextArc].arcListNode.previous = prevArc;
      dec->arcs[prevArc].arcListNode.next = nextArc;
 
      if( dec->members[member].firstArc == arc )
      {
         dec->members[member].firstArc = nextArc;
      }
   }
 
   --( dec->members[member].numArcs );
}
 
/** Data structure for the algorithms to find fundamental cycle within the network matrix decomposition */
typedef struct
{
   spqr_arc arc;
   SCIP_Bool reversed;
} FindCycleCall;
 
/** Processes a single arc for the algorithm to find cycles in the network matrix decomposition.
 *
 * if virtual, pushes it on the callstack, if non-virtual, adds it to the found cycle
 */
static
void process_arc(
   spqr_row*             cyclearcs,          /**< The found cycle so far */
   int*                  num_cycle_arcs,     /**< The number of arcs in the cycle so far */
   FindCycleCall*        callStack,          /**< The call stack of virtual edges to process still */
   int*                  callStackSize,      /**< The number of virtual edges on the callstack */
   spqr_arc              arc,                /**< The current arc to process */
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   SCIP_Bool*            cycledir,           /**< Whether the current arc is reversed w.r.t to the cycle/path */
   SCIP_Bool             arcIsReversed       /**< The arcIsReversed status from the network matrix decomposition */
   )
{
   assert(arcIsTree(dec, arc));
 
   if( !arcIsChildMarker(dec, arc))
   {
      spqr_member current_member = findArcMemberNoCompression(dec, arc);
      if( markerToParent(dec, current_member) == arc )
      {
         spqr_arc other_arc = markerOfParent(dec, current_member);
         assert(!arcIsTree(dec, other_arc));
         callStack[*callStackSize].arc = other_arc;
         callStack[*callStackSize].reversed = arcIsReversed;
         ++( *callStackSize );
      }
      else
      {
         spqr_element element = arcGetElement(dec, arc);
         assert(SPQRelementIsRow(element));
         spqr_row row = SPQRelementToRow(element);
         cyclearcs[*num_cycle_arcs] = row;
         cycledir[*num_cycle_arcs] = arcIsReversed;
         ++( *num_cycle_arcs );
      }
   }
   else
   {
      spqr_member child_member = findArcChildMemberNoCompression(dec, arc);
      spqr_arc other_arc = markerToParent(dec, child_member);
      assert(!arcIsTree(dec, other_arc));
      callStack[*callStackSize].arc = other_arc;
      callStack[*callStackSize].reversed = arcIsReversed;
      ++( *callStackSize );
   }
}
 
/** Find the fundamental path of a cycle.
 *
 * This is a slow method and only intended for debugging and testing.
 */
static
int decompositionGetFundamentalCycleRows(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_col              column,             /**< The column to find the fundamental path for */
   spqr_row*             output,             /**< preallocated array to store fundamental path in. Must have at least
                                              * the number of rows in the decomposition allocated */
   SCIP_Bool*            computedSignStorage /**< Boolean array for storage of whether the path occurs forwards or
                                              * backwards. Must have at least the same size as output array. */
   )
{
   /*Basic idea; for each component, do a dfs over the tree formed by the row arcs to find the relevant edges.
   This is easy for SPQ-nodes, for R nodes we need to search */
   spqr_arc arc = getDecompositionColumnArc(dec, column);
   if( SPQRarcIsInvalid(arc))
   {
      return 0;
   }
   int num_rows = 0;
 
   FindCycleCall* callStack;
   if( BMSallocBlockMemoryArray(dec->env, &callStack, dec->memRows) == NULL )
   {
      return -1;
   }
   int callStackSize = 1;
   callStack[0].arc = arc;
   callStack[0].reversed = FALSE;
 
   SCIP_Bool* nodeVisited;
   if( BMSallocBlockMemoryArray(dec->env, &nodeVisited, dec->numNodes) == NULL )
   {
      return -1;
   }
   for( int i = 0; i < dec->numNodes; ++i )
   {
      nodeVisited[i] = FALSE;
   }
 
   typedef struct
   {
      spqr_node node;    /* cppcheck-suppress unusedStructMember */
      spqr_arc nodeArc;  /* cppcheck-suppress unusedStructMember */
   } DFSCallData;
   DFSCallData* pathSearchCallStack;
   if( BMSallocBlockMemoryArray(dec->env, &pathSearchCallStack, dec->numNodes) == NULL )
   {
      return -1;
   }
   int pathSearchCallStackSize = 0;
 
   while( callStackSize > 0 )
   {
      spqr_arc column_arc = callStack[callStackSize - 1].arc;
      SCIP_Bool reverseEverything = callStack[callStackSize - 1].reversed;
      --callStackSize;
      spqr_member column_arc_member = findArcMemberNoCompression(dec, column_arc);
      switch( getMemberType(dec, column_arc_member))
      {
         case SPQR_MEMBERTYPE_RIGID:
         {
            spqr_node source = findEffectiveArcTailNoCompression(dec, column_arc);
            spqr_node target = findEffectiveArcHeadNoCompression(dec, column_arc);
 
            assert(pathSearchCallStackSize == 0);
            pathSearchCallStack[0].node = source;
            pathSearchCallStack[0].nodeArc = getFirstNodeArc(dec, source);
            pathSearchCallStackSize++;
            while( pathSearchCallStackSize > 0 )
            {
               DFSCallData* dfsData = &pathSearchCallStack[pathSearchCallStackSize - 1];
               nodeVisited[dfsData->node] = TRUE;
               //cannot be a tree arc which is its parent
               if( arcIsTree(dec, dfsData->nodeArc) &&
                   ( pathSearchCallStackSize <= 1 ||
                     dfsData->nodeArc != pathSearchCallStack[pathSearchCallStackSize - 2].nodeArc ))
               {
                  spqr_node head = findEffectiveArcHeadNoCompression(dec, dfsData->nodeArc);
                  spqr_node tail = findEffectiveArcTailNoCompression(dec, dfsData->nodeArc);
                  spqr_node other = head == dfsData->node ? tail : head;
                  assert(other != dfsData->node);
                  assert(!nodeVisited[other]);
                  if( other == target )
                  {
                     break;
                  }
                  //We go up a level: add new node to the call stack
 
                  pathSearchCallStack[pathSearchCallStackSize].node = other;
                  pathSearchCallStack[pathSearchCallStackSize].nodeArc = getFirstNodeArc(dec, other);
                  ++pathSearchCallStackSize;
                  continue;
               }
               do
               {
                  dfsData->nodeArc = getNextNodeArcNoCompression(dec, dfsData->nodeArc, dfsData->node);
                  if( dfsData->nodeArc == getFirstNodeArc(dec, dfsData->node))
                  {
                     --pathSearchCallStackSize;
                     dfsData = &pathSearchCallStack[pathSearchCallStackSize - 1];
                  }
                  else
                  {
                     break;
                  }
               }
               while( pathSearchCallStackSize > 0 );
            }
            for( int i = 0; i < pathSearchCallStackSize; ++i )
            {
               if( arcIsTree(dec, pathSearchCallStack[i].nodeArc))
               {
                  SCIP_Bool arcReversedInPath =
                     findEffectiveArcHeadNoCompression(dec, pathSearchCallStack[i].nodeArc) ==
                     pathSearchCallStack[i].node;
                  process_arc(output, &num_rows, callStack, &callStackSize, pathSearchCallStack[i].nodeArc, dec,
                              computedSignStorage, arcReversedInPath != reverseEverything);
               }
            }
 
            pathSearchCallStackSize = 0;
            break;
         }
         case SPQR_MEMBERTYPE_PARALLEL:
         {
            SCIP_Bool columnReversed = arcIsReversedNonRigid(dec, column_arc);
 
            spqr_arc first_arc = getFirstMemberArc(dec, column_arc_member);
            spqr_arc iter_arc = first_arc;
            int tree_count = 0;
            do
            {
               if( arcIsTree(dec, iter_arc))
               {
                  SCIP_Bool treeIsReversed = arcIsReversedNonRigid(dec, iter_arc);
                  process_arc(output, &num_rows, callStack, &callStackSize, iter_arc, dec,
                              computedSignStorage, ( columnReversed != treeIsReversed ) != reverseEverything);
                  tree_count++;
               }
               iter_arc = getNextMemberArc(dec, iter_arc);
            }
            while( iter_arc != first_arc );
            if( tree_count != 1 )
            {
               return -1;
            }
            break;
         }
         case SPQR_MEMBERTYPE_LOOP:
         case SPQR_MEMBERTYPE_SERIES:
         {
            SCIP_Bool columnReversed = arcIsReversedNonRigid(dec, column_arc);
            spqr_arc first_arc = getFirstMemberArc(dec, column_arc_member);
            spqr_arc iter_arc = first_arc;
            int nontree_count = 0;
            do
            {
               if( arcIsTree(dec, iter_arc))
               {
                  SCIP_Bool treeIsReversed = arcIsReversedNonRigid(dec, iter_arc);
                  process_arc(output, &num_rows, callStack, &callStackSize, iter_arc, dec,
                              computedSignStorage, ( columnReversed == treeIsReversed ) != reverseEverything);
               }
               else
               {
                  nontree_count++;
               }
               iter_arc = getNextMemberArc(dec, iter_arc);
            }
            while( iter_arc != first_arc );
            if( nontree_count != 1 )
            {
               return -1;
            }
            break;
         }
         case SPQR_MEMBERTYPE_UNASSIGNED:{
            SCIPABORT();
            return -1;
         }
      }
   }
   BMSfreeBlockMemoryArray(dec->env, &pathSearchCallStack, dec->numNodes);
   BMSfreeBlockMemoryArray(dec->env, &nodeVisited, dec->numNodes);
   BMSfreeBlockMemoryArray(dec->env, &callStack, dec->memRows);
 
   return num_rows;
}
 
/** Given a cycle (e.g. a matrix column), checks if the column's cycle matches the cycle in the
 * network matrix decomposition.
 */
static
SCIP_Bool netMatDecDataVerifyCycle(
   BMS_BUFMEM*           bufmem,             /**< Buffer memory */
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   int                   column,             /**< The column to check */
   const int*            nonzrowidx,         /**< Array with the nonzero row indices of the column */
   const double*         nonzvals,           /**< Array with the nonzero entry values of the column's row indices */
   int                   num_rows,           /**< The number of nonzeros in the column */
   int*                  pathrowstorage,     /**< Temporary storage vector for storing the fundamental path. Must have
                                              * at least as many entries allocated as the number of rows in dec. */
   SCIP_Bool*            pathsignstorage     /**< Temporary storage for the fundamental path directions. Must have
                                              * at least as many entries allocated as the number of rows in dec. */
   )
{
   int num_found_rows = decompositionGetFundamentalCycleRows(dec, column, pathrowstorage, pathsignstorage);
 
   if( num_found_rows != num_rows )
   {
      return FALSE;
   }
   if( num_rows == 0 )
   {
      return TRUE;
   }
   spqr_row * pathRow;
   int * pathRowReversed;
 
   if( BMSallocBufferMemoryArray(bufmem, &pathRow, num_rows) == NULL )
   {
      return FALSE;
   }
 
   if( BMSallocBufferMemoryArray(bufmem, &pathRowReversed, num_rows) == NULL )
   {
      BMSfreeBufferMemoryArray(bufmem, &pathRow);
      return FALSE;
   }
   for( int i = 0; i < num_rows; ++i )
   {
      pathRow[i] = pathrowstorage[i];
      pathRowReversed[i] = pathsignstorage[i] ? 1 : 0;
   }
   SCIPsortIntInt(pathRow, pathRowReversed, num_rows);
 
   spqr_row * secondPathRow;
   int * secondPathRowReversed;
   if( BMSallocBufferMemoryArray(bufmem, &secondPathRow, num_rows) == NULL )
   {
      BMSfreeBufferMemoryArray(bufmem, &pathRow);
      BMSfreeBufferMemoryArray(bufmem, &pathRowReversed);
      return FALSE;
   }
 
   if( BMSallocBufferMemoryArray(bufmem, &secondPathRowReversed, num_rows) == NULL )
   {
      BMSfreeBufferMemoryArray(bufmem, &pathRow);
      BMSfreeBufferMemoryArray(bufmem, &pathRowReversed);
      BMSfreeBufferMemoryArray(bufmem, &secondPathRow);
      return FALSE;
   }
   for( int i = 0; i < num_rows; ++i )
   {
      secondPathRow[i] = nonzrowidx[i];
      secondPathRowReversed[i] = nonzvals[i] < 0.0 ? 1 : 0;
   }
 
   SCIPsortIntInt(secondPathRow, secondPathRowReversed, num_rows);
 
   SCIP_Bool good = TRUE;
   for( int i = 0; i < num_rows; ++i )
   {
      if( pathRow[i] != secondPathRow[i] || pathRowReversed[i] != secondPathRowReversed[i] )
      {
         good = FALSE;
         break;
      }
   }
   BMSfreeBufferMemoryArray(bufmem, &secondPathRowReversed);
   BMSfreeBufferMemoryArray(bufmem, &secondPathRow);
   BMSfreeBufferMemoryArray(bufmem, &pathRowReversed);
   BMSfreeBufferMemoryArray(bufmem, &pathRow);
 
   return good;
}
 
/** Returns the largest member id that is currently in the decomposition. */
static
spqr_member largestMemberID(
   const SCIP_NETMATDECDATA* dec             /**< The network matrix decomposition */
   )
{
   return dec->numMembers;
}
 
/** Returns the largest arc id that is currently in the decomposition. */
static
spqr_arc largestArcID(
   const SCIP_NETMATDECDATA* dec             /**< The network matrix decomposition */
   )
{
   return dec->numArcs;
}
 
/** Returns the largest node id that is currently in the decomposition. */
static
spqr_node largestNodeID(
   const SCIP_NETMATDECDATA* dec             /**< The network matrix decomposition */
   )
{
   return dec->numNodes;
}
 
/** Returns the number of SPQR trees in the SPQR forest, i.e. the number of connected components. */
static
int numConnectedComponents(
   const SCIP_NETMATDECDATA* dec             /**< The network matrix decomposition */
   )
{
   return dec->numConnectedComponents;
}
 
/** Creates a child marker in the network decomposition. */
static
SCIP_RETCODE createChildMarker(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member,             /**< The member to create the arc in */
   spqr_member           child,              /**< The member that the arc points to */
   SCIP_Bool             isTree,             /**< Indicates if the new arc is a tree arc */
   spqr_arc*             pArc,               /**< Out-pointer to store the new arc's id */
   SCIP_Bool             reversed            /**< Sets the reversed field of the arc */
   )
{
   SCIP_CALL( createArc(dec, member, reversed, pArc) );
   dec->arcs[*pArc].element = isTree ? MARKER_ROW_ELEMENT : MARKER_COLUMN_ELEMENT;
   dec->arcs[*pArc].childMember = child;
 
   addArcToMemberArcList(dec, *pArc, member);
 
   return SCIP_OKAY;
}
 
/** Creates a parent marker in the network decomposition. */
static
SCIP_RETCODE createParentMarker(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member,             /**< The member to create the arc in */
   SCIP_Bool             isTree,             /**< Indicates if the new arc is a tree arc */
   spqr_member           parent,             /**< The member that the arc points to */
   spqr_arc              parentMarker,       /**< The parent arc in the parent that points to this member */
   spqr_arc*             arc,                /**< Out-pointer to store the new arc's id */
   SCIP_Bool             reversed            /**< Sets the reversed field of the arc */
   )
{
   SCIP_CALL( createArc(dec, member, reversed, arc) );
   dec->arcs[*arc].element = isTree ? MARKER_ROW_ELEMENT : MARKER_COLUMN_ELEMENT;
 
   addArcToMemberArcList(dec, *arc, member);
 
   dec->members[member].parentMember = parent;
   dec->members[member].markerOfParent = parentMarker;
   dec->members[member].markerToParent = *arc;
 
   return SCIP_OKAY;
}
 
/** Creates a child-marker parent-marker pair in the network decomposition. */
static
SCIP_RETCODE createMarkerPair(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           parentMember,       /**< The parent member */
   spqr_member           childMember,        /**< The child member */
   SCIP_Bool             parentIsTree,       /**< Is the edge in the parent member (the child marker) a tree edge? */
   SCIP_Bool             childMarkerReversed, /**< Is the child marker arc reversed?*/
   SCIP_Bool             parentMarkerReversed /**< IS the parent marker arc reversed? */
   )
{
   spqr_arc parentToChildMarker = SPQR_INVALID_ARC;
   SCIP_CALL( createChildMarker(dec, parentMember, childMember, parentIsTree, &parentToChildMarker, childMarkerReversed) );
 
   spqr_arc childToParentMarker = SPQR_INVALID_ARC;
   SCIP_CALL( createParentMarker(dec, childMember, !parentIsTree, parentMember, parentToChildMarker,
      &childToParentMarker, parentMarkerReversed) );
 
   return SCIP_OKAY;
}
 
/** Creates a child-marker parent-marker pair in the network decomposition, and returns the assigned arc id's. */
static
SCIP_RETCODE createMarkerPairWithReferences(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           parentMember,       /**< The parent member */
   spqr_member           childMember,        /**< The child member */
   SCIP_Bool             parentIsTree,       /**< Is the edge in the parent member (the child marker) a tree edge? */
   SCIP_Bool             childMarkerReversed,  /**< Is the child marker arc reversed?*/
   SCIP_Bool             parentMarkerReversed, /**< IS the parent marker arc reversed? */
   spqr_arc*             parentToChild,      /**< Output-pointer containing arc id of the arc in the parent member */
   spqr_arc*             childToParent       /**< Output-pointer containing arc id of the arc in the child member */
   )
{
   SCIP_CALL( createChildMarker(dec, parentMember, childMember, parentIsTree, parentToChild, childMarkerReversed) );
   SCIP_CALL( createParentMarker(dec, childMember, !parentIsTree, parentMember, *parentToChild, childToParent,
      parentMarkerReversed) );
 
   return SCIP_OKAY;
}
 
/** Moves a given arc from one member to another, updating the linked lists it is contained in and the parent/child
 * information of the relevant members.
 */
static
void moveArcToNewMember(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The arc to move */
   spqr_member           oldMember,          /**< The member that currently contains the arc */
   spqr_member           newMember           /**< The member to move the arc to */
   )
{
   assert(SPQRarcIsValid(arc));
   assert(arc < dec->memArcs);
   assert(dec);
 
   assert(memberIsRepresentative(dec, oldMember));
   assert(memberIsRepresentative(dec, newMember));
   //Need to change the arc's member, remove it from the current member list and add it to the new member list
   assert(findArcMemberNoCompression(dec, arc) == oldMember);
 
   removeArcFromMemberArcList(dec, arc, oldMember);
   addArcToMemberArcList(dec, arc, newMember);
 
   dec->arcs[arc].member = newMember;
 
   //If this arc has a childMember, update the information correctly!
   spqr_member childMember = dec->arcs[arc].childMember;
   if( SPQRmemberIsValid(childMember))
   {
      spqr_member childRepresentative = findArcChildMember(dec, arc);
      dec->members[childRepresentative].parentMember = newMember;
   }
   //If this arc is a marker to the parent, update the child arc marker of the parent to reflect the move
   if( dec->members[oldMember].markerToParent == arc )
   {
      dec->members[newMember].markerToParent = arc;
      dec->members[newMember].parentMember = dec->members[oldMember].parentMember;
      dec->members[newMember].markerOfParent = dec->members[oldMember].markerOfParent;
 
      assert(findArcChildMemberNoCompression(dec, dec->members[oldMember].markerOfParent) == oldMember);
      dec->arcs[dec->members[oldMember].markerOfParent].childMember = newMember;
   }
}
 
/** Merges the arc linked list of two members into one linked list. */
static
void mergeMemberArcList(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           toMergeInto,        /**< The member id that gets the new large linked list containing both */
   spqr_member           toRemove            /**< The member id that is invalidated, whose linked list is moved away. */
   )
{
   spqr_arc firstIntoArc = getFirstMemberArc(dec, toMergeInto);
   spqr_arc firstFromArc = getFirstMemberArc(dec, toRemove);
   assert(SPQRarcIsValid(firstIntoArc));
   assert(SPQRarcIsValid(firstFromArc));
 
   spqr_arc lastIntoArc = getPreviousMemberArc(dec, firstIntoArc);
   spqr_arc lastFromArc = getPreviousMemberArc(dec, firstFromArc);
 
   //Relink linked lists to merge them effectively
   dec->arcs[firstIntoArc].arcListNode.previous = lastFromArc;
   dec->arcs[lastIntoArc].arcListNode.next = firstFromArc;
   dec->arcs[firstFromArc].arcListNode.previous = lastIntoArc;
   dec->arcs[lastFromArc].arcListNode.next = firstIntoArc;
 
   //Clean up old
   dec->members[toMergeInto].numArcs += dec->members[toRemove].numArcs;
   dec->members[toRemove].numArcs = 0;
   dec->members[toRemove].firstArc = SPQR_INVALID_ARC;
}
 
/** Changes the type of a member from loop to series. */
static
void changeLoopToSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member              /**< The member whose type is changed */
   )
{
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
   assert(dec);
   assert(( getMemberType(dec, member) == SPQR_MEMBERTYPE_PARALLEL ||
            getMemberType(dec, member) == SPQR_MEMBERTYPE_SERIES ||
            getMemberType(dec, member) == SPQR_MEMBERTYPE_LOOP ) &&
          getNumMemberArcs(dec, member) == 2);
   assert(memberIsRepresentative(dec, member));
   dec->members[member].type = SPQR_MEMBERTYPE_SERIES;
}
 
/** Changes the type of a member from loop to parallel. */
static
void changeLoopToParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member              /**< The member whose type is changed */
   )
{
   assert(SPQRmemberIsValid(member));
   assert(member < dec->memMembers);
   assert(dec);
   assert(( getMemberType(dec, member) == SPQR_MEMBERTYPE_PARALLEL ||
            getMemberType(dec, member) == SPQR_MEMBERTYPE_SERIES ||
            getMemberType(dec, member) == SPQR_MEMBERTYPE_LOOP ) &&
          getNumMemberArcs(dec, member) == 2);
   assert(memberIsRepresentative(dec, member));
   dec->members[member].type = SPQR_MEMBERTYPE_PARALLEL;
}
 
/** Checks if the network decomposition is minimal, i.e. if it does not contain two adjacent parallel or series
 * members.
 */
static
SCIP_Bool netMatDecDataIsMinimal(
   const SCIP_NETMATDECDATA* dec             /**< The network matrix decomposition */
   )
{
   //Relies on parents/children etc. being set correctly in the tree
   SCIP_Bool isMinimal = TRUE;
   for( spqr_member member = 0; member < dec->numMembers; ++member )
   {
      if( !memberIsRepresentative(dec, member) || getMemberType(dec, member) == SPQR_MEMBERTYPE_UNASSIGNED )
      {
         continue;
      }
      spqr_member memberParent = findMemberParentNoCompression(dec, member);
      if( SPQRmemberIsValid(memberParent))
      {
         assert(memberIsRepresentative(dec, memberParent));
         SPQRMemberType memberType = getMemberType(dec, member);
         SPQRMemberType parentType = getMemberType(dec, memberParent);
         if( memberType == parentType && memberType != SPQR_MEMBERTYPE_RIGID )
         {
            isMinimal = FALSE;
            break;
         }
      }
   }
   return isMinimal;
}
 
/** Decreases the count of the number of connected components in the network matrix decomposition. */
static
void decreaseNumConnectedComponents(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   int                   by                  /**< The number of connected components to remove. */
   )
{
   dec->numConnectedComponents -= by;
   assert(dec->numConnectedComponents >= 1);
}
 
/** Reorders the arborescence of the SPQR that contains a given member so that the given member becomes the new root
 * of the arborescence.
 */
static
void reorderComponent(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           newRoot             /**< The member to make the new root */
   )
{
   assert(dec);
   assert(memberIsRepresentative(dec, newRoot));
   //If the newRoot has no parent, it is already the root, so then there's no need to reorder.
   if( SPQRmemberIsValid(dec->members[newRoot].parentMember))
   {
      spqr_member member = findMemberParent(dec, newRoot);
      spqr_member newParent = newRoot;
      spqr_arc newMarkerToParent = dec->members[newRoot].markerOfParent;
      spqr_arc markerOfNewParent = dec->members[newRoot].markerToParent;
 
      //Recursively update the parent
      do
      {
         assert(SPQRmemberIsValid(member));
         assert(SPQRmemberIsValid(newParent));
         spqr_member oldParent = findMemberParent(dec, member);
         spqr_arc oldMarkerToParent = dec->members[member].markerToParent;
         spqr_arc oldMarkerOfParent = dec->members[member].markerOfParent;
 
         dec->members[member].markerToParent = newMarkerToParent;
         dec->members[member].markerOfParent = markerOfNewParent;
         dec->members[member].parentMember = newParent;
         dec->arcs[markerOfNewParent].childMember = member;
         dec->arcs[newMarkerToParent].childMember = SPQR_INVALID_MEMBER;
 
         if( SPQRmemberIsValid(oldParent))
         {
            newParent = member;
            member = oldParent;
            newMarkerToParent = oldMarkerOfParent;
            markerOfNewParent = oldMarkerToParent;
         }
         else
         {
            break;
         }
      }
      while( TRUE ); /*lint !e506*/
      dec->members[newRoot].parentMember = SPQR_INVALID_MEMBER;
      dec->members[newRoot].markerToParent = SPQR_INVALID_ARC;
      dec->members[newRoot].markerOfParent = SPQR_INVALID_ARC;
   }
}
 
/** Deletes the SPQR tree (connected component) containing the given component rows and columns.
 *
 * Note that the implementation of this method does not actually modify the SPQR tree, but rather unlinks the rows and
 * columns from the relevant arcs. Thus, this method is a bit hacky and should be used with care.
 */
static
void netMatDecDataRemoveComponent(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   const int*            componentRows,      /**< The rows of the connected component*/
   int                   numRows,            /**< The number of rows */
   const int*            componentCols,      /**< The columns of the connected component*/
   int                   numCols             /**< The number of columns */
   )
{
   //The below just removes the 'link' but not the internal datastructures.
   //This is sufficient for our purposes, as long as we do not re-introduce any of the 'negated' rows/columns back into the decomposition.
 
   for( int i = 0; i < numRows; ++i )
   {
      spqr_row row = componentRows[i];
      if( SPQRarcIsValid(dec->rowArcs[row]) )
      {
         dec->rowArcs[row] = SPQR_INVALID_ARC;
      }
   }
 
   for( int i = 0; i < numCols; ++i )
   {
      spqr_col col = componentCols[i];
      if( SPQRarcIsValid(dec->columnArcs[col]) )
      {
         dec->columnArcs[col] = SPQR_INVALID_ARC;
      }
   }
}
 
#ifdef SCIP_DEBUG
/** Converts the members type to an associated character */                                                                                                                        //Debugging functions to print the decomposition
static
char typeToChar(
   SPQRMemberType        type                /**< The member type */
   )
{
   switch (type)
   {
      case SPQR_MEMBERTYPE_RIGID:
         return 'R';
      case SPQR_MEMBERTYPE_PARALLEL:
         return 'P';
      case SPQR_MEMBERTYPE_SERIES:
         return 'S';
      case SPQR_MEMBERTYPE_LOOP:
         return 'L';
      default:
         return '?';
   }
}
 
/** Prints an arc in DOT format */
static
void arcToDot(
   FILE*                 stream,             /**< The stream to write the arc to */
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   spqr_arc              arc,                /**< The arc to write */
   unsigned long         dot_head,           /**< The head id of the arc */
   unsigned long         dot_tail,           /**< The tail id of the arc */
   SCIP_Bool             useElementNames     /**< If TRUE, prints the corresponding row/column index. If FALSE,
                                              **< prints the spqr_arc id instead. */
   )
{
   assert(SPQRarcIsValid(arc));
   spqr_member member = findArcMemberNoCompression(dec, arc);
   SPQRMemberType member_type = getMemberType(dec, member);
   char type = typeToChar(member_type);
   const char *color = arcIsTree(dec, arc) ? ",color=red" : ",color=blue";
 
   int arc_name = arc;
 
   if( markerToParent(dec, member) == arc )
   {
      if( useElementNames )
      {
         arc_name = -1;
      }
      fprintf(stream, "    %c_%d_%lu -> %c_p_%d [label=\"%d\",style=dashed%s];\n", type, member, dot_tail, type, member, arc_name, color);
      fprintf(stream, "    %c_p_%d -> %c_%d_%lu [label=\"%d\",style=dashed%s];\n", type, member, type, member, dot_head, arc_name, color);
      fprintf(stream, "    %c_%d_%lu [shape=box];\n", type, member, dot_tail);
      fprintf(stream, "    %c_%d_%lu [shape=box];\n", type, member, dot_head);
      fprintf(stream, "    %c_p_%d [style=dashed];\n", type, member);
   }
   else if( arcIsChildMarker(dec, arc) )
   {
      spqr_member child = findArcChildMemberNoCompression(dec, arc);
      char childType = typeToChar(getMemberType(dec, child));
      if( useElementNames )
      {
         arc_name = -1;
      }
      fprintf(stream, "    %c_%d_%lu -> %c_c_%d [label=\"%d\",style=dotted%s];\n", type, member, dot_tail, type, child, arc_name, color);
      fprintf(stream, "    %c_c_%d -> %c_%d_%lu [label=\"%d\",style=dotted%s];\n", type, child, type, member, dot_head, arc_name, color);
      fprintf(stream, "    %c_%d_%lu [shape=box];\n", type, member, dot_tail);
      fprintf(stream, "    %c_%d_%lu [shape=box];\n", type, member, dot_head);
      fprintf(stream, "    %c_c_%d [style=dotted];\n", type, child);
      fprintf(stream, "    %c_p_%d -> %c_c_%d [style=dashed,dir=forward];\n", childType, child, type, child);
   }
   else
   {
      if( useElementNames )
      {
         spqr_element element = dec->arcs[arc].element;
         if( SPQRelementIsRow(element) )
         {
            arc_name = (int) SPQRelementToRow(element);
         }
         else
         {
            arc_name = (int) SPQRelementToColumn(element);
         }
      }
 
      fprintf(stream, "    %c_%d_%lu -> %c_%d_%lu [label=\"%d \",style=bold%s];\n", type, member, dot_tail, type, member, dot_head,
              arc_name, color);
      fprintf(stream, "    %c_%d_%lu [shape=box];\n", type, member, dot_tail);
      fprintf(stream, "    %c_%d_%lu [shape=box];\n", type, member, dot_head);
   }
}
 
/** Outputs the network decomposition as a DOT file. */
static
void decompositionToDot(
   FILE*                 stream,             /**< The stream to write to */
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   SCIP_Bool             useElementNames     /**< If TRUE, prints the corresponding row/column index. If FALSE,
                                              * prints the spqr_arc id instead. */
   )
{
   fprintf(stream, "//decomposition\ndigraph decomposition{\n   compound = TRUE;\n");
   for( spqr_member member = 0; member < dec->numMembers; ++member )
   {
      if( !memberIsRepresentative(dec, member) )
         continue;
      fprintf(stream, "   subgraph member_%d{\n", member);
      switch( getMemberType(dec, member) )
      {
         case SPQR_MEMBERTYPE_RIGID:
         {
            spqr_arc first_arc = getFirstMemberArc(dec, member);
            spqr_arc arc = first_arc;
            do
            {
               unsigned long arcHead = (unsigned long) findEffectiveArcHeadNoCompression(dec, arc);
               unsigned long arcTail = (unsigned long) findEffectiveArcTailNoCompression(dec, arc);
               arcToDot(stream, dec, arc, arcHead, arcTail, useElementNames);
               arc = getNextMemberArc(dec, arc);
            }
            while( arc != first_arc );
            break;
         }
         case SPQR_MEMBERTYPE_LOOP:
         case SPQR_MEMBERTYPE_PARALLEL:
         {
            spqr_arc first_arc = getFirstMemberArc(dec, member);
            spqr_arc arc = first_arc;
            do
            {
               if( arcIsReversedNonRigid(dec, arc) )
               {
                  arcToDot(stream, dec, arc, 1, 0, useElementNames);
               }
               else
               {
                  arcToDot(stream, dec, arc, 0, 1, useElementNames);
               }
               arc = getNextMemberArc(dec, arc);
            }
            while( arc != first_arc );
            break;
         }
         case SPQR_MEMBERTYPE_SERIES:
         {
            unsigned long i = 0;
            unsigned long num_member_arcs = (unsigned long) getNumMemberArcs(dec, member);
            spqr_arc first_arc = getFirstMemberArc(dec, member);
            spqr_arc arc = first_arc;
            do
            {
               unsigned long head = i;
               unsigned long tail = (i + 1) % num_member_arcs;
               if( arcIsReversedNonRigid(dec, arc) )
               {
                  unsigned long temp = head;
                  head = tail;
                  tail = temp;
               }
               arcToDot(stream, dec, arc, head, tail, useElementNames);
               arc = getNextMemberArc(dec, arc);
               i++;
            }
            while( arc != first_arc );
            break;
         }
         case SPQR_MEMBERTYPE_UNASSIGNED:
            break;
      }
      fprintf(stream, "   }\n");
   }
   fprintf(stream, "}\n");
}
#endif
 
static
SCIP_RETCODE mergeGivenMemberIntoParent(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           member,             /**< The member to merge */
   spqr_member           parent,             /**< The parent of the member to merge into */
   spqr_arc              parentToChild,      /**< The arc from the parent pointing to the member */
   spqr_arc              childToParent,      /**< The arc in the child pointing to the parent */
   SCIP_Bool             headToHead,         /**< Identify the head of parentToChild with the head of childToParent?*/
   spqr_member*          mergedMember        /**< Out-pointer to the member id of the final member */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(memberIsRepresentative(dec, member));
   assert(SPQRmemberIsValid(parent));
   assert(memberIsRepresentative(dec, parent));
   assert(findMemberParentNoCompression(dec, member) == parent);
   assert(markerOfParent(dec, member) == parentToChild);
   assert(markerToParent(dec, member) == childToParent);
 
   removeArcFromMemberArcList(dec, parentToChild, parent);
   removeArcFromMemberArcList(dec, childToParent, member);
 
   spqr_node parentTail = findEffectiveArcTail(dec, parentToChild) ;
   spqr_node parentHead = findEffectiveArcHead(dec, parentToChild);
   spqr_node childTail =  findEffectiveArcTail(dec, childToParent);
   spqr_node childHead = findEffectiveArcHead(dec, childToParent);
   spqr_node parentArcNodes[2] = { parentTail, parentHead };
   spqr_node childArcNodes[2] = { childTail, childHead };
 
   clearArcHeadAndTail(dec, parentToChild);
   clearArcHeadAndTail(dec, childToParent);
 
   spqr_node first = childArcNodes[headToHead ? 0 : 1];
   spqr_node second = childArcNodes[headToHead ? 1 : 0];
   {
      spqr_node newNode = mergeNodes(dec, parentArcNodes[0], first);
      spqr_node toRemoveFrom = newNode == first ? parentArcNodes[0] : first;
      mergeNodeArcList(dec, newNode, toRemoveFrom);
   }
   {
      spqr_node newNode = mergeNodes(dec, parentArcNodes[1], second);
      spqr_node toRemoveFrom = newNode == second ? parentArcNodes[1] : second;
      mergeNodeArcList(dec, newNode, toRemoveFrom);
   }
 
   spqr_member newMember = mergeMembers(dec, member, parent);
   spqr_member toRemoveFrom = newMember == member ? parent : member;
   mergeMemberArcList(dec, newMember, toRemoveFrom);
   if( toRemoveFrom == parent )
   {
      updateMemberParentInformation(dec, newMember, toRemoveFrom);
   }
   updateMemberType(dec, newMember, SPQR_MEMBERTYPE_RIGID);
   *mergedMember = newMember;
 
   return SCIP_OKAY;
}
 
static
SCIP_RETCODE netMatDecDataCreateDiGraph(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   BMS_BLKMEM *          blkmem,             /**< The block memory to use for the created digraph */
   SCIP_DIGRAPH**        pdigraph,           /**< Pointer to the pointer to store the created digraph */
   SCIP_Bool             createrowarcs       /**< Should the row arcs be added to the created digraph? */
   )
{
   /* Compute the number of rows m in the network matrix decomposition. The underlying graph has m+1 vertices. */
   int nrows = 0;
   for( int i = 0; i < dec->memRows; ++i )
      if( netMatDecDataContainsRow(dec, i) )
         ++nrows;
 
   int nvertices = nrows + 1;
   SCIP_CALL( SCIPdigraphCreate(pdigraph, blkmem, nvertices) );
 
   /* Map decomposition nodes to graph nodes. The first node of each component is mapped to node 0 */
   int largestNode = largestNodeID(dec);
   int* dectographnode;
   SCIP_ALLOC( BMSallocBlockMemoryArray(blkmem, &dectographnode, largestNode) );
   for( int i = 0; i < largestNode; ++i )
      dectographnode[i] = -1;
 
   SCIP_DIGRAPH* digraph = *pdigraph;
   /* Recursively explore the decomposition, adding the edges of each component and identifying them as needed */
 
   typedef struct {
      spqr_member member;
      spqr_arc arc;
      int graphfirstarchead;
      int graphfirstarctail;
   } CallData;
   spqr_member largestmember = largestMemberID(dec);
   CallData* calldata;
   int ncalldata = 0;
   SCIP_ALLOC( BMSallocBlockMemoryArray(blkmem, &calldata, largestmember) );
 
   SCIP_Bool* rowprocessed;
   SCIP_ALLOC( BMSallocClearBlockMemoryArray(blkmem, &rowprocessed, dec->memRows) );
 
   /* This outer loop loops over all components; this is a bit ugly unfortunately  */
   int nextnodeindex = 1; /* 0 is assigned to the first arc of the root members' head */
   for( int i = 0; i < dec->memRows ; ++i )
   {
      spqr_arc rowarc = dec->rowArcs[i];
      if( SPQRarcIsInvalid(rowarc) )
         continue;
 
      assert(netMatDecDataContainsRow(dec, i)) ;
      if( rowprocessed[i] )
         continue;
 
      /* Find the root member of the SPQR tree */
      spqr_member arcmember = findArcMember(dec, rowarc);
      spqr_member rootmember = arcmember;
      do
      {
         spqr_member parent = findMemberParent(dec, rootmember);
         if( SPQRmemberIsInvalid(parent) )
            break;
         rootmember = parent;
      }
      while( TRUE ); /*lint !e506*/
 
      /* We identify all the SPQR trees at node 0 */
      calldata[0].member = rootmember;
      calldata[0].arc = getFirstMemberArc(dec, rootmember);
      calldata[0].graphfirstarchead = 0;
      calldata[0].graphfirstarctail = nextnodeindex;
      ++nextnodeindex;
      ++ncalldata;
 
      while( ncalldata != 0 )
      {
         /* Pop the next member to process of the call stack */
         CallData explore = calldata[ncalldata-1];
         --ncalldata;
 
         switch( getMemberType(dec, explore.member) )
         {
            case SPQR_MEMBERTYPE_RIGID:
            {
               /* First, we set the initial arc's nodes */
               {
                  assert(dectographnode[findEffectiveArcHeadNoCompression(dec, explore.arc)] == -1);
                  assert(dectographnode[findEffectiveArcTailNoCompression(dec, explore.arc)] == -1);
                  spqr_node exploreHead = findArcHead(dec, explore.arc);
                  spqr_node exploreTail = findArcTail(dec, explore.arc);
                  if( findArcSign(dec, explore.arc).reversed )
                     SCIPswapInts(&exploreTail, &exploreTail);
                  dectographnode[exploreHead] = explore.graphfirstarchead;
                  dectographnode[exploreTail] = explore.graphfirstarctail;
               }
 
               /* Add all the members arcs to the graph */
               spqr_arc firstArc = getFirstMemberArc(dec, explore.member);
               spqr_arc arc = firstArc;
               do
               {
                  spqr_node head = findArcHead(dec, arc);
                  spqr_node tail = findArcTail(dec, arc);
                  if( findArcSign(dec, arc).reversed )
                     SCIPswapInts(&head, &tail);
 
                  if( dectographnode[head] == -1 )
                  {
                     dectographnode[head] = nextnodeindex;
                     ++nextnodeindex;
                  }
                  if( dectographnode[tail] == -1 )
                  {
                     dectographnode[tail] = nextnodeindex;
                     ++nextnodeindex;
                  }
 
                  /* If an arc is a marker to a child node, we add it to the call stack */
                  if( arcIsChildMarker(dec, arc))
                  {
                     spqr_member child = findArcChildMember(dec, arc);
                     spqr_arc toparent = markerToParent(dec, child);
 
                     /* Identify head with head and tail with tail */
                     /* Push member onto the processing stack (recursive call) */
                     calldata[ncalldata].member = child;
                     calldata[ncalldata].arc = toparent;
                     calldata[ncalldata].graphfirstarchead = dectographnode[head];
                     calldata[ncalldata].graphfirstarctail = dectographnode[tail];
 
                     ++ncalldata;
                  }
                  else if( arc != markerToParent(dec, explore.member) )
                  {
                     /* We only realize non-virtual arcs */
                     if( createrowarcs || !arcIsTree(dec, arc) )
                     {
                        spqr_element element = arcGetElement(dec, arc);
                        size_t ind;
                        if( SPQRelementIsRow(element) )
                        {
                           ind = SPQRelementToRow(element);  /*lint !e732 */
                        }
                        else
                        {
                           ind = SPQRelementToColumn(element) + dec->memRows; /*lint !e732 !e776 */
                        }
                        SCIP_CALL( SCIPdigraphAddArc(digraph, dectographnode[tail], dectographnode[head],
                                                     (void*) ind) );
                     }
                  }
                  spqr_element element = arcGetElement(dec, arc);
                  if( SPQRelementIsRow(element) && element != MARKER_ROW_ELEMENT )
                  {
                     spqr_row row = SPQRelementToRow(element);
                     assert(row < dec->memRows);
                     rowprocessed[row] = TRUE;
                  }
                  arc = getNextMemberArc(dec, arc);
               }
               while( arc != firstArc );
               break;
            }
 
            case SPQR_MEMBERTYPE_LOOP:
            case SPQR_MEMBERTYPE_PARALLEL:
            {
               spqr_arc firstArc = getFirstMemberArc(dec, explore.member);
               spqr_arc arc = firstArc;
               do
               {
                  /* If an edge is a marker to a child node, we add it to the call stack */
                  if( arcIsChildMarker(dec, arc) )
                  {
                     spqr_member child = findArcChildMember(dec, arc);
                     spqr_arc toparent = markerToParent(dec, child);
                     SCIP_Bool directionsmatch =
                        arcIsReversedNonRigid(dec, explore.arc) == arcIsReversedNonRigid(dec, arc);
 
                     /* Identify head with head and tail with tail */
                     /* Push member onto the processing stack (recursive call) */
                     calldata[ncalldata].member = child;
                     calldata[ncalldata].arc = toparent;
                     calldata[ncalldata].graphfirstarchead = directionsmatch ? explore.graphfirstarchead
                                                                             : explore.graphfirstarctail;
                     calldata[ncalldata].graphfirstarctail = directionsmatch ? explore.graphfirstarctail
                                                                             : explore.graphfirstarchead;
 
                     ++ncalldata;
                  }
                  else if( arc != markerToParent(dec, explore.member) )
                  {
                     /* We only realize non-virtual arcs */
                     if( createrowarcs || !arcIsTree(dec, arc) )
                     {
                        spqr_element element = arcGetElement(dec, arc);
                        size_t ind;
                        if( SPQRelementIsRow(element) )
                        {
                           ind = SPQRelementToRow(element);  /*lint !e732 */
                        }
                        else
                        {
                           ind = SPQRelementToColumn(element) + dec->memRows;  /*lint !e732 !e776 */
                        }
                        if( arcIsReversedNonRigid(dec, explore.arc) == arcIsReversedNonRigid(dec, arc) )
                        {
                           SCIP_CALL( SCIPdigraphAddArc(digraph, explore.graphfirstarctail,
                                                        explore.graphfirstarchead, (void*) ind) );
                        }
                        else
                        {
                           SCIP_CALL( SCIPdigraphAddArc(digraph, explore.graphfirstarchead,
                                                        explore.graphfirstarctail, (void*) ind) );
                        }
                     }
                  }
                  spqr_element element = arcGetElement(dec, arc);
                  if( SPQRelementIsRow(element) && element != MARKER_ROW_ELEMENT )
                  {
                     spqr_row row = SPQRelementToRow(element);
                     assert(row < dec->memRows);
                     rowprocessed[row] = TRUE;
                  }
                  arc = getNextMemberArc(dec, arc);
               }
               while( arc != firstArc );
               break;
            }
 
            case SPQR_MEMBERTYPE_SERIES:
            {
               int count = getNumMemberArcs(dec, explore.member);
               spqr_arc arc = explore.arc;
               int firstnode = explore.graphfirstarchead;
               int secondnode = explore.graphfirstarctail;
               for( int j = 0; j < count; ++j )
               {
                  if( arcIsChildMarker(dec, arc) )
                  {
                     spqr_member child = findArcChildMember(dec, arc);
                     spqr_arc toparent = markerToParent(dec, child);
                     SCIP_Bool directionsmatch =
                        arcIsReversedNonRigid(dec, explore.arc) == arcIsReversedNonRigid(dec, arc);
 
                     /* Identify head with head and tail with tail */
                     /* Push member onto the processing stack (recursive call) */
                     calldata[ncalldata].member = child;
                     calldata[ncalldata].arc = toparent;
                     calldata[ncalldata].graphfirstarchead = directionsmatch ? firstnode : secondnode;
                     calldata[ncalldata].graphfirstarctail = directionsmatch ? secondnode : firstnode;
 
                     ++ncalldata;
                  }
                  else if( arc != markerToParent(dec, explore.member) )
                  {
                     /* We only realize non-virtual arcs */
                     if( createrowarcs || !arcIsTree(dec, arc) )
                     {
                        spqr_element element = arcGetElement(dec,arc);
                        size_t ind;
                        if( SPQRelementIsRow(element) )
                        {
                           ind = SPQRelementToRow(element);  /*lint !e732 */
                        }
                        else
                        {
                           ind = SPQRelementToColumn(element) + dec->memRows;  /*lint !e732 !e776 */
                        }
 
                        if( arcIsReversedNonRigid(dec, explore.arc) == arcIsReversedNonRigid(dec, arc) )
                        {
                           SCIP_CALL( SCIPdigraphAddArc(digraph, secondnode, firstnode, (void*) ind) );
                        }
                        else
                        {
                           SCIP_CALL( SCIPdigraphAddArc(digraph, firstnode, secondnode, (void*) ind) );
                        }
                     }
                  }
 
                  spqr_element element = arcGetElement(dec, arc);
                  if( SPQRelementIsRow(element) && element != MARKER_ROW_ELEMENT )
                  {
                     spqr_row row = SPQRelementToRow(element);
                     rowprocessed[row] = TRUE;
                  }
 
                  arc = getNextMemberArc(dec, arc);
                  secondnode = firstnode;
                  if( j >= count - 2 )
                  {
                     firstnode = explore.graphfirstarctail;
                  }
                  else
                  {
                     firstnode = nextnodeindex;
                     ++nextnodeindex;
                  }
               }
               assert(arc == explore.arc); /* Check that we added all arcs */
               break;
            }
 
            case SPQR_MEMBERTYPE_UNASSIGNED:
            {
               SCIPerrorMessage("Can not create graph for unassigned member type, exiting.\n");
               SCIPABORT();
               return SCIP_ERROR;
            }
         }
      }
   }
 
   /* We cannot have more vertices then there are in the graph.
    * If we processed everything right, all vertices should have been hit.
    */
   assert(nextnodeindex == nvertices);
 
   BMSfreeBlockMemoryArray(blkmem, &rowprocessed, dec->memRows);
   BMSfreeBlockMemoryArray(blkmem, &calldata, largestmember);
   BMSfreeBlockMemoryArray(blkmem, &dectographnode, largestNode);
 
   return SCIP_OKAY;
}
 
/* ---------- START functions for column addition ------------------------------------------------------------------- */
 
/** Path arcs are all those arcs that correspond to nonzeros of the column to be added. */
typedef int path_arc_id;
#define INVALID_PATH_ARC (-1)
 
/** Returns true if the path arc is invalid. */
static
SCIP_Bool pathArcIsInvalid(
   const path_arc_id     arc                 /**< The path arc to check */
   )
{
   return arc < 0;
}
 
/** Returns true if the path arc is valid. */
static
SCIP_Bool pathArcIsValid(
   const path_arc_id     arc                 /**< The path arc to check */
   )
{
   return !pathArcIsInvalid(arc);
}
 
/** A forward linked list-node for the path arcs.
 *
 * Contains a pointer to the next path arc in the member graph and the
 * next path arc in the SPQR tree. We additionally store copies of the corresponding arc's node indices.
 */
typedef struct
{
   spqr_arc              arc;                /**< The arc corresponding to the path ar c*/
   spqr_node             arcHead;            /**< A copy of the arc's head node index */
   spqr_node             arcTail;            /**< A copy of the arc's tail node index */
   path_arc_id           nextMember;         /**< Array index of the next path arc in the member path arc linked list */
   path_arc_id           nextOverall;        /**< Array index of the next path arc in the total path arc linked list */
   SCIP_Bool             reversed;           /**< Is the path arc occuring forwards or backwards in the path?
                                              *   Corresponds to the sign of the nonzero */
} PathArcListNode;
 
/** Index for the reduced members, which are the members of the sub-SPQR tree containing all path arcs.
 *
 * Note that these are indexed separately from the members of the SPQR tree!
 */
typedef int reduced_member_id;
#define INVALID_REDUCED_MEMBER (-1)
 
/** Returns true if the reduced member is invalid. */
static
SCIP_Bool reducedMemberIsInvalid(
   const reduced_member_id id                /**< The reduced member to check */
   )
{
   return id < 0;
}
 
/** Returns true if the reduced member is valid. */
static
SCIP_Bool reducedMemberIsValid(
   const reduced_member_id id                /**< The reduced member to check */
   )
{
   return !reducedMemberIsInvalid(id);
}
 
/** Array index for the children of a reduced member */
typedef int children_idx;
 
/** Type of the member, signifies to what degree we processed the member and how to treat with it when updating the
 * graph.
 */
typedef enum
{
   REDUCEDMEMBER_TYPE_UNASSIGNED = 0,        /**< We have not yet decided if the reduced member contains a valid path */
   REDUCEDMEMBER_TYPE_CYCLE = 1,             /**< The reduced member is a leaf node of the SPQR tree and contains a path
                                                * that forms a cycle with the corresponding virtual edge, i.e.
                                                * it is propagated */
   REDUCEDMEMBER_TYPE_MERGED = 2,            /**< The reduced member contains a path and is not propagated */
   REDUCEDMEMBER_TYPE_NOT_NETWORK = 3        /**< The reduced member does not have a valid path or can not be oriented
                                                * to form a valid path with the other members. */
} ReducedMemberType;
 
/** Defines the structure of the path in the reduced member */
typedef enum
{
   INTO_HEAD = 0,                            /**< The directed path goes into the head of the virtual arc */
   INTO_TAIL = 1,                            /**< The directed path goes into the tail of the virtual arc */
   OUT_HEAD = 2,                             /**< The directed path goes out of the head of the virtual arc */
   OUT_TAIL = 3                              /**< The directed path goes out of the tail of the virtual arc */
} MemberPathType;
 
/** Check if the path type is into. */
static
SCIP_Bool isInto(
   MemberPathType        type                /**< The path type to check */
   )
{
   return type == INTO_HEAD || type == INTO_TAIL;
}
 
/** Check if the path end node is the head or tail node of the corresponding arc. */
static
SCIP_Bool isHead(
   MemberPathType        type                /**< The path type to check */
   )
{
   return type == INTO_HEAD || type == OUT_HEAD;
}
 
/** A struct that keeps track of the relevant data for the members that are in the subtree given by the specified row
 * arcs.
 *
 * We typically call these 'reduced' members (members of the reduced tree).
 */
typedef struct
{
   spqr_member           member;             /**< The id of the member */
   spqr_member           rootMember;         /**< The root member of the arborescence that contains this member */
   int                   depth;              /**< The depth of this member in the arborescence */
   ReducedMemberType     type;               /**< The type of the member */
   reduced_member_id     parent;             /**< The reduced member id of the parent of this reduced member */
 
   children_idx          firstChild;         /**< The index of the first child in the children array. */
   children_idx          numChildren;        /**< The number of children in the arborescence of this reduced member */
 
   path_arc_id           firstPathArc;       /**< Head of the linked list containing the path arcs */
   int                   numPathArcs;        /**< The number of path arcs in the linked list */
 
   SCIP_Bool             reverseArcs;        /**< Will the arcs in this component be reversed? */
   spqr_node             rigidPathStart;     /**< The start node of the path. Only used for Rigid/3-connected nodes */
   spqr_node             rigidPathEnd;       /**< The end node of the path. Only used for Rigid/3-connected nodes */
 
   SCIP_Bool             pathBackwards;      /**< Indicates if the path direction is reversed with respect to the
                                                * default orientation within series and parallel members. */
 
   int                   numPropagatedChildren; /**< Counts the number of children that are cycles that propagated to this
                                                  * reduced member */
   int                   componentIndex;     /**< Stores the index of the component of the SPQR forest that this reduced
                                                * member is contained in. */
 
   MemberPathType        pathType;           /**< The type of the path with respect to the virtual arc */
   reduced_member_id     nextPathMember;     /**< Indicates the id of the next reduced member in the path during merging.
                                                * During merging, the SPQR tree must be a path itself. */
   SCIP_Bool             nextPathMemberIsParent; /**< Indicates if the next reduced member in the path is a parent of
                                                    * this member */
   spqr_arc              pathSourceArc;      /**< The virtual arc from where the path originates */
   spqr_arc              pathTargetArc;      /**< The virtual arc where the path has to go */
} SPQRColReducedMember;
 
/** Keeps track of the data relevant for each SPQR tree in the SPQR forest. */
typedef struct
{
   int                   rootDepth;          /**< The depth of the root node of the subtree in the arborescence */
   reduced_member_id     root;               /**< The reduced member id of the root */
 
   reduced_member_id     pathEndMembers[2];  /**< The reduced members that contain the ends of the path */
   int                   numPathEndMembers;  /**< The number of reduced members that contain an end of the path */
} SPQRColReducedComponent;
 
/** Keeps track of the reduced member and the reduced member that is the root of the arborescence for a single member */
typedef struct
{
   reduced_member_id     reducedMember;      /**< The ID of the associated reduced member */
   reduced_member_id     rootDepthMinimizer; /**< The ID of the reduced member that is the root of the arborescence this
                                                * reduced member is contained in. */
} MemberInfo;
 
/** Data to be used for the recursive algorithms that creates the sub-SPQR trees that contain the path edges */
typedef struct
{
   spqr_member           member;             /**< The current member */
} CreateReducedMembersCallstack;
 
/** The main datastructure that manages all the data for column-addition in network matrices */
typedef struct
{
   SCIP_Bool             remainsNetwork;     /**< Does the addition of the current column give a network matrix? */
 
   SPQRColReducedMember* reducedMembers;     /**< The array of reduced members, that form the subtree containing the
                                                * rows of the current column. */
   int                   memReducedMembers;  /**< Number of allocated slots in the reduced member array */
   int                   numReducedMembers;  /**< Number of used slots in the reduced member array */
 
   SPQRColReducedComponent* reducedComponents;/**< The array of reduced components,
                                                 * that represent the SPQR trees in the SPQR forest */
   int                   memReducedComponents;/**< Number of allocated slots in the reduced component array */
   int                   numReducedComponents;/**< Number of used slots in the reduced component array */
 
   MemberInfo*           memberInformation;  /**< Array with member information; tracks the reduced member id that
                                                * corresponds to every member in the decomposition. */
   int                   memMemberInformation;/**< Number of allocated slots in the member information array */
   int                   numMemberInformation;/**< Number of used slots in the member information array */
 
   reduced_member_id*    childrenStorage;    /**< Array that stores the children of the reduced member arborescences.
                                                * Each reduced member has a 'firstChild' field and a length, that points
                                                * to the subarray within this array with its children. This array is
                                                * shared here in order to minimize allocations across iterations. */
   int                   memChildrenStorage; /**< Number of allocated slots for the children storage array */
   int                   numChildrenStorage; /**< Number of used slots for the children storage array */
 
   PathArcListNode*      pathArcs;           /**< Array that contains the linked-list nodes of the path arcs, that
                                                * correspond to the rows of the current column. */
   int                   memPathArcs;        /**< Number of allocated slots for the path arc array */
   int                   numPathArcs;        /**< Number of used slots for the path arc array */
   path_arc_id           firstOverallPathArc;/**< Head node of the linked list containing all path arcs */
 
   int*                  nodeInPathDegree;   /**< Array that contains the in degree of all nodes */
   int*                  nodeOutPathDegree;  /**< Array that contains the out degree of all nodes */
   int                   memNodePathDegree;  /**< The number of allocated slots for the node-degree arrays */
 
   SCIP_Bool*            arcInPath;          /**< Is the given arc in the path? */
   SCIP_Bool*            arcInPathReversed;  /**< Is the given arc's direction reversed in the path? */
   int                   memArcsInPath;      /**< The number of allocated slots for the arcInPath(Reversed) arrays */
 
   CreateReducedMembersCallstack* createReducedMembersCallStack; /**< Callstack for createReducedMembers() */
   int                   memCreateReducedMembersCallStack; /**< Allocated memory for callstack for createReducedMembers() */
 
   spqr_col              newColIndex;        /**< The index of the new column to be added */
 
   spqr_row*             newRowArcs;         /**< The row indices of the nonzeros of the column to be added, that are
                                                * not yet in the decomposition. */
   SCIP_Bool*            newRowArcReversed;  /**< True if the nonzero corresponding to the row index is -1,
                                                * false otherwise */
   int                   memNewRowArcs;      /**< Number of allocated slots in newRowArcs(Reversed) */
   int                   numNewRowArcs;      /**< Number of new rows in the column to be added */
 
   spqr_arc*             decompositionRowArcs;     /**< For each row nonzero that is in the decomposition,
                                                      * stores the corresponding decomposition arc */
   SCIP_Bool*            decompositionArcReversed; /**< For each row nonzero that is in the decomposition,
                                                      * stores whether the corresponding decomposition arc is reversed */
   int                   memDecompositionRowArcs;  /**< Number of allocated slots in decompositionRowArcs(Reversed) */
   int                   numDecompositionRowArcs;  /**< Number of used slots in decompositionRowArcs(Reversed) */
 
   spqr_member*          leafMembers;        /**< Array that stores the leaf members of the SPQR forest */
   int                   numLeafMembers;     /**< Number of used slots in leafMembers array */
   int                   memLeafMembers;     /**< Number of allocated slots in leafMembers array */
} SCIP_NETCOLADD;
 
/** Clean up internal temporary data structures that were used in the previous column iteration. */
static
void cleanupPreviousIteration(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol              /**< The network matrix column addition data structure */
   )
{
   assert(dec);
   assert(newCol);
 
   path_arc_id pathArc = newCol->firstOverallPathArc;
   while( pathArcIsValid(pathArc) )
   {
      spqr_node head = newCol->pathArcs[pathArc].arcHead;
      spqr_node tail = newCol->pathArcs[pathArc].arcTail;
      if( SPQRnodeIsValid(head) )
      {
         newCol->nodeInPathDegree[head] = 0;
      }
      if( SPQRnodeIsValid(tail) )
      {
         newCol->nodeOutPathDegree[tail] = 0;
      }
 
      spqr_arc arc = newCol->pathArcs[pathArc].arc;
      if( arc < newCol->memArcsInPath )
      {
         newCol->arcInPath[arc] = FALSE;
         newCol->arcInPathReversed[arc] = FALSE;
      }
      pathArc = newCol->pathArcs[pathArc].nextOverall;
   }
#ifndef NDEBUG
   for( int i = 0; i < newCol->memArcsInPath; ++i )
   {
      assert(newCol->arcInPath[i] == FALSE);
      assert(newCol->arcInPathReversed[i] == FALSE);
   }
 
   for( int i = 0; i < newCol->memNodePathDegree; ++i )
   {
      assert(newCol->nodeInPathDegree[i] == 0);
      assert(newCol->nodeOutPathDegree[i] == 0);
   }
#endif
 
   newCol->firstOverallPathArc = INVALID_PATH_ARC;
   newCol->numPathArcs = 0;
}
 
/** Create a new network column addition datastructure. */
static
SCIP_RETCODE netcoladdCreate(
   BMS_BLKMEM*           blkmem,             /**< Block memory */
   SCIP_NETCOLADD**      pcoladd             /**< Out-pointer for the created network column addition datastructure */
   )
{
   assert(blkmem);
 
   SCIP_ALLOC( BMSallocBlockMemory(blkmem, pcoladd) );
   SCIP_NETCOLADD* newCol = *pcoladd;
 
   newCol->remainsNetwork = FALSE;
   newCol->reducedMembers = NULL;
   newCol->memReducedMembers = 0;
   newCol->numReducedMembers = 0;
 
   newCol->reducedComponents = NULL;
   newCol->memReducedComponents = 0;
   newCol->numReducedComponents = 0;
 
   newCol->memberInformation = NULL;
   newCol->memMemberInformation = 0;
   newCol->numMemberInformation = 0;
 
   newCol->childrenStorage = NULL;
   newCol->memChildrenStorage = 0;
   newCol->numChildrenStorage = 0;
 
   newCol->pathArcs = NULL;
   newCol->memPathArcs = 0;
   newCol->numPathArcs = 0;
   newCol->firstOverallPathArc = INVALID_PATH_ARC;
 
   newCol->nodeInPathDegree = NULL;
   newCol->nodeOutPathDegree = NULL;
   newCol->memNodePathDegree = 0;
 
   newCol->arcInPath = NULL;
   newCol->arcInPathReversed = NULL;
   newCol->memArcsInPath = 0;
 
   newCol->createReducedMembersCallStack = NULL;
   newCol->memCreateReducedMembersCallStack = 0;
 
   newCol->newColIndex = SPQR_INVALID_COL;
 
   newCol->newRowArcs = NULL;
   newCol->newRowArcReversed = NULL;
   newCol->memNewRowArcs = 0;
   newCol->numNewRowArcs = 0;
 
   newCol->decompositionRowArcs = NULL;
   newCol->decompositionArcReversed = NULL;
   newCol->memDecompositionRowArcs = 0;
   newCol->numDecompositionRowArcs = 0;
 
   newCol->leafMembers = NULL;
   newCol->numLeafMembers = 0;
   newCol->memLeafMembers = 0;
 
   return SCIP_OKAY;
}
 
/** Free a network column addition datastructure */
static
void netcoladdFree(
   BMS_BLKMEM*           blkmem,             /**< Block memory */
   SCIP_NETCOLADD**      pcoladd             /**< Pointer to the network column addition datastructure to be freed */
   )
{
   assert(blkmem);
 
   SCIP_NETCOLADD* newCol = *pcoladd;
   BMSfreeBlockMemoryArray(blkmem, &newCol->decompositionRowArcs, newCol->memDecompositionRowArcs);
   BMSfreeBlockMemoryArray(blkmem, &newCol->decompositionArcReversed, newCol->memDecompositionRowArcs);
   BMSfreeBlockMemoryArray(blkmem, &newCol->newRowArcs, newCol->memNewRowArcs);
   BMSfreeBlockMemoryArray(blkmem, &newCol->newRowArcReversed, newCol->memNewRowArcs);
   BMSfreeBlockMemoryArray(blkmem, &newCol->createReducedMembersCallStack, newCol->memCreateReducedMembersCallStack);
   BMSfreeBlockMemoryArray(blkmem, &newCol->arcInPath, newCol->memArcsInPath);
   BMSfreeBlockMemoryArray(blkmem, &newCol->arcInPathReversed, newCol->memArcsInPath);
   BMSfreeBlockMemoryArray(blkmem, &newCol->nodeInPathDegree, newCol->memNodePathDegree);
   BMSfreeBlockMemoryArray(blkmem, &newCol->nodeOutPathDegree, newCol->memNodePathDegree);
   BMSfreeBlockMemoryArray(blkmem, &newCol->pathArcs, newCol->memPathArcs);
   BMSfreeBlockMemoryArray(blkmem, &newCol->childrenStorage, newCol->memChildrenStorage);
   BMSfreeBlockMemoryArray(blkmem, &newCol->memberInformation, newCol->memMemberInformation);
   BMSfreeBlockMemoryArray(blkmem, &newCol->reducedComponents, newCol->memReducedComponents);
   BMSfreeBlockMemoryArray(blkmem, &newCol->reducedMembers, newCol->memReducedMembers);
   BMSfreeBlockMemoryArray(blkmem, &newCol->leafMembers, newCol->memLeafMembers);
 
   BMSfreeBlockMemory(blkmem, pcoladd);
}
 
/** Adds members to the reduced member tree, by starting at the given member, jumping up to the parent, repeating this
 * procedure until the root has been added.
 */
static
reduced_member_id createReducedMembersToRoot(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   const spqr_member     firstMember         /**< The member to create a reduced member for */
   )
{
   assert(SPQRmemberIsValid(firstMember));
 
   /* Originally a recursive algorithm, but for large matrices we need to unroll recursion to prevent stack overflows
    * from too many recursive calls */
   CreateReducedMembersCallstack* callstack = newCol->createReducedMembersCallStack;
   callstack[0].member = firstMember;
   int callDepth = 0;
 
   while( callDepth >= 0 )
   {
      spqr_member member = callstack[callDepth].member;
      reduced_member_id reducedMember = newCol->memberInformation[member].reducedMember;
 
      SCIP_Bool reducedValid = reducedMemberIsValid(reducedMember);
      if( !reducedValid )
      {
         //reduced member was not yet created; we create it
         reducedMember = newCol->numReducedMembers;
 
         SPQRColReducedMember* reducedMemberData = &newCol->reducedMembers[reducedMember];
         ++newCol->numReducedMembers;
 
         reducedMemberData->member = member;
         reducedMemberData->numChildren = 0;
 
         reducedMemberData->type = REDUCEDMEMBER_TYPE_UNASSIGNED;
         reducedMemberData->numPropagatedChildren = 0;
         reducedMemberData->firstPathArc = INVALID_PATH_ARC;
         reducedMemberData->numPathArcs = 0;
         reducedMemberData->rigidPathStart = SPQR_INVALID_NODE;
         reducedMemberData->rigidPathEnd = SPQR_INVALID_NODE;
 
         reducedMemberData->componentIndex = -1;
         //The children are set later
 
         newCol->memberInformation[member].reducedMember = reducedMember;
         assert(memberIsRepresentative(dec, member));
         spqr_member parentMember = findMemberParent(dec, member);
 
         if( SPQRmemberIsValid(parentMember) )
         {
            //recursive call to parent member
            ++callDepth;
            assert(callDepth < newCol->memCreateReducedMembersCallStack);
            callstack[callDepth].member = parentMember;
            continue;
         }
         else
         {
            //we found a new reduced decomposition component
 
            reducedMemberData->parent = INVALID_REDUCED_MEMBER;
            reducedMemberData->depth = 0;
            reducedMemberData->rootMember = member;
            reducedMemberData->componentIndex = newCol->numReducedComponents;
 
            assert(newCol->numReducedComponents < newCol->memReducedComponents);
            newCol->reducedComponents[newCol->numReducedComponents].root = reducedMember;
            newCol->reducedComponents[newCol->numReducedComponents].numPathEndMembers = 0;
            newCol->reducedComponents[newCol->numReducedComponents].pathEndMembers[0] = INVALID_REDUCED_MEMBER;
            newCol->reducedComponents[newCol->numReducedComponents].pathEndMembers[1] = INVALID_REDUCED_MEMBER;
            ++newCol->numReducedComponents;
         }
      }
      if( reducedValid )
      {
         assert(reducedMember < newCol->numReducedMembers);
         //Reduced member was already created in earlier call
         //update the depth of the root if appropriate
         reduced_member_id* depthMinimizer = &newCol->memberInformation[newCol->reducedMembers[reducedMember].rootMember].rootDepthMinimizer;
         if( reducedMemberIsInvalid(*depthMinimizer) ||
             newCol->reducedMembers[reducedMember].depth < newCol->reducedMembers[*depthMinimizer].depth )
         {
            *depthMinimizer = reducedMember;
         }
      }
      while( TRUE ) /*lint !e716*/
      {
         --callDepth;
         if( callDepth < 0 )
            break;
         spqr_member parentMember = callstack[callDepth + 1].member;
         reduced_member_id parentReducedMember = newCol->memberInformation[parentMember].reducedMember;
         spqr_member currentMember = callstack[callDepth].member;
         reduced_member_id currentReducedMember = newCol->memberInformation[currentMember].reducedMember;
 
         SPQRColReducedMember* parentReducedMemberData = &newCol->reducedMembers[parentReducedMember];
         SPQRColReducedMember* reducedMemberData = &newCol->reducedMembers[currentReducedMember];
 
         reducedMemberData->parent = parentReducedMember;
         reducedMemberData->depth = parentReducedMemberData->depth + 1;
         reducedMemberData->rootMember = parentReducedMemberData->rootMember;
         //ensure that all newly created reduced members are pointing to the correct component
         assert(parentReducedMemberData->componentIndex >= 0);
         reducedMemberData->componentIndex = parentReducedMemberData->componentIndex;
 
         newCol->reducedMembers[parentReducedMember].numChildren++;
      }
   }
 
   reduced_member_id returnedMember = newCol->memberInformation[callstack[0].member].reducedMember;
   return returnedMember;
}
 
/** Construct the reduced decomposition, which is the smallest subtree containing all members path arcs. */
static
SCIP_RETCODE constructReducedDecomposition(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol              /**< The network matrix column addition data structure */
   )
{
   assert(dec);
   assert(newCol);
#ifndef NDEBUG
   for( int i = 0; i < newCol->memMemberInformation; ++i )
   {
      assert(reducedMemberIsInvalid(newCol->memberInformation[i].reducedMember));
   }
#endif
 
   newCol->numReducedComponents = 0;
   newCol->numReducedMembers = 0;
   if( newCol->numDecompositionRowArcs == 0 )
   {//Early return in case the reduced decomposition will be empty
      return SCIP_OKAY;
   }
   assert(newCol->numReducedMembers == 0);
   assert(newCol->numReducedComponents == 0);
 
   int newSize = largestMemberID(dec);//Is this sufficient?
   if( newSize > newCol->memReducedMembers )
   {
      int newArraySize = MAX(2 * newCol->memReducedMembers, newSize);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->reducedMembers, newCol->memReducedMembers, newArraySize) );
      newCol->memReducedMembers = newArraySize;
   }
   if( newSize > newCol->memMemberInformation )
   {
      int updatedSize = MAX(2 * newCol->memMemberInformation, newSize);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->memberInformation, newCol->memMemberInformation, updatedSize) );
      for( int i = newCol->memMemberInformation; i < updatedSize; ++i )
      {
         newCol->memberInformation[i].reducedMember = INVALID_REDUCED_MEMBER;
         newCol->memberInformation[i].rootDepthMinimizer = INVALID_REDUCED_MEMBER;
      }
      newCol->memMemberInformation = updatedSize;
   }
 
   int numComponents = numConnectedComponents(dec);
   if( numComponents > newCol->memReducedComponents )
   {
      int updatedSize = MAX(2 * newCol->memReducedComponents, numComponents);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->reducedComponents, newCol->memReducedComponents, updatedSize) );
      newCol->memReducedComponents = updatedSize;
   }
 
   int numMembers = getNumMembers(dec);
   if( newCol->memCreateReducedMembersCallStack < numMembers )
   {
      int updatedSize = MAX(2 * newCol->memCreateReducedMembersCallStack, numMembers);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->createReducedMembersCallStack,
                                             newCol->memCreateReducedMembersCallStack, updatedSize) );
      newCol->memCreateReducedMembersCallStack = updatedSize;
   }
 
   //Create the reduced members (recursively)
   for( int i = 0; i < newCol->numDecompositionRowArcs; ++i )
   {
      assert(i < newCol->memDecompositionRowArcs);
      spqr_arc arc = newCol->decompositionRowArcs[i];
      spqr_member arcMember = findArcMember(dec, arc);
      reduced_member_id reducedMember = createReducedMembersToRoot(dec, newCol, arcMember);
      reduced_member_id* depthMinimizer = &newCol->memberInformation[newCol->reducedMembers[reducedMember].rootMember].rootDepthMinimizer;
      if( reducedMemberIsInvalid(*depthMinimizer) )
      {
         *depthMinimizer = reducedMember;
      }
   }
 
   //Set the reduced roots according to the root depth minimizers
   for( int i = 0; i < newCol->numReducedComponents; ++i )
   {
      SPQRColReducedComponent* component = &newCol->reducedComponents[i];
      spqr_member rootMember = newCol->reducedMembers[component->root].member;
      reduced_member_id reducedMinimizer = newCol->memberInformation[rootMember].rootDepthMinimizer;
      component->rootDepth = newCol->reducedMembers[reducedMinimizer].depth;
      component->root = reducedMinimizer;
 
      //This simplifies code further down which does not need to be component-aware; just pretend that the reduced member is the new root.
      newCol->reducedMembers[component->root].parent = INVALID_REDUCED_MEMBER;
      assert(memberIsRepresentative(dec, rootMember));
   }
 
   //update the children array
   int numTotalChildren = 0;
   for( int i = 0; i < newCol->numReducedMembers; ++i )
   {
      SPQRColReducedMember* reducedMember = &newCol->reducedMembers[i];
      reduced_member_id minimizer = newCol->memberInformation[reducedMember->rootMember].rootDepthMinimizer;
      if( reducedMember->depth >= newCol->reducedMembers[minimizer].depth )
      {
         reducedMember->firstChild = numTotalChildren;
         numTotalChildren += reducedMember->numChildren;
         reducedMember->numChildren = 0;
      }
   }
 
   if( newCol->memChildrenStorage < numTotalChildren )
   {
      int newMemSize = MAX(newCol->memChildrenStorage * 2, numTotalChildren);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->childrenStorage, newCol->memChildrenStorage, newMemSize) );
      newCol->memChildrenStorage = newMemSize;
   }
   newCol->numChildrenStorage = numTotalChildren;
 
   //Fill up the children array`
   for( reduced_member_id reducedMember = 0; reducedMember < newCol->numReducedMembers; ++reducedMember )
   {
      SPQRColReducedMember* reducedMemberData = &newCol->reducedMembers[reducedMember];
      if( reducedMemberData->depth <=
          newCol->reducedMembers[newCol->memberInformation[reducedMemberData->rootMember].rootDepthMinimizer].depth )
      {
         continue;
      }
      spqr_member parentMember = findMemberParent(dec, reducedMemberData->member);
      reduced_member_id parentReducedMember = SPQRmemberIsValid(parentMember)
                                              ? newCol->memberInformation[parentMember].reducedMember
                                              : INVALID_REDUCED_MEMBER;
      if( reducedMemberIsValid(parentReducedMember))
      {
         SPQRColReducedMember* parentReducedMemberData = &newCol->reducedMembers[parentReducedMember];
         newCol->childrenStorage[parentReducedMemberData->firstChild +
                                 parentReducedMemberData->numChildren] = reducedMember;
         ++parentReducedMemberData->numChildren;
      }
   }
 
   //Clean up the root depth minimizers.
   for( int i = 0; i < newCol->numReducedMembers; ++i )
   {
      SPQRColReducedMember* reducedMember = &newCol->reducedMembers[i];
      assert(reducedMember);
      spqr_member rootMember = reducedMember->rootMember;
      assert(rootMember >= 0);
      assert(rootMember < dec->memMembers);
      newCol->memberInformation[rootMember].rootDepthMinimizer = INVALID_REDUCED_MEMBER;
   }
 
   return SCIP_OKAY;
}
 
/** Clean up the memberinformation array at the end of an iteration. */
static
void cleanUpMemberInformation(
   SCIP_NETCOLADD*       newCol              /**< The network matrix column addition data structure */
   )
{
   //This loop is at the end as memberInformation is also used to assign the cut arcs during propagation
   //Clean up the memberInformation array
   for( int i = 0; i < newCol->numReducedMembers; ++i )
   {
      newCol->memberInformation[newCol->reducedMembers[i].member].reducedMember = INVALID_REDUCED_MEMBER;
   }
#ifndef NDEBUG
   for( int i = 0; i < newCol->memMemberInformation; ++i )
   {
      assert(reducedMemberIsInvalid(newCol->memberInformation[i].reducedMember));
   }
#endif
}
 
/** Marks the given arc as a path arc and adds it to the relevant data structures. */
static
void createPathArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   const spqr_arc        arc,                /**< The arc to mark as a path arc */
   const reduced_member_id reducedMember,    /**< The reduced member containing the arc */
   SCIP_Bool             reversed            /**< Indicates if the new column entry has +1 or -1 (TRUE) for the arc */
   )
{
   assert(dec);
   assert(newCol);
 
   path_arc_id path_arc = newCol->numPathArcs;
   PathArcListNode* listNode = &newCol->pathArcs[path_arc];
   listNode->arc = arc;
 
   listNode->nextMember = newCol->reducedMembers[reducedMember].firstPathArc;
   newCol->reducedMembers[reducedMember].firstPathArc = path_arc;
   newCol->reducedMembers[reducedMember].numPathArcs += 1;
 
   listNode->nextOverall = newCol->firstOverallPathArc;
   newCol->firstOverallPathArc = path_arc;
 
   ++newCol->numPathArcs;
   assert(newCol->numPathArcs <= newCol->memPathArcs);
 
   assert(arc < newCol->memArcsInPath);
   newCol->arcInPath[arc] = TRUE;
   newCol->arcInPathReversed[arc] = reversed;
   assert(memberIsRepresentative(dec, newCol->reducedMembers[reducedMember].member));
   if( getMemberType(dec, newCol->reducedMembers[reducedMember].member) == SPQR_MEMBERTYPE_RIGID )
   {
      listNode->arcHead = findEffectiveArcHead(dec, arc);
      listNode->arcTail = findEffectiveArcTail(dec, arc);
      if( reversed )
      {
         SCIPswapInts(&listNode->arcHead, &listNode->arcTail);
      }
      assert(SPQRnodeIsValid(listNode->arcHead) && SPQRnodeIsValid(listNode->arcTail));
      assert(listNode->arcHead < newCol->memNodePathDegree && listNode->arcTail < newCol->memNodePathDegree);
      ++newCol->nodeInPathDegree[listNode->arcHead];
      ++newCol->nodeOutPathDegree[listNode->arcTail];
   }
   else
   {
      listNode->arcHead = SPQR_INVALID_NODE;
      listNode->arcTail = SPQR_INVALID_NODE;
   }
   listNode->reversed = reversed;
}
 
/** Mark all the row indices of the new column as path arcs */
static
SCIP_RETCODE createPathArcs(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol              /**< The network matrix column addition data structure */
   )
{
   int maxNumPathArcs = newCol->numDecompositionRowArcs + getNumMembers(dec);
   if( newCol->memPathArcs < maxNumPathArcs )
   {
      int newMaxNumArcs = 2 * maxNumPathArcs;//safety factor to prevent very frequent reallocations
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->pathArcs, newCol->memPathArcs, newMaxNumArcs) );
      newCol->memPathArcs = newMaxNumArcs;
   }
   int maxPathArcIndex = largestArcID(dec);
   if( newCol->memArcsInPath < maxPathArcIndex )
   {
      int newSize = 2 * maxPathArcIndex;//safety factor to prevent very frequent reallocations
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->arcInPath, newCol->memArcsInPath, newSize) );
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->arcInPathReversed, newCol->memArcsInPath, newSize) );
 
      for( int i = newCol->memArcsInPath; i < newSize; ++i )
      {
         newCol->arcInPath[i] = FALSE;
         newCol->arcInPathReversed[i] = FALSE;
      }
      newCol->memArcsInPath = newSize;
   }
   int maxNumNodes = largestNodeID(dec);
   if( newCol->memNodePathDegree < maxNumNodes )
   {
      int newSize = 2 * maxNumNodes;//safety factor to prevent very frequent reallocations
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->nodeInPathDegree, newCol->memNodePathDegree, newSize) );
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->nodeOutPathDegree, newCol->memNodePathDegree, newSize) );
      for( int i = newCol->memNodePathDegree; i < newSize; ++i )
      {
         newCol->nodeInPathDegree[i] = 0;
         newCol->nodeOutPathDegree[i] = 0;
      }
      newCol->memNodePathDegree = newSize;
   }
   for( int i = 0; i < newCol->numDecompositionRowArcs; ++i )
   {
      spqr_arc arc = newCol->decompositionRowArcs[i];
      spqr_member member = findArcMember(dec, arc);
      reduced_member_id reducedMember = newCol->memberInformation[member].reducedMember;
      createPathArc(dec, newCol, arc, reducedMember, newCol->decompositionArcReversed[i]);
   }
 
   return SCIP_OKAY;
}
 
 
/** Saves the information of the current row and partitions it based on whether or not the given columns are
 * already part of the decomposition.
 */
static
SCIP_RETCODE newColUpdateColInformation(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   spqr_col              column,             /**< The column that is checked */
   const spqr_row*       nonzeroRows,        /**< The column's row indices */
   const double*         nonzeroValues,      /**< The column's nonzero values */
   int                   numNonzeros         /**< The number of nonzeros in the column */
   )
{
   newCol->newColIndex = column;
 
   newCol->numDecompositionRowArcs = 0;
   newCol->numNewRowArcs = 0;
 
   for( int i = 0; i < numNonzeros; ++i )
   {
      spqr_arc rowArc = getDecompositionRowArc(dec, nonzeroRows[i]);
      SCIP_Bool reversed = nonzeroValues[i] < 0.0;
      if( SPQRarcIsValid(rowArc) )
      {//If the arc is the current decomposition: save it in the array
         if( newCol->numDecompositionRowArcs == newCol->memDecompositionRowArcs )
         {
            int newNumArcs = newCol->memDecompositionRowArcs == 0 ? 8 : 2 * newCol->memDecompositionRowArcs;
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->decompositionRowArcs,
                                                   newCol->memDecompositionRowArcs, newNumArcs) );
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->decompositionArcReversed,
                                                   newCol->memDecompositionRowArcs, newNumArcs) );
            newCol->memDecompositionRowArcs = newNumArcs;
         }
         newCol->decompositionRowArcs[newCol->numDecompositionRowArcs] = rowArc;
         newCol->decompositionArcReversed[newCol->numDecompositionRowArcs] = reversed;
         ++newCol->numDecompositionRowArcs;
      }
      else
      {
         //Not in the decomposition: add it to the set of arcs which are newly added with this row.
         if( newCol->numNewRowArcs == newCol->memNewRowArcs )
         {
            int newNumArcs = newCol->memNewRowArcs == 0 ? 8 : 2 * newCol->memNewRowArcs;
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->newRowArcs,
                                                   newCol->memNewRowArcs, newNumArcs) );
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->newRowArcReversed,
                                                   newCol->memNewRowArcs, newNumArcs) );
            newCol->memNewRowArcs = newNumArcs;
         }
         newCol->newRowArcs[newCol->numNewRowArcs] = nonzeroRows[i];
         newCol->newRowArcReversed[newCol->numNewRowArcs] = reversed;
         newCol->numNewRowArcs++;
      }
   }
 
   return SCIP_OKAY;
}
 
/** Compute and store the leaf members of the reduced SPQR forest */
static
SCIP_RETCODE computeLeafMembers(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol              /**< The network matrix column addition data structure */
   )
{
   if( newCol->numReducedMembers > newCol->memLeafMembers )
   {
      int newSize = MAX(newCol->numReducedMembers, 2 * newCol->memLeafMembers);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newCol->leafMembers, newCol->memLeafMembers, newSize) );
      newCol->memLeafMembers = newSize;
   }
   newCol->numLeafMembers = 0;
 
   for( reduced_member_id reducedMember = 0; reducedMember < newCol->numReducedMembers; ++reducedMember )
   {
      if( newCol->reducedMembers[reducedMember].numChildren == 0 )
      {
         newCol->leafMembers[newCol->numLeafMembers] = reducedMember;
         ++newCol->numLeafMembers;
      }
   }
 
   return SCIP_OKAY;
}
 
/** Checks if the path arcs in the given rigid member form a path */
static
void determineRigidPath(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   SPQRColReducedMember* redMem              /**< The rigid reduced member to determine the path in */
   )
{
   assert(dec);
   assert(newCol);
   assert(redMem);
 
   /* Simply count the in and out degrees of the nodes to check if the path arcs form a path. We have a valid path if
    * and only if the head of the tail of the path are the only nodes with 1 adjacent edge, and all other nodes
    * have 2 adjacent edges*/
   SCIP_Bool isValidPath = TRUE;
   redMem->rigidPathStart = SPQR_INVALID_NODE;
   redMem->rigidPathEnd = SPQR_INVALID_NODE;
   for( path_arc_id pathArc = redMem->firstPathArc; pathArcIsValid(pathArc); pathArc = newCol->pathArcs[pathArc].nextMember )
   {
      spqr_node head = newCol->pathArcs[pathArc].arcHead;
      spqr_node tail = newCol->pathArcs[pathArc].arcTail;
      assert(nodeIsRepresentative(dec, head) && nodeIsRepresentative(dec, tail));
 
      if( newCol->nodeInPathDegree[head] > 1 || newCol->nodeOutPathDegree[tail] > 1 )
      {
         //not network -> stop
         isValidPath = FALSE;
         break;
      }
      if( newCol->nodeOutPathDegree[head] == 0 )
      {
         //found end node
         //If this is the second, stop
         if( SPQRnodeIsValid(redMem->rigidPathEnd) )
         {
            isValidPath = FALSE;
            break;
         }
         redMem->rigidPathEnd = head;
      }
      if( newCol->nodeInPathDegree[tail] == 0 )
      {
         //Found start node.
         //If this is the second, stop.
         if( SPQRnodeIsValid(redMem->rigidPathStart) )
         {
            isValidPath = FALSE;
            break;
         }
         redMem->rigidPathStart = tail;
      }
   }
   //assert that both a start and end node have been found
   assert(!isValidPath || ( SPQRnodeIsValid(redMem->rigidPathStart) && SPQRnodeIsValid(redMem->rigidPathEnd)));
   if( !isValidPath )
   {
      redMem->rigidPathStart = SPQR_INVALID_NODE;
      redMem->rigidPathEnd = SPQR_INVALID_NODE;
      redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
      newCol->remainsNetwork = FALSE;
   }
}
 
/** Determines the member's type for the case where the reduced tree consists of a single rigid member. */
static
void determineSingleRigidType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMember       /**< The reduced member to check */
   )
{
   assert(dec);
   assert(newCol);
   assert(reducedMemberIsValid(reducedMember));
 
   SPQRColReducedMember* redMem = &newCol->reducedMembers[reducedMember];
   assert(pathArcIsValid(redMem->firstPathArc));
   determineRigidPath(dec, newCol, redMem);
   if( redMem->type != REDUCEDMEMBER_TYPE_NOT_NETWORK )
   {
      redMem->type = REDUCEDMEMBER_TYPE_MERGED;
   }
}
 
/** Determines the member's type for the case where the reduced tree consists of a single member. */
static
void determineSingleComponentType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMember       /**< The reduced member to check */
   )
{
   assert(dec);
   assert(newCol);
 
   int numNonPropagatedAdjacent =
      newCol->reducedMembers[reducedMember].numChildren - newCol->reducedMembers[reducedMember].numPropagatedChildren;
   if( reducedMemberIsValid(newCol->reducedMembers[reducedMember].parent) &&
       newCol->reducedMembers[newCol->reducedMembers[reducedMember].parent].type != REDUCEDMEMBER_TYPE_CYCLE )
   {
      ++numNonPropagatedAdjacent;
   }
 
   if( numNonPropagatedAdjacent > 2 )
   {
      newCol->reducedMembers[reducedMember].type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
      newCol->remainsNetwork = FALSE;
      return;
   }
 
   spqr_member member = findMember(dec, newCol->reducedMembers[reducedMember].member);
   SPQRMemberType type = getMemberType(dec, member);
   switch( type )
   {
      case SPQR_MEMBERTYPE_RIGID:
      {
         determineSingleRigidType(dec, newCol, reducedMember);
         break;
      }
      case SPQR_MEMBERTYPE_PARALLEL:
      {
         SPQRColReducedMember* redMem = &newCol->reducedMembers[reducedMember];
         assert(pathArcIsValid(redMem->firstPathArc));
         SCIP_Bool pathForwards = newCol->pathArcs[redMem->firstPathArc].reversed ==
                                  arcIsReversedNonRigid(dec, newCol->pathArcs[redMem->firstPathArc].arc);
         redMem->pathBackwards = !pathForwards;
         redMem->type = REDUCEDMEMBER_TYPE_CYCLE;
         break;
      }
      case SPQR_MEMBERTYPE_SERIES:
      case SPQR_MEMBERTYPE_LOOP:
      {
         SPQRColReducedMember* redMem = &newCol->reducedMembers[reducedMember];
         int countedPathArcs = 0;
         SCIP_Bool good = TRUE;
         SCIP_Bool passesForwards = TRUE;
         for( path_arc_id pathArc = redMem->firstPathArc; pathArcIsValid(pathArc);
              pathArc = newCol->pathArcs[pathArc].nextMember )
         {
            if( countedPathArcs == 0 )
            {
               passesForwards =
                  newCol->pathArcs[pathArc].reversed != arcIsReversedNonRigid(dec, newCol->pathArcs[pathArc].arc);
            }
            else if(
               (newCol->pathArcs[pathArc].reversed != arcIsReversedNonRigid(dec, newCol->pathArcs[pathArc].arc)) !=
               passesForwards )
            {
               good = FALSE;
               break;
            }
            ++countedPathArcs;
         }
         if( !good )
         {
            redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
            newCol->remainsNetwork = FALSE;
            break;
         }
 
         redMem->pathBackwards = !passesForwards;
         if( countedPathArcs == getNumMemberArcs(dec, findMember(dec, redMem->member)) - 1 )
         {
            //Type -> Cycle;
            //Propagate arc
            redMem->type = REDUCEDMEMBER_TYPE_CYCLE;
         }
         else
         {
            //Type -> single_end
            redMem->type = REDUCEDMEMBER_TYPE_MERGED;
         }
         break;
      }
      case SPQR_MEMBERTYPE_UNASSIGNED:
      {
         SCIPABORT();
         newCol->reducedMembers[reducedMember].type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         break;
      }
   }
}
 
/** Determines the path type of a series member. */
static
void determinePathSeriesType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMember,      /**< The reduced member to check */
   spqr_member           member,             /**< The reduced member's member id */
   MemberPathType        previousType,       /**< Type of the previous reduced member in the path */
   spqr_arc              source,             /**< The marker connecting to the previous reduced member in the path */
   spqr_arc              target              /**< The marker connecting to the next reduced member in the path */
   )
{
   assert(dec);
   assert(newCol);
   assert(reducedMemberIsValid(reducedMember));
   assert(SPQRmemberIsValid(member) && memberIsRepresentative(dec, member));
   assert(getMemberType(dec, member) == SPQR_MEMBERTYPE_SERIES);
 
   SPQRColReducedMember* redMem = &newCol->reducedMembers[reducedMember];
   int countedPathArcs = 0;
 
   SCIP_Bool good = TRUE;
   SCIP_Bool passesForwards = TRUE;
   for( path_arc_id pathArc = redMem->firstPathArc; pathArcIsValid(pathArc);
        pathArc = newCol->pathArcs[pathArc].nextMember )
   {
      if( countedPathArcs == 0 )
      {
         passesForwards =
            newCol->pathArcs[pathArc].reversed != arcIsReversedNonRigid(dec, newCol->pathArcs[pathArc].arc);
      }
      else if(( newCol->pathArcs[pathArc].reversed != arcIsReversedNonRigid(dec, newCol->pathArcs[pathArc].arc)) !=
              passesForwards )
      {
         good = FALSE;
         break;
      }
      ++countedPathArcs;
   }
   //If the internal directions of the arcs do not agree, we have no way to realize
   if( !good )
   {
      redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
      newCol->remainsNetwork = FALSE;
      return;
   }
   //If we are in the first skeleton processed, ignore the previous member type
   if( !SPQRarcIsValid(source))
   {
      assert(countedPathArcs > 0);
      assert(SPQRarcIsValid(target));
      SCIP_Bool firstReversed = arcIsReversedNonRigid(dec, newCol->pathArcs[redMem->firstPathArc].arc);
      SCIP_Bool targetReversed = arcIsReversedNonRigid(dec, target);
      SCIP_Bool reversePath = newCol->pathArcs[redMem->firstPathArc].reversed;
 
      if(( firstReversed == targetReversed ) == reversePath )
      {
         redMem->pathType = INTO_HEAD;
      }
      else
      {
         redMem->pathType = OUT_HEAD;
      }
      redMem->pathBackwards = !passesForwards;
      return;
   }
   SCIP_Bool sourceReversed = arcIsReversedNonRigid(dec, source);
   if( countedPathArcs > 0 )
   {
      SCIP_Bool isIntoHeadOrOutTail = isInto(previousType) == isHead(previousType);
      SCIP_Bool isGood = isIntoHeadOrOutTail == ( sourceReversed == passesForwards );
      if( !isGood )
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
         return;
      }
   }
   redMem->pathBackwards = !passesForwards;
   if( SPQRarcIsValid(target) )
   {
      SCIP_Bool targetReversed = arcIsReversedNonRigid(dec, target);
      SCIP_Bool inSameDirection = sourceReversed == targetReversed;
 
      MemberPathType currentType;
      switch( previousType )
      {
         case INTO_HEAD:
         {
            currentType = inSameDirection ? INTO_TAIL : INTO_HEAD;
            break;
         }
         case INTO_TAIL:
         {
            currentType = inSameDirection ? INTO_HEAD : INTO_TAIL;
            break;
         }
         case OUT_HEAD:
         {
            currentType = inSameDirection ? OUT_TAIL : OUT_HEAD;
            break;
         }
         case OUT_TAIL:
         default:
         {
            assert(previousType == OUT_TAIL);
            currentType = inSameDirection ? OUT_HEAD : OUT_TAIL;
            break;
         }
      }
      redMem->pathType = currentType;
      return;
   }
   //If we are in the last skeleton, we only have a source, so nothing further to do
   assert(countedPathArcs > 0);
   //Strictly speaking below are no-ops within the algorithm, but help with debugging
   if( isInto(previousType))
   {
      redMem->pathType = INTO_HEAD;
   }
   else
   {
      redMem->pathType = OUT_HEAD;
   }
}
 
/** Determines the path type of a parallel member. */
static
void determinePathParallelType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMember,      /**< The reduced member to check */
   spqr_member           member,             /**< The reduced member's member id */
   MemberPathType        previousType,       /**< Type of the previous reduced member in the path */
   spqr_arc              source,             /**< The marker connecting to the previous reduced member in the path */
   spqr_arc              target              /**< The marker connecting to the next reduced member in the path */
   )
{
   assert(dec);
   assert(newCol);
   assert(reducedMemberIsValid(reducedMember));
   assert(SPQRmemberIsValid(member) && memberIsRepresentative(dec, member));
   assert(getMemberType(dec, member) == SPQR_MEMBERTYPE_PARALLEL);
 
   //Parallel members must always be of degree two; if they are a leaf, they must contain an edge, which could have been propagated
   assert(SPQRarcIsValid(source) && SPQRarcIsValid(target));
   SCIP_Bool sourceReversed = arcIsReversedNonRigid(dec, source);
   SCIP_Bool targetReversed = arcIsReversedNonRigid(dec, target);
   SCIP_Bool inSameDirection = sourceReversed == targetReversed;
 
   SPQRColReducedMember* redMem = &newCol->reducedMembers[reducedMember];
 
   path_arc_id pathArc = redMem->firstPathArc;
 
   SCIP_Bool arcPresent = FALSE;
   if( pathArcIsValid(pathArc))
   {
      SCIP_Bool pathArcReversed =
         newCol->pathArcs[pathArc].reversed != arcIsReversedNonRigid(dec, newCol->pathArcs[pathArc].arc);
      SCIP_Bool intoHeadOrOutTail = isInto(previousType) == isHead(previousType);
      SCIP_Bool good = intoHeadOrOutTail == ( pathArcReversed != sourceReversed );
      if( !good )
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
         return;
      }
      arcPresent = TRUE;
   }
 
   SCIP_Bool swapHeadTail = arcPresent != inSameDirection;
   switch( previousType )
   {
      case INTO_HEAD:
      {
         redMem->pathType = swapHeadTail ? INTO_HEAD : INTO_TAIL;
         break;
      }
      case INTO_TAIL:
      {
         redMem->pathType = swapHeadTail ? INTO_TAIL : INTO_HEAD;
         break;
      }
      case OUT_HEAD:
      {
         redMem->pathType = swapHeadTail ? OUT_HEAD : OUT_TAIL;
         break;
      }
      case OUT_TAIL:
      {
         redMem->pathType = swapHeadTail ? OUT_TAIL : OUT_HEAD;
         break;
      }
   }
}
 
/** Determines the path type of a rigid member. */
static
void determinePathRigidType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMember,      /**< The reduced member to check */
   MemberPathType        previousType,       /**< Type of the previous reduced member in the path */
   spqr_arc              source,             /**< The marker connecting to the previous reduced member in the path */
   spqr_arc              target              /**< The marker connecting to the next reduced member in the path */
   )
{
   SPQRColReducedMember* redMem = &newCol->reducedMembers[reducedMember];
   if( pathArcIsInvalid(redMem->firstPathArc))
   {
      assert(SPQRarcIsValid(source));
      assert(SPQRarcIsValid(target));
      //In this case, we need to check if the source and target are adjacent in any node
 
      spqr_node sourceTail = findEffectiveArcTail(dec, source);
      spqr_node sourceHead = findEffectiveArcHead(dec, source);
      spqr_node targetTail = findEffectiveArcTail(dec, target);
      spqr_node targetHead = findEffectiveArcHead(dec, target);
      SCIP_Bool sourceHeadIsTargetHead = sourceHead == targetHead;
      SCIP_Bool sourceTailIsTargetHead = sourceTail == targetHead;
      SCIP_Bool sourceHeadIsTargetTail = sourceHead == targetTail;
      SCIP_Bool sourceTailIsTargetTail = sourceTail == targetTail;
 
      if( !(sourceHeadIsTargetHead || sourceTailIsTargetHead || sourceHeadIsTargetTail || sourceTailIsTargetTail) )
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
         return;
      }
      assert(
         ( sourceHeadIsTargetHead ? 1 : 0 ) + ( sourceHeadIsTargetTail ? 1 : 0 ) + ( sourceTailIsTargetHead ? 1 : 0 ) +
         ( sourceTailIsTargetTail ? 1 : 0 ) == 1);
      //assert simplicity; they can be adjacent in only exactly one node
      SCIP_Bool isSourceHead = sourceHeadIsTargetHead || sourceHeadIsTargetTail;
      SCIP_Bool isTargetTail = sourceHeadIsTargetTail || sourceTailIsTargetTail;
      if( isHead(previousType) == isSourceHead )
      {
         //no need to reflect
         redMem->reverseArcs = FALSE;
         if( isInto(previousType))
         {
            if( isTargetTail )
            {
               redMem->pathType = INTO_TAIL;
            }
            else
            {
               redMem->pathType = INTO_HEAD;
            }
         }
         else
         {
            if( isTargetTail )
            {
               redMem->pathType = OUT_TAIL;
            }
            else
            {
               redMem->pathType = OUT_HEAD;
            }
         }
      }
      else
      {
         redMem->reverseArcs = TRUE;
         //because of the reversal, all the heads/tails are switched below
         if( isInto(previousType))
         {
            if( isTargetTail )
            {
               redMem->pathType = INTO_HEAD;
            }
            else
            {
               redMem->pathType = INTO_TAIL;
            }
         }
         else
         {
            if( isTargetTail )
            {
               redMem->pathType = OUT_HEAD;
            }
            else
            {
               redMem->pathType = OUT_TAIL;
            }
         }
      }
      assert(isInto(redMem->pathType) == isInto(previousType));
      return;
   }
   determineRigidPath(dec, newCol, redMem);
   if( redMem->type == REDUCEDMEMBER_TYPE_NOT_NETWORK )
   {
      return;
   }
   if( SPQRarcIsInvalid(source) )
   {
      assert(SPQRarcIsValid(target));
      spqr_node targetTail = findEffectiveArcTail(dec, target);
      spqr_node targetHead = findEffectiveArcHead(dec, target);
      redMem->reverseArcs = FALSE;
      if( redMem->rigidPathEnd == targetHead )
      {
         redMem->pathType = INTO_HEAD;
      }
      else if( redMem->rigidPathEnd == targetTail )
      {
         redMem->pathType = INTO_TAIL;
      }
      else if( redMem->rigidPathStart == targetHead )
      {
         redMem->pathType = OUT_HEAD;
      }
      else if( redMem->rigidPathStart == targetTail )
      {
         redMem->pathType = OUT_TAIL;
      }
      else
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
      }
      return;
   }
   assert(SPQRarcIsValid(source));
   spqr_node sourceTail = findEffectiveArcTail(dec, source);
   spqr_node sourceHead = findEffectiveArcHead(dec, source);
 
   SCIP_Bool startsAtHead = sourceHead == redMem->rigidPathStart;
   SCIP_Bool endsAtTail = sourceTail == redMem->rigidPathEnd;
   SCIP_Bool startsAtTail = sourceTail == redMem->rigidPathStart;
   SCIP_Bool endsAtHead = sourceHead == redMem->rigidPathEnd;
 
   SCIP_Bool isIntoHeadOrOutTail = isInto(previousType) == isHead(previousType);
   if( isIntoHeadOrOutTail )
   {//into head or outTail
      //Check if path starts at head or ends at tail
      if( !startsAtHead && !endsAtTail )
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
         return;
      }
      assert(startsAtHead || endsAtTail);//both can hold; they can form cycle but other components can not be reduced
      //        redMem->reverseArcs = isInto(previousType) != startsAtHead; //Reverse only if there is no path starting at head
   }
   else
   {//Into tail or outHead
      //Check if path starts at tail or ends at head
      if( !startsAtTail && !endsAtHead )
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
         return;
      }
      assert(startsAtTail || endsAtHead);// both can hold; they can form cycle but other components can not be reduced
      //        redMem->reverseArcs = isInto(previousType) != startsAtTail; //Reverse only if there is no path starting at tail
   }
 
   if( SPQRarcIsValid(target) )
   {
      spqr_node targetTail = findEffectiveArcTail(dec, target);
      spqr_node targetHead = findEffectiveArcHead(dec, target);
 
      //Check if they are not parallel; (below logic relies on this fact)
      assert(!(( targetHead == sourceHead && targetTail == sourceTail ) ||
               ( targetHead == sourceTail && targetTail == sourceHead )));
 
      SCIP_Bool startsAtTargetHead = redMem->rigidPathStart == targetHead;
      SCIP_Bool startsAtTargetTail = redMem->rigidPathStart == targetTail;
      SCIP_Bool endsAtTargetHead = redMem->rigidPathEnd == targetHead;
      SCIP_Bool endsAtTargetTail = redMem->rigidPathEnd == targetTail;
 
      if( !(startsAtTargetHead || startsAtTargetTail || endsAtTargetHead || endsAtTargetTail) )
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
         return;
      }
      SCIP_Bool outReverse = FALSE;
      SCIP_Bool outHead = FALSE;
 
      if( isInto(previousType) == isHead(previousType) )
      {
         if( startsAtHead && endsAtTail )
         {
            outReverse = ( startsAtTargetHead || startsAtTargetTail ) == isInto(previousType);
         }
         else if( startsAtHead )
         {
            outReverse = !isInto(previousType);
         }
         else
         {
            assert(endsAtTail);
            outReverse = isInto(previousType);
         }
      }
      else
      {
         if( startsAtTail && endsAtHead )
         {
            outReverse = ( startsAtTargetHead || startsAtTargetTail ) == isInto(previousType);
         }
         else if( startsAtTail )
         {
            outReverse = !isInto(previousType);
         }
         else
         {
            assert(endsAtHead);
            outReverse = isInto(previousType);
         }
      }
 
      //TODO: this if-else tree to compute two booleans can probably be simplified significantly
      SCIP_Bool isBad = FALSE;
      if( isInto(previousType) == isHead(previousType) )
      {
         if( startsAtHead && endsAtTail )
         {
            outHead = ( startsAtTargetTail || endsAtTargetHead ) == isInto(previousType);
         }
         else if( startsAtHead )
         {
            if( endsAtTargetHead )
            {
               outHead = isInto(previousType);
            }
            else if( endsAtTargetTail )
            {
               outHead = !isInto(previousType);
            }
            else
            {
               isBad = TRUE;
            }
         }
         else
         {
            assert(endsAtTail);
            if( startsAtTargetTail )
            {
               outHead = isInto(previousType);
            }
            else if( startsAtTargetHead )
            {
               outHead = !isInto(previousType);
            }
            else
            {
               isBad = TRUE;
            }
         }
      }
      else
      {
         if( startsAtTail && endsAtHead )
         {
            outHead = ( startsAtTargetTail || endsAtTargetHead ) == isInto(previousType);
         }
         else if( startsAtTail )
         {
            if( endsAtTargetHead )
            {
               outHead = isInto(previousType);
            }
            else if( endsAtTargetTail )
            {
               outHead = !isInto(previousType);
            }
            else
            {
               isBad = TRUE;
            }
         }
         else
         {
            assert(endsAtHead);
            if( startsAtTargetTail )
            {
               outHead = isInto(previousType);
            }
            else if( startsAtTargetHead )
            {
               outHead = !isInto(previousType);
            }
            else
            {
               isBad = TRUE;
            }
         }
      }
      if( isBad )
      {
         redMem->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         newCol->remainsNetwork = FALSE;
         return;
      }
 
      redMem->reverseArcs = outReverse;
      if( isInto(previousType) )
      {
         redMem->pathType = outHead ? INTO_HEAD : INTO_TAIL;
      }
      else
      {
         redMem->pathType = outHead ? OUT_HEAD : OUT_TAIL;
      }
      return;
   }
 
   //TODO: is this simplifyable?
   if( isInto(previousType) == isHead(previousType) )
   {
      redMem->reverseArcs = startsAtHead != isInto(previousType);
   }
   else
   {
      redMem->reverseArcs = startsAtTail != isInto(previousType);
   }
   //last member of the path. Since we already checked the source,
   //Below is technically no op, but helps with debugging
   if( isInto(previousType) )
   {
      redMem->pathType = INTO_HEAD;
   }
   else
   {
      redMem->pathType = OUT_HEAD;
   }
}
 
/** Determines the path type of a single member. */
static
void determinePathMemberType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMember,      /**< The reduced member to check */
   spqr_member           member,             /**< The reduced member's member id */
   MemberPathType        previousType,       /**< Type of the previous reduced member in the path */
   spqr_arc              source,             /**< The marker connecting to the previous reduced member in the path */
   spqr_arc              target              /**< The marker connecting to the next reduced member in the path */
   )
{
   newCol->reducedMembers[reducedMember].pathSourceArc = source;
   newCol->reducedMembers[reducedMember].pathTargetArc = target;
   //Check if the marked edges with the given signs
   //form a (reverse) directed path from one of the source's end nodes to one of the target's end nodes
   switch( getMemberType(dec, member) )
   {
      case SPQR_MEMBERTYPE_RIGID:
      {
         determinePathRigidType(dec, newCol, reducedMember, previousType, source, target);
         break;
      }
      case SPQR_MEMBERTYPE_PARALLEL:
      {
         determinePathParallelType(dec, newCol, reducedMember, member, previousType, source, target);
         break;
      }
      case SPQR_MEMBERTYPE_SERIES:
      {
         determinePathSeriesType(dec, newCol, reducedMember, member, previousType, source, target);
         break;
      }
      case SPQR_MEMBERTYPE_LOOP:
      case SPQR_MEMBERTYPE_UNASSIGNED:
      {
         //In release
         newCol->remainsNetwork = FALSE;
         SCIPABORT();
         break;
      }
   }
}
 
/** Determines the path types of all reduced members.
 *
 * The reduced members themselves also form a path in the reduced decomposition.
 */
static
void determinePathTypes(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   SPQRColReducedComponent* component        /**< The component to determine the path types for */
   )
{
   assert(dec);
   assert(newCol);
   assert(component);
   assert(component->numPathEndMembers == 2);
 
   assert(component->pathEndMembers[0] != component->root);
 
   //We check the path by going from end to end. We start at the leaf and process every component,
   //walking down until we hit the root.
   //Then, we walk up from the root and process each component in the same manner.
   reduced_member_id reducedStart = component->pathEndMembers[0];
   spqr_arc toPrevious = SPQR_INVALID_ARC;
   spqr_arc toNext = SPQR_INVALID_ARC;
   MemberPathType previousType = INTO_HEAD;//Arbitrary, is ignored in the first call
 
   spqr_member member = newCol->reducedMembers[reducedStart].member;
   reduced_member_id reducedMember = reducedStart;
   reduced_member_id previousReducedMember = reducedStart;
   while( reducedMember != component->root )
   {
      toNext = markerToParent(dec, member);
      determinePathMemberType(dec, newCol, reducedMember, member, previousType, toPrevious, toNext);
      if( !newCol->remainsNetwork )
      {
         return;
      }
      previousType = newCol->reducedMembers[reducedMember].pathType;
      toPrevious = markerOfParent(dec, member);
      member = findMemberParent(dec, newCol->reducedMembers[reducedMember].member);
      previousReducedMember = reducedMember;
      reducedMember = newCol->memberInformation[member].reducedMember;
      newCol->reducedMembers[previousReducedMember].nextPathMember = reducedMember;
      newCol->reducedMembers[previousReducedMember].nextPathMemberIsParent = TRUE;
   }
 
   while( reducedMember != component->pathEndMembers[1] )
   {
      //Search the (other) child node
      reduced_member_id child = INVALID_REDUCED_MEMBER;
      //a bit ugly linear search, but not a problem for time complexity
      for( children_idx i = newCol->reducedMembers[reducedMember].firstChild;
           i <
           newCol->reducedMembers[reducedMember].firstChild + newCol->reducedMembers[reducedMember].numChildren; ++i )
      {
         reduced_member_id childReduced = newCol->childrenStorage[i];
         if( newCol->reducedMembers[childReduced].type != REDUCEDMEMBER_TYPE_CYCLE &&
             childReduced != previousReducedMember )
         {
            child = childReduced;
            break;
         }
      }
      assert(reducedMemberIsValid(child));
 
      spqr_member childMember = newCol->reducedMembers[child].member;
      toNext = markerOfParent(dec, childMember);
 
      determinePathMemberType(dec, newCol, reducedMember, member, previousType, toPrevious, toNext);
      if( !newCol->remainsNetwork )
      {
         return;
      }
      previousType = newCol->reducedMembers[reducedMember].pathType;
      toPrevious = markerToParent(dec, childMember);
      member = childMember;
      previousReducedMember = reducedMember;
      reducedMember = child;
      newCol->reducedMembers[previousReducedMember].nextPathMember = reducedMember;
      newCol->reducedMembers[previousReducedMember].nextPathMemberIsParent = FALSE;
   }
   //The last iteration is not performed by the loops above.
   //We explicitly set the target arc to invalid in order to indicate that this is the last iteration.
   toNext = SPQR_INVALID_ARC;
   determinePathMemberType(dec, newCol, reducedMember, member, previousType, toPrevious, toNext);
   newCol->reducedMembers[reducedMember].nextPathMember = INVALID_REDUCED_MEMBER;
   //since we return anyways, no need to check newCol->remainsNetwork explicitly
}
 
/** Check if a rigid leaf closes a cycle with its child.
 *
 * If so, we can propagate this cycle to a virtual arc of the child node member and shrink the decomposition.
 */
static
void checkRigidLeaf(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     leaf,               /**< The leaf node of the reduced SPQR tree */
   spqr_arc              toParent,           /**< The virtual arc to the leaf node's neighbour */
   reduced_member_id     parent,             /**< The neighbouring member of the leaf node. */
   spqr_arc              toChild             /**< The virtual arc from the neighbouring member pointing to the leaf. */
   )
{
   SPQRColReducedMember* leafMember = &newCol->reducedMembers[leaf];
   determineRigidPath(dec, newCol, leafMember);
   if( leafMember->type == REDUCEDMEMBER_TYPE_NOT_NETWORK )
   {
      return;
   }
   spqr_node targetHead = findEffectiveArcHead(dec, toParent);
   spqr_node targetTail = findEffectiveArcTail(dec, toParent);
   SCIP_Bool matches = leafMember->rigidPathStart == targetTail && leafMember->rigidPathEnd == targetHead;
   SCIP_Bool opposite = leafMember->rigidPathStart == targetHead && leafMember->rigidPathEnd == targetTail;
   if( matches || opposite )
   {
      leafMember->type = REDUCEDMEMBER_TYPE_CYCLE;
      createPathArc(dec, newCol, toChild, parent, opposite);
      return;
   }
   leafMember->type = REDUCEDMEMBER_TYPE_MERGED;
}
 
/** Check if a leaf node closes a cycle with its child.
 *
 * If so, we can propagate this cycle to a virtual arc of the child node member and shrink the decomposition.
 */
static
ReducedMemberType checkLeaf(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     leaf,               /**< The leaf node of the reduced SPQR tree */
   spqr_arc              toParent,           /**< The virtual arc to the leaf node's neighbour */
   reduced_member_id     parent,             /**< The neighbouring member of the leaf node. */
   spqr_arc              toChild             /**< The virtual arc from the neighbouring member pointing to the leaf. */
   )
{
   assert(dec);
   assert(newCol);
   assert(SPQRarcIsValid(toParent));
   assert(SPQRarcIsValid(toChild));
   assert(!arcIsTree(dec, toParent));
   assert(reducedMemberIsValid(leaf));
   assert(reducedMemberIsValid(parent));
 
   switch( getMemberType(dec, newCol->reducedMembers[leaf].member) )
   {
      case SPQR_MEMBERTYPE_RIGID:
      {
         checkRigidLeaf(dec, newCol, leaf, toParent, parent, toChild);
         break;
      }
      case SPQR_MEMBERTYPE_PARALLEL:
      {
         SPQRColReducedMember* reducedMember = &newCol->reducedMembers[leaf];
         assert(pathArcIsValid(reducedMember->firstPathArc));
         reducedMember->type = REDUCEDMEMBER_TYPE_CYCLE;
 
         SCIP_Bool pathArcReversed = newCol->pathArcs[reducedMember->firstPathArc].reversed;
         SCIP_Bool arcPathArcIsReverse = arcIsReversedNonRigid(dec, newCol->pathArcs[reducedMember->firstPathArc].arc);
         SCIP_Bool parentReversed = arcIsReversedNonRigid(dec, toParent);
         createPathArc(dec, newCol, toChild, parent, ( arcPathArcIsReverse == parentReversed ) == pathArcReversed);
         break;
      }
      case SPQR_MEMBERTYPE_SERIES:
      case SPQR_MEMBERTYPE_LOOP:
      {
         SPQRColReducedMember* reducedMember = &newCol->reducedMembers[leaf];
         int countedPathArcs = 0;
         SCIP_Bool good = TRUE;
         SCIP_Bool passesForwards = TRUE;
         for( path_arc_id pathArc = reducedMember->firstPathArc; pathArcIsValid(pathArc);
              pathArc = newCol->pathArcs[pathArc].nextMember )
         {
            if( countedPathArcs == 0 )
            {
               passesForwards =
                  newCol->pathArcs[pathArc].reversed != arcIsReversedNonRigid(dec, newCol->pathArcs[pathArc].arc);
            }
            else if(
               (newCol->pathArcs[pathArc].reversed != arcIsReversedNonRigid(dec, newCol->pathArcs[pathArc].arc)) !=
               passesForwards )
            {
               good = FALSE;
               break;
            }
            ++countedPathArcs;
         }
         if( !good )
         {
            reducedMember->type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
            newCol->remainsNetwork = FALSE;
            break;
         }
 
         reducedMember->pathBackwards = !passesForwards;
         if( countedPathArcs == getNumMemberArcs(dec, findMember(dec, reducedMember->member)) - 1 )
         {
            //Type -> Cycle;
            //Propagate arc
            reducedMember->type = REDUCEDMEMBER_TYPE_CYCLE;
 
            SCIP_Bool firstArcReversed = arcIsReversedNonRigid(dec, newCol->pathArcs[reducedMember->firstPathArc].arc);
            SCIP_Bool firstArcInPathReverse = newCol->pathArcs[reducedMember->firstPathArc].reversed;
            SCIP_Bool parentReversed = arcIsReversedNonRigid(dec, toParent);
            createPathArc(dec, newCol, toChild, parent,
                          ( parentReversed == firstArcReversed ) != firstArcInPathReverse);
         }
         else
         {
            //Type -> single_end
            reducedMember->type = REDUCEDMEMBER_TYPE_MERGED;
         }
 
         break;
      }
      case SPQR_MEMBERTYPE_UNASSIGNED:
      {
         SCIPABORT();
         newCol->reducedMembers[leaf].type = REDUCEDMEMBER_TYPE_NOT_NETWORK;
         break;
      }
   }
   return newCol->reducedMembers[leaf].type;
}
 
/** Recursively removes leaf nodes whose path forms cycles with the virtual arc to its children. */
static
void propagateCycles(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol              /**< The network matrix column addition data structure */
   )
{
   assert(dec);
   assert(newCol);
 
   int leafArrayIndex = 0;
   while( leafArrayIndex != newCol->numLeafMembers )
   {
      reduced_member_id leaf = newCol->leafMembers[leafArrayIndex];
      //next is invalid if the member is not in the reduced decomposition.
      reduced_member_id next = newCol->reducedMembers[leaf].parent;
      spqr_arc parentMarker = markerToParent(dec, newCol->reducedMembers[leaf].member);
      if( reducedMemberIsValid(next) && !arcIsTree(dec, parentMarker))
      {
         assert(reducedMemberIsValid(next));
         assert(SPQRarcIsValid(parentMarker));
         ReducedMemberType type = checkLeaf(dec, newCol, leaf, parentMarker, next,
                                            markerOfParent(dec, newCol->reducedMembers[leaf].member));
         if( type == REDUCEDMEMBER_TYPE_CYCLE )
         {
            ++newCol->reducedMembers[next].numPropagatedChildren;
            if( newCol->reducedMembers[next].numPropagatedChildren == newCol->reducedMembers[next].numChildren )
            {
               newCol->leafMembers[leafArrayIndex] = next;
            }
            else
            {
               ++leafArrayIndex;
            }
         }
         else if( type == REDUCEDMEMBER_TYPE_NOT_NETWORK )
         {
            return;
         }
         else
         {
            assert(type == REDUCEDMEMBER_TYPE_MERGED);
            ++leafArrayIndex;
            int component = newCol->reducedMembers[leaf].componentIndex;
            if( newCol->reducedComponents[component].numPathEndMembers >= 2 )
            {
               newCol->remainsNetwork = FALSE;
               return;
            }
            assert(newCol->reducedComponents[component].numPathEndMembers < 2);
            newCol->reducedComponents[component].pathEndMembers[newCol->reducedComponents[component].numPathEndMembers] = leaf;
            ++newCol->reducedComponents[component].numPathEndMembers;
         }
      }
      else
      {
         ++leafArrayIndex;
         int component = newCol->reducedMembers[leaf].componentIndex;
         if( newCol->reducedComponents[component].numPathEndMembers >= 2 )
         {
            newCol->remainsNetwork = FALSE;
            return;
         }
         assert(newCol->reducedComponents[component].numPathEndMembers < 2);
         newCol->reducedComponents[component].pathEndMembers[newCol->reducedComponents[component].numPathEndMembers] = leaf;
         ++newCol->reducedComponents[component].numPathEndMembers;
      }
   }
 
   for( int j = 0; j < newCol->numReducedComponents; ++j )
   {
      //The reduced root might be a leaf as well: we propagate it last
      reduced_member_id root = newCol->reducedComponents[j].root;
 
      while( TRUE ) /*lint !e716*/
      {
         if( newCol->reducedMembers[root].numPropagatedChildren != newCol->reducedMembers[root].numChildren - 1 )
         {
            break;
         }
         //TODO: bit ugly, have to do a linear search for the child
         reduced_member_id child = INVALID_REDUCED_MEMBER;
         spqr_arc markerToChild = SPQR_INVALID_ARC;
         for( children_idx i = newCol->reducedMembers[root].firstChild;
              i < newCol->reducedMembers[root].firstChild + newCol->reducedMembers[root].numChildren; ++i )
         {
            reduced_member_id childReduced = newCol->childrenStorage[i];
            if( newCol->reducedMembers[childReduced].type != REDUCEDMEMBER_TYPE_CYCLE )
            {
               child = childReduced;
               markerToChild = markerOfParent(dec, newCol->reducedMembers[child].member);
               break;
            }
         }
         assert(SPQRmemberIsValid(newCol->reducedMembers[child].member));
         assert(SPQRarcIsValid(markerToChild));
         if( !arcIsTree(dec, markerToChild) )
         {
            ReducedMemberType type = checkLeaf(dec, newCol, root, markerToChild, child,
                                               markerToParent(dec, newCol->reducedMembers[child].member));
            if( type == REDUCEDMEMBER_TYPE_CYCLE )
            {
               root = child;
               continue;
            }
            else if( type == REDUCEDMEMBER_TYPE_NOT_NETWORK )
            {
               return;
            }
         }
         //If the root has exactly one neighbour and is not contained, it is also considered a path end member
         int component = newCol->reducedMembers[root].componentIndex;
         SCIP_Bool rootPresent = FALSE;
         for( int i = 0; i < newCol->reducedComponents[component].numPathEndMembers; ++i )
         {
            rootPresent = rootPresent || ( newCol->reducedComponents[component].pathEndMembers[i] == root );
         }
         if( !rootPresent )
         {
            if( newCol->reducedComponents[component].numPathEndMembers >= 2 )
            {
               newCol->remainsNetwork = FALSE;
               return;
            }
            newCol->reducedComponents[component].pathEndMembers[newCol->reducedComponents[component].numPathEndMembers] = root;
            ++newCol->reducedComponents[component].numPathEndMembers;
         }
         break;
      }
 
      newCol->reducedComponents[j].root = root;
      newCol->reducedMembers[root].parent = INVALID_REDUCED_MEMBER;
   }
}
 
/** Determine the type of a single component. */
static
void determineComponentTypes(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   SPQRColReducedComponent* component        /**< The component to determine the types for */
   )
{
   assert(dec);
   assert(newCol);
   assert(component);
 
   if( component->numPathEndMembers == 1 )
   {
      assert(component->root == component->pathEndMembers[0]);
      determineSingleComponentType(dec, newCol, component->root);
   }
   else
   {
      assert(component->numPathEndMembers == 2);
      determinePathTypes(dec, newCol, component);
   }
}
 
/** Checks if the given column can be added to the network matrix decomposition.
 *
 * See header for more info.
 */
static
SCIP_RETCODE netcoladdCheck(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       coladd,             /**< The network matrix column addition data structure */
   int                   column,             /**< The column to add */
   const int*            nonzrows,           /**< The column's nonzero row indices */
   const double*         nonzvals,           /**< The column's nonzero entries */
   int                   nnonzs              /**< The number of nonzeros in the column */
   )
{
   assert(dec);
   assert(coladd);
   assert(nnonzs == 0 || ( nonzrows && nonzvals ));
 
   /* A column can only be added once */
   if( netMatDecDataContainsColumn(dec,column) )
   {
      return SCIP_INVALIDDATA;
   }
   coladd->remainsNetwork = TRUE;
   cleanupPreviousIteration(dec, coladd);
   //assert that previous iteration was cleaned up
 
   //Store call data
   SCIP_CALL( newColUpdateColInformation(dec, coladd, column, nonzrows, nonzvals, nnonzs) );
 
   //compute reduced decomposition
   SCIP_CALL( constructReducedDecomposition(dec, coladd) );
   //initialize path arcs in reduced decomposition
   SCIP_CALL( createPathArcs(dec, coladd) );
   SCIP_CALL( computeLeafMembers(dec, coladd) );
   propagateCycles(dec, coladd);
   //determine types
   if( coladd->remainsNetwork )
   {
      for( int i = 0; i < coladd->numReducedComponents; ++i )
      {
         determineComponentTypes(dec, coladd, &coladd->reducedComponents[i]);
      }
   }
   //clean up memberInformation
   cleanUpMemberInformation(coladd);
 
   return SCIP_OKAY;
}
 
/** Struct that contains the data that tells us how to add the new column after the graph has been modified.
 *
 * In the case the member is a series or parallel node, the new column and rows are placed in series or parallel,
 * respectively. Otherwise, the edge can be added between head and tail in a rigid member.
 */
typedef struct
{
   spqr_member           member;             /**< The member where the new column should be added */
   spqr_node             head;               /**< The head node of the new column (rigid members only) */
   spqr_node             tail;               /**< The tail node of the new column (rigid members only) */
   spqr_arc              representative;     /**< The representative arc of the new column */
   SCIP_Bool             reversed;           /**< Is the new column reversed? */
} NewColInformation;
 
#define NEWCOLINFORMATION_EMPTY { SPQR_INVALID_MEMBER, SPQR_INVALID_NODE, SPQR_INVALID_NODE, SPQR_INVALID_ARC, FALSE }
 
/** Set the head node of the new column edge to be added. */
static
void setTerminalHead(
   NewColInformation*    info,               /**< The new column information */
   spqr_node             node                /**< The head node of the new column edge */
   )
{
   assert(SPQRnodeIsValid(node));
   assert(SPQRnodeIsInvalid(info->head));
   assert(info);
 
   info->head = node;
}
 
/** Set the tail node of the new column edge to be added. */
static
void setTerminalTail(
   NewColInformation*    info,               /**< The new column information */
   spqr_node             node                /**< The tail node of the new column edge */
   )
{
   assert(SPQRnodeIsValid(node));
   assert(info);
   assert(SPQRnodeIsInvalid(info->tail));
 
   info->tail = node;
}
 
/** Set whether the new column arc should be reversed. */
static
void setTerminalReversed(
   NewColInformation*    info,               /**< The new column information */
   SCIP_Bool             reversed            /**< Should the new column arc be reversed? */
   )
{
   assert(info);
 
   info->reversed = reversed;
}
 
/** Set the member that contains the new column arc. */
static
void setTerminalMember(
   NewColInformation*    info,               /**< The new column information */
   spqr_member           member              /**< The decomposition member that contains the new column arc */
   )
{
   assert(info);
 
   info->member = member;
}
 
/** Set the representative arc of the new column arc. */
static
void setTerminalRepresentative(
   NewColInformation*    info,               /**< The new column information */
   spqr_arc              representative      /**< The representative arc of the new column arc */
   )
{
   assert(info);
 
   info->representative = representative;
}
 
/** Splits a parallel member into two adjacent parallel members connected by a virtual edge pair.
 *
 * One member keeps the two arcs passed to this function, the other member gets all other arcs.
 */
static
SCIP_RETCODE splitParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   spqr_member           parallel,           /**< The parallel member */
   spqr_arc              arc1,               /**< First arc to keep. */
   spqr_arc              arc2,               /**< Second arc to keep. */
   spqr_member*          childParallel       /**< Out pointer to the new child parallel member. */
   )
{
   assert(dec);
   assert(SPQRarcIsValid(arc1));
   assert(SPQRarcIsValid(arc2));
   assert(SPQRmemberIsValid(parallel));
 
   SCIP_Bool childContainsTree = arcIsTree(dec, arc1) || arcIsTree(dec, arc2);
   spqr_arc toParent = markerToParent(dec, parallel);
   SCIP_Bool parentMoved = toParent == arc1 || toParent == arc2;
   SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, childParallel) );
 
   moveArcToNewMember(dec, arc1, parallel, *childParallel);
   moveArcToNewMember(dec, arc2, parallel, *childParallel);
 
   if( parentMoved )
   {
      SCIP_CALL( createMarkerPair(dec, *childParallel, parallel, !childContainsTree, FALSE, FALSE) );
   }
   else
   {
      SCIP_CALL( createMarkerPair(dec, parallel, *childParallel, childContainsTree, FALSE, FALSE) );
   }
 
   return SCIP_OKAY;
}
 
/** Very elaborate function that splits a series member into multiple members based on the structure of the path arcs.
 *
 * The updated member reflects the structure of the updated SPQR tree after the new column arc is added.
 */
static
SCIP_RETCODE splitSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   SPQRColReducedMember* reducedMember,      /**< The reduced member of the series member to split. */
   spqr_member           member,             /**< The series member to split. */
   spqr_member*          loopMember,         /**< Out-pointer to a new loop member that may be created */
   NewColInformation*    newColInfo          /**< New column information struct */
   )
{
   assert(dec);
   assert(reducedMember);
   assert(SPQRmemberIsValid(member));
   assert(memberIsRepresentative(dec, member));
 
   assert(reducedMember->numPathArcs != 0);
   SCIP_Bool createPathSeries = reducedMember->numPathArcs > 1;
   SCIP_Bool convertOriginal = reducedMember->numPathArcs == getNumMemberArcs(dec, member) - 1;
 
   //TODO: for now very elaborate to first get logic correct. Can probably merge some branches later...
   if( !createPathSeries && !convertOriginal )
   {
      spqr_member parallel;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &parallel) );
      path_arc_id pathArcId = reducedMember->firstPathArc;
      assert(pathArcIsValid(pathArcId));
      spqr_arc marked = newCol->pathArcs[pathArcId].arc;
      assert(marked != markerToParent(dec, member));//TODO: handle this case later
      moveArcToNewMember(dec, marked, member, parallel);
      SCIP_Bool reversed = arcIsReversedNonRigid(dec, marked);
      SCIP_CALL( createMarkerPair(dec, member, parallel, TRUE, reversed, reversed) );
      *loopMember = parallel;
 
      if( reversed == reducedMember->pathBackwards )
      {
         setTerminalReversed(newColInfo, !reversed);
      }
      else
      {
         setTerminalReversed(newColInfo, reversed);
      }
 
      setTerminalMember(newColInfo, *loopMember);
      return SCIP_OKAY;
   }
   if( !createPathSeries && convertOriginal )
   {
      //only one path arc; we are in a loop; no need to change anything
      assert(getNumMemberArcs(dec, member) == 2);
      assert(reducedMember->numPathArcs == 1);
      *loopMember = member;
      changeLoopToParallel(dec, member);
 
      path_arc_id pathArcId = reducedMember->firstPathArc;
      spqr_arc marked = newCol->pathArcs[pathArcId].arc;
      //The 'reversed' field has different meaning for parallels, so we need to change orientation when converting to a parallel
      arcFlipReversed(dec, marked);
 
      setTerminalReversed(newColInfo, reducedMember->pathBackwards);
      setTerminalMember(newColInfo, *loopMember);
      return SCIP_OKAY;
   }
   if( createPathSeries && !convertOriginal )
   {
      spqr_member pathMember;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &pathMember) );
 
      path_arc_id pathArcId = reducedMember->firstPathArc;
      SCIP_Bool parentMoved = FALSE;
      while( pathArcIsValid(pathArcId))
      {
         spqr_arc pathArc = newCol->pathArcs[pathArcId].arc;
         pathArcId = newCol->pathArcs[pathArcId].nextMember;
         if( pathArc == markerToParent(dec, member))
         {
            parentMoved = TRUE;
         }
         moveArcToNewMember(dec, pathArc, member, pathMember);
      }
 
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, loopMember) );
 
      if( !parentMoved )
      {
         SCIP_CALL( createMarkerPair(dec, member, *loopMember, TRUE, FALSE, FALSE) );
         SCIP_CALL( createMarkerPair(dec, *loopMember, pathMember, TRUE, FALSE, TRUE) );
      }
      else
      {
         SCIP_CALL( createMarkerPair(dec, pathMember, *loopMember, FALSE, FALSE, TRUE) );
         SCIP_CALL( createMarkerPair(dec, *loopMember, member, FALSE, FALSE, FALSE) );
      }
 
      setTerminalReversed(newColInfo, !reducedMember->pathBackwards);
      setTerminalMember(newColInfo, *loopMember);
      return SCIP_OKAY;
   }
   assert(createPathSeries && convertOriginal);
   //There's one exception in this case
   //if the single unmarked (column) marker is a parent or child marker to a parallel member, we add the edge there
   {
      spqr_member adjacentMember = SPQR_INVALID_MEMBER;
      spqr_arc adjacentMarker = SPQR_INVALID_ARC;
      spqr_arc memberMarker = SPQR_INVALID_ARC;
      spqr_arc firstArc = getFirstMemberArc(dec, reducedMember->member);
      spqr_arc arc = firstArc;
      do
      {
         if( !newCol->arcInPath[arc] )
         {
            if( arc == markerToParent(dec, reducedMember->member))
            {
               adjacentMember = findMemberParent(dec, reducedMember->member);
               adjacentMarker = markerOfParent(dec, reducedMember->member);
               memberMarker = arc;
            }
            else if( arcIsChildMarker(dec, arc))
            {
               adjacentMember = findArcChildMember(dec, arc);
               adjacentMarker = markerToParent(dec, adjacentMember);
               memberMarker = arc;
            }
 
            break;//There is only a singular such arc
         }
         arc = getNextMemberArc(dec, arc);
      }
      while( arc != firstArc );
 
      if( SPQRmemberIsValid(adjacentMember))
      {
         SPQRMemberType adjacentType = getMemberType(dec, adjacentMember);
         if( adjacentType == SPQR_MEMBERTYPE_PARALLEL )
         {
            //Figure out if the markers are the same or opposite orientations
            //If they are the same, we can proceed as normal, otherwise, we need to flip the placed edge
            SCIP_Bool markersHaveSameOrientation =
               arcIsReversedNonRigid(dec, adjacentMarker) == arcIsReversedNonRigid(dec, memberMarker);
            setTerminalReversed(newColInfo, reducedMember->pathBackwards == markersHaveSameOrientation);
            setTerminalMember(newColInfo, adjacentMember);
            return SCIP_OKAY;
         }
      }
   }
 
   spqr_member pathMember;
   SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &pathMember) );
 
   path_arc_id pathArcId = reducedMember->firstPathArc;
   SCIP_Bool parentMoved = FALSE;
   while( pathArcIsValid(pathArcId))
   {
      spqr_arc pathArc = newCol->pathArcs[pathArcId].arc;
      pathArcId = newCol->pathArcs[pathArcId].nextMember;
      if( pathArc == markerToParent(dec, member))
      {
         parentMoved = TRUE;
      }
      moveArcToNewMember(dec, pathArc, member, pathMember);
   }
   if( parentMoved )
   {
      SCIP_CALL( createMarkerPair(dec, pathMember, member, FALSE, FALSE, FALSE) );
   }
   else
   {
      SCIP_CALL( createMarkerPair(dec, member, pathMember, TRUE, FALSE, FALSE) );
   }
 
   changeLoopToParallel(dec, member);
 
   *loopMember = member;
   setTerminalReversed(newColInfo, reducedMember->pathBackwards);
   setTerminalMember(newColInfo, *loopMember);
   return SCIP_OKAY;
}
 
/** Very elaborate function that splits a series member into multiple members based on the structure of the path arcs.
 *
 * The updated member reflects the structure of the updated SPQR tree after the new column arc is added.
 * This variant is only used on series members that are part of a reduced tree that is not a single member.
 */
static
SCIP_RETCODE splitSeriesMerging(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   SPQRColReducedMember* reducedMember,      /**< The reduced member of the series member to split. */
   spqr_member           member,             /**< The series member to split. */
   spqr_arc*             pathRepresentative, /**< Out pointer pointing to the tree arc in the final series node */
   spqr_arc*             nonPathRepresentative, /**< Out pointer pointing to the non-tree arc in the final series node*/
   spqr_arc              exceptionArc1,      /**< The first exception arc. Set to SPQR_INVALID_ARC to ignore */
   spqr_arc              exceptionArc2       /**< The second exception arc. Set to SPQR_INVALID_ARC to ignore */
   )
{
   assert(dec);
   assert(reducedMember);
   assert(SPQRmemberIsValid(member));
   assert(memberIsRepresentative(dec, member));
 
   int numExceptionArcs = ( exceptionArc1 == SPQR_INVALID_ARC ? 0 : 1 ) + ( exceptionArc2 == SPQR_INVALID_ARC ? 0 : 1 );
   int numNonPathArcs = getNumMemberArcs(dec, member) - reducedMember->numPathArcs - numExceptionArcs;
   SCIP_Bool createPathSeries = reducedMember->numPathArcs > 1;
   //If this holds, there are 2 or more non-parent marker non-path arcs
   SCIP_Bool createNonPathSeries = numNonPathArcs > 1;
   assert(exceptionArc1 == SPQR_INVALID_ARC || !newCol->arcInPath[exceptionArc1]);
   assert(exceptionArc2 == SPQR_INVALID_ARC || !newCol->arcInPath[exceptionArc2]);
 
   if( createPathSeries )
   {
      spqr_member pathMember;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &pathMember) );
 
      path_arc_id pathArcId = reducedMember->firstPathArc;
      SCIP_Bool parentMoved = FALSE;
      while( pathArcIsValid(pathArcId) )
      {
         spqr_arc pathArc = newCol->pathArcs[pathArcId].arc;
         pathArcId = newCol->pathArcs[pathArcId].nextMember;
         assert(pathArc != exceptionArc1 && pathArc != exceptionArc2);
         parentMoved = parentMoved || markerToParent(dec, member) == pathArc;
         moveArcToNewMember(dec, pathArc, member, pathMember);
      }
      assert(getNumMemberArcs(dec, pathMember) >= 2);
 
      spqr_arc ignored;
      SCIP_Bool inOldReversed = TRUE;
      SCIP_Bool inNewReversed = FALSE;
      if( parentMoved )
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, pathMember, member, FALSE, inNewReversed, inOldReversed,
                                                   &ignored, pathRepresentative) );
      }
      else
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, member, pathMember, TRUE, inOldReversed, inNewReversed,
                                                   pathRepresentative, &ignored) );
      }
   }
   else
   {
      if( pathArcIsValid(reducedMember->firstPathArc) )
      {
         *pathRepresentative = newCol->pathArcs[reducedMember->firstPathArc].arc;
      }
      else
      {
         *pathRepresentative = SPQR_INVALID_ARC;
      }
   }
 
   if( createNonPathSeries )
   {
      spqr_member nonPathMember;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &nonPathMember) );
 
      spqr_arc arc = getFirstMemberArc(dec, member);
      SCIP_Bool parentMoved = FALSE;
      SCIP_Bool canStop = FALSE;//hack when the first arc is moved in the below loop to prevent that we immediately terminate
      do
      {
         spqr_arc nextArc = getNextMemberArc(dec, arc);
         if( arc != *pathRepresentative && arc != exceptionArc1 && arc != exceptionArc2 )
         {
            parentMoved = parentMoved || markerToParent(dec, member) == arc;
            moveArcToNewMember(dec, arc, member, nonPathMember);
         }
         else
         {
            canStop = TRUE;
         }
         arc = nextArc;
         if( canStop && arc == getFirstMemberArc(dec, member))
         {
            break;
         }
      }
      while( TRUE ); /*lint !e506*/
      assert(getNumMemberArcs(dec, nonPathMember) >= 2);
      SCIP_Bool representativeIsTree = !arcIsTree(dec, exceptionArc1);
      if( SPQRarcIsValid(exceptionArc2) )
      {
         representativeIsTree = representativeIsTree || !arcIsTree(dec, exceptionArc2);
      }
      spqr_arc ignored;
      SCIP_Bool inOldReversed = TRUE;
      SCIP_Bool inNewReversed = FALSE;
      if( parentMoved )
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, nonPathMember, member, !representativeIsTree,
                                                   inNewReversed, inOldReversed, &ignored, nonPathRepresentative) );
      }
      else
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, member, nonPathMember, representativeIsTree,
                                                   inOldReversed, inNewReversed, nonPathRepresentative, &ignored) );
      }
   }
   else
   {
      *nonPathRepresentative = SPQR_INVALID_ARC;
      if( numNonPathArcs != 0 )
      {
         spqr_arc firstArc = getFirstMemberArc(dec, member);
         spqr_arc arc = firstArc;
         do
         {
            if( arc != *pathRepresentative && arc != exceptionArc1 && arc != exceptionArc2 )
            {
               *nonPathRepresentative = arc;
               break;
            }
            arc = getNextMemberArc(dec, arc);
         }
         while( arc != firstArc );
         assert(*nonPathRepresentative != SPQR_INVALID_ARC);
      }
   }
 
   return SCIP_OKAY;
}
 
/** Transforms the first member in the path of members to reflect the new column update. */
static
SCIP_RETCODE transformFirstPathMember(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMember,      /**< The reduced member to transform */
   NewColInformation*    newColInfo,         /**< The new column information */
   spqr_arc*             representativeArc,  /**< Pointer to the representative of the member, needed for merging.*/
   spqr_member*          mergedMember        /**< Pointer to the merged member */
   )
{
   spqr_member member = newCol->reducedMembers[reducedMember].member;
   SPQRMemberType type = getMemberType(dec, member);
   if( type == SPQR_MEMBERTYPE_RIGID )
   {
      //The nodes are already created, we only need to assign the correct start/end node
      switch( newCol->reducedMembers[reducedMember].pathType )
      {
         case INTO_HEAD:
         case INTO_TAIL:
            setTerminalTail(newColInfo, newCol->reducedMembers[reducedMember].rigidPathStart);
            break;
         case OUT_HEAD:
         case OUT_TAIL:
            setTerminalHead(newColInfo, newCol->reducedMembers[reducedMember].rigidPathEnd);
            break;
      }
      *representativeArc = findArcSign(dec, newCol->reducedMembers[reducedMember].pathTargetArc).representative;
      *mergedMember = member;
 
      return SCIP_OKAY;
   }
   assert(type == SPQR_MEMBERTYPE_SERIES);
   //Split off sets of multiple path non-path edges so that the series has exactly 3 edges
 
   spqr_arc target = newCol->reducedMembers[reducedMember].pathTargetArc;
   SPQRColReducedMember* redMem = &newCol->reducedMembers[reducedMember];
   spqr_arc pathRepresentative = SPQR_INVALID_ARC;
   spqr_arc nonPathRepresentative = SPQR_INVALID_ARC;
   SCIP_CALL( splitSeriesMerging(dec, newCol, redMem, member, &pathRepresentative, &nonPathRepresentative, target,
                                 SPQR_INVALID_ARC) );
 
   assert(
      target != pathRepresentative && target != nonPathRepresentative && pathRepresentative != nonPathRepresentative);
   assert(SPQRarcIsValid(pathRepresentative) && SPQRarcIsValid(nonPathRepresentative) && SPQRarcIsValid(target));
   assert(getNumMemberArcs(dec, member) == 3);
 
   //Create nodes
   spqr_node a = SPQR_INVALID_NODE;
   spqr_node b = SPQR_INVALID_NODE;
   spqr_node c = SPQR_INVALID_NODE;
   SCIP_CALL( createNode(dec, &a) );
   SCIP_CALL( createNode(dec, &b) );
   SCIP_CALL( createNode(dec, &c) );
 
   // a -- b
   //  \  /
   //   c
 
   //Set arc nodes
   //Set target from b to c,
   SCIP_Bool targetReversed = arcIsReversedNonRigid(dec, target);
   setArcHeadAndTail(dec, target, c, b);
 
   MemberPathType pathType = newCol->reducedMembers[reducedMember].pathType;
   assert(pathType == INTO_HEAD || pathType == OUT_HEAD);
   if( arcIsReversedNonRigid(dec, pathRepresentative) == targetReversed )
   {
      setArcHeadAndTail(dec, pathRepresentative, a, c);
   }
   else
   {
      setArcHeadAndTail(dec, pathRepresentative, c, a);
   }
   if( arcIsReversedNonRigid(dec, nonPathRepresentative) == targetReversed )
   {
      setArcHeadAndTail(dec, nonPathRepresentative, b, a);
   }
   else
   {
      setArcHeadAndTail(dec, nonPathRepresentative, a, b);
   }
   //setup signed union find; all arcs are placed are not reversed. We pick an arbitrary arc as 'root' arc for this skeleton
   arcSetReversed(dec, target, FALSE);
   arcSetReversed(dec, pathRepresentative, FALSE);
   arcSetReversed(dec, nonPathRepresentative, FALSE);
   arcSetRepresentative(dec, target, SPQR_INVALID_ARC);
   arcSetRepresentative(dec, pathRepresentative, target);
   arcSetRepresentative(dec, nonPathRepresentative, target);
   *representativeArc = target;
 
   if( pathType == INTO_HEAD )
   {
      setTerminalTail(newColInfo, a);
   }
   else
   {
      setTerminalHead(newColInfo, a);
   }
 
   *mergedMember = member;
 
   return SCIP_OKAY;
}
 
/** Transforms the next parallel member in the path of members and merge it into the current member. */
static
SCIP_RETCODE transformAndMergeParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     current,            /**< The current reduced member id */
   reduced_member_id     next,               /**< The next reduced member */
   spqr_member           nextMember,         /**< The member of the next reduced member in the path */
   SCIP_Bool             nextIsParent,       /**< Is the next reduced member the parent of the current member? */
   spqr_arc*             representativeArc,  /**< Pointer to the representative of the member, needed for merging.*/
   spqr_member*          mergedMember        /**< Pointer to the merged member */
   )
{
   //Split off edges not in current subtree to form one parallel (or one edge)
   spqr_member childParallel = INVALID_REDUCED_MEMBER;
   spqr_arc source = newCol->reducedMembers[next].pathSourceArc;
   spqr_arc target = newCol->reducedMembers[next].pathTargetArc;
   if( getNumMemberArcs(dec, nextMember) > 3 )
   {
      SCIP_CALL( splitParallel(dec, nextMember, source, target, &childParallel) );
      nextMember = childParallel;
      newCol->reducedMembers[next].member = childParallel;
   }
   assert(getNumMemberArcs(dec, nextMember) == 3);
 
   spqr_node sourceHead = SPQR_INVALID_NODE;
   spqr_node sourceTail = SPQR_INVALID_NODE;
   SCIP_CALL( createNode(dec, &sourceHead) );
   SCIP_CALL( createNode(dec, &sourceTail) );
 
   //set edge nodes and arc union-find data
   {
      spqr_arc firstArc = getFirstMemberArc(dec, nextMember);
      spqr_arc arc = firstArc;
 
      SCIP_Bool sourceReversed = arcIsReversedNonRigid(dec, source);
      do
      {
         if( arcIsReversedNonRigid(dec, arc) == sourceReversed )
         {
            setArcHeadAndTail(dec, arc, sourceHead, sourceTail);
         }
         else
         {
            setArcHeadAndTail(dec, arc, sourceTail, sourceHead);
         }
         arcSetRepresentative(dec, arc, source);
         arcSetReversed(dec, arc, FALSE);
 
         arc = getNextMemberArc(dec, arc);
      }
      while( arc != firstArc );
 
      arcSetRepresentative(dec, source, SPQR_INVALID_ARC);
   }
 
   //fix arc orientations of members; we cannot reflect for parallels.
   *representativeArc = mergeArcSigns(dec, *representativeArc, source, FALSE);
 
   spqr_member newMergedMember = SPQR_INVALID_MEMBER;
   if( nextIsParent )
   {
      SCIP_CALL( mergeGivenMemberIntoParent(dec, *mergedMember, nextMember,
                                            source, newCol->reducedMembers[current].pathTargetArc, TRUE,
                                            &newMergedMember) );
   }
   else
   {
      SCIP_CALL( mergeGivenMemberIntoParent(dec, nextMember, *mergedMember,
                                            newCol->reducedMembers[current].pathTargetArc, source, TRUE,
                                            &newMergedMember) );
   }
   *mergedMember = newMergedMember;
 
   return SCIP_OKAY;
}
 
/** Transforms the next series member in the path of members and merge it into the current member. */
static
SCIP_RETCODE transformAndMergeSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     current,            /**< The current reduced member id */
   reduced_member_id     next,               /**< The next reduced member */
   spqr_member           nextMember,         /**< The member of the next reduced member in the path */
   SCIP_Bool             nextIsParent,       /**< Is the next reduced member the parent of the current member? */
   spqr_arc*             representativeArc,  /**< Pointer to the representative of the member, needed for merging.*/
   spqr_member*          mergedMember,       /**< Pointer to the merged member */
   NewColInformation*    info                /**< The new column information */
   )
{
   SPQRColReducedMember* redMem = &newCol->reducedMembers[next];
   spqr_arc source = redMem->pathSourceArc;
   spqr_arc target = redMem->pathTargetArc;
 
   spqr_arc pathRepresentative = SPQR_INVALID_ARC;
   spqr_arc nonPathRepresentative = SPQR_INVALID_ARC;
   SCIP_CALL(
      splitSeriesMerging(dec, newCol, redMem, nextMember, &pathRepresentative, &nonPathRepresentative, source, target) );
   //After splitting there is the following possibilities for nodes a-d:
   //(a)-source-(b)-path-(c)-target-(d)-nonpath-(a)
   //(a)-source-(b)-path-(c)-target-(d==a)
   //(a)-source-(b)=(c)-target-(d)-nonpath-(a)
   //(a)-source-(b)-path-(c)=(d) -nonpath-(a)
   //Note that the given arc is always between the same nodes
   assert(getNumMemberArcs(dec, nextMember) == 3 || getNumMemberArcs(dec, nextMember) == 4);
   assert(pathRepresentative != source && nonPathRepresentative != source &&
          ( SPQRarcIsInvalid(target) || ( target != pathRepresentative && target != nonPathRepresentative )));
   spqr_node a = SPQR_INVALID_NODE;
   spqr_node b = SPQR_INVALID_NODE;
   spqr_node c = SPQR_INVALID_NODE;
   spqr_node d = SPQR_INVALID_NODE;
   SCIP_CALL( createNode(dec, &a) );
   SCIP_CALL( createNode(dec, &b) );
   if( SPQRarcIsValid(pathRepresentative) )
   {
      SCIP_CALL( createNode(dec, &c) );
   }
   else
   {
      c = b;
   }
   SCIP_Bool hasNonPath = SPQRarcIsValid(nonPathRepresentative);
   SCIP_Bool hasTarget = SPQRarcIsValid(target);
   if( hasNonPath && hasTarget )
   {
      SCIP_CALL( createNode(dec, &d) );
   }
   else
   {
      if( hasNonPath )
      {
         d = c;
      }
      else
      {
         d = a;
      }
   }
 
   SCIP_Bool sourceReversed = arcIsReversedNonRigid(dec, source);
   SCIP_Bool pathStartInHead = isHead(newCol->reducedMembers[current].pathType);
   if( pathStartInHead )
   {
      setArcHeadAndTail(dec, source, b, a);
   }
   else
   {
      setArcHeadAndTail(dec, source, a, b);
   }
   if( SPQRarcIsValid(pathRepresentative))
   {
      if( (arcIsReversedNonRigid(dec, pathRepresentative) == sourceReversed) == pathStartInHead )
      {
         setArcHeadAndTail(dec, pathRepresentative, c, b);
      }
      else
      {
         setArcHeadAndTail(dec, pathRepresentative, b, c);
      }
      arcSetReversed(dec, pathRepresentative, FALSE);
      arcSetRepresentative(dec, pathRepresentative, source);
   }
   if( hasTarget )
   {
      if( (arcIsReversedNonRigid(dec, target) == sourceReversed) == pathStartInHead )
      {
         setArcHeadAndTail(dec, target, d, c);
      }
      else
      {
         setArcHeadAndTail(dec, target, c, d);
      }
      arcSetReversed(dec, target, FALSE);
      arcSetRepresentative(dec, target, source);
   }
   if( hasNonPath )
   {
      if( (arcIsReversedNonRigid(dec, nonPathRepresentative) == sourceReversed) == pathStartInHead )
      {
         setArcHeadAndTail(dec, nonPathRepresentative, a, d);
      }
      else
      {
         setArcHeadAndTail(dec, nonPathRepresentative, d, a);
      }
      arcSetReversed(dec, nonPathRepresentative, FALSE);
      arcSetRepresentative(dec, nonPathRepresentative, source);
   }
 
   arcSetReversed(dec, source, FALSE);
   arcSetRepresentative(dec, source, SPQR_INVALID_ARC);
 
   //fix arc orientations of members; we cannot reflect for series
 
   spqr_member newMergedMember = SPQR_INVALID_MEMBER;
   if( nextIsParent )
   {
      SCIP_CALL( mergeGivenMemberIntoParent(dec, *mergedMember, nextMember,
                                            source, newCol->reducedMembers[current].pathTargetArc, TRUE,
                                            &newMergedMember) );
   }
   else
   {
      SCIP_CALL( mergeGivenMemberIntoParent(dec, nextMember, *mergedMember,
                                            newCol->reducedMembers[current].pathTargetArc, source, TRUE,
                                            &newMergedMember) );
   }
   *mergedMember = newMergedMember;
 
   *representativeArc = mergeArcSigns(dec, *representativeArc, source, FALSE);
   if( !hasTarget )
   {
      //We are in the last node; finish the path
      setTerminalReversed(info, FALSE);
      if( isInto(newCol->reducedMembers[current].pathType))
      {
         setTerminalHead(info, c);
      }
      else
      {
         setTerminalTail(info, c);
      }
      setTerminalMember(info, *mergedMember);
      setTerminalRepresentative(info, *representativeArc);
   }
 
   return SCIP_OKAY;
}
 
/** Transforms the next rigid member in the path of members and merge it into the current member. */
static
SCIP_RETCODE transformAndMergeRigid(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     current,            /**< The current reduced member id */
   reduced_member_id     next,               /**< The next reduced member */
   spqr_member           nextMember,         /**< The member of the next reduced member in the path */
   SCIP_Bool             nextIsParent,       /**< Is the next reduced member the parent of the current member? */
   spqr_arc*             representativeArc,  /**< Pointer to the representative of the member, needed for merging.*/
   spqr_member*          mergedMember,       /**< Pointer to the merged member */
   NewColInformation*    info                /**< The new column information */
   )
{
   SPQRColReducedMember* redMem = &newCol->reducedMembers[next];
   spqr_arc source = redMem->pathSourceArc;
   spqr_arc sourceRepresentative = findArcSign(dec, source).representative;
 
   spqr_member newMergedMember = SPQR_INVALID_MEMBER;
 
   if( nextIsParent )
   {
      SCIP_CALL( mergeGivenMemberIntoParent(dec, *mergedMember, nextMember,
                                            source, newCol->reducedMembers[current].pathTargetArc, !redMem->reverseArcs,
                                            &newMergedMember) );
   }
   else
   {
      SCIP_CALL( mergeGivenMemberIntoParent(dec, nextMember, *mergedMember,
                                            newCol->reducedMembers[current].pathTargetArc, source, !redMem->reverseArcs,
                                            &newMergedMember) );
   }
 
   *mergedMember = newMergedMember;
 
   *representativeArc = mergeArcSigns(dec, *representativeArc, sourceRepresentative, redMem->reverseArcs);
 
   if( SPQRarcIsInvalid(redMem->pathTargetArc) )
   {
      //We are in the last node; finish the path
      setTerminalReversed(info, FALSE);
      if( isInto(newCol->reducedMembers[current].pathType) )
      {
         if( redMem->reverseArcs )
         {
            setTerminalHead(info, redMem->rigidPathStart);
         }
         else
         {
            setTerminalHead(info, redMem->rigidPathEnd);
         }
      }
      else
      {
         if( redMem->reverseArcs )
         {
            setTerminalTail(info, redMem->rigidPathEnd);
         }
         else
         {
            setTerminalTail(info, redMem->rigidPathStart);
         }
      }
      setTerminalMember(info, *mergedMember);
      setTerminalRepresentative(info, *representativeArc);
   }
 
   return SCIP_OKAY;
}
 
/** Transforms the next member in the path of members and merge it into the current member. */
static
SCIP_RETCODE transformAndMerge(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     current,            /**< The current reduced member id */
   reduced_member_id     next,               /**< The next reduced member */
   spqr_arc*             representativeArc,  /**< Pointer to the representative of the member, needed for merging.*/
   spqr_member*          mergedMember,       /**< Pointer to the merged member */
   SCIP_Bool             nextIsParent,       /**< Is the next reduced member the parent of the current member? */
   NewColInformation*    info                /**< The new column information */
   )
{
   spqr_member nextMember = newCol->reducedMembers[next].member;
   switch( getMemberType(dec, nextMember) )
   {
      case SPQR_MEMBERTYPE_RIGID:
      {
         SCIP_CALL( transformAndMergeRigid(dec, newCol, current, next, nextMember, nextIsParent,
                                           representativeArc, mergedMember, info) );
         break;
      }
      case SPQR_MEMBERTYPE_PARALLEL:
      {
         SCIP_CALL( transformAndMergeParallel(dec, newCol, current, next, nextMember, nextIsParent,
                                              representativeArc, mergedMember) );
         break;
      }
      case SPQR_MEMBERTYPE_SERIES:
      {
         SCIP_CALL( transformAndMergeSeries(dec, newCol, current, next, nextMember, nextIsParent,
                                            representativeArc, mergedMember, info) );
         break;
      }
      case SPQR_MEMBERTYPE_LOOP:
      case SPQR_MEMBERTYPE_UNASSIGNED:
      {
         SCIPABORT();
         return SCIP_ERROR;
      }
   }
   return SCIP_OKAY;
}
 
/** Transforms a single component when it contains multiple reduced members. */
static
SCIP_RETCODE transformPath(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   SPQRColReducedComponent* component,       /**< The component to transform */
   NewColInformation*    newColInfo          /**< The new column information */
   )
{
   //Realize first member
   reduced_member_id firstPathMember = component->pathEndMembers[0];
 
   spqr_arc representativeArc = SPQR_INVALID_ARC;
   spqr_member mergedMember = SPQR_INVALID_MEMBER;
   SCIP_CALL( transformFirstPathMember(dec, newCol, firstPathMember, newColInfo, &representativeArc, &mergedMember) );
   //Iteratively call function which realizes next member and merges them together.
   reduced_member_id current = firstPathMember;
   reduced_member_id next = newCol->reducedMembers[current].nextPathMember;
   SCIP_Bool nextIsParent = newCol->reducedMembers[current].nextPathMemberIsParent;
   while( reducedMemberIsValid(next) )
   {
      SCIP_CALL(
         transformAndMerge(dec, newCol, current, next, &representativeArc, &mergedMember, nextIsParent, newColInfo));
      current = next;
      next = newCol->reducedMembers[current].nextPathMember;
      nextIsParent = newCol->reducedMembers[current].nextPathMemberIsParent;
   }
 
   return SCIP_OKAY;
}
 
/** Transform a single parallel member to add the new column. */
static
SCIP_RETCODE columnTransformSingleParallel(
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMemberId,    /**< The reduced member to transform */
   spqr_member           member,             /**< The member to transform */
   NewColInformation*    newColInfo          /**< The new column information */
   )
{
   SPQRColReducedMember* reducedMember = &newCol->reducedMembers[reducedMemberId];
   assert(pathArcIsValid(reducedMember->firstPathArc) && reducedMember->numPathArcs == 1);
   //The new arc can be placed in parallel; just add it to this member
   setTerminalReversed(newColInfo, reducedMember->pathBackwards);
   setTerminalMember(newColInfo, member);
 
   return SCIP_OKAY;
}
 
/** Transform a single series member to add the new column. */
static
SCIP_RETCODE columnTransformSingleSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMemberId,    /**< The reduced member to transform */
   spqr_member           member,             /**< The member to transform */
   NewColInformation*    newColInfo          /**< The new column information */
   )
{
   if( getNumMemberArcs(dec, member) == 1 )
   {
      newColInfo->member = member;
      newColInfo->reversed = newCol->arcInPathReversed[getFirstMemberArc(dec, member)];
      return SCIP_OKAY;
   }
   //Isolated single cycle
   spqr_member loopMember;
   SPQRColReducedMember* reducedMember = &newCol->reducedMembers[reducedMemberId];
   SCIP_CALL( splitSeries(dec, newCol, reducedMember, member, &loopMember, newColInfo) );
 
   return SCIP_OKAY;
}
 
/** Transform a single rigid member to add the new column. */
static
SCIP_RETCODE columnTransformSingleRigid(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   reduced_member_id     reducedMemberId,    /**< The reduced member to transform */
   spqr_member           member,             /**< The member to transform */
   NewColInformation*    newColInfo          /**< The new column information */
   )
{
   assert(dec);
   assert(newCol);
   assert(newColInfo);
   assert(reducedMemberIsValid(reducedMemberId));
 
   //The path is already computed, so we can simply take the start and end nodes.
   //However, there is one exception, which is that an arc connecting these two nodes already exists in the member
   //If so, we create a new parallel member with the new arc and this member, unless the existing arc already points
   //to a parallel member
   SPQRColReducedMember* reducedMember = &newCol->reducedMembers[reducedMemberId];
   assert(SPQRnodeIsValid(reducedMember->rigidPathStart) && SPQRnodeIsValid(reducedMember->rigidPathEnd));
   {
      spqr_arc existingArcWithPath = SPQR_INVALID_ARC;
      spqr_arc firstArc = getFirstNodeArc(dec, reducedMember->rigidPathStart);
      spqr_arc arc = firstArc;
      SCIP_Bool pathInSameDirection = FALSE;
      do
      {
         spqr_node head = findArcHead(dec, arc);
         spqr_node tail = findArcTail(dec, arc);
         spqr_node other = head == reducedMember->rigidPathStart ? tail : head;
         if( other == reducedMember->rigidPathEnd )
         {
            existingArcWithPath = arc;
            pathInSameDirection = ( head == other ) != findArcSign(dec, existingArcWithPath).reversed;
            break;
         }
         arc = getNextNodeArc(dec, arc, reducedMember->rigidPathStart);
      }
      while( arc != firstArc );
      if( SPQRarcIsValid(existingArcWithPath) )
      {
         SCIP_Bool isParent = FALSE;
         spqr_member adjacentMember = arcIsChildMarker(dec, existingArcWithPath) ?
                                      findArcChildMember(dec, existingArcWithPath) : SPQR_INVALID_MEMBER;
         if( existingArcWithPath == markerToParent(dec, member) )
         {
            adjacentMember = findMemberParent(dec, member);
            isParent = TRUE;
         }
         if( SPQRmemberIsValid(adjacentMember) && getMemberType(dec, adjacentMember) == SPQR_MEMBERTYPE_PARALLEL )
         {
            spqr_arc parallelMarker = isParent ? markerOfParent(dec, member) : markerToParent(dec, adjacentMember);
            SCIP_Bool markerReversed = arcIsReversedNonRigid(dec, parallelMarker);
            setTerminalMember(newColInfo, adjacentMember);
            setTerminalReversed(newColInfo, markerReversed == pathInSameDirection);
         }
         else
         {
            //create a new parallel and move the edge there
            //This is a bit painful, because we cannot actually remove edges because of the union-find data structure
            //So what we do instead, is convert the current edge to a marker edge, and 'duplicate'
            //it in the new parallel member, and add the new marker there too, manually
            spqr_member adjacentParallel = SPQR_INVALID_MEMBER;
            SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &adjacentParallel) );
            //'duplicate' a new arc in the parallel to be the current arc
            spqr_arc duplicate = SPQR_INVALID_ARC;
            spqr_element element = arcGetElement(dec, existingArcWithPath);
            if( element != MARKER_COLUMN_ELEMENT && element != MARKER_ROW_ELEMENT )
            {
               if( SPQRelementIsColumn(element) )
               {
                  SCIP_CALL( createColumnArc(dec, adjacentParallel, &duplicate, SPQRelementToColumn(element), FALSE) );
               }
               else
               {
                  SCIP_CALL( createRowArc(dec, adjacentParallel, &duplicate, SPQRelementToRow(element), FALSE) );
               }
            }
            else if( isParent )
            {
               SCIP_CALL( createParentMarker(dec, adjacentParallel, arcIsTree(dec, existingArcWithPath), adjacentMember,
                                             markerOfParent(dec, member), &duplicate, FALSE) );
            }
            else
            {
               SCIP_CALL( createChildMarker(dec, adjacentParallel, adjacentMember, arcIsTree(dec, existingArcWithPath),
                                            &duplicate, FALSE) );
               dec->members[adjacentMember].parentMember = adjacentParallel;
               dec->members[adjacentMember].markerOfParent = duplicate;
            }
            //Create the other marker edge
            spqr_arc parallelMarker = SPQR_INVALID_ARC;
            if( isParent )
            {
               SCIP_CALL( createChildMarker(dec, adjacentParallel, member, !arcIsTree(dec, existingArcWithPath),
                                            &parallelMarker, FALSE) );
            }
            else
            {
               SCIP_CALL( createParentMarker(dec, adjacentParallel, !arcIsTree(dec, existingArcWithPath),
                                             member, existingArcWithPath, &parallelMarker, FALSE) );
            }
 
            //Change the existing edge to a marker
            if( isParent )
            {
               assert(markerToParent(dec, member) == existingArcWithPath);
               dec->arcs[markerOfParent(dec, member)].childMember = adjacentParallel;
               dec->members[member].parentMember = adjacentParallel;
               dec->members[member].markerToParent = existingArcWithPath;
               dec->members[member].markerOfParent = parallelMarker;
               dec->arcs[existingArcWithPath].element = arcIsTree(dec, existingArcWithPath) ? MARKER_ROW_ELEMENT
                                                                                            : MARKER_COLUMN_ELEMENT;
               dec->arcs[existingArcWithPath].childMember = adjacentParallel;
            }
            else
            {
               dec->arcs[existingArcWithPath].element = arcIsTree(dec, existingArcWithPath) ? MARKER_ROW_ELEMENT
                                                                                            : MARKER_COLUMN_ELEMENT;
               dec->arcs[existingArcWithPath].childMember = adjacentParallel;
            }
 
            setTerminalMember(newColInfo, adjacentParallel);
            setTerminalReversed(newColInfo, !pathInSameDirection);
         }
         return SCIP_OKAY;
      }
   }
 
   setTerminalMember(newColInfo, member);
   setTerminalReversed(newColInfo, FALSE);
   setTerminalTail(newColInfo, reducedMember->rigidPathStart);
   setTerminalHead(newColInfo, reducedMember->rigidPathEnd);
   setTerminalRepresentative(newColInfo,
                             findArcSign(dec, newCol->pathArcs[reducedMember->firstPathArc].arc).representative);
 
   return SCIP_OKAY;
}
 
/** Transform a component to reflect the new column. */
static
SCIP_RETCODE transformComponent(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol,             /**< The network matrix column addition data structure */
   SPQRColReducedComponent* component,       /**< The component to transform */
   NewColInformation*    newColInfo          /**< The new column information */
   )
{
   assert(dec);
   assert(newCol);
   assert(component);
   assert(newColInfo);
 
   if( newCol->reducedMembers[component->root].numChildren ==
       newCol->reducedMembers[component->root].numPropagatedChildren )
   {
      //No merging necessary, only a single component
      reduced_member_id reducedMember = component->root;
      assert(reducedMemberIsValid(reducedMember));
      spqr_member member = newCol->reducedMembers[reducedMember].member;
      SPQRMemberType type = getMemberType(dec, member);
 
      switch( type )
      {
         case SPQR_MEMBERTYPE_RIGID:
         {
            SCIP_CALL( columnTransformSingleRigid(dec, newCol, reducedMember, member, newColInfo) );
            break;
         }
         case SPQR_MEMBERTYPE_PARALLEL:
         {
            SCIP_CALL( columnTransformSingleParallel(newCol, reducedMember, member, newColInfo) );
            break;
         }
         case SPQR_MEMBERTYPE_LOOP:
         case SPQR_MEMBERTYPE_SERIES:
         {
            SCIP_CALL( columnTransformSingleSeries(dec, newCol, reducedMember, member, newColInfo) );
            break;
         }
         case SPQR_MEMBERTYPE_UNASSIGNED:
         default:
         {
            SCIPABORT();
            return SCIP_ERROR;
         }
      }
      return SCIP_OKAY;
   }
   // Otherwise, the reduced members form a path which can be merged into a single component of type R
   SCIP_CALL( transformPath(dec, newCol, component, newColInfo) );
 
   return SCIP_OKAY;
}
 
/** Check if the submatrix stored remains a network matrix with the new column update. */
static
SCIP_Bool netcoladdRemainsNetwork(
   const SCIP_NETCOLADD* newCol              /**< The network matrix column addition data structure */
   )
{
   return newCol->remainsNetwork;
}
 
/** Add the new column to the network decomposition as an arc.
 *
 * Only use this function after SCIPnetcoladdCheck() has been called.
 */
static
SCIP_RETCODE netcoladdAdd(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETCOLADD*       newCol              /**< The network matrix column addition data structure */
   )
{
   assert(dec);
   assert(newCol);
   assert(netcoladdRemainsNetwork(newCol));
 
   if( newCol->numReducedComponents == 0 )
   {
      spqr_member member;
      SCIP_CALL( createStandaloneSeries(dec, newCol->newRowArcs, newCol->newRowArcReversed,
                                        newCol->numNewRowArcs, newCol->newColIndex, &member) );
   }
   else if( newCol->numReducedComponents == 1 )
   {
      NewColInformation information = NEWCOLINFORMATION_EMPTY;
      SCIP_CALL( transformComponent(dec, newCol, &newCol->reducedComponents[0], &information) );
      assert(memberIsRepresentative(dec, information.member));
      if( newCol->numNewRowArcs == 0 )
      {
         spqr_arc colArc = SPQR_INVALID_ARC;
         SCIP_CALL( createColumnArc(dec, information.member, &colArc, newCol->newColIndex, information.reversed) );
         if( SPQRnodeIsValid(information.head) )
         {
            assert(SPQRnodeIsValid(information.tail));
            assert(SPQRarcIsValid(information.representative));
            setArcHeadAndTail(dec, colArc, findNode(dec, information.head), findNode(dec, information.tail));
            arcSetRepresentative(dec, colArc, information.representative);
            arcSetReversed(dec, colArc, information.reversed != arcIsReversedNonRigid(dec, information.representative));
         }
      }
      else
      {
         spqr_member newSeries = SPQR_INVALID_MEMBER;
         SCIP_CALL( createConnectedSeries(dec, newCol->newRowArcs, newCol->newRowArcReversed, newCol->numNewRowArcs,
                                          newCol->newColIndex, &newSeries) );
         spqr_arc markerArc = SPQR_INVALID_ARC;
         spqr_arc ignore = SPQR_INVALID_ARC;
         SCIP_CALL( createMarkerPairWithReferences(dec, information.member, newSeries, FALSE, information.reversed, TRUE,
                                                   &markerArc, &ignore) );
         if( SPQRnodeIsValid(information.head) )
         {
            assert(SPQRnodeIsValid(information.tail));
            assert(SPQRarcIsValid(information.representative));
            setArcHeadAndTail(dec, markerArc, findNode(dec, information.head), findNode(dec, information.tail));
            arcSetRepresentative(dec, markerArc, information.representative);
            arcSetReversed(dec, markerArc,
                           information.reversed != arcIsReversedNonRigid(dec, information.representative));
         }
      }
      if( getMemberType(dec, information.member) == SPQR_MEMBERTYPE_LOOP )
      {
         assert(getNumMemberArcs(dec, information.member) == 2 || getNumMemberArcs(dec, information.member) == 3);
         if( getNumMemberArcs(dec, information.member) == 3 )
         {
            changeLoopToParallel(dec, information.member);
         }
      }
   }
   else
   {
#ifndef NDEBUG
      int numDecComponentsBefore = numConnectedComponents(dec);
#endif
      spqr_member newSeries = SPQR_INVALID_MEMBER;
      SCIP_CALL( createConnectedSeries(dec, newCol->newRowArcs, newCol->newRowArcReversed,
                                       newCol->numNewRowArcs, newCol->newColIndex, &newSeries) );
      for( int i = 0; i < newCol->numReducedComponents; ++i )
      {
         NewColInformation information = NEWCOLINFORMATION_EMPTY;
         SCIP_CALL( transformComponent(dec, newCol, &newCol->reducedComponents[i], &information) );
         if( getMemberType(dec, information.member) == SPQR_MEMBERTYPE_LOOP )
         {
            assert(getNumMemberArcs(dec, information.member) == 1);
            spqr_arc arc = getFirstMemberArc(dec, information.member);
            assert(newCol->arcInPath[arc]);
            moveArcToNewMember(dec, arc, information.member, newSeries);
            arcSetReversed(dec, arc, !newCol->arcInPathReversed[arc]);
            dec->members[information.member].type = SPQR_MEMBERTYPE_UNASSIGNED;
         }
         else
         {
            reorderComponent(dec, information.member);//reorder the subtree so that the newly series member is a parent
            spqr_arc markerArc = SPQR_INVALID_ARC;
            spqr_arc ignore = SPQR_INVALID_ARC;
            SCIP_CALL( createMarkerPairWithReferences(dec, newSeries, information.member, TRUE, information.reversed,
                                                      TRUE, &ignore, &markerArc) );
            if( SPQRnodeIsValid(information.head) )
            {
               assert(SPQRnodeIsValid(information.tail));
               assert(SPQRarcIsValid(information.representative));
               setArcHeadAndTail(dec, markerArc, findNode(dec, information.head), findNode(dec, information.tail));
               arcSetRepresentative(dec, markerArc, information.representative);
               arcSetReversed(dec, markerArc,
                              information.reversed == arcIsReversedNonRigid(dec, information.representative));
            }
         }
      }
      decreaseNumConnectedComponents(dec, newCol->numReducedComponents - 1);
      assert(numConnectedComponents(dec) == ( numDecComponentsBefore - newCol->numReducedComponents + 1 ));
   }
 
   return SCIP_OKAY;
}
 
/* ---------- END functions for column addition --------------------------------------------------------------------- */
 
/* ---------- START functions for row addition ---------------------------------------------------------------------- */
 
/** Index type for the nonzeros of the new row, e.g. the columns whose tree path must be elongated with the new row */
typedef int cut_arc_id;
#define INVALID_CUT_ARC (-1)
 
/** Checks if the given cut arc is invalid (negative). */
static
SCIP_Bool cutArcIsInvalid(
   const cut_arc_id      arc                 /**< The cut arc to check */
   )
{
   return arc < 0;
}
 
/** Checks if the given cut arc is valid (nonnegative). */
static SCIP_Bool cutArcIsValid(
   const cut_arc_id      arc                 /**< The cut arc to check */
   )
{
   return !cutArcIsInvalid(arc);
}
 
/** Linked list node for the cut arcs.
 *
 * Contains links to the next cut arc in the whole decomposition and the next cut arc in the current member.
 */
typedef struct
{
   spqr_arc              arc;                /**< The arc id */
   spqr_node             arcHead;            /**< The arc's head node */
   spqr_node             arcTail;            /**< The arc's tail node */
   cut_arc_id            nextMember;         /**< Index to next linked list node of the linked list containing the cut arcs
                                                * of the arcs member.*/
   cut_arc_id            nextOverall;        /**< Index to next linked list node of the linked list containing the cut arcs
                                                * of the complete decomposition.*/
   SCIP_Bool             arcReversed;        /**< Should the new row have reverse direction in the cut arcs path? */
} CutArcListNode;
 
/** Type of the reduced member
 *
 * Indicates whether the member is processed, and whether it should be merged or left the same.
 */
typedef enum
{
   TYPE_UNDETERMINED = 0,                    /**< The type of this member has not yet been determined */
   TYPE_PROPAGATED = 1,                      /**< The member contains cut arcs, but should not be merged */
   TYPE_MERGED = 2,                          /**< This member should be merged into a rigid member */
   TYPE_NOT_NETWORK = 3                      /**< This member implies that the addition of the new row
                                                * does not create a network matrix */
} RowReducedMemberType;
 
/** Stores for every vertex information needed for computing articulation nodes in rigid members. */
typedef struct
{
   int                   low;                /**< What is the lowest discovery time vertex that can be reached from this
                                                * subtree?*/
   int                   discoveryTime;      /**< When was the vertex first discovered? */
} ArticulationNodeInformation;
 
/** Call stack data structure for performing DFS on the rigid member graphs. */
typedef struct
{
   spqr_node             node;               /**< The current node of the DFS call */
   spqr_arc              nodeArc;            /**< The current arc of the node that is being processed */
} DFSCallData;
 
/** Call stack data structure for merging the SPQR tree into a single rigid member. */
typedef struct
{
   children_idx          currentChild;       /**< The index of the current child that is being merged */
   reduced_member_id     id;                 /**< The index of the current member */
} MergeTreeCallData;
 
/** Call stack data structure that determines whether a bipartition of the nodes exists that satisfies the requirements. */
typedef struct
{
   spqr_node             node;               /**< The current node of the call */
   spqr_arc              arc;                /**< The current arc that is being processed */
} ColorDFSCallData;
 
/** Call stack data structure for recursive algorithm to find articulation point in rigid member graphs (Tarjan). */
typedef struct
{
   spqr_arc              arc;                /**< The arc that is currently being processed */
   spqr_node             node;               /**< The node that is currently being processed */
   spqr_node             parent;             /**< The node's parent */
   SCIP_Bool             isAP;               /**< Is the current node an articulation point? */
} ArticulationPointCallStack;
 
/** Colors assigned to the node in the partitioning algorithm.
 *
 * It must either be in the source or the sink partition.
 */
typedef enum
{
   UNCOLORED = 0,                            /**< The current node has not yet been processed */
   COLOR_SOURCE = 1,                         /**< The current node belongs to the source partition */
   COLOR_SINK = 2                            /**< The current node belongs to the sink partition */
} COLOR_STATUS;
 
/** Struct that stores the data of a single reduced member. */
typedef struct
{
   spqr_member           member;             /**< The id of the decomposition member */
   spqr_member           rootMember;         /**< The decomposition member that is the root node of the arborescence
                                                * containing this member */
   int                   depth;              /**< The depth of this member in the arborescence */
   RowReducedMemberType  type;               /**< The type of the member */
   reduced_member_id     parent;             /**< The reduced member id of the parent of this reduced member */
 
   children_idx          firstChild;         /**< The index of the first child in the children array. */
   children_idx          numChildren;        /**< The number of children in the arborescence of this reduced member */
   children_idx          numPropagatedChildren; /**< Counts the number of children that are propagated to this reduced
                                                  * member */
 
   cut_arc_id            firstCutArc;        /**< Head of the linked list containing the cut arcs */
   int                   numCutArcs;         /**< The number of cut arcs in the linked list */
 
   spqr_arc              splitArc;           /**< An arc adjacent to the split node. */
   SCIP_Bool             splitHead;          /**< Is the head or the tail of the split arc split in the realization? */
   SCIP_Bool             otherIsSource;      /**< Is the nonsplit node of the split arc in the source or the sink
                                                * partition? In rigid members this refers to the articulation arc. */
 
   /* Rigid member fields */
   spqr_node             otherNode;          /**< The other nonsplit node adjacent to the virtual edge */
   spqr_node             splitNode;          /**< The node to be split */
   SCIP_Bool             allHaveCommonNode;  /**< Do all cut edges share a common node? */
   SCIP_Bool             otherNodeSplit;     /**< Is the other node a split node, too? */
   SCIP_Bool             willBeReversed;     /**< Will all the arcs in this component be reversed? */
   spqr_arc              articulationArc;    /**< Indicates the arc between the split node and the other ndoe, if both
                                                * are splittable. */
   spqr_node             coloredNode;        /**< Points to a colored node so that we can efficiently zero out colors
                                                * by backtracking our DFS */
} SPQRRowReducedMember;
 
/** Keeps track of the data relevant for each SPQR tree in the SPQR forest. */
typedef struct
{
   int                   rootDepth;          /**< The depth of the root node of the subtree in the arborescence */
   reduced_member_id     root;               /**< The reduced member id of the root */
} SPQRRowReducedComponent;
 
/** The main datastructure that manages all the data for row-addition in network matrices */
typedef struct
{
   SCIP_Bool             remainsNetwork;     /**< Does the addition of the current row give a network matrix? */
 
   SPQRRowReducedMember* reducedMembers;     /**< The array of reduced members, that form the subtree containing the
                                                * rows of the current column.*/
   int                   memReducedMembers;  /**< Number of allocated slots in the reduced member array */
   int                   numReducedMembers;  /**< Number of used slots in the reduced member array */
 
   SPQRRowReducedComponent* reducedComponents; /**< The array of reduced components,
                                                  * that represent the SPQR trees in the SPQR forest */
   int                   memReducedComponents; /**< Number of allocated slots in the reduced component array */
   int                   numReducedComponents; /**< Number of used slots in the reduced component array */
 
   MemberInfo*           memberInformation;  /**< Array with member information; tracks the reduced member id that
                                                * corresponds to every member in the decomposition. */
   int                   memMemberInformation; /**< Number of allocated slots in the member information array */
   int                   numMemberInformation; /**< Number of used slots in the member information array */
 
   reduced_member_id*    childrenStorage;    /**< Array that stores the children of the reduced member arborescences.
                                                * Each reduced member has a 'firstChild' field and a length, that points
                                                * to the subarray within this array with its children. This array is
                                                * shared here in order to minimize allocations across iterations. */
   int                   memChildrenStorage; /**< Number of allocated slots for the children storage array */
   int                   numChildrenStorage; /**< Number of used slots for the children storage array */
 
   CutArcListNode*       cutArcs;            /**< Array containing the linked list nodes of the cut arcs */
   int                   memCutArcs;         /**< Number of allocated entries in cutArcs */
   int                   numCutArcs;         /**< Number of used entries in cutArcs */
   cut_arc_id            firstOverallCutArc; /**< Index of the head node of the linked list containing all cut arcs */
 
   spqr_row              newRowIndex;        /**< The index of the new row to be added */
 
   spqr_col*             newColumnArcs;      /**< The nonzero columns in the new row that do not yet occur in the
                                                * decomposition */
   SCIP_Bool*            newColumnReversed;  /**< True if the nonzero entry of the new column is -1, False otherwise */
   int                   memColumnArcs;      /**< Number of allocated slots in newColumnArcs/newColumnReversed */
   int                   numColumnArcs;      /**< Number of new columns in the row to be added */
 
   reduced_member_id*    leafMembers;        /**< Array that stores the leaf members of the SPQR forest */
   int                   numLeafMembers;     /**< Number of used slots in leafMembers array */
   int                   memLeafMembers;     /**< Number of allocated slots in leafMembers array */
 
   spqr_arc*             decompositionColumnArcs;        /**< For each nonzero column of the new row that is in the decomposition,
                                                           * stores the corresponding decomposition arc */
   SCIP_Bool*            decompositionColumnArcReversed; /**< For each nonzero column of the new row that is in the decomposition,
                                                            * stores whether the corresponding decomposition arc is reversed */
   int                   memDecompositionColumnArcs;     /**< Number of allocated slots in decompositionColumnArcs(Reversed) */
   int                   numDecompositionColumnArcs;     /**< Number of used slots in decompositionColumnArcs(Reversed) */
 
   SCIP_Bool*            isArcCut;           /**< Stores for each arc, if the arc a cut arc? */
   SCIP_Bool*            isArcCutReversed;   /**< Is the new row in reverse direction on the arcs cycle? */
   int                   memIsArcCut;        /**< The allocated size of the isArcCut(Reversed) arrays */
 
   COLOR_STATUS*         nodeColors;         /**< Stores the color of each node */
   int                   memNodeColors;      /**< The allocated size of the nodeColors array */
 
   spqr_node*            articulationNodes;    /**< Temp. array for storing articulation nodes of member graph-cut arcs */
   int                   numArticulationNodes; /**< Number of used slots in articulation nodes array */
   int                   memArticulationNodes; /**< Number of allocated slots in articulation nodes array */
 
   ArticulationNodeInformation* articulationNodeSearchInfo; /**< Stores for each node information necessary to find
                                                               * articulation nodes. */
   int                   memNodeSearchInfo;  /**< The number of allocated entries in articulationNodeSearchInfo array*/
 
   int*                  crossingPathCount;    /**< Stores for each arc, how many cut arc cycles contain it */
   int                   memCrossingPathCount; /**< The number of allocated entries for the crossingPathCount array */
 
   DFSCallData*          intersectionDFSData;    /**< Call stack for computing the intersection of all cut arc paths */
   int                   memIntersectionDFSData; /**< Number of allocated entries for intersectionDFSData */
 
   ColorDFSCallData*     colorDFSData;       /**< Call stack for computing source/sink coloring */
   int                   memColorDFSData;    /**< Number of allocated entries for colorDFSData */
 
   ArticulationPointCallStack* artDFSData;   /**< Call stack for computing articulation points */
   int                   memArtDFSData;      /**< Number of allocated entries for artDFSData */
 
   CreateReducedMembersCallstack* createReducedMembersCallstack; /**< Call stack for createReducedMembers() */
   int                   memCreateReducedMembersCallstack;       /**< Number of allocated entries for createReducedMembersCallStack */
 
   int*                  intersectionPathDepth;    /**< Tracks depth of each node in the intersection of all paths algorithm */
   int                   memIntersectionPathDepth; /**< Number of allocated entries in intersectionPathDepth array */
 
   spqr_node*            intersectionPathParent;    /**< Tracks the parents of each node in the intersection of all paths
                                                       * algorithm. */
   int                   memIntersectionPathParent; /**< Number of allocated entries in intersectionPathParent array */
 
   MergeTreeCallData*    mergeTreeCallData;    /**< Call stack for mergeTree */
   int                   memMergeTreeCallData; /**< Number of allocated elements for mergeTreeCallData */
 
   COLOR_STATUS*         temporaryColorArray;    /**< A temporary array used for saving some colors */
   int                   memTemporaryColorArray; /**< The number of allocated elements in temporaryColorArray */
} SCIP_NETROWADD;
 
/** Struct that contains information on how to place the new row arc in the decomposition */
typedef struct
{
   spqr_member           member;             /**< The member to place the new row in */
   spqr_node             head;               /**< The head node of the new row arc (only used for rigid members) */
   spqr_node             tail;               /**< The tail node of the new row arc (only used for rigid members) */
   spqr_arc              representative;     /**< The representative arc of the new row arc */
   SCIP_Bool             reversed;           /**< Orientation of the arc w.r.t. the representative */
} NewRowInformation;
 
#define NEWROWINFORMATION_EMPTY { SPQR_INVALID_MEMBER, SPQR_INVALID_NODE, SPQR_INVALID_NODE, SPQR_INVALID_ARC, FALSE }
 
/** Saves the information of the current row and partitions it based on whether or not the given columns are
 * already part of the decomposition.
 */
static
SCIP_RETCODE newRowUpdateRowInformation(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition datastructure */
   const spqr_row        row,                /**< The row to check */
   const spqr_col*       columns,            /**< The column indices of the nonzeros in the row */
   const double*         columnValues,       /**< The matrix entries of the nonzeros in the row */
   const int             numColumns          /**< The number of nonzeros in the row */
   )
{
   newRow->newRowIndex = row;
 
   newRow->numDecompositionColumnArcs = 0;
   newRow->numColumnArcs = 0;
 
   for( int i = 0; i < numColumns; ++i )
   {
      spqr_arc columnArc = getDecompositionColumnArc(dec, columns[i]);
      SCIP_Bool reversed = columnValues[i] < 0.0;
      if( SPQRarcIsValid(columnArc) )
      {//If the arc is the current decomposition: save it in the array
         if( newRow->numDecompositionColumnArcs == newRow->memDecompositionColumnArcs )
         {
            int newNumArcs = newRow->memDecompositionColumnArcs == 0 ? 8 : 2 * newRow->memDecompositionColumnArcs;
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->decompositionColumnArcs,
                                                   newRow->memDecompositionColumnArcs, newNumArcs) );
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->decompositionColumnArcReversed,
                                                   newRow->memDecompositionColumnArcs, newNumArcs) );
            newRow->memDecompositionColumnArcs = newNumArcs;
         }
         newRow->decompositionColumnArcs[newRow->numDecompositionColumnArcs] = columnArc;
         newRow->decompositionColumnArcReversed[newRow->numDecompositionColumnArcs] = reversed;
         ++newRow->numDecompositionColumnArcs;
      }
      else
      {
         //Not in the decomposition: add it to the set of arcs which are newly added with this row.
         if( newRow->numColumnArcs == newRow->memColumnArcs )
         {
            int newNumArcs = newRow->memColumnArcs == 0 ? 8 : 2 * newRow->memColumnArcs;
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->newColumnArcs,
                                                   newRow->memColumnArcs, newNumArcs) );
            SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->newColumnReversed,
                                                   newRow->memColumnArcs, newNumArcs) );
            newRow->memColumnArcs = newNumArcs;
         }
         newRow->newColumnArcs[newRow->numColumnArcs] = columns[i];
         newRow->newColumnReversed[newRow->numColumnArcs] = reversed;
         newRow->numColumnArcs++;
      }
   }
 
   return SCIP_OKAY;
}
 
/** Adds members to the reduced member tree, by starting at the given member, jumping up to the parent, repeating this
 * procedure until the root has been added.
 */
static
reduced_member_id createRowReducedMembersToRoot(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition datastructure */
   const spqr_member     firstMember         /**< The member to create a reduced member for */
   )
{
   assert(SPQRmemberIsValid(firstMember));
 
   CreateReducedMembersCallstack* callstack = newRow->createReducedMembersCallstack;
   callstack[0].member = firstMember;
   int callDepth = 0;
 
   while( callDepth >= 0 )
   {
      spqr_member member = callstack[callDepth].member;
      reduced_member_id reducedMember = newRow->memberInformation[member].reducedMember;
 
      SCIP_Bool reducedValid = reducedMemberIsValid(reducedMember);
      if( !reducedValid )
      {
         //reduced member was not yet created; we create it
         reducedMember = newRow->numReducedMembers;
 
         SPQRRowReducedMember* reducedMemberData = &newRow->reducedMembers[reducedMember];
         ++newRow->numReducedMembers;
 
         reducedMemberData->member = member;
         reducedMemberData->numChildren = 0;
         reducedMemberData->numCutArcs = 0;
         reducedMemberData->firstCutArc = INVALID_CUT_ARC;
         reducedMemberData->type = TYPE_UNDETERMINED;
         reducedMemberData->numPropagatedChildren = 0;
         reducedMemberData->articulationArc = SPQR_INVALID_ARC;
         reducedMemberData->splitNode = SPQR_INVALID_NODE;
         reducedMemberData->otherNode = SPQR_INVALID_NODE;
         reducedMemberData->splitArc = SPQR_INVALID_ARC;
         reducedMemberData->splitHead = FALSE;
         reducedMemberData->allHaveCommonNode = FALSE;
         reducedMemberData->otherNodeSplit = FALSE;
         reducedMemberData->willBeReversed = FALSE;
         reducedMemberData->coloredNode = SPQR_INVALID_NODE;
 
         newRow->memberInformation[member].reducedMember = reducedMember;
         assert(memberIsRepresentative(dec, member));
         spqr_member parentMember = findMemberParent(dec, member);
 
         if( SPQRmemberIsValid(parentMember) )
         {
            //recursive call to parent member
            ++callDepth;
            assert(callDepth < newRow->memCreateReducedMembersCallstack);
            callstack[callDepth].member = parentMember;
            continue;
         }
         else
         {
            //we found a new reduced decomposition component
 
            reducedMemberData->parent = INVALID_REDUCED_MEMBER;
            reducedMemberData->depth = 0;
            reducedMemberData->rootMember = member;
 
            assert(newRow->numReducedComponents < newRow->memReducedComponents);
            newRow->reducedComponents[newRow->numReducedComponents].root = reducedMember;
            ++newRow->numReducedComponents;
         }
      }
      if( reducedValid )
      {
         assert(reducedMember < newRow->numReducedMembers);
         //Reduced member was already created in earlier call
         //update the depth of the root if appropriate
         reduced_member_id* depthMinimizer = &newRow->memberInformation[newRow->reducedMembers[reducedMember].rootMember].rootDepthMinimizer;
         if( reducedMemberIsInvalid(*depthMinimizer) ||
             newRow->reducedMembers[reducedMember].depth < newRow->reducedMembers[*depthMinimizer].depth )
         {
            *depthMinimizer = reducedMember;
         }
      }
      while( TRUE ) /*lint !e716*/
      {
         --callDepth;
         if( callDepth < 0 )
            break;
         spqr_member parentMember = callstack[callDepth + 1].member;
         reduced_member_id parentReducedMember = newRow->memberInformation[parentMember].reducedMember;
         spqr_member currentMember = callstack[callDepth].member;
         reduced_member_id currentReducedMember = newRow->memberInformation[currentMember].reducedMember;
 
         SPQRRowReducedMember* parentReducedMemberData = &newRow->reducedMembers[parentReducedMember];
         SPQRRowReducedMember* reducedMemberData = &newRow->reducedMembers[currentReducedMember];
 
         reducedMemberData->parent = parentReducedMember;
         reducedMemberData->depth = parentReducedMemberData->depth + 1;
         reducedMemberData->rootMember = parentReducedMemberData->rootMember;
 
         newRow->reducedMembers[parentReducedMember].numChildren++;
      }
   }
 
   reduced_member_id returnedMember = newRow->memberInformation[callstack[0].member].reducedMember;
   return returnedMember;
}
 
 
/** Construct the reduced decomposition, which is the smallest subtree containing all members cut arcs. */
static
SCIP_RETCODE constructRowReducedDecomposition(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition datastructure */
   )
{
#ifndef NDEBUG
   for( int i = 0; i < newRow->memMemberInformation; ++i )
   {
      assert(reducedMemberIsInvalid(newRow->memberInformation[i].reducedMember));
   }
#endif
 
   newRow->numReducedComponents = 0;
   newRow->numReducedMembers = 0;
   if( newRow->numDecompositionColumnArcs == 0 )
   {//Early return in case the reduced decomposition will be empty
      return SCIP_OKAY;
   }
   assert(newRow->numReducedMembers == 0);
   assert(newRow->numReducedComponents == 0);
 
   int newSize = largestMemberID(dec);//Is this sufficient?
   if( newSize > newRow->memReducedMembers )
   {
      int updatedSize = MAX(2 * newRow->memReducedMembers, newSize);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->reducedMembers, newRow->memReducedMembers, updatedSize) );
      newRow->memReducedMembers = updatedSize;
   }
   if( newSize > newRow->memMemberInformation )
   {
      int updatedSize = MAX(2 * newRow->memMemberInformation, newSize);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->memberInformation, newRow->memMemberInformation, updatedSize) );
      for( int i = newRow->memMemberInformation; i < updatedSize; ++i )
      {
         newRow->memberInformation[i].reducedMember = INVALID_REDUCED_MEMBER;
         newRow->memberInformation[i].rootDepthMinimizer = INVALID_REDUCED_MEMBER;
      }
      newRow->memMemberInformation = updatedSize;
   }
 
   int numComponents = numConnectedComponents(dec);
   if( numComponents > newRow->memReducedComponents )
   {
      int updatedSize = MAX(2 * newRow->memReducedComponents, numComponents);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->reducedComponents, newRow->memReducedComponents, updatedSize) );
      newRow->memReducedComponents = updatedSize;
   }
 
   int numMembers = getNumMembers(dec);
   if( newRow->memCreateReducedMembersCallstack < numMembers )
   {
      int updatedSize = MAX(2 * newRow->memCreateReducedMembersCallstack, numMembers);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->createReducedMembersCallstack,
                                             newRow->memCreateReducedMembersCallstack, updatedSize) );
      newRow->memCreateReducedMembersCallstack = updatedSize;
   }
 
   //Create the reduced members (recursively)
   for( int i = 0; i < newRow->numDecompositionColumnArcs; ++i )
   {
      assert(i < newRow->memDecompositionColumnArcs);
      spqr_arc arc = newRow->decompositionColumnArcs[i];
      spqr_member arcMember = findArcMember(dec, arc);
      reduced_member_id reducedMember = createRowReducedMembersToRoot(dec, newRow, arcMember);
      reduced_member_id* depthMinimizer = &newRow->memberInformation[newRow->reducedMembers[reducedMember].rootMember].rootDepthMinimizer;
      if( reducedMemberIsInvalid(*depthMinimizer) )
      {
         *depthMinimizer = reducedMember;
      }
   }
 
   //Set the reduced roots according to the root depth minimizers
   for( int i = 0; i < newRow->numReducedComponents; ++i )
   {
      SPQRRowReducedComponent* component = &newRow->reducedComponents[i];
      spqr_member rootMember = newRow->reducedMembers[component->root].member;
      reduced_member_id reducedMinimizer = newRow->memberInformation[rootMember].rootDepthMinimizer;
      component->rootDepth = newRow->reducedMembers[reducedMinimizer].depth;
      component->root = reducedMinimizer;
 
      //This simplifies code further down which does not need to be component-aware; just pretend that the reduced member is the new root.
      newRow->reducedMembers[component->root].parent = INVALID_REDUCED_MEMBER;
      assert(memberIsRepresentative(dec, rootMember));
   }
 
   //update the children array
   int numTotalChildren = 0;
   for( int i = 0; i < newRow->numReducedMembers; ++i )
   {
      SPQRRowReducedMember* reducedMember = &newRow->reducedMembers[i];
      reduced_member_id minimizer = newRow->memberInformation[reducedMember->rootMember].rootDepthMinimizer;
      if( reducedMember->depth >= newRow->reducedMembers[minimizer].depth )
      {
         reducedMember->firstChild = numTotalChildren;
         numTotalChildren += reducedMember->numChildren;
         reducedMember->numChildren = 0;
      }
   }
 
   if( newRow->memChildrenStorage < numTotalChildren )
   {
      int newMemSize = MAX(newRow->memChildrenStorage * 2, numTotalChildren);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->childrenStorage, newRow->memChildrenStorage,
                                             newMemSize) );
      newRow->memChildrenStorage = newMemSize;
   }
   newRow->numChildrenStorage = numTotalChildren;
 
   //Fill up the children array`
   for( reduced_member_id reducedMember = 0; reducedMember < newRow->numReducedMembers; ++reducedMember )
   {
      SPQRRowReducedMember* reducedMemberData = &newRow->reducedMembers[reducedMember];
      if( reducedMemberData->depth <=
          newRow->reducedMembers[newRow->memberInformation[reducedMemberData->rootMember].rootDepthMinimizer].depth )
      {
         continue;
      }
      spqr_member parentMember = findMemberParent(dec, reducedMemberData->member);
      reduced_member_id parentReducedMember = SPQRmemberIsValid(parentMember)
                                              ? newRow->memberInformation[parentMember].reducedMember
                                              : INVALID_REDUCED_MEMBER;
      if( reducedMemberIsValid(parentReducedMember) )
      {
         SPQRRowReducedMember* parentReducedMemberData = &newRow->reducedMembers[parentReducedMember];
         newRow->childrenStorage[parentReducedMemberData->firstChild +
                                 parentReducedMemberData->numChildren] = reducedMember;
         ++parentReducedMemberData->numChildren;
      }
   }
 
   //Clean up the root depth minimizers.
   for( int i = 0; i < newRow->numReducedMembers; ++i )
   {
      SPQRRowReducedMember* reducedMember = &newRow->reducedMembers[i];
      assert(reducedMember);
      spqr_member rootMember = reducedMember->rootMember;
      assert(rootMember >= 0);
      assert(rootMember < dec->memMembers);
      newRow->memberInformation[rootMember].rootDepthMinimizer = INVALID_REDUCED_MEMBER;
   }
 
   return SCIP_OKAY;
}
 
/** Marks an arc as 'cut'.
 *
 * This implies that its cycle in the decomposition must be elongated.
 */
static
void createCutArc(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition datastructure */
   const spqr_arc        arc,                /**< The arc to mark as a cut arc */
   const reduced_member_id reducedMember,    /**< The reduced member containing the arc */
   SCIP_Bool             reversed            /**< Indicates if the new row entry has +1 or -1 (TRUE) for the arc */
   )
{
   cut_arc_id cut_arc = newRow->numCutArcs;
 
   CutArcListNode* listNode = &newRow->cutArcs[cut_arc];
   listNode->arc = arc;
 
   listNode->nextMember = newRow->reducedMembers[reducedMember].firstCutArc;
   newRow->reducedMembers[reducedMember].firstCutArc = cut_arc;
 
   listNode->nextOverall = newRow->firstOverallCutArc;
   newRow->firstOverallCutArc = cut_arc;
 
   newRow->numCutArcs++;
   newRow->reducedMembers[reducedMember].numCutArcs++;
   assert(newRow->numCutArcs <= newRow->memCutArcs);
 
   assert(arc < newRow->memIsArcCut);
   newRow->isArcCut[arc] = TRUE;
   newRow->isArcCutReversed[arc] = reversed;
 
   assert(memberIsRepresentative(dec, newRow->reducedMembers[reducedMember].member));
   if( getMemberType(dec, newRow->reducedMembers[reducedMember].member) == SPQR_MEMBERTYPE_RIGID )
   {
      listNode->arcHead = findEffectiveArcHead(dec, arc);
      listNode->arcTail = findEffectiveArcTail(dec, arc);
      if( reversed )
      {
         SCIPswapInts(&listNode->arcHead, &listNode->arcTail);
      }
      assert(SPQRnodeIsValid(listNode->arcHead) && SPQRnodeIsValid(listNode->arcTail));
   }
   else
   {
      listNode->arcHead = SPQR_INVALID_NODE;
      listNode->arcTail = SPQR_INVALID_NODE;
   }
 
   listNode->arcReversed = reversed;
}
 
/** Creates all cut arcs within the decomposition for the new row.
 *
 * Note this preallocates memory for cut arcs which may be created by propagation.
 */
static
SCIP_RETCODE createReducedDecompositionCutArcs(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition datastructure */
   )
{
   //Allocate memory for cut arcs
   spqr_arc maxArcID = largestArcID(dec);
   if( maxArcID > newRow->memIsArcCut )
   {
      int newSize = MAX(maxArcID, 2 * newRow->memIsArcCut);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->isArcCut, newRow->memIsArcCut, newSize) );
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->isArcCutReversed, newRow->memIsArcCut, newSize) );
      for( int i = newRow->memIsArcCut; i < newSize; ++i )
      {
         newRow->isArcCut[i] = FALSE;
         newRow->isArcCutReversed[i] = FALSE;
      }
      newRow->memIsArcCut = newSize;
   }
#ifndef NDEBUG
   for( int i = 0; i < newRow->memIsArcCut; ++i )
   {
      assert(!newRow->isArcCut[i]);
      assert(!newRow->isArcCutReversed[i]);
   }
#endif
 
   int numNeededArcs = newRow->numDecompositionColumnArcs * 4;
   if( numNeededArcs > newRow->memCutArcs )
   {
      int newSize = MAX(newRow->memCutArcs * 2, numNeededArcs);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->cutArcs, newRow->memCutArcs, newSize) );
      newRow->memCutArcs = newSize;
   }
   newRow->numCutArcs = 0;
   newRow->firstOverallCutArc = INVALID_CUT_ARC;
   for( int i = 0; i < newRow->numDecompositionColumnArcs; ++i )
   {
      spqr_arc arc = newRow->decompositionColumnArcs[i];
      spqr_member member = findArcMember(dec, arc);
      reduced_member_id reduced_member = newRow->memberInformation[member].reducedMember;
      assert(reducedMemberIsValid(reduced_member));
      createCutArc(dec, newRow, arc, reduced_member, newRow->decompositionColumnArcReversed[i]);
   }
 
   return SCIP_OKAY;
}
 
/** Determines the members of the reduced decomposition which are leafs.
 *
 * This is used in propagation to ensure
 * propagation is only checked for components which have at most one neighbour that is not propagated.
 */
static
SCIP_RETCODE determineLeafReducedMembers(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition datastructure */
   )
{
   if( newRow->numDecompositionColumnArcs > newRow->memLeafMembers )
   {
      int updatedSize = MAX(newRow->numDecompositionColumnArcs, 2 * newRow->memLeafMembers);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->leafMembers, newRow->memLeafMembers, updatedSize) );
      newRow->memLeafMembers = updatedSize;
   }
   newRow->numLeafMembers = 0;
 
   for( reduced_member_id reducedMember = 0; reducedMember < newRow->numReducedMembers; ++reducedMember )
   {
      if( newRow->reducedMembers[reducedMember].numChildren == 0 )
      {
         newRow->leafMembers[newRow->numLeafMembers] = reducedMember;
         ++newRow->numLeafMembers;
      }
   }
 
   return SCIP_OKAY;
}
 
/** Preallocates memory arrays necessary for searching rigid components. */
static
SCIP_RETCODE allocateRigidSearchMemory(
   const SCIP_NETMATDECDATA* dec,            /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition datastructure */
   )
{
   int totalNumNodes = getNumNodes(dec);
   int maxNumNodes = 2 * dec->numArcs;
   if( maxNumNodes > newRow->memNodeColors )
   {
      int newSize = MAX(2 * newRow->memNodeColors, maxNumNodes);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->nodeColors, newRow->memNodeColors, newSize) );
      for( int i = newRow->memNodeColors; i < newSize; ++i )
      {
         newRow->nodeColors[i] = UNCOLORED;
      }
      newRow->memNodeColors = newSize;
   }
 
   if( totalNumNodes > newRow->memArticulationNodes )
   {
      int newSize = MAX(2 * newRow->memArticulationNodes, totalNumNodes);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->articulationNodes, newRow->memArticulationNodes, newSize) );
      newRow->memArticulationNodes = newSize;
   }
   if( totalNumNodes > newRow->memNodeSearchInfo )
   {
      int newSize = MAX(2 * newRow->memNodeSearchInfo, totalNumNodes);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->articulationNodeSearchInfo, newRow->memNodeSearchInfo,
                                             newSize) );
      newRow->memNodeSearchInfo = newSize;
   }
   if( totalNumNodes > newRow->memCrossingPathCount )
   {
      int newSize = MAX(2 * newRow->memCrossingPathCount, totalNumNodes);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->crossingPathCount, newRow->memCrossingPathCount, newSize) );
      newRow->memCrossingPathCount = newSize;
   }
   if( totalNumNodes > newRow->memTemporaryColorArray )
   {
      int newSize = MAX(2 * newRow->memTemporaryColorArray, totalNumNodes);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->temporaryColorArray,
                                             newRow->memTemporaryColorArray, newSize) );
      newRow->memTemporaryColorArray = newSize;
   }
 
   //TODO: see if tradeoff for performance bound by checking max # of nodes of rigid is worth it to reduce size
   //of the following allocations
   int largestID = largestNodeID(dec);
   //TODO: only update the stack sizes of the following when needed? The preallocation may not be worth it.
   if( largestID > newRow->memIntersectionDFSData )
   {
      int newSize = MAX(2 * newRow->memIntersectionDFSData, largestID);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->intersectionDFSData, newRow->memIntersectionDFSData, newSize) );
      newRow->memIntersectionDFSData = newSize;
   }
   if( largestID > newRow->memColorDFSData )
   {
      int newSize = MAX(2 * newRow->memColorDFSData, largestID);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->colorDFSData, newRow->memColorDFSData, newSize) );
      newRow->memColorDFSData = newSize;
   }
   if( largestID > newRow->memArtDFSData )
   {
      int newSize = MAX(2 * newRow->memArtDFSData, largestID);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->artDFSData, newRow->memArtDFSData, newSize) );
      newRow->memArtDFSData = newSize;
   }
 
   for( int i = 0; i < newRow->memIntersectionPathDepth; ++i )
   {
      newRow->intersectionPathDepth[i] = -1;
   }
 
   if( largestID > newRow->memIntersectionPathDepth )
   {
      int newSize = MAX(2 * newRow->memIntersectionPathDepth, largestID);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->intersectionPathDepth, newRow->memIntersectionPathDepth,
                                             newSize) );
      for( int i = newRow->memIntersectionPathDepth; i < newSize; ++i )
      {
         newRow->intersectionPathDepth[i] = -1;
      }
      newRow->memIntersectionPathDepth = newSize;
   }
   for( int i = 0; i < newRow->memIntersectionPathParent; ++i )
   {
      newRow->intersectionPathParent[i] = SPQR_INVALID_NODE;
   }
   if( largestID > newRow->memIntersectionPathParent )
   {
      int newSize = MAX(2 * newRow->memIntersectionPathParent, largestID);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->intersectionPathParent, newRow->memIntersectionPathParent,
                                             newSize) );
      for( int i = newRow->memIntersectionPathParent; i < newSize; ++i )
      {
         newRow->intersectionPathParent[i] = SPQR_INVALID_NODE;
      }
      newRow->memIntersectionPathParent = newSize;
   }
 
   return SCIP_OKAY;
}
 
/** Clears the colors for all nodes.
 *
 * We do DFS in reverse (reverse exploration order), as zeroing out the entire
 * array is more expensive.
 */
static
void zeroOutColors(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition datastructure */
   const spqr_node       firstRemoveNode     /**< The first node that was colored in the original DFS */
   )
{
   assert(firstRemoveNode < newRow->memNodeColors);
 
   newRow->nodeColors[firstRemoveNode] = UNCOLORED;
   ColorDFSCallData* data = newRow->colorDFSData;
   if( newRow->colorDFSData == NULL )
   {
      return;
   }
 
   data[0].node = firstRemoveNode;
   data[0].arc = getFirstNodeArc(dec, firstRemoveNode);
   if( SPQRarcIsInvalid(data[0].arc) )
   {
      return;
   }
 
   int depth = 0;
 
   while( depth >= 0 )
   {
      assert(depth < newRow->memColorDFSData);
      ColorDFSCallData* callData = &data[depth];
      spqr_node head = findArcHead(dec, callData->arc);
      spqr_node tail = findArcTail(dec, callData->arc);
      spqr_node otherNode = callData->node == head ? tail : head;
      assert(otherNode < newRow->memNodeColors);
      if( newRow->nodeColors[otherNode] != UNCOLORED )
      {
         callData->arc = getNextNodeArc(dec, callData->arc, callData->node);
 
         newRow->nodeColors[otherNode] = UNCOLORED;
         ++depth;
         data[depth].node = otherNode;
         data[depth].arc = getFirstNodeArc(dec, otherNode);
         continue;
      }
 
      callData->arc = getNextNodeArc(dec, callData->arc, callData->node);
      while( depth >= 0 && data[depth].arc == getFirstNodeArc(dec, data[depth].node) )
      {
         --depth;
      }
   }
}
 
/** Cleans up various arrays used in previous iterations.
 *
 * This is cheaper than reallocating empty memory.
 */
static
void cleanUpPreviousIteration(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition datastructure */
   )
{
   //zero out coloring information from previous check
   for( int i = 0; i < newRow->numReducedMembers; ++i )
   {
      if( SPQRnodeIsValid(newRow->reducedMembers[i].coloredNode))
      {
         zeroOutColors(dec, newRow, newRow->reducedMembers[i].coloredNode);
      }
   }
 
#ifndef NDEBUG
   for( int i = 0; i < newRow->memNodeColors; ++i )
   {
      assert(newRow->nodeColors[i] == UNCOLORED);
   }
#endif
 
   //For cut arcs: clear them from the array from previous iteration
   cut_arc_id cutArcIdx = newRow->firstOverallCutArc;
   while( cutArcIsValid(cutArcIdx) )
   {
      spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
      cutArcIdx = newRow->cutArcs[cutArcIdx].nextOverall;
      newRow->isArcCut[cutArc] = FALSE;
      newRow->isArcCutReversed[cutArc] = FALSE;
   }
#ifndef NDEBUG
   for( int i = 0; i < newRow->memIsArcCut; ++i )
   {
      assert(!newRow->isArcCut[i]);
      assert(!newRow->isArcCutReversed[i]);
   }
#endif
}
 
/** Finds all the star nodes, i.e. nodes that are adjacent to all cut arcs, in a rigid member. */
static
void rigidFindStarNodes(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheck           /**< The reduced member to check */
   )
{
   //4 cases:
   //Only a single edge; both head/tail are okay => network
   //All are adjacent to a single node, but do not have it as head or tail => not network
   //All are adjacent to a single node, and have it as head or tail => network
   //Not all are adjacent to a single node => check articulation nodes
   assert(newRow->reducedMembers[toCheck].numCutArcs > 0);//calling this function otherwise is nonsensical
 
   cut_arc_id cutArcIdx = newRow->reducedMembers[toCheck].firstCutArc;
   spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
   spqr_node head = findArcHead(dec, cutArc);
   spqr_node tail = findArcTail(dec, cutArc);
 
   SCIP_Bool reverse = findArcSign(dec, cutArc).reversed != newRow->cutArcs[cutArcIdx].arcReversed;
   spqr_node cutArcsHead = reverse ? tail : head;
   spqr_node cutArcsTail = reverse ? head : tail;
 
   if( newRow->reducedMembers[toCheck].numCutArcs == 1 )
   {
      newRow->reducedMembers[toCheck].articulationArc = cutArc;
      newRow->reducedMembers[toCheck].splitNode = cutArcsHead;
      newRow->reducedMembers[toCheck].otherNode = cutArcsTail;
      newRow->reducedMembers[toCheck].otherIsSource = TRUE;
      newRow->reducedMembers[toCheck].allHaveCommonNode = TRUE;
      return;// Only a single cut arc
   }
 
   spqr_node intersectionNodes[2] = {head, tail};
 
   while( cutArcIsValid(newRow->cutArcs[cutArcIdx].nextMember) )
   {
      cutArcIdx = newRow->cutArcs[cutArcIdx].nextMember;
      cutArc = newRow->cutArcs[cutArcIdx].arc;
      head = findArcHead(dec, cutArc);
      tail = findArcTail(dec, cutArc);
      reverse = findArcSign(dec, cutArc).reversed != newRow->cutArcs[cutArcIdx].arcReversed;
      spqr_node effectiveHead = reverse ? tail : head;
      spqr_node effectiveTail = reverse ? head : tail;
      if( effectiveHead != cutArcsHead )
      {
         cutArcsHead = SPQR_INVALID_NODE;
      }
      if( effectiveTail != cutArcsTail )
      {
         cutArcsTail = SPQR_INVALID_NODE;
      }
 
      //intersection between intersectionNodes and head and tail
      for( int i = 0; i < 2; ++i )
      {
         if( intersectionNodes[i] != head && intersectionNodes[i] != tail )
         {
            intersectionNodes[i] = SPQR_INVALID_NODE;
         }
      }
      if( SPQRnodeIsInvalid(intersectionNodes[0]) && SPQRnodeIsInvalid(intersectionNodes[1]) )
      {
         newRow->reducedMembers[toCheck].splitNode = SPQR_INVALID_NODE;
         newRow->reducedMembers[toCheck].allHaveCommonNode = FALSE;
         return;//not all arcs are adjacent to a single node, need to check articulation nodes
      }
   }
   if( SPQRnodeIsInvalid(cutArcsHead) && SPQRnodeIsInvalid(cutArcsTail) )
   {
      //All arcs adjacent to a single node, but not in same direction; not network
      newRow->remainsNetwork = FALSE;
      newRow->reducedMembers[toCheck].type = TYPE_NOT_NETWORK;
      return;
   }
   SCIP_Bool headSplittable = SPQRnodeIsValid(cutArcsHead);
   //Check if the n arcs are in a n+1 degree node; if so, the other endpoint of this non split arc is also splittable
   //By virtue of the spanning tree, this arc must be a tree arc.
   spqr_node splitNode = headSplittable ? cutArcsHead : cutArcsTail;
   newRow->reducedMembers[toCheck].splitNode = splitNode;
   newRow->reducedMembers[toCheck].otherIsSource = headSplittable;
   newRow->reducedMembers[toCheck].allHaveCommonNode = TRUE;
   if( newRow->reducedMembers[toCheck].numCutArcs == nodeDegree(dec, splitNode) - 1 )
   {
      spqr_arc firstNodeArc = getFirstNodeArc(dec, splitNode);
      spqr_arc neighbourArc = firstNodeArc;
      do
      {
         if( arcIsTree(dec, neighbourArc))
         {
            break;
         }
         neighbourArc = getNextNodeArc(dec, neighbourArc, splitNode);
      } while( neighbourArc != firstNodeArc );
 
      newRow->reducedMembers[toCheck].articulationArc = neighbourArc;
      spqr_arc arcHead = findArcHead(dec, neighbourArc);
      newRow->reducedMembers[toCheck].otherNode = arcHead == splitNode ? findArcTail(dec, neighbourArc) : arcHead;
   }
}
 
/** Clears the colors for all nodes, but the neighbours.
 *
 * We do DFS in reverse (reverse exploration order), as zeroing out the entire array is more expensive.
 */
static
void zeroOutColorsExceptNeighbourhood(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const spqr_node       articulationNode,   /**< The node whose neighbours we want to keep */
   const spqr_node       startRemoveNode     /**< The node where DFS started */
   )
{
   COLOR_STATUS* neighbourColors = newRow->temporaryColorArray;
   assert(nodeDegree(dec, articulationNode) <= newRow->memTemporaryColorArray);
   {
      int i = 0;
      spqr_arc artFirstArc = getFirstNodeArc(dec, articulationNode);
      spqr_arc artItArc = artFirstArc;
      do
      {
         spqr_node head = findArcHead(dec, artItArc);
         spqr_node tail = findArcTail(dec, artItArc);
         spqr_node otherNode = articulationNode == head ? tail : head;
         neighbourColors[i] = newRow->nodeColors[otherNode];
         i++;
         assert(i <= nodeDegree(dec, articulationNode));
         artItArc = getNextNodeArc(dec, artItArc, articulationNode);
      }
      while( artItArc != artFirstArc );
   }
   zeroOutColors(dec, newRow, startRemoveNode);
 
   {
      int i = 0;
      spqr_arc artFirstArc = getFirstNodeArc(dec, articulationNode);
      spqr_arc artItArc = artFirstArc;
      do
      {
         spqr_node head = findArcHead(dec, artItArc);
         spqr_node tail = findArcTail(dec, artItArc);
         spqr_node otherNode = articulationNode == head ? tail : head;
         newRow->nodeColors[otherNode] = neighbourColors[i];
         i++;
         assert(i <= nodeDegree(dec, articulationNode));
         artItArc = getNextNodeArc(dec, artItArc, articulationNode);
      }
      while( artItArc != artFirstArc );
   }
}
 
/** Find the intersection of all cut arc paths in the given rigid member.
 *
 * Theoretically, there is a faster algorithm using lowest common ancestor queries, but it is quite complicated.
 * Thus, we stick with the 'simple' version below, which is typically also faster in practice.
 */
static
void intersectionOfAllPaths(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheck,          /**< The rigid member to check */
   int* const            nodeNumPaths        /**< Tracks for each node, how many cut arc paths cross it */
   )
{
   int* intersectionPathDepth = newRow->intersectionPathDepth;
   spqr_node* intersectionPathParent = newRow->intersectionPathParent;
 
   //First do a dfs over the tree, storing all the tree-parents and depths for each node
   //TODO: maybe cache this tree and also update it so we can prevent this DFS call?
 
   //pick an arbitrary node as root; we just use the first cutArc here
   {
      spqr_node root = findArcHead(dec, newRow->cutArcs[newRow->reducedMembers[toCheck].firstCutArc].arc);
      DFSCallData* pathSearchCallStack = newRow->intersectionDFSData;
 
      assert(intersectionPathDepth[root] == -1);
      assert(intersectionPathParent[root] == SPQR_INVALID_NODE);
 
      int pathSearchCallStackSize = 0;
 
      intersectionPathDepth[root] = 0;
      intersectionPathParent[root] = SPQR_INVALID_NODE;
 
      pathSearchCallStack[0].node = root;
      pathSearchCallStack[0].nodeArc = getFirstNodeArc(dec, root);
      pathSearchCallStackSize++;
      while( pathSearchCallStackSize > 0 )
      {
         assert(pathSearchCallStackSize <= newRow->memIntersectionDFSData);
         DFSCallData* dfsData = &pathSearchCallStack[pathSearchCallStackSize - 1];
         //cannot be a tree arc which is its parent
         if( arcIsTree(dec, dfsData->nodeArc) &&
             ( pathSearchCallStackSize <= 1 ||
               dfsData->nodeArc != pathSearchCallStack[pathSearchCallStackSize - 2].nodeArc ) )
         {
            spqr_node head = findArcHeadNoCompression(dec, dfsData->nodeArc);
            spqr_node tail = findArcTailNoCompression(dec, dfsData->nodeArc);
            spqr_node other = head == dfsData->node ? tail : head;
            assert(other != dfsData->node);
 
            //We go up a level: add new node to the call stack
            pathSearchCallStack[pathSearchCallStackSize].node = other;
            pathSearchCallStack[pathSearchCallStackSize].nodeArc = getFirstNodeArc(dec, other);
            //Every time a new node is discovered/added, we update its parent and depth information
            assert(intersectionPathDepth[other] == -1);
            assert(intersectionPathParent[other] == SPQR_INVALID_NODE);
            intersectionPathParent[other] = dfsData->node;
            intersectionPathDepth[other] = pathSearchCallStackSize;
            ++pathSearchCallStackSize;
            continue;
         }
         do
         {
            dfsData->nodeArc = getNextNodeArc(dec, dfsData->nodeArc, dfsData->node);
            if( dfsData->nodeArc == getFirstNodeArc(dec, dfsData->node) )
            {
               --pathSearchCallStackSize;
               dfsData = &pathSearchCallStack[pathSearchCallStackSize - 1];
            }
            else
            {
               break;
            }
         }
         while( pathSearchCallStackSize > 0 );
      }
   }
 
   //For each cut arc, trace back both ends until they meet
   cut_arc_id cutArc = newRow->reducedMembers[toCheck].firstCutArc;
   do
   {
      spqr_arc arc = newRow->cutArcs[cutArc].arc;
      cutArc = newRow->cutArcs[cutArc].nextMember;
 
      //Iteratively jump up to the parents until they reach a common parent
      spqr_node source = findArcHead(dec, arc);
      spqr_node target = findArcTail(dec, arc);
      int sourceDepth = intersectionPathDepth[source];
      int targetDepth = intersectionPathDepth[target];
      nodeNumPaths[source]++;
      nodeNumPaths[target]++;
 
      while( sourceDepth > targetDepth )
      {
         assert(source != target);
         source = intersectionPathParent[source];
         nodeNumPaths[source]++;
         --sourceDepth;
      }
      while( targetDepth > sourceDepth )
      {
         assert(source != target);
         target = intersectionPathParent[target];
         nodeNumPaths[target]++;
         --targetDepth;
      }
      while( source != target && targetDepth >= 0 )
      {
         source = intersectionPathParent[source];
         target = intersectionPathParent[target];
         nodeNumPaths[source]++;
         nodeNumPaths[target]++;
         --targetDepth;
      }
      //In all the above, the lowest common ancestor is increased twice, so we correct for it ad-hoc
      nodeNumPaths[source]--;
      assert(SPQRnodeIsValid(source) && SPQRnodeIsValid(target));
      assert(source == target);
   }
   while( cutArcIsValid(cutArc));
}
 
/** Add a node to array of articulation nodes. */
static
void addArticulationNode(
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   spqr_node             articulationNode    /**< The node to add */
   )
{
#ifndef NDEBUG
   for( int i = 0; i < newRow->numArticulationNodes; ++i )
   {
      assert(newRow->articulationNodes[i] != articulationNode);
   }
#endif
   newRow->articulationNodes[newRow->numArticulationNodes] = articulationNode;
   ++newRow->numArticulationNodes;
}
 
/** Find all the articulation points of the rigid member graph where the cut arcs are removed.
 *
 * Articulation points are nodes whose removal disconnects the remaining graph.
 */
static
void articulationPoints(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   ArticulationNodeInformation* nodeInfo,    /**< Stores information about the found articulation nodes */
   reduced_member_id     reducedMember       /**< The reduced member to find the articulation nodes for */
   )
{
   const SCIP_Bool* arcRemoved = newRow->isArcCut;
 
   int rootChildren = 0;
   spqr_node root_node = findArcHead(dec, getFirstMemberArc(dec, newRow->reducedMembers[reducedMember].member));
 
   ArticulationPointCallStack* callStack = newRow->artDFSData;
 
   int depth = 0;
   int time = 1;
 
   callStack[depth].arc = getFirstNodeArc(dec, root_node);
   callStack[depth].node = root_node;
   callStack[depth].parent = SPQR_INVALID_NODE;
   callStack[depth].isAP = FALSE;
 
   nodeInfo[root_node].low = time;
   nodeInfo[root_node].discoveryTime = time;
 
   while( depth >= 0 )
   {
      if( !arcRemoved[callStack[depth].arc] )
      {
         spqr_node node = callStack[depth].node;
         spqr_node head = findArcHead(dec, callStack[depth].arc);
         spqr_node tail = findArcTail(dec, callStack[depth].arc);
         spqr_node otherNode = node == head ? tail : head;
         if( otherNode != callStack[depth].parent )
         {
            if( nodeInfo[otherNode].discoveryTime == 0 )
            {
               if( depth == 0 )
               {
                  rootChildren++;
               }
               //recursive call
               ++depth;
               assert(depth < newRow->memArtDFSData);
               callStack[depth].parent = node;
               callStack[depth].node = otherNode;
               callStack[depth].arc = getFirstNodeArc(dec, otherNode);
               callStack[depth].isAP = FALSE;
 
               ++time;
               nodeInfo[otherNode].low = time;
               nodeInfo[otherNode].discoveryTime = time;
               continue;
            }
            else
            {
               nodeInfo[node].low = MIN(nodeInfo[node].low, nodeInfo[otherNode].discoveryTime);
            }
         }
      }
 
      while( TRUE ) /*lint !e716*/
      {
         callStack[depth].arc = getNextNodeArc(dec, callStack[depth].arc, callStack[depth].node);
         if( callStack[depth].arc != getFirstNodeArc(dec, callStack[depth].node)) break;
         --depth;
         if( depth < 0 ) break;
 
         spqr_node current_node = callStack[depth].node;
         spqr_node other_node = callStack[depth + 1].node;
         nodeInfo[current_node].low = MIN(nodeInfo[current_node].low, nodeInfo[other_node].low);
         if( depth != 0 &&
             !callStack[depth].isAP &&
             nodeInfo[current_node].discoveryTime <= nodeInfo[other_node].low )
         {
            addArticulationNode(newRow, current_node);
            callStack[depth].isAP = TRUE;
         }
      }
   }
   if( rootChildren > 1 )
   {
      addArticulationNode(newRow, root_node);
   }
}
 
/** For a given articulation node, partitions the rigid member's graph where it is removed into a SOURCE and SINK
 * partition.
 *
 * All cut arcs must point (after reversal) from the source partition to the sink partition. This is akin
 * to finding a 2-coloring, and uses a DFS to do so. This function specifically executes the DFS/recursive part.
 */
static
void rigidConnectedColoringRecursive(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   spqr_node             articulationNode,   /**< The articulation node to obtain the coloring for */
   spqr_node             firstProcessNode,   /**< The first node to process for the DFS */
   COLOR_STATUS          firstColor,         /**< The partition that the first node lies in. */
   SCIP_Bool*            isGood              /**< Returns whether the coloring was consistent */
   )
{
   const SCIP_Bool* isArcCut = newRow->isArcCut;
   COLOR_STATUS* nodeColors = newRow->nodeColors;
   ColorDFSCallData* data = newRow->colorDFSData;
 
   data[0].node = firstProcessNode;
   data[0].arc = getFirstNodeArc(dec, firstProcessNode);
   newRow->nodeColors[firstProcessNode] = firstColor;
 
   int depth = 0;
   while( depth >= 0 )
   {
      assert(depth < newRow->memColorDFSData);
      assert(newRow->nodeColors[articulationNode] == UNCOLORED);
 
      ColorDFSCallData* callData = &data[depth];
      spqr_node head = findArcHead(dec, callData->arc);
      spqr_node tail = findArcTail(dec, callData->arc);
      spqr_node otherNode = callData->node == head ? tail : head;
      COLOR_STATUS currentColor = nodeColors[callData->node];
      COLOR_STATUS otherColor = nodeColors[otherNode];
      //Checks the direction of the arc; in the rest of the algorithm, we just need to check partition
      if( isArcCut[callData->arc] && currentColor != otherColor )
      {
         SCIP_Bool otherIsTail = callData->node == head;
         SCIP_Bool arcReversed = findArcSign(dec, callData->arc).reversed != newRow->isArcCutReversed[callData->arc];
         SCIP_Bool good = ( currentColor == COLOR_SOURCE ) == ( otherIsTail == arcReversed );
         if( !good )
         {
            *isGood = FALSE;
            break;
         }
      }
      if( otherNode != articulationNode )
      {
         if( otherColor == UNCOLORED )
         {
            if( isArcCut[callData->arc] )
            {
               nodeColors[otherNode] = currentColor == COLOR_SOURCE ? COLOR_SINK : COLOR_SOURCE;//reverse the colors
            }
            else
            {
               nodeColors[otherNode] = currentColor;
            }
            callData->arc = getNextNodeArc(dec, callData->arc, callData->node);
 
            depth++;
            assert(depth < newRow->memColorDFSData);
            data[depth].node = otherNode;
            data[depth].arc = getFirstNodeArc(dec, otherNode);
            continue;
         }
         if( isArcCut[callData->arc] != ( currentColor != otherColor ) )
         {
            *isGood = FALSE;
            break;
         }
      }
      callData->arc = getNextNodeArc(dec, callData->arc, callData->node);
      while( depth >= 0 && data[depth].arc == getFirstNodeArc(dec, data[depth].node) )
      {
         --depth;
      }
   }
}
 
/** For a given articulation node, partitions the rigid member's graph where it is removed into a SOURCE and SINK
 * partition.
 *
 * All cut arcs must point (after reversal) from the source partition to the sink partition. This is akin
 * to finding a 2-coloring, and uses a DFS to do so.
 */
static
void rigidConnectedColoring(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id reducedMember,    /**< The rigid member whose graph to color */
   const spqr_node       node,               /**< The articulation node to obtain the coloring for */
   SCIP_Bool* const      isGood              /**< Returns whether the coloring was consistent */
   )
{
   //we should only perform this function if there's more than one cut arc
   assert(newRow->reducedMembers[reducedMember].numCutArcs > 1);
#ifndef NDEBUG
   {
      spqr_member member = newRow->reducedMembers[reducedMember].member;
      spqr_arc firstArc = getFirstMemberArc(dec, member);
      spqr_arc memberArc = firstArc;
      do
      {
         assert(newRow->nodeColors[findArcHeadNoCompression(dec, memberArc)] == UNCOLORED);
         assert(newRow->nodeColors[findArcTailNoCompression(dec, memberArc)] == UNCOLORED);
         memberArc = getNextMemberArc(dec, memberArc);
      }
      while( firstArc != memberArc );
   }
#endif
 
   spqr_node firstProcessNode;
   COLOR_STATUS firstColor;
   {
      cut_arc_id cutArc = newRow->reducedMembers[reducedMember].firstCutArc;
      spqr_arc arc = newRow->cutArcs[cutArc].arc;
      assert(SPQRarcIsValid(arc));
      spqr_node head = findArcHead(dec, arc);
      spqr_node tail = findArcTail(dec, arc);
      if( findArcSign(dec, arc).reversed != newRow->cutArcs[cutArc].arcReversed )
      {
         spqr_node temp = head;
         head = tail;
         tail = temp;
      }
      if( tail != node )
      {
         firstProcessNode = tail;
         firstColor = COLOR_SOURCE;
      }
      else
      {
         assert(head != node);
         firstProcessNode = head;
         firstColor = COLOR_SINK;
      }
   }
   assert(SPQRnodeIsValid(firstProcessNode) && firstProcessNode != node);
   *isGood = TRUE;
   newRow->reducedMembers[reducedMember].coloredNode = firstProcessNode;
   rigidConnectedColoringRecursive(dec, newRow, node, firstProcessNode, firstColor, isGood);
 
   // Need to zero all colors for next attempts if we failed
   if( !( *isGood ) )
   {
      zeroOutColors(dec, newRow, firstProcessNode);
      newRow->reducedMembers[reducedMember].coloredNode = SPQR_INVALID_NODE;
   }
   else
   {
      //Otherwise, we zero out all colors but the ones which we need
      zeroOutColorsExceptNeighbourhood(dec, newRow, node, firstProcessNode);
      newRow->reducedMembers[reducedMember].coloredNode = node;
   }
}
 
/** Given a coloring for an articulation node, we can prove that a neighbouring node is splittable if and only if it is
 * the unique node in the neighbourhood of the articulation node within the SOURCE or SINK partition. In this function,
 * we check for a splittable articulation node if such an adjacent node exists, and return it if possible.
 */
static
spqr_node checkNeighbourColoringArticulationNode(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const spqr_node       articulationNode,   /**< The articulation whose neighbours are to be checked */
   spqr_arc* const       adjacentSplittingArc/**< The arc connecting the two splittable nodes. */
   )
{
   spqr_node firstSideCandidate = SPQR_INVALID_NODE;
   spqr_node secondSideCandidate = SPQR_INVALID_NODE;
   spqr_arc firstSideArc = SPQR_INVALID_ARC;
   spqr_arc secondSideArc = SPQR_INVALID_ARC;
   int numFirstSide = 0;
   int numSecondSide = 0;
 
   spqr_arc firstArc = getFirstNodeArc(dec, articulationNode);
   spqr_arc moveArc = firstArc;
   do
   {
      spqr_node head = findArcHead(dec, moveArc);
      spqr_node tail = findArcTail(dec, moveArc);
      spqr_node otherNode = articulationNode == head ? tail : head;
      assert(newRow->nodeColors[otherNode] != UNCOLORED);
      if(( newRow->nodeColors[otherNode] == COLOR_SOURCE ) != newRow->isArcCut[moveArc] )
      {
         if( numFirstSide == 0 && arcIsTree(dec, moveArc))
         {
            firstSideCandidate = otherNode;
            firstSideArc = moveArc;
         }
         else if( numFirstSide > 0 )
         {
            firstSideCandidate = SPQR_INVALID_NODE;
         }
         ++numFirstSide;
      }
      else
      {
         if( numSecondSide == 0 && arcIsTree(dec, moveArc))
         {
            secondSideCandidate = otherNode;
            secondSideArc = moveArc;
         }
         else if( numSecondSide > 0 )
         {
            secondSideCandidate = SPQR_INVALID_NODE;
         }
         ++numSecondSide;
      }
      moveArc = getNextNodeArc(dec, moveArc, articulationNode);
   }
   while( moveArc != firstArc );
 
   if( numFirstSide == 1 )
   {
      *adjacentSplittingArc = firstSideArc;
      return firstSideCandidate;
   }
   else if( numSecondSide == 1 )
   {
      *adjacentSplittingArc = secondSideArc;
      return secondSideCandidate;
   }
   return SPQR_INVALID_NODE;
}
 
/** Find all the splittable articulation points that lie on the intersection of all cut arc cycles.
 *
 * firstNode and secondNode can be set to limit the nodes that this function checks to the given nodes.
 */
static
void rigidGetSplittableArticulationPointsOnPath(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheck,          /**< The rigid member to check */
   spqr_node             firstNode,          /**< Optional: the first given node that should be checked */
   spqr_node             secondNode          /**< Optional: the second given node that should be checked */
   )
{
   assert(newRow->reducedMembers[toCheck].numCutArcs > 1);
 
   int totalNumNodes = getNumNodes(dec);
   int* nodeNumPaths = newRow->crossingPathCount;
 
   for( int i = 0; i < totalNumNodes; ++i )
   {
      nodeNumPaths[i] = 0;
   }
 
   intersectionOfAllPaths(dec, newRow, toCheck, nodeNumPaths);
 
   newRow->numArticulationNodes = 0;
 
   ArticulationNodeInformation* artNodeInfo = newRow->articulationNodeSearchInfo;
   //TODO: ugly; we clean up over all decomposition nodes for every component
   //clean up can not easily be done in the search, unfortunately
   for( int i = 0; i < totalNumNodes; ++i )
   {
      artNodeInfo[i].low = 0;
      artNodeInfo[i].discoveryTime = 0;
   }
 
   articulationPoints(dec, newRow, artNodeInfo, toCheck);
 
   int numCutArcs = newRow->reducedMembers[toCheck].numCutArcs;
   for( int i = 0; i < newRow->numArticulationNodes; i++ )
   {
      spqr_node articulationNode = newRow->articulationNodes[i];
      assert(nodeIsRepresentative(dec, articulationNode));
      SCIP_Bool isOnPath = nodeNumPaths[articulationNode] == numCutArcs;
      if( isOnPath &&
          (( SPQRnodeIsInvalid(firstNode) && SPQRnodeIsInvalid(secondNode)) || articulationNode == firstNode ||
           articulationNode == secondNode ) )
      {
         SCIP_Bool isGood = TRUE;
         rigidConnectedColoring(dec, newRow, toCheck, articulationNode, &isGood);
         if( !isGood )
         {
            continue;
         }
         newRow->reducedMembers[toCheck].splitNode = articulationNode;
 
         //Once we have found one node, we can (possibly) find another by looking at the coloring of the neighbourhood of it.
 
         spqr_arc adjacentSplittingArc = SPQR_INVALID_ARC;
         spqr_node adjacentSplittingNode = checkNeighbourColoringArticulationNode(dec, newRow, articulationNode,
                                                                                  &adjacentSplittingArc);
 
         //If the neighbour-coloring works, we still need to check that the adjacent node
         //is also an articulation node
         if( SPQRnodeIsValid(adjacentSplittingNode) &&
             (( SPQRnodeIsInvalid(firstNode) && SPQRnodeIsInvalid(secondNode)) || adjacentSplittingNode == firstNode ||
              adjacentSplittingNode == secondNode ) )
         {
            SCIP_Bool isArticulationNode = FALSE;
            for( int j = 0; j < newRow->numArticulationNodes; ++j )
            {
               if( newRow->articulationNodes[j] == adjacentSplittingNode )
               {
                  isArticulationNode = TRUE;
                  break;
               }
            }
            if( isArticulationNode )
            {
               newRow->reducedMembers[toCheck].articulationArc = adjacentSplittingArc;
               newRow->reducedMembers[toCheck].otherNode = adjacentSplittingNode;
               newRow->reducedMembers[toCheck].otherIsSource =
                  newRow->nodeColors[adjacentSplittingNode] == COLOR_SOURCE;
 
               //Cleaning up the colors
               {
                  spqr_arc firstNodeArc = getFirstNodeArc(dec, articulationNode);
                  spqr_arc itArc = firstNodeArc;
                  do
                  {
                     spqr_node head = findArcHead(dec, itArc);
                     spqr_node tail = findArcTail(dec, itArc);
                     spqr_node otherNode = articulationNode == head ? tail : head;
                     newRow->nodeColors[otherNode] = UNCOLORED;
                     itArc = getNextNodeArc(dec, itArc, articulationNode);
                  }
                  while( itArc != firstNodeArc );
               }
            }
         }
         return;
      }
   }
 
   newRow->reducedMembers[toCheck].type = TYPE_NOT_NETWORK;
   newRow->remainsNetwork = FALSE;
}
 
/** Checks if a leaf parallel member can be propagated away from the reduced decomposition. */
static
void determineParallelType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheckMember,    /**< The parallel leaf member to check */
   const spqr_arc        markerToOther,      /**< Marker to the non-leaf member */
   const reduced_member_id otherMember,      /**< The connected non-leaf member */
   const spqr_arc        markerToCheck       /**< Marker from the non-leaf to the leaf parallel member */
   )
{
   SPQRRowReducedMember* member = &newRow->reducedMembers[toCheckMember];
   assert(cutArcIsValid(member->firstCutArc));
 
   SCIP_Bool good = TRUE;
   SCIP_Bool isReversed = TRUE;
   int countedCutArcs = 0;
   for( cut_arc_id cutArc = member->firstCutArc; cutArcIsValid(cutArc);
        cutArc = newRow->cutArcs[cutArc].nextMember )
   {
      spqr_arc arc = newRow->cutArcs[cutArc].arc;
      SCIP_Bool arcIsReversed = arcIsReversedNonRigid(dec, arc) != newRow->cutArcs[cutArc].arcReversed;
      if( countedCutArcs == 0 )
      {
         isReversed = arcIsReversed;
      }
      else if( arcIsReversed != isReversed )
      {
         good = FALSE;
         break;
      }
      ++countedCutArcs;
   }
   if( !good )
   {
      member->type = TYPE_NOT_NETWORK;
      newRow->remainsNetwork = FALSE;
      return;
   }
   //we can only propagate if the marker arc is a tree arc and all other arcs are cut
   if( !arcIsTree(dec, markerToOther) ||
       countedCutArcs != ( getNumMemberArcs(dec, newRow->reducedMembers[toCheckMember].member) - 1 ) )
   {
      //In all other cases, the bond can be split so that the result will be okay!
      newRow->reducedMembers[toCheckMember].type = TYPE_MERGED;
   }
   else
   {
      SCIP_Bool markerIsReversed = arcIsReversedNonRigid(dec, markerToOther);
      createCutArc(dec, newRow, markerToCheck, otherMember, markerIsReversed != isReversed);
      newRow->reducedMembers[toCheckMember].type = TYPE_PROPAGATED;
   }
}
 
/** Checks if a leaf series member can be propagated away from the reduced decomposition. */
static
void determineSeriesType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheckMember,    /**< The series leaf member to check */
   const spqr_arc        markerToOther,      /**< Marker to the non-leaf member */
   const reduced_member_id otherMember,      /**< The connected non-leaf member */
   const spqr_arc        markerToCheck       /**< Marker from the non-leaf to the leaf series member */
   )
{
   //Propagation only calls this function if the arc is tree already, so we do not check it here.
   assert(arcIsTree(dec, markerToOther));
   assert(newRow->reducedMembers[toCheckMember].numCutArcs == 1);
   assert(cutArcIsValid(newRow->reducedMembers[toCheckMember].firstCutArc));
   spqr_arc cutArc = newRow->reducedMembers[toCheckMember].firstCutArc;
   spqr_arc arc = newRow->cutArcs[cutArc].arc;
   newRow->reducedMembers[toCheckMember].type = TYPE_PROPAGATED;
   createCutArc(dec, newRow, markerToCheck, otherMember,
                ( arcIsReversedNonRigid(dec, arc) == arcIsReversedNonRigid(dec, markerToOther)) !=
                newRow->cutArcs[cutArc].arcReversed);
}
 
/** Checks if a leaf rigid member can be propagated away from the reduced decomposition. */
static
void determineRigidType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheckMember,    /**< The rigid leaf member to check */
   const spqr_arc        markerToOther,      /**< Marker to the non-leaf member */
   const reduced_member_id otherMember,      /**< The connected non-leaf member */
   const spqr_arc        markerToCheck       /**< Marker from the non-leaf to the rigid leaf member */
   )
{
   //Checking for propagation only makes sense if there is at least one cut arc
   assert(newRow->reducedMembers[toCheckMember].numCutArcs > 0);
 
   rigidFindStarNodes(dec, newRow, toCheckMember);
   if( !newRow->remainsNetwork )
   {
      return;
   }
   spqr_node markerHead = findArcHead(dec, markerToOther);
   spqr_node markerTail = findArcTail(dec, markerToOther);
   if( findArcSign(dec, markerToOther).reversed )
   {
      spqr_node temp = markerHead;
      markerHead = markerTail;
      markerTail = temp;
   }
   if( SPQRnodeIsInvalid(newRow->reducedMembers[toCheckMember].splitNode) )
   {
      //not a star => attempt to find splittable nodes using articulation node algorithms
      //We save some work by telling the methods that only the marker nodes should be checked
      rigidGetSplittableArticulationPointsOnPath(dec, newRow, toCheckMember, markerHead, markerTail);
   }
   if( !newRow->remainsNetwork )
   {
      return;
   }
 
   if( SPQRarcIsValid(newRow->reducedMembers[toCheckMember].articulationArc) &&
       newRow->reducedMembers[toCheckMember].articulationArc == markerToOther )
   {
      newRow->reducedMembers[toCheckMember].type = TYPE_PROPAGATED;
      SCIP_Bool reverse = ( markerHead == newRow->reducedMembers[toCheckMember].splitNode ) !=
                          newRow->reducedMembers[toCheckMember].otherIsSource;
 
      createCutArc(dec, newRow, markerToCheck, otherMember, reverse);
   }
   else if( newRow->reducedMembers[toCheckMember].splitNode == markerHead ||
            newRow->reducedMembers[toCheckMember].splitNode == markerTail )
   {
      newRow->reducedMembers[toCheckMember].type = TYPE_MERGED;
   }
   else if( SPQRarcIsValid(newRow->reducedMembers[toCheckMember].articulationArc) &&
            ( newRow->reducedMembers[toCheckMember].otherNode == markerHead ||
              newRow->reducedMembers[toCheckMember].otherNode == markerTail ) )
   {
      newRow->reducedMembers[toCheckMember].type = TYPE_MERGED;
   }
   else
   {
      //Found source or sinks, but not adjacent to the marker
      newRow->reducedMembers[toCheckMember].type = TYPE_NOT_NETWORK;
      newRow->remainsNetwork = FALSE;
   }
}
 
/** Checks if a leaf member can be propagated away from the reduced decomposition. */
static
RowReducedMemberType determineType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheckMember,    /**< The leaf member to check */
   const spqr_arc        markerToOther,      /**< Marker to the non-leaf member */
   const reduced_member_id otherMember,      /**< The connected non-leaf member */
   const spqr_arc        markerToCheck       /**< Marker from the non-leaf to the leaf member */
   )
{
   assert(newRow->reducedMembers[toCheckMember].type == TYPE_UNDETERMINED);
   switch( getMemberType(dec, newRow->reducedMembers[toCheckMember].member) )
   {
      case SPQR_MEMBERTYPE_RIGID:
      {
         determineRigidType(dec, newRow, toCheckMember, markerToOther, otherMember, markerToCheck);
         break;
      }
      case SPQR_MEMBERTYPE_LOOP:
      case SPQR_MEMBERTYPE_PARALLEL:
      {
         determineParallelType(dec, newRow, toCheckMember, markerToOther, otherMember, markerToCheck);
         break;
      }
      case SPQR_MEMBERTYPE_SERIES:
      {
         determineSeriesType(dec, newRow, toCheckMember, markerToOther, otherMember, markerToCheck);
         break;
      }
      case SPQR_MEMBERTYPE_UNASSIGNED:
      default:
         newRow->reducedMembers[toCheckMember].type = TYPE_NOT_NETWORK;
         SCIPABORT();
   }
 
   return newRow->reducedMembers[toCheckMember].type;
}
 
/** Propagates away all leaf members that are propagatable to shrink the reduced decomposition. */
static
void propagateComponents(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition data structure */
   )
{
   int leafArrayIndex = 0;
 
   reduced_member_id leaf;
   reduced_member_id next;
 
   while( leafArrayIndex != newRow->numLeafMembers )
   {
      leaf = newRow->leafMembers[leafArrayIndex];
      //next is invalid if the member is not in the reduced decomposition.
      next = newRow->reducedMembers[leaf].parent;
      spqr_arc parentMarker = markerToParent(dec, newRow->reducedMembers[leaf].member);
      if( next != INVALID_REDUCED_MEMBER && arcIsTree(dec, parentMarker) )
      {
         assert(reducedMemberIsValid(next));
         assert(SPQRarcIsValid(parentMarker));
         RowReducedMemberType type = determineType(dec, newRow, leaf, parentMarker, next,
                                                   markerOfParent(dec, newRow->reducedMembers[leaf].member));
         if( type == TYPE_PROPAGATED )
         {
            ++newRow->reducedMembers[next].numPropagatedChildren;
            if( newRow->reducedMembers[next].numPropagatedChildren == newRow->reducedMembers[next].numChildren )
            {
               newRow->leafMembers[leafArrayIndex] = next;
            }
            else
            {
               ++leafArrayIndex;
            }
         }
         else if( type == TYPE_NOT_NETWORK )
         {
            return;
         }
         else
         {
            assert(type == TYPE_MERGED);
            ++leafArrayIndex;
         }
      }
      else
      {
         ++leafArrayIndex;
      }
   }
 
   for( int j = 0; j < newRow->numReducedComponents; ++j )
   {
      //The reduced root might be a leaf as well: we propagate it last
      reduced_member_id root = newRow->reducedComponents[j].root;
 
      while( TRUE ) /*lint !e716*/
      {
         if( newRow->reducedMembers[root].numPropagatedChildren == newRow->reducedMembers[root].numChildren - 1 )
         {
            //TODO: bit ugly, have to do a linear search for the child
            reduced_member_id child = INVALID_REDUCED_MEMBER;
            spqr_arc markerToChild = SPQR_INVALID_ARC;
            for( children_idx i = newRow->reducedMembers[root].firstChild;
                 i < newRow->reducedMembers[root].firstChild + newRow->reducedMembers[root].numChildren; ++i )
            {
               reduced_member_id childReduced = newRow->childrenStorage[i];
               if( newRow->reducedMembers[childReduced].type != TYPE_PROPAGATED )
               {
                  child = childReduced;
                  markerToChild = markerOfParent(dec, newRow->reducedMembers[child].member);
                  break;
               }
            }
            assert(SPQRmemberIsValid(newRow->reducedMembers[child].member));
            assert(SPQRarcIsValid(markerToChild));
            if( !arcIsTree(dec, markerToChild) )
            {
               break;
            }
            RowReducedMemberType type = determineType(dec, newRow, root, markerToChild, child,
                                                      markerToParent(dec, newRow->reducedMembers[child].member));
            if( type == TYPE_PROPAGATED )
            {
               root = child;
            }
            else if( type == TYPE_NOT_NETWORK )
            {
               return;
            }
            else
            {
               break;
            }
         }
         else
         {
            break;
         }
      }
      newRow->reducedComponents[j].root = root;
      newRow->reducedMembers[root].parent = INVALID_REDUCED_MEMBER;
   }
}
 
/** A data structure representing a node pair. */
typedef struct
{
   spqr_node             first;
   spqr_node             second;
} Nodes;
 
/** Computes the intersection nodes of all markers that point to reduced tree members.
 *
 * These are the only nodes that may become Y-splittable, after propagation.
 */
static
Nodes rigidDetermineCandidateNodesFromAdjacentComponents(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id toCheck           /**< The rigid member to check */
   )
{
   Nodes pair;
   pair.first = SPQR_INVALID_NODE;
   pair.second = SPQR_INVALID_NODE;
 
   //take union of children's arcs nodes to find one or two candidates
   for( children_idx i = newRow->reducedMembers[toCheck].firstChild;
        i < newRow->reducedMembers[toCheck].firstChild + newRow->reducedMembers[toCheck].numChildren; ++i )
   {
      reduced_member_id reducedChild = newRow->childrenStorage[i];
      if( newRow->reducedMembers[reducedChild].type != TYPE_PROPAGATED )
      {
         spqr_arc arc = markerOfParent(dec, newRow->reducedMembers[reducedChild].member);
         spqr_node head = findArcHead(dec, arc);
         spqr_node tail = findArcTail(dec, arc);
         if( SPQRnodeIsInvalid(pair.first) && SPQRnodeIsInvalid(pair.second) )
         {
            pair.first = head;
            pair.second = tail;
         }
         else
         {
            if( pair.first != head && pair.first != tail )
            {
               pair.first = SPQR_INVALID_NODE;
            }
            if( pair.second != head && pair.second != tail )
            {
               pair.second = SPQR_INVALID_NODE;
            }
         }
         if( SPQRnodeIsInvalid(pair.first) && SPQRnodeIsInvalid(pair.second) )
         {
            return pair;
         }
      }
   }
   if( reducedMemberIsValid(newRow->reducedMembers[toCheck].parent) &&
       newRow->reducedMembers[newRow->reducedMembers[toCheck].parent].type != TYPE_PROPAGATED )
   {
      spqr_arc arc = markerToParent(dec, newRow->reducedMembers[toCheck].member);
      spqr_node head = findArcHead(dec, arc);
      spqr_node tail = findArcTail(dec, arc);
      if( SPQRnodeIsInvalid(pair.first) && SPQRnodeIsInvalid(pair.second) )
      {
         pair.first = head;
         pair.second = tail;
      }
      else
      {
         if( pair.first != head && pair.first != tail )
         {
            pair.first = SPQR_INVALID_NODE;
         }
         if( pair.second != head && pair.second != tail )
         {
            pair.second = SPQR_INVALID_NODE;
         }
      }
   }
   return pair;
}
 
/** Allocates memory for various procedures that need to do tree-search for rigid members (e.g. DFS or BFS). */
static
SCIP_RETCODE allocateTreeSearchMemory(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition data structure */
   )
{
   int necessarySpace = newRow->numReducedMembers;
   if( necessarySpace > newRow->memMergeTreeCallData )
   {
      int updatedSize = MAX(2 * newRow->memMergeTreeCallData, necessarySpace);
      SCIP_ALLOC( BMSreallocBlockMemoryArray(dec->env, &newRow->mergeTreeCallData, newRow->memMergeTreeCallData,
                                             updatedSize) );
      newRow->memMergeTreeCallData = updatedSize;
   }
   return SCIP_OKAY;
}
 
/** Determine the type of a rigid member when it is the only member in the reduced decomposition. */
static
void determineSingleRowRigidType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedMember       /**< The rigid member to determine the type for */
   )
{
   //Checking for propagation only makes sense if there is at least one cut arc
   assert(newRow->reducedMembers[reducedMember].numCutArcs > 0);
 
   rigidFindStarNodes(dec, newRow, reducedMember);
   if( !newRow->remainsNetwork )
   {
      return;
   }
 
   if( SPQRnodeIsInvalid(newRow->reducedMembers[reducedMember].splitNode) )
   {
      //not a star => attempt to find splittable nodes using articulation node algorithms
      rigidGetSplittableArticulationPointsOnPath(dec, newRow, reducedMember, SPQR_INVALID_NODE, SPQR_INVALID_NODE);
   }
   if( SPQRnodeIsValid(newRow->reducedMembers[reducedMember].splitNode) )
   {
      newRow->reducedMembers[reducedMember].type = TYPE_MERGED;
   }
   else
   {
      newRow->reducedMembers[reducedMember].type = TYPE_NOT_NETWORK;
      newRow->remainsNetwork = FALSE;
   }
}
 
/** Determine the type of a parallel member when it is the only member in the reduced decomposition. */
static
void determineSingleParallelType(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedMember       /**< The parallel member to determine the type for */
   )
{
   SPQRRowReducedMember* redMember = &newRow->reducedMembers[reducedMember];
   assert(cutArcIsValid(redMember->firstCutArc));
 
   SCIP_Bool good = TRUE;
   SCIP_Bool isReversed = TRUE;
   int countedCutArcs = 0;
   for( cut_arc_id cutArc = redMember->firstCutArc; cutArcIsValid(cutArc);
        cutArc = newRow->cutArcs[cutArc].nextMember )
   {
      spqr_arc arc = newRow->cutArcs[cutArc].arc;
      SCIP_Bool arcIsReversed = arcIsReversedNonRigid(dec, arc) != newRow->cutArcs[cutArc].arcReversed;
      if( countedCutArcs == 0 )
      {
         isReversed = arcIsReversed;
      }
      else if( arcIsReversed != isReversed )
      {
         good = FALSE;
         break;
      }
      ++countedCutArcs;
   }
   if( !good )
   {
      redMember->type = TYPE_NOT_NETWORK;
      newRow->remainsNetwork = FALSE;
   }
   else
   {
      redMember->type = TYPE_MERGED;
   }
}
 
/** Determine the type of a series member when it is the only member in the reduced decomposition. */
static
void determineSingleSeriesType(
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedMember       /**< The series member to determine the type for */
   )
{
   assert(newRow->reducedMembers[reducedMember].numCutArcs == 1);
   assert(cutArcIsValid(newRow->reducedMembers[reducedMember].firstCutArc));
   newRow->reducedMembers[reducedMember].type = TYPE_MERGED;
}
 
/** Sets the given split nodes; performs bookkeeping so that we have an easier time updating the graph in many
 * edge cases.
 *
 * Algorithmically speaking, does nothing important.
 */
static
spqr_node determineAndColorSplitNode(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     id,                 /**< The reduced member that we compute the split node for */
   spqr_node             candidateOne,       /**< The first candidate node */
   spqr_node             candidateTwo        /**< The second candidate node */
   )
{
   if( SPQRnodeIsInvalid(newRow->reducedMembers[id].splitNode))
   {
      return SPQR_INVALID_NODE;
   }
   spqr_node splitNode = newRow->reducedMembers[id].splitNode;
   if( splitNode == candidateOne || splitNode == candidateTwo )
   {
      if( newRow->reducedMembers[id].allHaveCommonNode )
      {
         spqr_arc firstNodeArc = getFirstNodeArc(dec, splitNode);
         spqr_arc iterArc = firstNodeArc;
         COLOR_STATUS color = newRow->reducedMembers[id].otherIsSource ? COLOR_SOURCE : COLOR_SINK;
         do
         {
            spqr_node head = findArcHead(dec, iterArc);
            spqr_node other = head == splitNode ? findArcTail(dec, iterArc) : head;
            newRow->nodeColors[other] = color;
            iterArc = getNextNodeArc(dec, iterArc, splitNode);
         }
         while( iterArc != firstNodeArc );
         newRow->reducedMembers[id].coloredNode = splitNode;
      }
      return splitNode;
   }
   splitNode = newRow->reducedMembers[id].otherNode;
   if( SPQRnodeIsInvalid(splitNode) || ( splitNode != candidateOne && splitNode != candidateTwo ) )
   {
      return SPQR_INVALID_NODE;
   }
   assert(SPQRarcIsValid(newRow->reducedMembers[id].articulationArc));
   if( newRow->reducedMembers[id].allHaveCommonNode )
   {
      spqr_arc firstNodeArc = getFirstNodeArc(dec, splitNode);
      spqr_arc iterArc = firstNodeArc;
      COLOR_STATUS color;
      if( newRow->reducedMembers[id].numCutArcs == 1 )
      {
         color = newRow->reducedMembers[id].otherIsSource ? COLOR_SINK : COLOR_SOURCE;
      }
      else
      {
         color = newRow->reducedMembers[id].otherIsSource ? COLOR_SOURCE : COLOR_SINK;
      }
      do
      {
         spqr_node head = findArcHead(dec, iterArc);
         spqr_node other = head == splitNode ? findArcTail(dec, iterArc) : head;
         newRow->nodeColors[other] = color;
         iterArc = getNextNodeArc(dec, iterArc, splitNode);
      }
      while( iterArc != firstNodeArc );
      newRow->nodeColors[newRow->reducedMembers[id].splitNode] = newRow->reducedMembers[id].otherIsSource ? COLOR_SINK
                                                                                                          : COLOR_SOURCE;
   }
   else
   {
      COLOR_STATUS splitColor = newRow->nodeColors[splitNode];
      spqr_arc firstNodeArc = getFirstNodeArc(dec, splitNode);
      spqr_arc iterArc = firstNodeArc;
      do
      {
         spqr_node head = findArcHead(dec, iterArc);
         spqr_node other = head == splitNode ? findArcTail(dec, iterArc) : head;
         newRow->nodeColors[other] = splitColor;
         iterArc = getNextNodeArc(dec, iterArc, splitNode);
      }
      while( iterArc != firstNodeArc );
      newRow->nodeColors[newRow->reducedMembers[id].splitNode] = splitColor == COLOR_SOURCE ? COLOR_SINK : COLOR_SOURCE;
      newRow->nodeColors[splitNode] = UNCOLORED;
   }
 
   newRow->reducedMembers[id].coloredNode = splitNode;
   return splitNode;
}
 
/** After propagation, determines the split type of the first leaf node of the reduced decomposition.
 *
 * The leaf nodes of the decomposition after propagation can only be of type P or R.
 */
static
void determineSplitTypeFirstLeaf(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId           /**< The member to determine the split type for */
   )
{
   spqr_member member = newRow->reducedMembers[reducedId].member;
   SPQRMemberType type = getMemberType(dec, member);
   assert(type == SPQR_MEMBERTYPE_PARALLEL || type == SPQR_MEMBERTYPE_RIGID);
   assert(cutArcIsValid(newRow->reducedMembers[reducedId].firstCutArc));
   SPQRRowReducedMember* redMember = &newRow->reducedMembers[reducedId];
 
   if( type == SPQR_MEMBERTYPE_PARALLEL )
   {
      //TODO: duplicate-ish
 
      SCIP_Bool good = TRUE;
      SCIP_Bool isReversed = TRUE;
      int countedCutArcs = 0;
      for( cut_arc_id cutArc = redMember->firstCutArc; cutArcIsValid(cutArc);
           cutArc = newRow->cutArcs[cutArc].nextMember )
      {
         spqr_arc arc = newRow->cutArcs[cutArc].arc;
         SCIP_Bool arcIsReversed = arcIsReversedNonRigid(dec, arc) != newRow->cutArcs[cutArc].arcReversed;
         if( countedCutArcs == 0 )
         {
            isReversed = arcIsReversed;
         }
         else if( arcIsReversed != isReversed )
         {
            good = FALSE;
            break;
         }
         ++countedCutArcs;
      }
      if( !good )
      {
         redMember->type = TYPE_NOT_NETWORK;
         newRow->remainsNetwork = FALSE;
      }
      else
      {
         spqr_arc marker = markerToParent(dec, member);
         redMember->type = TYPE_MERGED;
         redMember->splitArc = marker;
         redMember->splitHead = TRUE;
         redMember->otherIsSource = arcIsReversedNonRigid(dec, marker) == isReversed;
      }
      return;
   }
   assert(type == SPQR_MEMBERTYPE_RIGID);
 
   spqr_arc marker = markerToParent(dec, member);
   spqr_node markerHead = findArcHead(dec, marker);
   spqr_node markerTail = findArcTail(dec, marker);
   if( findArcSign(dec, marker).reversed )
   {
      spqr_node temp = markerHead;
      markerHead = markerTail;
      markerTail = temp;
   }
 
   if( !SPQRnodeIsValid(newRow->reducedMembers[reducedId].splitNode) )
   {
      //Checking for propagation only makes sense if there is at least one cut arc
      assert(newRow->reducedMembers[reducedId].numCutArcs > 0);
 
      rigidFindStarNodes(dec, newRow, reducedId);
      if( !newRow->remainsNetwork )
      {
         return;
      }
 
      if( SPQRnodeIsInvalid(newRow->reducedMembers[reducedId].splitNode) )
      {
         //not a star => attempt to find splittable nodes using articulation node algorithms
         //We save some work by telling the methods that only the marker nodes should be checked
         rigidGetSplittableArticulationPointsOnPath(dec, newRow, reducedId, markerHead, markerTail);
      }
      if( !newRow->remainsNetwork )
      {
         return;
      }
      if( SPQRnodeIsInvalid(newRow->reducedMembers[reducedId].splitNode) )
      {
         redMember->type = TYPE_NOT_NETWORK;
         newRow->remainsNetwork = FALSE;
         return;
      }
   }
 
   spqr_node splitNode = newRow->reducedMembers[reducedId].splitNode;
#ifndef NDEBUG
   spqr_node otherNode = newRow->reducedMembers[reducedId].otherNode;
#endif
   //We cannot have both splittable (should have been propagated)
   assert(!(( splitNode == markerTail || splitNode == markerHead ) &&
            ( otherNode == markerTail || otherNode == markerHead )));
 
   splitNode = determineAndColorSplitNode(dec, newRow, reducedId, markerHead, markerTail);
   if( SPQRnodeIsInvalid(splitNode) )
   {
      redMember->type = TYPE_NOT_NETWORK;
      newRow->remainsNetwork = FALSE;
      return;
   }
   assert(splitNode == markerHead || splitNode == markerTail);
 
   newRow->reducedMembers[reducedId].splitNode = splitNode;
   newRow->reducedMembers[reducedId].willBeReversed = FALSE;
   redMember->type = TYPE_MERGED;
}
 
/** A data structure that tells us if the head or tail of a marked arc is split, and if the other node is in the
 * source or the sink partition.
 */
typedef struct
{
   SCIP_Bool             headSplit;          /**< Is the head or tail of the marked arc split?*/
   SCIP_Bool             otherIsSource;      /**< Is the non-split node in the source or sink partition? */
} SplitOrientation;
 
/** Get the split orientation for a given rigid member and marked arc. */
static
SplitOrientation getRelativeOrientationRigid(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId,          /**< The member to determine the split orientation for */
   spqr_arc              arcToNext           /**< The marked arc to determine the orientation for */
   )
{
   assert(findArcMemberNoCompression(dec, arcToNext) == newRow->reducedMembers[reducedId].member);
   assert(SPQRnodeIsValid(newRow->reducedMembers[reducedId].splitNode));
 
   SplitOrientation orientation;
   if( newRow->reducedMembers[reducedId].numCutArcs == 0 )
   {
      spqr_node splitNode = newRow->reducedMembers[reducedId].splitNode;
      spqr_node head = findEffectiveArcHead(dec, arcToNext);
 
      assert(head == splitNode || splitNode == findEffectiveArcTailNoCompression(dec, arcToNext));
 
      orientation.headSplit = newRow->reducedMembers[reducedId].willBeReversed == ( head != splitNode );
      orientation.otherIsSource = newRow->reducedMembers[reducedId].otherIsSource;
      return orientation;
   }
   spqr_node splitNode = newRow->reducedMembers[reducedId].splitNode;
   spqr_node arcHead = findArcHead(dec, arcToNext);
   spqr_node arcTail = findArcTail(dec, arcToNext);
   if( findArcSign(dec, arcToNext).reversed )
   {
      spqr_node temp = arcHead;
      arcHead = arcTail;
      arcTail = temp;
   }
   assert(arcHead == splitNode || arcTail == splitNode);
   spqr_node other = arcHead == splitNode ? arcTail : arcHead;
 
   assert(newRow->nodeColors[other] == COLOR_SOURCE || newRow->nodeColors[other] == COLOR_SINK);
 
   if( newRow->reducedMembers[reducedId].willBeReversed )
   {
      orientation.headSplit = arcHead != splitNode;
      orientation.otherIsSource = newRow->nodeColors[other] != COLOR_SOURCE;
   }
   else
   {
      orientation.headSplit = arcHead == splitNode;
      orientation.otherIsSource = newRow->nodeColors[other] == COLOR_SOURCE;
   }
   return orientation;
}
 
/** Get the split orientation for a given parallel member and marked arc. */
static
SplitOrientation getRelativeOrientationParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId,          /**< The member to determine the split orientation for */
   spqr_arc              arcToNext           /**< The marked arc to determine the orientaiton for */
   )
{
   assert(findArcMemberNoCompression(dec, arcToNext) == newRow->reducedMembers[reducedId].member);
   assert(SPQRarcIsValid(newRow->reducedMembers[reducedId].splitArc) && SPQRarcIsValid(arcToNext));
 
   SplitOrientation orientation;
   orientation.otherIsSource = newRow->reducedMembers[reducedId].otherIsSource;
   if( arcIsReversedNonRigid(dec, arcToNext) == arcIsReversedNonRigid(dec, newRow->reducedMembers[reducedId].splitArc))
   {
      orientation.headSplit = newRow->reducedMembers[reducedId].splitHead;
   }
   else
   {
      orientation.headSplit = !newRow->reducedMembers[reducedId].splitHead;
   }
   return orientation;
}
 
/** Get the split orientation for a given series member and marked arc. */
static
SplitOrientation getRelativeOrientationSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId,          /**< The member to determine the split orientation for */
   spqr_arc              arcToNext           /**< The marked arc to determine the orientaiton for */
   )
{
   assert(findArcMemberNoCompression(dec, arcToNext) == newRow->reducedMembers[reducedId].member);
   assert(SPQRarcIsValid(newRow->reducedMembers[reducedId].splitArc) && SPQRarcIsValid(arcToNext));
 
   SplitOrientation orientation;
   orientation.otherIsSource = newRow->reducedMembers[reducedId].otherIsSource;
   if( arcIsReversedNonRigid(dec, arcToNext) == arcIsReversedNonRigid(dec, newRow->reducedMembers[reducedId].splitArc))
   {
      orientation.headSplit = !newRow->reducedMembers[reducedId].splitHead;
   }
   else
   {
      orientation.headSplit = newRow->reducedMembers[reducedId].splitHead;
   }
   return orientation;
}
 
/** Get the split orientation for a given member and marked arc. */
static
SplitOrientation getRelativeOrientation(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId,          /**< The member to determine the split orientation for */
   spqr_arc              arcToNext           /**< The marked arc to determine the orientaiton for */
   )
{
   switch( getMemberType(dec, newRow->reducedMembers[reducedId].member) )
   {
      case SPQR_MEMBERTYPE_RIGID:
         return getRelativeOrientationRigid(dec, newRow, reducedId, arcToNext);
      case SPQR_MEMBERTYPE_PARALLEL:
         return getRelativeOrientationParallel(dec, newRow, reducedId, arcToNext);
      case SPQR_MEMBERTYPE_SERIES:
         return getRelativeOrientationSeries(dec, newRow, reducedId, arcToNext);
      case SPQR_MEMBERTYPE_LOOP:
      case SPQR_MEMBERTYPE_UNASSIGNED:
      default:
      {
         SCIPABORT();
         SplitOrientation orientation; /*lint !e527*/
         orientation.headSplit = FALSE; /*lint !e527*/
         orientation.otherIsSource = FALSE;
         return orientation;
      }
   }
}
 
/** Determine the split type of a series node when the SPQR tree is not a singular member. */
static
void determineSplitTypeSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId,          /**< The member to determine the split orientation for */
   spqr_arc              marker,             /**< The marker to the previous member whose type was already determined */
   SplitOrientation      previousOrientation /**< The orientation to the previous member */
   )
{
   int numAdjacentMembers =
      newRow->reducedMembers[reducedId].numChildren - newRow->reducedMembers[reducedId].numPropagatedChildren;
   if( reducedMemberIsValid(newRow->reducedMembers[reducedId].parent) &&
       newRow->reducedMembers[newRow->reducedMembers[reducedId].parent].type != TYPE_PROPAGATED )
   {
      ++numAdjacentMembers;
   }
   assert(numAdjacentMembers > 1);
   if( numAdjacentMembers > 2 )
   {
      newRow->remainsNetwork = FALSE;
      newRow->reducedMembers[reducedId].type = TYPE_NOT_NETWORK;
      return;
   }
   cut_arc_id cutArc = newRow->reducedMembers[reducedId].firstCutArc;
   if( cutArcIsValid(cutArc) )
   {
      spqr_arc arc = newRow->cutArcs[cutArc].arc;
      SCIP_Bool good = ((( arcIsReversedNonRigid(dec, arc) == arcIsReversedNonRigid(dec, marker)) ==
                         newRow->cutArcs[cutArc].arcReversed ) == previousOrientation.headSplit ) ==
                       previousOrientation.otherIsSource;
      if( !good )
      {
         newRow->remainsNetwork = FALSE;
         newRow->reducedMembers[reducedId].type = TYPE_NOT_NETWORK;
         return;
      }
      newRow->reducedMembers[reducedId].splitArc = marker;
      newRow->reducedMembers[reducedId].splitHead = previousOrientation.headSplit;
      newRow->reducedMembers[reducedId].otherIsSource = !previousOrientation.otherIsSource;
      newRow->reducedMembers[reducedId].type = TYPE_MERGED;
      return;
   }
 
   newRow->reducedMembers[reducedId].splitArc = marker;
   newRow->reducedMembers[reducedId].splitHead = previousOrientation.headSplit;
   newRow->reducedMembers[reducedId].otherIsSource = previousOrientation.otherIsSource;
   newRow->reducedMembers[reducedId].type = TYPE_MERGED;
}
 
/** Determine the split type of a parallel node when the SPQR tree is not a singular member. */
static
void determineSplitTypeParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId,          /**< The member to determine the split orientation for */
   spqr_arc              marker,             /**< The marker to the previous member whose type was already determined */
   SplitOrientation      previousOrientation /**< The orientation to the previous member */
   )
{
   SPQRRowReducedMember* redMember = &newRow->reducedMembers[reducedId];
 
   SCIP_Bool good = TRUE;
   SCIP_Bool isReversed = TRUE;
   int countedCutArcs = 0;
   for( cut_arc_id cutArc = redMember->firstCutArc; cutArcIsValid(cutArc);
        cutArc = newRow->cutArcs[cutArc].nextMember )
   {
      spqr_arc arc = newRow->cutArcs[cutArc].arc;
      SCIP_Bool arcIsReversed = arcIsReversedNonRigid(dec, arc) != newRow->cutArcs[cutArc].arcReversed;
      if( countedCutArcs == 0 )
      {
         isReversed = arcIsReversed;
      }
      else if( arcIsReversed != isReversed )
      {
         good = FALSE;
         break;
      }
      ++countedCutArcs;
   }
   if( !good )
   {
      redMember->type = TYPE_NOT_NETWORK;
      newRow->remainsNetwork = FALSE;
      return;
   }
   if( countedCutArcs == 0 )
   {
      redMember->splitArc = marker;
      redMember->splitHead = previousOrientation.headSplit;
      redMember->otherIsSource = previousOrientation.otherIsSource;
      redMember->type = TYPE_MERGED;
      return;
   }
   SCIP_Bool isHeadSourceOrTailTarget = previousOrientation.headSplit == previousOrientation.otherIsSource;
   SCIP_Bool isOkay = isHeadSourceOrTailTarget == ( isReversed == arcIsReversedNonRigid(dec, marker));
   if( !isOkay )
   {
      redMember->type = TYPE_NOT_NETWORK;
      newRow->remainsNetwork = FALSE;
      return;
   }
   redMember->splitArc = marker;
   redMember->splitHead = previousOrientation.headSplit;
   redMember->otherIsSource = previousOrientation.otherIsSource;
   redMember->type = TYPE_MERGED;
}
 
/** Determine the split type of a rigid node when the SPQR tree is not a singular member. */
static
void determineSplitTypeRigid(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedId,          /**< The reduced member to determine the split orientation for */
   spqr_member           member,             /**< The member belonging to the reduced member */
   spqr_arc              marker,             /**< The marker to the previous member whose type was already determined */
   SplitOrientation      previousOrientation /**< The orientation to the previous member */
   )
{
   assert(dec);
   assert(newRow);
   assert(getMemberType(dec, member) == SPQR_MEMBERTYPE_RIGID);
 
   Nodes nodes = rigidDetermineCandidateNodesFromAdjacentComponents(dec, newRow, reducedId);
   if( SPQRnodeIsInvalid(nodes.first) && SPQRnodeIsInvalid(nodes.second) )
   {
      newRow->remainsNetwork = FALSE;
      newRow->reducedMembers[reducedId].type = TYPE_NOT_NETWORK;
      return;
   }
   if( SPQRnodeIsInvalid(nodes.first) && SPQRnodeIsValid(nodes.second) )
   {
      nodes.first = nodes.second;
      nodes.second = SPQR_INVALID_NODE;
   }
 
   spqr_node markerHead = findArcHead(dec, marker);
   spqr_node markerTail = findArcTail(dec, marker);
   if( findArcSign(dec, marker).reversed )
   {
      spqr_node temp = markerHead;
      markerHead = markerTail;
      markerTail = temp;
   }
 
   if( newRow->reducedMembers[reducedId].numCutArcs == 0 )
   {
      assert(SPQRnodeIsInvalid(nodes.second));//There must be at least two adjacent components
      if( nodes.first != markerHead && nodes.first != markerTail )
      {
         newRow->remainsNetwork = FALSE;
         newRow->reducedMembers[reducedId].type = TYPE_NOT_NETWORK;
         return;
      }
      SCIP_Bool reverse = previousOrientation.headSplit == ( nodes.first == markerTail );
      newRow->reducedMembers[reducedId].splitNode = nodes.first;
      newRow->reducedMembers[reducedId].otherIsSource = previousOrientation.otherIsSource;
      newRow->reducedMembers[reducedId].willBeReversed = reverse;
      newRow->reducedMembers[reducedId].type = TYPE_MERGED;
      return;
   }
   if( !SPQRnodeIsValid(newRow->reducedMembers[reducedId].splitNode) )
   {
      //Checking for propagation only makes sense if there is at least one cut arc
      assert(newRow->reducedMembers[reducedId].numCutArcs > 0);
 
      rigidFindStarNodes(dec, newRow, reducedId);
      if( !newRow->remainsNetwork )
      {
         return;
      }
 
      if( SPQRnodeIsInvalid(newRow->reducedMembers[reducedId].splitNode) )
      {
         //not a star => attempt to find splittable nodes using articulation node algorithms
         //We save some work by telling the methods that only the marker nodes should be checked
         rigidGetSplittableArticulationPointsOnPath(dec, newRow, reducedId, nodes.first, nodes.second);
      }
      if( !newRow->remainsNetwork )
      {
         return;
      }
      if( SPQRnodeIsInvalid(newRow->reducedMembers[reducedId].splitNode) )
      {
         newRow->remainsNetwork = FALSE;
         newRow->reducedMembers[reducedId].type = TYPE_NOT_NETWORK;
         return;
      }
   }
   spqr_node splitNode = determineAndColorSplitNode(dec, newRow, reducedId, nodes.first, nodes.second);
 
   if( SPQRnodeIsInvalid(splitNode) )
   {
      newRow->remainsNetwork = FALSE;
      newRow->reducedMembers[reducedId].type = TYPE_NOT_NETWORK;
      return;
   }
   assert(splitNode == nodes.first || splitNode == nodes.second);
   assert(splitNode == markerHead || splitNode == markerTail);
 
   spqr_node otherNode = splitNode == markerHead ? markerTail : markerHead;
   SCIP_Bool headsMatch = previousOrientation.headSplit == ( splitNode == markerHead );
 
   COLOR_STATUS otherColor = newRow->nodeColors[otherNode];
   assert(otherColor == COLOR_SOURCE || otherColor == COLOR_SINK);
   SCIP_Bool otherIsSource = otherColor == COLOR_SOURCE;
 
   SCIP_Bool good = headsMatch == ( previousOrientation.otherIsSource == otherIsSource );
 
   if( !good )
   {
      newRow->remainsNetwork = FALSE;
      newRow->reducedMembers[reducedId].type = TYPE_NOT_NETWORK;
      return;
   }
 
   newRow->reducedMembers[reducedId].splitNode = splitNode;
   newRow->reducedMembers[reducedId].willBeReversed = !headsMatch;
   newRow->reducedMembers[reducedId].type = TYPE_MERGED;
}
 
/** Determine the split type of a node when the SPQR tree is not a singular member.
 *
 * This function is used for all the nodes that are not first in the given ordering.
 */
static
void determineSplitTypeNext(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     current,            /**< The current node, whose type has already been determined */
   reduced_member_id     next,               /**< The next node to determine the type of, adjacent to the current node */
   SCIP_Bool             currentIsParent     /**< Is the current node a parent of the next node? */
   )
{
   spqr_member member = newRow->reducedMembers[next].member;
   SPQRMemberType type = getMemberType(dec, member);
   spqr_arc nextArc = currentIsParent ? markerToParent(dec, member) : markerOfParent(dec,
                                                                                     newRow->reducedMembers[current].member);
   spqr_arc currentArc = currentIsParent ? markerOfParent(dec, member) : markerToParent(dec,
                                                                                        newRow->reducedMembers[current].member);
   SplitOrientation orientation = getRelativeOrientation(dec, newRow, current, currentArc);
   assert(type == SPQR_MEMBERTYPE_PARALLEL || type == SPQR_MEMBERTYPE_RIGID || type == SPQR_MEMBERTYPE_SERIES);
   switch( type )
   {
      case SPQR_MEMBERTYPE_RIGID:
      {
         determineSplitTypeRigid(dec, newRow, next, member, nextArc, orientation);
         break;
      }
      case SPQR_MEMBERTYPE_PARALLEL:
      {
         determineSplitTypeParallel(dec, newRow, next, nextArc, orientation);
         break;
      }
      case SPQR_MEMBERTYPE_SERIES:
      {
         determineSplitTypeSeries(dec, newRow, next, nextArc, orientation);
         break;
      }
 
      case SPQR_MEMBERTYPE_LOOP:
      case SPQR_MEMBERTYPE_UNASSIGNED:
      default:
         newRow->remainsNetwork = FALSE;
         SCIPABORT();
   }
}
 
/** For the given root reduced member of a component, determine if the component is updateable/transformable. */
static
void determineMergeableTypes(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     root                /**< The root of the given component */
   )
{
   assert(newRow->numReducedMembers <= newRow->memMergeTreeCallData);
   if( newRow->reducedMembers[root].numPropagatedChildren == newRow->reducedMembers[root].numChildren )
   {
      //Determine single component;
      if( newRow->reducedMembers[root].type == TYPE_UNDETERMINED )
      {
         spqr_member member = newRow->reducedMembers[root].member;
         switch( getMemberType(dec, member) )
         {
            case SPQR_MEMBERTYPE_RIGID:
               determineSingleRowRigidType(dec, newRow, root);
               break;
            case SPQR_MEMBERTYPE_PARALLEL:
               determineSingleParallelType(dec, newRow, root);
               break;
            case SPQR_MEMBERTYPE_LOOP:
            case SPQR_MEMBERTYPE_SERIES:
               determineSingleSeriesType( newRow, root);
               break;
            case SPQR_MEMBERTYPE_UNASSIGNED:
            default:
               newRow->remainsNetwork = FALSE;
               SCIPABORT();
         }
      }
      return;
   }
 
   //Go to a leaf. We need to start in a leaf to avoid the ambiguity of choosing an orientation
   //in members which have no cut arcs; otherwise, we might choose the wrong one
   reduced_member_id leaf = root;
   while( newRow->reducedMembers[leaf].numChildren != newRow->reducedMembers[leaf].numPropagatedChildren )
   {
      for( int i = 0; i < newRow->reducedMembers[leaf].numChildren; ++i )
      {
         children_idx idx = newRow->reducedMembers[leaf].firstChild + i;
         reduced_member_id child = newRow->childrenStorage[idx];
         if( newRow->reducedMembers[child].type != TYPE_PROPAGATED )
         {
            leaf = child;
            break;
         }
      }
   }
   determineSplitTypeFirstLeaf(dec, newRow, leaf);
 
   if( !newRow->remainsNetwork )
   {
      return;
   }
   reduced_member_id baseNode = leaf;
   reduced_member_id nextNode = newRow->reducedMembers[baseNode].parent;
 
   while( reducedMemberIsValid(nextNode) )
   {
      //check this node
      determineSplitTypeNext(dec, newRow, baseNode, nextNode, FALSE);
      if( !newRow->remainsNetwork )
      {
         return;
      }
      //Add other nodes in the subtree
      //use a while loop to avoid recursion; we may get stack overflows for large graphs
      MergeTreeCallData* data = newRow->mergeTreeCallData;
 
      data[0].id = nextNode;
      data[0].currentChild = newRow->reducedMembers[nextNode].firstChild ;
      int depth = 0;
      while( depth >= 0 )
      {
         reduced_member_id id = data[depth].id;
         children_idx childidx = data[depth].currentChild;
         if( childidx == newRow->reducedMembers[id].firstChild + newRow->reducedMembers[id].numChildren )
         {
            --depth;
            continue;
         }
         reduced_member_id currentchild = newRow->childrenStorage[childidx];
         data[depth].currentChild += 1;
         //skip this child if we already processed it or it is not merged
         if( currentchild == baseNode || newRow->reducedMembers[currentchild].type == TYPE_PROPAGATED )
         {
            continue;
         }
         determineSplitTypeNext(dec,newRow,id,currentchild,TRUE);
         if( !newRow->remainsNetwork )
         {
            return;
         }
         //recursively process the child
         depth += 1;
         assert(depth < newRow->memMergeTreeCallData);
         data[depth].id = currentchild;
         data[depth].currentChild = newRow->reducedMembers[currentchild].firstChild;
      }
      //Move up one layer
      baseNode = nextNode;
      nextNode = newRow->reducedMembers[nextNode].parent;
   }
}
 
/** Empty the new member information array. */
static
void cleanUpRowMemberInformation(
   SCIP_NETROWADD*       newRow              /**< The network matrix row addition data structure */
   )
{
   //This loop is at the end as memberInformation is also used to assign the cut arcs during propagation
   //Clean up the memberInformation array
   for( int i = 0; i < newRow->numReducedMembers; ++i )
   {
      newRow->memberInformation[newRow->reducedMembers[i].member].reducedMember = INVALID_REDUCED_MEMBER;
   }
#ifndef NDEBUG
   for( int i = 0; i < newRow->memMemberInformation; ++i )
   {
      assert(reducedMemberIsInvalid(newRow->memberInformation[i].reducedMember));
   }
#endif
}
 
/** Transforms a rigid arc by putting it in series with the new column arc.
 *
 * We need to do some magic to keep our the internal datastructures consistent in this case.
 */
static
SCIP_RETCODE rigidTransformArcIntoCycle(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   const spqr_member     member,             /**< The rigid member that contains the arc that is moved */
   const spqr_arc        arc,                /**< The arc that is moved to a new series member */
   const SCIP_Bool       reverseArcDirection,/**< Is the given arc reversed? */
   NewRowInformation* const newRowInfo       /**< Stores information on how to add the new row */
   )
{
   //If a cycle already exists, just expand it with the new arc.
   spqr_member markerCycleMember = SPQR_INVALID_MEMBER;
   spqr_arc markerCycleArc = SPQR_INVALID_ARC;
   SCIP_Bool isParent = arc == markerToParent(dec, member);
   spqr_member adjacentMember = SPQR_INVALID_MEMBER;
   if( isParent )
   {
      adjacentMember = findMemberParent(dec, member);
      if( getMemberType(dec, adjacentMember) == SPQR_MEMBERTYPE_SERIES )
      {
         markerCycleMember = adjacentMember;
         markerCycleArc = markerOfParent(dec, member);
      }
   }
   else if( arcIsChildMarker(dec, arc) )
   {
      adjacentMember = findArcChildMember(dec, arc);
      if( getMemberType(dec, adjacentMember) == SPQR_MEMBERTYPE_SERIES )
      {
         markerCycleMember = adjacentMember;
         markerCycleArc = markerToParent(dec, adjacentMember);
      }
   }
   if( markerCycleMember != SPQR_INVALID_MEMBER )
   {
      newRowInfo->member = markerCycleMember;
      if( arcIsReversedNonRigid(dec, markerCycleArc) )
      {
         newRowInfo->reversed = reverseArcDirection;
      }
      else
      {
         newRowInfo->reversed = !reverseArcDirection;
      }
 
      return SCIP_OKAY;
   }
 
   //Otherwise, we create a new cycle
   spqr_member newCycle;
   SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &newCycle) );
   //We would like to move the edge but unfortunately cannot do so without destroying the arc union-find datastructure.
   //Thus, we 'convert' the arc into a marker and add the new series
 
   spqr_arc duplicate = SPQR_INVALID_ARC;
   spqr_element element = arcGetElement(dec, arc);
   if( element != MARKER_COLUMN_ELEMENT && element != MARKER_ROW_ELEMENT )
   {
      if( SPQRelementIsColumn(element) )
      {
         SCIP_CALL( createColumnArc(dec, newCycle, &duplicate, SPQRelementToColumn(element), TRUE) );
      }
      else
      {
         SCIP_CALL( createRowArc(dec, newCycle, &duplicate, SPQRelementToRow(element), TRUE) );
      }
   }
   else if( isParent )
   {
      //create parent marker
      SCIP_CALL( createParentMarker(dec, newCycle, arcIsTree(dec, arc), adjacentMember,
                                    markerOfParent(dec, member), &duplicate, TRUE) );
   }
   else
   {
      //create child marker
      SCIP_CALL( createChildMarker(dec, newCycle, adjacentMember, arcIsTree(dec, arc), &duplicate, TRUE) );
      dec->members[adjacentMember].parentMember = newCycle;
      dec->members[adjacentMember].markerOfParent = duplicate;
   }
   //Create the other marker edge
   spqr_arc cycleMarker = SPQR_INVALID_ARC;
   if( isParent )
   {
      SCIP_CALL( createChildMarker(dec, newCycle, member, !arcIsTree(dec, arc),
                                   &cycleMarker, FALSE) );
   }
   else
   {
      SCIP_CALL( createParentMarker(dec, newCycle, !arcIsTree(dec, arc),
                                    member, arc, &cycleMarker, FALSE) );
   }
   //Change the existing edge to a marker
   if( isParent )
   {
      assert(markerToParent(dec, member) == arc);
      dec->arcs[markerOfParent(dec, member)].childMember = newCycle;
      dec->members[member].parentMember = newCycle;
      dec->members[member].markerToParent = arc;
      dec->members[member].markerOfParent = cycleMarker;
      dec->arcs[arc].element = arcIsTree(dec, arc) ? MARKER_ROW_ELEMENT : MARKER_COLUMN_ELEMENT;
      dec->arcs[arc].childMember = SPQR_INVALID_MEMBER;
   }
   else
   {
      dec->arcs[arc].element = arcIsTree(dec, arc) ? MARKER_ROW_ELEMENT : MARKER_COLUMN_ELEMENT;
      dec->arcs[arc].childMember = newCycle;
   }
   newRowInfo->member = newCycle;
   newRowInfo->reversed = !reverseArcDirection;
 
   return SCIP_OKAY;
}
 
/** Updates a single rigid member to reflect the new row. */
static
SCIP_RETCODE transformSingleRigid(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id reducedMember,    /**< The reduced member to transform */
   const spqr_member     member,             /**< The member belonging to the reduced member */
   NewRowInformation* const newRowInfo       /**< Stores information about the new row placement */
   )
{
   if( SPQRarcIsValid(newRow->reducedMembers[reducedMember].articulationArc) )
   {
      spqr_arc arc = newRow->reducedMembers[reducedMember].articulationArc;
      //Cut arc is propagated into a cycle with new arc
      assert(newRow->reducedMembers[reducedMember].splitNode == findEffectiveArcHeadNoCompression(dec, arc) ||
             newRow->reducedMembers[reducedMember].splitNode == findEffectiveArcTailNoCompression(dec, arc));
 
      SCIP_Bool reversed;
 
      if( newRow->isArcCut[arc] )
      {
         reversed = ( newRow->reducedMembers[reducedMember].splitNode == findEffectiveArcHead(dec, arc)) ==
                    newRow->reducedMembers[reducedMember].otherIsSource;
      }
      else
      {
         reversed = ( newRow->reducedMembers[reducedMember].splitNode == findEffectiveArcHead(dec, arc)) !=
                    newRow->reducedMembers[reducedMember].otherIsSource;
      }
 
      SCIP_CALL( rigidTransformArcIntoCycle(dec, member, newRow->reducedMembers[reducedMember].articulationArc,
                                            reversed, newRowInfo) );
 
      return SCIP_OKAY;
   }
   //Single splittable node
   assert(SPQRnodeIsValid(newRow->reducedMembers[reducedMember].splitNode));
 
   spqr_node splitNode = newRow->reducedMembers[reducedMember].splitNode;
   if( newRow->reducedMembers[reducedMember].allHaveCommonNode )
   {
      //Create a new node; move all cut arcs end of split node to it and add new arc between new node and split node
      spqr_node newNode = SPQR_INVALID_NODE;
      SCIP_CALL( createNode(dec, &newNode) );
 
      cut_arc_id cutArcIdx = newRow->reducedMembers[reducedMember].firstCutArc;
      do
      {
         spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
         spqr_node arcHead = findArcHead(dec, cutArc);
         if( arcHead == splitNode )
         {
            changeArcHead(dec, cutArc, arcHead, newNode);
         }
         else
         {
            changeArcTail(dec, cutArc, findArcTail(dec, cutArc), newNode);
         }
 
         cutArcIdx = newRow->cutArcs[cutArcIdx].nextMember;
      }
      while( cutArcIsValid(cutArcIdx) );
 
      newRowInfo->member = member;
      if( newRow->reducedMembers[reducedMember].otherIsSource )
      {
         newRowInfo->head = newNode;
         newRowInfo->tail = splitNode;
      }
      else
      {
         newRowInfo->head = splitNode;
         newRowInfo->tail = newNode;
      }
      newRowInfo->representative = findArcSign(dec,
                                               newRow->cutArcs[newRow->reducedMembers[reducedMember].firstCutArc].arc).representative;
      newRowInfo->reversed = FALSE;
 
      return SCIP_OKAY;
   }
   //Articulation point was split (based on coloring)
 
   spqr_node newNode = SPQR_INVALID_NODE;
   SCIP_CALL( createNode(dec, &newNode) );
 
   spqr_arc firstNodeArc = getFirstNodeArc(dec, splitNode);
   spqr_arc iterArc = firstNodeArc;
 
   do
   {
      SCIP_Bool isCut = newRow->isArcCut[iterArc];
      spqr_node otherHead = findArcHead(dec, iterArc);
      spqr_node otherTail = findArcTail(dec, iterArc);
      spqr_node otherEnd = otherHead == splitNode ? otherTail : otherHead;
      SCIP_Bool isMoveColor = newRow->nodeColors[otherEnd] == COLOR_SOURCE;
      spqr_arc nextArc = getNextNodeArc(dec, iterArc, splitNode);//Need to do this before we modify the arc :)
 
      SCIP_Bool changeArcEnd = isCut == isMoveColor;
      if( changeArcEnd )
      {
         if( otherHead == splitNode )
         {
            changeArcHead(dec, iterArc, otherHead, newNode);
         }
         else
         {
            changeArcTail(dec, iterArc, otherTail, newNode);
         }
      }
      newRow->nodeColors[otherEnd] = UNCOLORED;//Clean up
 
      //Ugly hack to make sure we can iterate neighbourhood whilst changing arc ends.
      spqr_arc previousArc = iterArc;
      iterArc = nextArc;
      if( iterArc == firstNodeArc )
      {
         break;
      }
      if( changeArcEnd && previousArc == firstNodeArc )
      {
         firstNodeArc = iterArc;
      }
   }
   while( TRUE ); /*lint !e506*/
   newRow->reducedMembers[reducedMember].coloredNode = SPQR_INVALID_NODE;
 
   newRowInfo->member = member;
   newRowInfo->head = newNode;
   newRowInfo->tail = splitNode;
   newRowInfo->representative = findArcSign(dec,
                                            newRow->cutArcs[newRow->reducedMembers[reducedMember].firstCutArc].arc).representative;
   newRowInfo->reversed = FALSE;
 
   return SCIP_OKAY;
}
 
/** Splits a single parallel member into two adjacent ones, where the cut arcs and non-cut arcs get their own member. */
static
SCIP_RETCODE splitParallelRowAddition(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id reducedMember,    /**< The reduced member to transform */
   const spqr_member     member,             /**< The member belonging to the reduced member */
   NewRowInformation* const newRowInfo       /**< Stores information about the new row placement */
   )
{
   assert(newRow->reducedMembers[reducedMember].numCutArcs > 0);
 
   int numCutArcs = newRow->reducedMembers[reducedMember].numCutArcs;
   int numParallelArcs = getNumMemberArcs(dec, member);
 
   SCIP_Bool createCutParallel = numCutArcs > 1;
   SCIP_Bool convertOriginalParallel = ( numCutArcs + 1 ) == numParallelArcs;
 
   //Do linear search to find non-marked arc
   spqr_arc treeArc = getFirstMemberArc(dec, member);
   do
   {
      if( arcIsTree(dec, treeArc))
      {
         break;
      }
      treeArc = getNextMemberArc(dec, treeArc);
   }
   while( treeArc != getFirstMemberArc(dec, member) );
   assert(arcIsTree(dec, treeArc));
 
   SCIP_Bool treeReversed = arcIsReversedNonRigid(dec, treeArc);
 
   assert(!( !createCutParallel &&
             convertOriginalParallel ));//This can only happen if the parallel member is actually a loop, which means it is mislabeled
   if( createCutParallel )
   {
      if( convertOriginalParallel )
      {
         spqr_member adjacentMember = SPQR_INVALID_MEMBER;
         spqr_arc adjacentArc = SPQR_INVALID_ARC;
         if( treeArc == markerToParent(dec, member) )
         {
            adjacentMember = findMemberParent(dec, member);
            adjacentArc = markerOfParent(dec, member);
         }
         else if( arcIsChildMarker(dec, treeArc) )
         {
            adjacentMember = findArcChildMember(dec, treeArc);
            adjacentArc = markerToParent(dec, adjacentMember);
            assert(markerOfParent(dec, adjacentMember) == treeArc);
         }
         cut_arc_id firstCut = newRow->reducedMembers[reducedMember].firstCutArc;
         SCIP_Bool firstReversed =
            newRow->cutArcs[firstCut].arcReversed != arcIsReversedNonRigid(dec, newRow->cutArcs[firstCut].arc);
 
         if( SPQRmemberIsValid(adjacentMember) && getMemberType(dec, adjacentMember) == SPQR_MEMBERTYPE_SERIES )
         {
            newRowInfo->member = adjacentMember;
            if( arcIsReversedNonRigid(dec, treeArc) == arcIsReversedNonRigid(dec, adjacentArc) )
            {
               newRowInfo->reversed = !firstReversed;
            }
            else
            {
               newRowInfo->reversed = firstReversed;
            }
            return SCIP_OKAY;
         }
         spqr_member cutMember = SPQR_INVALID_MEMBER;
         SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &cutMember) );
 
         cut_arc_id cutArcIdx = newRow->reducedMembers[reducedMember].firstCutArc;
         assert(cutArcIsValid(cutArcIdx));
         SCIP_Bool parentCut = FALSE;
 
         while( cutArcIsValid(cutArcIdx) )
         {
            spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
            cutArcIdx = newRow->cutArcs[cutArcIdx].nextMember;
            moveArcToNewMember(dec, cutArc, member, cutMember);
            if( cutArc == markerToParent(dec, member) )
            {
               parentCut = TRUE;
            }
         }
         if( parentCut )
         {
            SCIP_CALL( createMarkerPair(dec, cutMember, member, TRUE, FALSE, TRUE) );
         }
         else
         {
            SCIP_CALL( createMarkerPair(dec, member, cutMember, FALSE, TRUE, FALSE) );
         }
         changeLoopToSeries(dec, member);
         newRowInfo->member = member;
         if( treeReversed )
         {
            newRowInfo->reversed = firstReversed == arcIsReversedNonRigid(dec, treeArc);
         }
         else
         {
            newRowInfo->reversed = firstReversed != arcIsReversedNonRigid(dec, treeArc);
         }
      }
      else
      {
         spqr_member cutMember = SPQR_INVALID_MEMBER;
         SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &cutMember) );
 
         cut_arc_id cutArcIdx = newRow->reducedMembers[reducedMember].firstCutArc;
         assert(cutArcIsValid(cutArcIdx));
         SCIP_Bool parentCut = FALSE;
 
         while( cutArcIsValid(cutArcIdx) )
         {
            spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
            cutArcIdx = newRow->cutArcs[cutArcIdx].nextMember;
            moveArcToNewMember(dec, cutArc, member, cutMember);
            if( cutArc == markerToParent(dec, member) )
            {
               parentCut = TRUE;
            }
         }
         spqr_member newSeries;
         SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &newSeries) );
         if( parentCut )
         {
            SCIP_CALL( createMarkerPair(dec, newSeries, member, TRUE, FALSE, FALSE) );
            SCIP_CALL( createMarkerPair(dec, cutMember, newSeries, TRUE, FALSE, TRUE) );
         }
         else
         {
            SCIP_CALL( createMarkerPair(dec, member, newSeries, FALSE, FALSE, FALSE) );
            SCIP_CALL( createMarkerPair(dec, newSeries, cutMember, FALSE, TRUE, FALSE) );
         }
         newRowInfo->member = newSeries;
         cut_arc_id firstCut = newRow->reducedMembers[reducedMember].firstCutArc;
         SCIP_Bool firstReversed =
            newRow->cutArcs[firstCut].arcReversed != arcIsReversedNonRigid(dec, newRow->cutArcs[firstCut].arc);
 
         newRowInfo->reversed = firstReversed;
      }
 
      return SCIP_OKAY;
   }
 
   assert(!createCutParallel && !convertOriginalParallel);
   assert(numCutArcs == 1);
#ifndef NDEBUG
   spqr_arc arc = newRow->cutArcs[newRow->reducedMembers[reducedMember].firstCutArc].arc;
   spqr_member adjacentMember = SPQR_INVALID_MEMBER;
   if( arc == markerToParent(dec, member) )
   {
      adjacentMember = findMemberParent(dec, member);
   }
   else if( arcIsChildMarker(dec, arc) )
   {
      adjacentMember = findArcChildMember(dec, arc);
   }
   if( SPQRmemberIsValid(adjacentMember) )
   {
      assert(getMemberType(dec, adjacentMember) != SPQR_MEMBERTYPE_SERIES);
   }
#endif
   spqr_member newSeries;
   SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &newSeries) );
   cut_arc_id cutArcIdx = newRow->reducedMembers[reducedMember].firstCutArc;
   assert(cutArcIsValid(cutArcIdx));
   SCIP_Bool parentCut = FALSE;
 
   while( cutArcIsValid(cutArcIdx) )
   {
      spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
      cutArcIdx = newRow->cutArcs[cutArcIdx].nextMember;
      moveArcToNewMember(dec, cutArc, member, newSeries);
      if( cutArc == markerToParent(dec, member) )
      {
         parentCut = TRUE;
      }
   }
   if( parentCut )
   {
      SCIP_CALL( createMarkerPair(dec, newSeries, member, TRUE, TRUE, FALSE) );
   }
   else
   {
      SCIP_CALL( createMarkerPair(dec, member, newSeries, FALSE, FALSE, TRUE) );
   }
   newRowInfo->member = newSeries;
   cut_arc_id cutArcId = newRow->reducedMembers[reducedMember].firstCutArc;
   newRowInfo->reversed =
      newRow->cutArcs[cutArcId].arcReversed == arcIsReversedNonRigid(dec, newRow->cutArcs[cutArcId].arc);
 
   return SCIP_OKAY;
}
 
/** Updates a single rigid member to reflect the new row. */
static
SCIP_RETCODE transformSingleParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id reducedMember,    /**< The reduced member to transform */
   const spqr_member     member,             /**< The member belonging to the reduced member */
   NewRowInformation*    info                /**< Stores information about the new row placement */
   )
{
   SCIP_CALL( splitParallelRowAddition(dec, newRow, reducedMember, member, info) );
   return SCIP_OKAY;
}
 
/** Split a series member into multiple series members for merging. */
static
SCIP_RETCODE splitSeriesMergingRowAddition(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   const reduced_member_id reducedMember,    /**< The reduced series member */
   const spqr_member     member,             /**< The member belonging to the reduced member */
   spqr_member* const    mergingMember,      /**< The member that contains the arcs that are to be merged */
   SCIP_Bool* const      isCut,              /**< Array that contains whether each arc is Cut */
   spqr_arc*             representativeEdge  /**< Pointer to the representative arc for the split off arcs */
   )
{
   assert(getNumMemberArcs(dec, member) >= 3);
   *isCut = newRow->reducedMembers[reducedMember].numCutArcs > 0;
 
   if( getNumMemberArcs(dec, member) == 3 )
   {
      spqr_arc splitArc = newRow->reducedMembers[reducedMember].splitArc;
      spqr_arc otherArc = SPQR_INVALID_ARC;
      for( children_idx i = newRow->reducedMembers[reducedMember].firstChild;
           i <
           newRow->reducedMembers[reducedMember].firstChild + newRow->reducedMembers[reducedMember].numChildren; ++i )
      {
         reduced_member_id child = newRow->childrenStorage[i];
         if( newRow->reducedMembers[child].type == TYPE_MERGED )
         {
            spqr_arc testArc = markerOfParent(dec, findMember(dec, newRow->reducedMembers[child].member));
            if( testArc != splitArc )
            {
               otherArc = testArc;
               break;
            }
         }
      }
      if( SPQRarcIsInvalid(otherArc) )
      {
#ifndef NDEBUG
         reduced_member_id parent = newRow->reducedMembers[reducedMember].parent;
#endif
         assert(newRow->reducedMembers[parent].type == TYPE_MERGED ||
                newRow->reducedMembers[parent].type == TYPE_PROPAGATED);
         assert(reducedMemberIsValid(parent) && newRow->reducedMembers[parent].type == TYPE_MERGED);
         otherArc = markerToParent(dec, member);
      }
      spqr_arc firstArc = getFirstMemberArc(dec, member);
      spqr_arc arc = firstArc;
      do
      {
         if( arc != splitArc && arc != otherArc )
         {
            *representativeEdge = arc;
            break;
         }
         arc = getNextMemberArc(dec, arc);
      }
      while( arc != firstArc );
      *mergingMember = member;
      return SCIP_OKAY;
   }
   //Split off the relevant part of the series member
   spqr_member mergingSeries = SPQR_INVALID_MEMBER;
   SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_SERIES, &mergingSeries) );
   //Move all marker arcs which point to another component in the reduced decomposition to the new member
   //This should be exactly 2, as with 3 the result is not network anymore
   //move all mergeable children and parent arcs to the mergingMember
 
   SCIP_Bool coTreeToMergingMember = FALSE;
   SCIP_Bool parentToMergingMember = FALSE;
   for( children_idx i = newRow->reducedMembers[reducedMember].firstChild;
        i < newRow->reducedMembers[reducedMember].firstChild + newRow->reducedMembers[reducedMember].numChildren; ++i )
   {
      reduced_member_id child = newRow->childrenStorage[i];
      assert(
         newRow->reducedMembers[child].type == TYPE_MERGED || newRow->reducedMembers[child].type == TYPE_PROPAGATED);
      if( newRow->reducedMembers[child].type == TYPE_MERGED )
      {
         spqr_arc moveArc = markerOfParent(dec, findMember(dec, newRow->reducedMembers[child].member));
         moveArcToNewMember(dec, moveArc, member, mergingSeries);
         if( !arcIsTree(dec, moveArc) )
         {
            coTreeToMergingMember = TRUE;
         }
      }
   }
 
   reduced_member_id parent = newRow->reducedMembers[reducedMember].parent;
   assert(reducedMemberIsInvalid(parent) || ( newRow->reducedMembers[parent].type == TYPE_MERGED ||
                                              newRow->reducedMembers[parent].type == TYPE_PROPAGATED ));
 
   if( reducedMemberIsValid(parent) &&
       newRow->reducedMembers[parent].type == TYPE_MERGED )
   {
      spqr_arc moveArc = markerToParent(dec, member);
      moveArcToNewMember(dec, moveArc, member, mergingSeries);
      parentToMergingMember = TRUE;
      if( !arcIsTree(dec, moveArc) )
      {
         coTreeToMergingMember = TRUE;
      }
   }
   spqr_arc ignoreArc = SPQR_INVALID_ARC;
   if( parentToMergingMember )
   {
      SCIP_CALL( createMarkerPairWithReferences(dec, mergingSeries, member, coTreeToMergingMember, TRUE, FALSE,
                                                representativeEdge, &ignoreArc) );
   }
   else
   {
      SCIP_CALL(
         createMarkerPairWithReferences(dec, member, mergingSeries, !coTreeToMergingMember, FALSE, TRUE, &ignoreArc,
                                        representativeEdge) );
   }
 
   *mergingMember = mergingSeries;
   assert(getNumMemberArcs(dec, mergingSeries) == 3);
   assert(getNumMemberArcs(dec, member) >= 3);
 
   return SCIP_OKAY;
}
 
/** Split a parallel member into multiple parallel members for merging. */
static
SCIP_RETCODE splitParallelMerging(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     reducedMember,      /**< The reduced parallel member */
   spqr_member           member,             /**< The member belonging to the reduced member */
   spqr_member* const    pMergeMember,       /**< The member that contains the arcs that are to be merged */
   spqr_arc* const       cutRepresentative   /**< Pointer to the representative arc for all cut arcs */
   )
{
   //When merging, we cannot have propagated members;
   assert(newRow->reducedMembers[reducedMember].numCutArcs < ( getNumMemberArcs(dec, member) - 1 ));
 
   int numMergeableAdjacent =
      newRow->reducedMembers[reducedMember].numChildren - newRow->reducedMembers[reducedMember].numPropagatedChildren;
   if( reducedMemberIsValid(newRow->reducedMembers[reducedMember].parent) &&
       newRow->reducedMembers[newRow->reducedMembers[reducedMember].parent].type == TYPE_MERGED )
   {
      numMergeableAdjacent++;
   }
 
   int numCutArcs = newRow->reducedMembers[reducedMember].numCutArcs;
   //All arcs which are not in the mergeable decomposition or cut
   int numBaseSplitAwayArcs = getNumMemberArcs(dec, member) - numMergeableAdjacent - numCutArcs;
 
   SCIP_Bool createCutParallel = numCutArcs > 1;
   SCIP_Bool keepOriginalParallel = numBaseSplitAwayArcs <= 1;
 
   spqr_member cutMember = SPQR_INVALID_MEMBER;
   //The below cases can probably be aggregated in some way, but for now we first focus on the correct logic
   if( createCutParallel && keepOriginalParallel )
   {
      SCIP_Bool parentCut = FALSE;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &cutMember) );
 
      cut_arc_id cutArcIdx = newRow->reducedMembers[reducedMember].firstCutArc;
      assert(cutArcIsValid(cutArcIdx));
 
      while( cutArcIsValid(cutArcIdx) )
      {
         spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
         cutArcIdx = newRow->cutArcs[cutArcIdx].nextMember;
         moveArcToNewMember(dec, cutArc, member, cutMember);
         if( cutArc == markerToParent(dec, member) )
         {
            parentCut = TRUE;
         }
      }
      spqr_arc ignoreArc = SPQR_INVALID_ARC;
      if( parentCut )
      {
         SCIP_CALL(
            createMarkerPairWithReferences(dec, cutMember, member, TRUE, FALSE, FALSE, &ignoreArc, cutRepresentative) );
      }
      else
      {
         SCIP_CALL(
            createMarkerPairWithReferences(dec, member, cutMember, FALSE, FALSE, FALSE, cutRepresentative, &ignoreArc) );
      }
 
      *pMergeMember = member;
   }
   else if( createCutParallel )
   {
      assert(!keepOriginalParallel);
 
      SCIP_Bool parentCut = FALSE;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &cutMember) );
 
      cut_arc_id cutArcIdx = newRow->reducedMembers[reducedMember].firstCutArc;
      assert(cutArcIsValid(cutArcIdx));
 
      while( cutArcIsValid(cutArcIdx) )
      {
         spqr_arc cutArc = newRow->cutArcs[cutArcIdx].arc;
         cutArcIdx = newRow->cutArcs[cutArcIdx].nextMember;
         moveArcToNewMember(dec, cutArc, member, cutMember);
         if( cutArc == markerToParent(dec, member) )
         {
            parentCut = TRUE;
         }
      }
      spqr_arc ignoreArc = SPQR_INVALID_ARC;
      if( parentCut )
      {
         SCIP_CALL(
            createMarkerPairWithReferences(dec, cutMember, member, TRUE, FALSE, FALSE, &ignoreArc, cutRepresentative) );
      }
      else
      {
         SCIP_CALL(
            createMarkerPairWithReferences(dec, member, cutMember, FALSE, FALSE, FALSE, cutRepresentative, &ignoreArc) );
      }
 
      spqr_arc noCutRepresentative = SPQR_INVALID_ARC;
      spqr_member mergingMember = member;
      SCIP_Bool parentToMergingMember = FALSE;
      SCIP_Bool treeToMergingMember = FALSE;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &mergingMember) );
      //move all mergeable children and parent arcs to the mergingMember
      for( children_idx i = newRow->reducedMembers[reducedMember].firstChild;
           i < newRow->reducedMembers[reducedMember].firstChild +
               newRow->reducedMembers[reducedMember].numChildren;
           ++i )
      {
         reduced_member_id child = newRow->childrenStorage[i];
         assert(
            newRow->reducedMembers[child].type == TYPE_MERGED || newRow->reducedMembers[child].type == TYPE_PROPAGATED);
         if( newRow->reducedMembers[child].type == TYPE_MERGED )
         {
            spqr_arc moveArc = markerOfParent(dec, findMember(dec, newRow->reducedMembers[child].member));
            moveArcToNewMember(dec, moveArc, member, mergingMember);
            if( arcIsTree(dec, moveArc) )
            {
               treeToMergingMember = TRUE;
            }
         }
      }
      reduced_member_id parent = newRow->reducedMembers[reducedMember].parent;
      if( reducedMemberIsValid(parent) &&
          newRow->reducedMembers[parent].type == TYPE_MERGED )
      {
         spqr_arc moveArc = markerToParent(dec, member);
         moveArcToNewMember(dec, moveArc, member, mergingMember);
         parentToMergingMember = TRUE;
         if( arcIsTree(dec, moveArc) )
         {
            treeToMergingMember = TRUE;
         }
      }
      //If there is only one cut arc, we also move it.
      if( SPQRarcIsValid(*cutRepresentative) )
      {
         if( *cutRepresentative == markerToParent(dec, member) )
         {
            parentToMergingMember = TRUE;
         }
         moveArcToNewMember(dec, *cutRepresentative, member, mergingMember);
      }
      spqr_arc ignoreArgument = SPQR_INVALID_ARC;
      if( parentToMergingMember || parentCut )
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, mergingMember, member, !treeToMergingMember, FALSE, FALSE,
                                                   &ignoreArgument, &noCutRepresentative) );
      }
      else
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, member, mergingMember, treeToMergingMember, FALSE, FALSE,
                                                   &noCutRepresentative, &ignoreArgument) );
      }
      *pMergeMember = mergingMember;
   }
   else if( keepOriginalParallel )
   {
      assert(!createCutParallel);
      if( cutArcIsValid(newRow->reducedMembers[reducedMember].firstCutArc) )
      {
         *cutRepresentative = newRow->cutArcs[newRow->reducedMembers[reducedMember].firstCutArc].arc;
      }
      *pMergeMember = member;
   }
   else
   {
      assert(!keepOriginalParallel && !createCutParallel);
 
      if( cutArcIsValid(newRow->reducedMembers[reducedMember].firstCutArc) )
      {
         *cutRepresentative = newRow->cutArcs[newRow->reducedMembers[reducedMember].firstCutArc].arc;
      }
 
      spqr_arc noCutRepresentative = SPQR_INVALID_ARC;
      spqr_member mergingMember = member;
      SCIP_Bool parentToMergingMember = FALSE;
      SCIP_Bool treeToMergingMember = FALSE;
      SCIP_CALL( createMember(dec, SPQR_MEMBERTYPE_PARALLEL, &mergingMember) );
      //move all mergeable children and parent arcs to the mergingMember
      for( children_idx i = newRow->reducedMembers[reducedMember].firstChild;
           i < newRow->reducedMembers[reducedMember].firstChild +
               newRow->reducedMembers[reducedMember].numChildren;
           ++i )
      {
         reduced_member_id child = newRow->childrenStorage[i];
         assert(
            newRow->reducedMembers[child].type == TYPE_MERGED || newRow->reducedMembers[child].type == TYPE_PROPAGATED);
         if( newRow->reducedMembers[child].type == TYPE_MERGED )
         {
            spqr_arc moveArc = markerOfParent(dec, findMember(dec, newRow->reducedMembers[child].member));
            moveArcToNewMember(dec, moveArc, member, mergingMember);
            if( arcIsTree(dec, moveArc) )
            {
               treeToMergingMember = TRUE;
            }
         }
      }
      reduced_member_id parent = newRow->reducedMembers[reducedMember].parent;
      if( reducedMemberIsValid(parent) &&
          newRow->reducedMembers[parent].type == TYPE_MERGED )
      {
         spqr_arc moveArc = markerToParent(dec, member);
         moveArcToNewMember(dec, moveArc, member, mergingMember);
         parentToMergingMember = TRUE;
         if( arcIsTree(dec, moveArc) )
         {
            treeToMergingMember = TRUE;
         }
      }
      //If there is only one cut arc, we also move it.
      if( SPQRarcIsValid(*cutRepresentative) )
      {
         if( *cutRepresentative == markerToParent(dec, member) )
         {
            parentToMergingMember = TRUE;
         }
         moveArcToNewMember(dec, *cutRepresentative, member, mergingMember);
      }
      spqr_arc ignoreArgument = SPQR_INVALID_ARC;
      if( parentToMergingMember )
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, mergingMember, member, !treeToMergingMember, FALSE, FALSE,
                                                   &ignoreArgument, &noCutRepresentative) );
      }
      else
      {
         SCIP_CALL( createMarkerPairWithReferences(dec, member, mergingMember, treeToMergingMember, FALSE, FALSE,
                                                   &noCutRepresentative, &ignoreArgument) );
      }
      *pMergeMember = mergingMember;
   }
 
   return SCIP_OKAY;
}
 
/** Update the first leaf to reflect the addition of the new row */
static
SCIP_RETCODE splitFirstLeaf(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     leaf,               /**< The leaf to split the first node for */
   NewRowInformation* const newRowInfo       /**< Stores how to add the new row */
   )
{
   assert(cutArcIsValid(newRow->reducedMembers[leaf].firstCutArc));
   assert(newRow->reducedMembers[leaf].numCutArcs > 0);
   spqr_member member = newRow->reducedMembers[leaf].member;
   if( getMemberType(dec, member) == SPQR_MEMBERTYPE_PARALLEL )
   {
      spqr_member mergeMember = SPQR_INVALID_MEMBER;
      spqr_arc cutRepresentative = SPQR_INVALID_ARC;
      SCIP_CALL( splitParallelMerging(dec, newRow, leaf, member, &mergeMember, &cutRepresentative) );
      newRow->reducedMembers[leaf].member = mergeMember;
 
      spqr_node firstNode = SPQR_INVALID_NODE;
      spqr_node secondNode = SPQR_INVALID_NODE;
      spqr_node thirdNode = SPQR_INVALID_NODE;
      SCIP_CALL( createNode(dec, &firstNode) );
      SCIP_CALL( createNode(dec, &secondNode) );
      SCIP_CALL( createNode(dec, &thirdNode) );
 
      spqr_arc splitArc = newRow->reducedMembers[leaf].splitArc;
      assert(findArcMemberNoCompression(dec, splitArc) == mergeMember);
      SCIP_Bool splitArcReversed = arcIsReversedNonRigid(dec, splitArc);
      SCIP_Bool splitHead = newRow->reducedMembers[leaf].splitHead;
      spqr_node splitArcHead = splitArcReversed ? secondNode : firstNode;
      spqr_node splitArcTail = splitArcReversed ? firstNode : secondNode;
      spqr_node splitNode = splitHead ? splitArcHead : splitArcTail;
      spqr_node otherNode = splitHead ? splitArcTail : splitArcHead;
 
      spqr_arc first_arc = getFirstMemberArc(dec, mergeMember);
      spqr_arc arc = first_arc;
 
      do
      {
         if( arc != cutRepresentative )
         {
            if( arcIsReversedNonRigid(dec, arc) )
            {
               setArcHeadAndTail(dec, arc, secondNode, firstNode);
            }
            else
            {
               setArcHeadAndTail(dec, arc, firstNode, secondNode);
            }
         }
         else
         {
            if( (arcIsReversedNonRigid(dec, arc) == splitArcReversed) == splitHead )
            {
               setArcHeadAndTail(dec, arc, thirdNode, otherNode);
            }
            else
            {
               setArcHeadAndTail(dec, arc, otherNode, thirdNode);
            }
         }
         arcSetReversed(dec, arc, FALSE);
         if( arc == splitArc )
         {
            arcSetRepresentative(dec, arc, SPQR_INVALID_ARC);
         }
         else
         {
            arcSetRepresentative(dec, arc, splitArc);
         }
         arc = getNextMemberArc(dec, arc);
      }
      while( arc != first_arc );
 
      updateMemberType(dec, mergeMember, SPQR_MEMBERTYPE_RIGID);
      newRowInfo->member = mergeMember;
      if( newRow->reducedMembers[leaf].otherIsSource )
      {
         newRowInfo->head = thirdNode;
         newRowInfo->tail = splitNode;
      }
      else
      {
         newRowInfo->head = splitNode;
         newRowInfo->tail = thirdNode;
      }
 
      newRowInfo->reversed = FALSE;
      newRowInfo->representative = splitArc;
 
      return SCIP_OKAY;
   }
   assert(getMemberType(dec, member) == SPQR_MEMBERTYPE_RIGID);
 
   spqr_node newNode = SPQR_INVALID_NODE;//Sink node
   SCIP_CALL( createNode(dec, &newNode) );
 
   spqr_node splitNode = newRow->reducedMembers[leaf].splitNode;
 
   spqr_arc firstNodeArc = getFirstNodeArc(dec, splitNode);
   spqr_arc iterArc = firstNodeArc;
   do
   {
      spqr_node otherHead = findArcHead(dec, iterArc);
      spqr_node otherTail = findArcTail(dec, iterArc);
      spqr_node otherEnd = otherHead == splitNode ? otherTail : otherHead;
      spqr_arc nextArc = getNextNodeArc(dec, iterArc, splitNode);//Need to do this before we modify the arc
 
      SCIP_Bool isCut = newRow->isArcCut[iterArc];
      SCIP_Bool isMoveColor = newRow->nodeColors[otherEnd] == COLOR_SOURCE;
      SCIP_Bool changeArcEnd = isCut == isMoveColor;
      if( changeArcEnd )
      {
         if( otherHead == splitNode )
         {
            changeArcHead(dec, iterArc, otherHead, newNode);
         }
         else
         {
            changeArcTail(dec, iterArc, otherTail, newNode);
         }
      }
      //Ugly hack to make sure we can iterate neighbourhood whilst changing arc ends.
      newRow->nodeColors[otherEnd] = UNCOLORED;
      spqr_arc previousArc = iterArc;
      iterArc = nextArc;
      if( iterArc == firstNodeArc )
      {
         break;
      }
      if( changeArcEnd && previousArc == firstNodeArc )
      {
         firstNodeArc = iterArc;
      }
   }
   while( TRUE ); /*lint !e506*/
   newRowInfo->head = newNode;
   newRowInfo->tail = splitNode;
   newRowInfo->member = member;
   newRowInfo->reversed = FALSE;
   newRowInfo->representative = findArcSign(dec, iterArc).representative;
 
   return SCIP_OKAY;
}
 
/** Merge an (updated) member into its parent.
 *
 * This function is mainly there to prevent duplication.
 */
static
SCIP_RETCODE mergeSplitMemberIntoParent(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   spqr_member           member,             /**< The member to merge */
   spqr_member           parent,             /**< The member's parent */
   spqr_arc              parentToChild,      /**< The marker pointing from the parent to child */
   spqr_arc              childToParent,      /**< The marker pointing from the child to the parent */
   SCIP_Bool             headToHead,         /**< Should the marker heads be identified with one another? */
   spqr_node             parentNode,         /**< A node in the parent that is not adjacent to the marker */
   spqr_node             childNode,          /**< A node in the child that is not adjacent to the marker */
   spqr_member*          mergedMember,       /**< Pointer to the member that contains both members after merging */
   spqr_node*            arcNodeOne,         /**< The first identified node of the two marker arcs */
   spqr_node*            arcNodeTwo,         /**< The second identified node of the two marker arcs */
   spqr_node*            thirdNode           /**< The node that parentNode and childNode are identified into */
   )
{
   assert(dec);
   assert(SPQRmemberIsValid(member));
   assert(memberIsRepresentative(dec, member));
   assert(SPQRmemberIsValid(parent));
   assert(memberIsRepresentative(dec, parent));
   assert(findMemberParentNoCompression(dec, member) == parent);
   assert(markerOfParent(dec, member) == parentToChild);
   assert(markerToParent(dec, member) == childToParent);
 
   removeArcFromMemberArcList(dec, parentToChild, parent);
   removeArcFromMemberArcList(dec, childToParent, member);
 
   int parentTail = findEffectiveArcTail(dec, parentToChild);
   int parentHead = findEffectiveArcHead(dec, parentToChild);
   int childTail = findEffectiveArcTail(dec, childToParent);
   int childHead = findEffectiveArcHead(dec, childToParent);
   spqr_node parentArcNodes[2] = { parentTail, parentHead };
   spqr_node childArcNodes[2] = { childTail, childHead };
 
   clearArcHeadAndTail(dec, parentToChild);
   clearArcHeadAndTail(dec, childToParent);
 
   spqr_node first = childArcNodes[headToHead ? 0 : 1];
   spqr_node second = childArcNodes[headToHead ? 1 : 0];
   {
      spqr_node newNode = mergeNodes(dec, parentArcNodes[0], first);
      spqr_node toRemoveFrom = newNode == first ? parentArcNodes[0] : first;
      mergeNodeArcList(dec, newNode, toRemoveFrom);
      *arcNodeOne = newNode;
      newRow->nodeColors[toRemoveFrom] = UNCOLORED;
   }
   {
      spqr_node newNode = mergeNodes(dec, parentArcNodes[1], second);
      spqr_node toRemoveFrom = newNode == second ? parentArcNodes[1] : second;
      mergeNodeArcList(dec, newNode, toRemoveFrom);
      *arcNodeTwo = newNode;
      newRow->nodeColors[toRemoveFrom] = UNCOLORED;
   }
   {
      spqr_node newNode = mergeNodes(dec, parentNode, childNode);
      spqr_node toRemoveFrom = newNode == childNode ? parentNode : childNode;
      mergeNodeArcList(dec, newNode, toRemoveFrom);
      *thirdNode = newNode;
      newRow->nodeColors[toRemoveFrom] = UNCOLORED;
   }
 
   spqr_member newMember = mergeMembers(dec, member, parent);
   spqr_member toRemoveFrom = newMember == member ? parent : member;
   mergeMemberArcList(dec, newMember, toRemoveFrom);
   if( toRemoveFrom == parent )
   {
      updateMemberParentInformation(dec, newMember, toRemoveFrom);
   }
   updateMemberType(dec, newMember, SPQR_MEMBERTYPE_RIGID);
   *mergedMember = newMember;
 
   return SCIP_OKAY;
}
 
/** Update a series member to reflect the addition of the new row, and merge it into the previous members that were
 * updated.
 */
static
SCIP_RETCODE splitAndMergeSeries(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     smallMember,        /**< The reduced series member */
   SCIP_Bool             largeIsParent,      /**< Whether the large member containing previously updated members is
                                              *   the parent of this member */
   NewRowInformation* const newRowInfo,      /**< Stores the information on how to add the new row */
   spqr_member           member              /**< The member belonging to the reduced series member */
   )
{
   SCIP_Bool isCut = FALSE;
   spqr_member mergingMember = SPQR_INVALID_MEMBER;
   spqr_arc nonVirtualArc = SPQR_INVALID_ARC;
 
   SCIP_CALL( splitSeriesMergingRowAddition(dec, newRow, smallMember, member, &mergingMember, &isCut, &nonVirtualArc) );
   assert(getNumMemberArcs(dec, mergingMember) == 3);
 
   //create the split series. There's two possible configurations, based on whether it contains a cut edge or not
   spqr_node a = SPQR_INVALID_NODE;
   spqr_node b = SPQR_INVALID_NODE;
   spqr_node c = SPQR_INVALID_NODE;
   spqr_node d = SPQR_INVALID_NODE;
   SCIP_CALL( createNode(dec, &a) );
   SCIP_CALL( createNode(dec, &b) );
   SCIP_CALL( createNode(dec, &c) );
   SCIP_CALL( createNode(dec, &d) );
 
   spqr_arc splitArc = newRow->reducedMembers[smallMember].splitArc;
 
   {
      SCIP_Bool splitHead = newRow->reducedMembers[smallMember].splitHead;
      spqr_arc firstArc = getFirstMemberArc(dec, mergingMember);
      spqr_arc arc = firstArc;
      SCIP_Bool splitReversed = arcIsReversedNonRigid(dec, splitArc);
      do
      {
         if( arc == splitArc )
         {
            if( splitHead )
            {
               setArcHeadAndTail(dec, splitArc, b, a);
            }
            else
            {
               setArcHeadAndTail(dec, splitArc, a, b);
            }
         }
         else if( arc == nonVirtualArc )
         {
            if( (arcIsReversedNonRigid(dec, arc) == splitReversed) == splitHead )
            {
               setArcHeadAndTail(dec, arc, a, d);
            }
            else
            {
               setArcHeadAndTail(dec, arc, d, a);
            }
         }
         else
         {
            spqr_node otherNode = cutArcIsValid(newRow->reducedMembers[smallMember].firstCutArc) ? c : b;
            if( (arcIsReversedNonRigid(dec, arc) == splitReversed) == splitHead )
            {
               setArcHeadAndTail(dec, arc, d, otherNode);
            }
            else
            {
               setArcHeadAndTail(dec, arc, otherNode, d);
            }
         }
         arcSetReversed(dec, arc, FALSE);
         arcSetRepresentative(dec, arc, splitArc);
         arc = getNextMemberArc(dec, arc);
      }
      while( arc != firstArc );
      arcSetRepresentative(dec, splitArc, SPQR_INVALID_ARC);
   }
 
   spqr_member otherMember = newRowInfo->member;
   spqr_arc otherMarker = largeIsParent ? markerOfParent(dec, mergingMember) : markerToParent(dec, otherMember);
 
   assert(nodeIsRepresentative(dec, newRowInfo->tail));
   assert(nodeIsRepresentative(dec, newRowInfo->head));
   spqr_node splitNode = newRow->reducedMembers[smallMember].splitHead ? findEffectiveArcHead(dec, otherMarker)
                                                                       : findEffectiveArcTail(dec, otherMarker);
 
   spqr_node otherNode = splitNode == newRowInfo->head ? newRowInfo->tail : newRowInfo->head;
   assert(splitNode == newRowInfo->head || splitNode == newRowInfo->tail);
   newRowInfo->representative = mergeArcSigns(dec, newRowInfo->representative, splitArc, FALSE);
 
   spqr_member mergedMember = SPQR_INVALID_MEMBER;
   spqr_node arcNodeOne;
   spqr_node arcNodeTwo;
   spqr_node thirdNode;
   if( largeIsParent )
   {
      SCIP_CALL( mergeSplitMemberIntoParent(dec, newRow, mergingMember, otherMember, otherMarker, splitArc, TRUE,
                                            otherNode, c, &mergedMember,
                                            &arcNodeOne,
                                            &arcNodeTwo,
                                            &thirdNode) );
   }
   else
   {
      SCIP_CALL( mergeSplitMemberIntoParent(dec, newRow, otherMember, mergingMember, splitArc, otherMarker, TRUE,
                                            c, otherNode, &mergedMember,
                                            &arcNodeOne,
                                            &arcNodeTwo,
                                            &thirdNode) );
   }
   newRow->reducedMembers[smallMember].member = mergedMember;
 
   newRowInfo->member = mergedMember;
   SCIP_Bool splitIsReferenceHead = newRow->reducedMembers[smallMember].splitHead;
   SCIP_Bool splitIsNewRowHead = splitNode == newRowInfo->head;
   if( !splitIsReferenceHead && !splitIsNewRowHead )
   {
      newRowInfo->head = thirdNode;
      newRowInfo->tail = arcNodeOne;
   }
   else if( !splitIsReferenceHead && splitIsNewRowHead )
   {
      newRowInfo->head = arcNodeOne;
      newRowInfo->tail = thirdNode;
   }
   else if( splitIsReferenceHead && !splitIsNewRowHead )
   {
      newRowInfo->head = thirdNode;
      newRowInfo->tail = arcNodeTwo;
   }
   else if( splitIsReferenceHead && splitIsNewRowHead )
   {
      newRowInfo->head = arcNodeTwo;
      newRowInfo->tail = thirdNode;
   }
 
   return SCIP_OKAY;
}
 
/** Update a parallel member to reflect the addition of the new row, and merge it into the previous members that were
 * updated.
 */
static
SCIP_RETCODE splitAndMergeParallel(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     smallMember,        /**< The reduced parallel member */
   SCIP_Bool             largeIsParent,      /**< Whether the large member containing previously updated members is
                                              *   the parent of this member */
   NewRowInformation* const newRowInfo,      /**< Stores the information on how to add the new row */
   spqr_member           member              /**< The member belonging to the reduced parallel member */
   )
{
   spqr_member mergeMember = SPQR_INVALID_MEMBER;
   spqr_arc cutRepresentative = SPQR_INVALID_ARC;
   SCIP_CALL( splitParallelMerging(dec, newRow, smallMember, member, &mergeMember, &cutRepresentative) );
   newRow->reducedMembers[smallMember].member = mergeMember;
 
   spqr_node firstNode = SPQR_INVALID_NODE;
   spqr_node secondNode = SPQR_INVALID_NODE;
   spqr_node thirdNode = SPQR_INVALID_NODE;
   SCIP_CALL( createNode(dec, &firstNode) );
   SCIP_CALL( createNode(dec, &secondNode) );
   SCIP_CALL( createNode(dec, &thirdNode) );
 
   spqr_arc splitArc = newRow->reducedMembers[smallMember].splitArc;
   assert(findArcMemberNoCompression(dec, splitArc) == mergeMember);
   SCIP_Bool splitArcReversed = arcIsReversedNonRigid(dec, splitArc);
   SCIP_Bool splitHead = newRow->reducedMembers[smallMember].splitHead;
 
   spqr_node splitArcHead = splitArcReversed ? secondNode : firstNode;
   spqr_node splitArcTail = splitArcReversed ? firstNode : secondNode;
   spqr_node otherNode = splitHead ? splitArcTail : splitArcHead;
 
   spqr_arc first_arc = getFirstMemberArc(dec, mergeMember);
   spqr_arc arc = first_arc;
 
   do
   {
      if( arc != cutRepresentative )
      {
         if( arcIsReversedNonRigid(dec, arc) )
         {
            setArcHeadAndTail(dec, arc, secondNode, firstNode);
         }
         else
         {
            setArcHeadAndTail(dec, arc, firstNode, secondNode);
         }
      }
      else
      {
         if( (arcIsReversedNonRigid(dec, arc) == splitArcReversed) == splitHead )
         {
            setArcHeadAndTail(dec, arc, thirdNode, otherNode);
         }
         else
         {
            setArcHeadAndTail(dec, arc, otherNode, thirdNode);
         }
      }
      arcSetReversed(dec, arc, FALSE);
      arcSetRepresentative(dec, arc, splitArc);
      arc = getNextMemberArc(dec, arc);
   }
   while( arc != first_arc );
   arcSetRepresentative(dec, splitArc, SPQR_INVALID_ARC);
 
   spqr_member otherMember = newRowInfo->member;
   spqr_arc otherMarker = largeIsParent ? markerOfParent(dec, mergeMember) : markerToParent(dec, otherMember);
 
   assert(nodeIsRepresentative(dec, newRowInfo->tail));
   assert(nodeIsRepresentative(dec, newRowInfo->head));
   spqr_node largeSplitNode = newRow->reducedMembers[smallMember].splitHead ? findEffectiveArcHead(dec, otherMarker)
                                                                            : findEffectiveArcTail(dec, otherMarker);
 
   spqr_node largeOtherNode =
      largeSplitNode == newRowInfo->head ? newRowInfo->tail : newRowInfo->head;
   assert(largeSplitNode == newRowInfo->head || largeSplitNode == newRowInfo->tail);
 
   newRowInfo->representative = mergeArcSigns(dec, newRowInfo->representative, splitArc, FALSE);
 
   spqr_member mergedMember = SPQR_INVALID_MEMBER;
   spqr_node arcNodeOne;
   spqr_node arcNodeTwo;
   spqr_node mergeNodeThree;
   if( largeIsParent )
   {
      SCIP_CALL( mergeSplitMemberIntoParent(dec, newRow, mergeMember, otherMember, otherMarker, splitArc, TRUE,
                                            largeOtherNode, thirdNode, &mergedMember,
                                            &arcNodeOne,
                                            &arcNodeTwo,
                                            &mergeNodeThree) );
   }
   else
   {
      SCIP_CALL( mergeSplitMemberIntoParent(dec, newRow, otherMember, mergeMember, splitArc, otherMarker, TRUE,
                                            thirdNode, largeOtherNode, &mergedMember,
                                            &arcNodeOne,
                                            &arcNodeTwo,
                                            &mergeNodeThree) );
   }
 
   newRowInfo->member = mergedMember;
 
   SCIP_Bool splitIsReferenceHead = newRow->reducedMembers[smallMember].splitHead;
   SCIP_Bool splitIsNewRowHead = largeSplitNode == newRowInfo->head;
   if( !splitIsReferenceHead && !splitIsNewRowHead )
   {
      newRowInfo->head = mergeNodeThree;
      newRowInfo->tail = arcNodeOne;
   }
   else if( !splitIsReferenceHead && splitIsNewRowHead )
   {
      newRowInfo->head = arcNodeOne;
      newRowInfo->tail = mergeNodeThree;
   }
   else if( splitIsReferenceHead && !splitIsNewRowHead )
   {
      newRowInfo->head = mergeNodeThree;
      newRowInfo->tail = arcNodeTwo;
   }
   else if( splitIsReferenceHead && splitIsNewRowHead )
   {
      newRowInfo->head = arcNodeTwo;
      newRowInfo->tail = mergeNodeThree;
   }
 
   return SCIP_OKAY;
}
 
/** Update a rigid member to reflect the addition of the new row, and merge it into the previous members that were
 * updated.
 */
static
SCIP_RETCODE splitAndMergeRigid(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     smallMember,        /**< The reduced rigid member */
   SCIP_Bool             largeIsParent,      /**< Whether the large member containing previously updated members is
                                              *   the parent of this member */
   NewRowInformation* const newRowInfo,      /**< Stores the information on how to add the new row */
   spqr_member           member              /**< The member belonging to the reduced rigid member */
   )
{
   spqr_node newNode = SPQR_INVALID_NODE;//Sink node
   SCIP_CALL( createNode(dec, &newNode) );
 
   spqr_member smallMemberMember = member;
   spqr_member largeMemberMember = newRowInfo->member;
 
   spqr_arc smallMarker = largeIsParent ? markerToParent(dec, smallMemberMember) : markerOfParent(dec,
                                                                                                  largeMemberMember);
   spqr_arc largeMarker = largeIsParent ? markerOfParent(dec, smallMemberMember) : markerToParent(dec,
                                                                                                  largeMemberMember);
 
   spqr_node splitNode = newRow->reducedMembers[smallMember].splitNode;
   spqr_node smallOtherNode = newNode;
 
   if( newRow->reducedMembers[smallMember].numCutArcs != 0 )
   {
      spqr_arc firstNodeArc = getFirstNodeArc(dec, splitNode);
      spqr_arc iterArc = firstNodeArc;
      do
      {
         spqr_node otherHead = findArcHead(dec, iterArc);
         spqr_node otherTail = findArcTail(dec, iterArc);
         spqr_node otherEnd = otherHead == splitNode ? otherTail : otherHead;
         spqr_arc nextArc = getNextNodeArc(dec, iterArc, splitNode);//Need to do this before we modify the arc
 
         SCIP_Bool isCut = newRow->isArcCut[iterArc];
         SCIP_Bool isMoveColor = newRow->nodeColors[otherEnd] == COLOR_SOURCE;
         SCIP_Bool changeArcEnd = isCut == isMoveColor;
         if( changeArcEnd )
         {
            if( otherHead == splitNode )
            {
               changeArcHead(dec, iterArc, otherHead, newNode);
            }
            else
            {
               changeArcTail(dec, iterArc, otherTail, newNode);
            }
            if( iterArc == smallMarker )
            {
               smallOtherNode = splitNode;
            }
         }
         newRow->nodeColors[otherEnd] = UNCOLORED;
         //Ugly hack to make sure we can iterate neighbourhood whilst changing arc ends.
         spqr_arc previousArc = iterArc;
         iterArc = nextArc;
         if( iterArc == firstNodeArc )
         {
            break;
         }
         if( changeArcEnd && previousArc == firstNodeArc )
         {
            firstNodeArc = iterArc;
         }
      }
      while( TRUE ); /*lint !e506*/
   }
 
   spqr_arc representative = findArcSign(dec, smallMarker).representative;
 
   newRowInfo->representative = mergeArcSigns(dec, newRowInfo->representative, representative,
                                              newRow->reducedMembers[smallMember].willBeReversed);
 
   spqr_node largeMarkerHead = findArcHead(dec, largeMarker);
   spqr_node largeMarkerTail = findArcTail(dec, largeMarker);
   if( findArcSign(dec, largeMarker).reversed )
   {
      spqr_node temp = largeMarkerHead;
      largeMarkerHead = largeMarkerTail;
      largeMarkerTail = temp;
   }
   assert(newRowInfo->head == largeMarkerHead || newRowInfo->head == largeMarkerTail ||
          newRowInfo->tail == largeMarkerHead || newRowInfo->tail == largeMarkerTail);
   spqr_node largeOtherNode = ( newRowInfo->head == largeMarkerHead || newRowInfo->head == largeMarkerTail )
                              ? newRowInfo->tail : newRowInfo->head;
 
   spqr_member mergedMember = SPQR_INVALID_MEMBER;
   spqr_node arcNodeOne;
   spqr_node arcNodeTwo;
   spqr_node mergeNodeThree;
   if( largeIsParent )
   {
      SCIP_CALL(
         mergeSplitMemberIntoParent(dec, newRow, smallMemberMember, largeMemberMember, largeMarker, smallMarker, TRUE,
                                    largeOtherNode, smallOtherNode, &mergedMember,
                                    &arcNodeOne,
                                    &arcNodeTwo,
                                    &mergeNodeThree) );
   }
   else
   {
      SCIP_CALL(
         mergeSplitMemberIntoParent(dec, newRow, largeMemberMember, smallMemberMember, smallMarker, largeMarker, TRUE,
                                    smallOtherNode, largeOtherNode, &mergedMember,
                                    &arcNodeOne,
                                    &arcNodeTwo,
                                    &mergeNodeThree) );
   }
   newRowInfo->member = mergedMember;
 
   SCIP_Bool otherIsHead = largeOtherNode == newRowInfo->head;
   SCIP_Bool adjacentToMarkerHead = ( newRowInfo->tail == largeMarkerHead ||
                                      newRowInfo->head == largeMarkerHead );
   if( adjacentToMarkerHead )
   {
      if( otherIsHead )
      {
         newRowInfo->head = mergeNodeThree;
         newRowInfo->tail = arcNodeTwo;
      }
      else
      {
         newRowInfo->head = arcNodeTwo;
         newRowInfo->tail = mergeNodeThree;
      }
   }
   else
   {
      if( otherIsHead )
      {
         newRowInfo->head = mergeNodeThree;
         newRowInfo->tail = arcNodeOne;
      }
      else
      {
         newRowInfo->head = arcNodeOne;
         newRowInfo->tail = mergeNodeThree;
      }
   }
 
   return SCIP_OKAY;
}
 
/** Update a member to reflect the addition of the new row, and merge it into the previous members that were updated. */
static
SCIP_RETCODE splitAndMerge(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     smallMember,        /**< The reduced rigid member */
   SCIP_Bool             largeIsParent,      /**< Whether the large member containing previously updated members is
                                              *   the parent of this member */
   NewRowInformation* const newRowInfo       /**< Stores the information on how to add the new row */
   )
{
   spqr_member member = newRow->reducedMembers[smallMember].member;
   switch( getMemberType(dec, member))
   {
      case SPQR_MEMBERTYPE_RIGID:
      {
         SCIP_CALL( splitAndMergeRigid(dec, newRow, smallMember, largeIsParent, newRowInfo, member) );
         break;
      }
      case SPQR_MEMBERTYPE_PARALLEL:
      {
         SCIP_CALL( splitAndMergeParallel(dec, newRow, smallMember, largeIsParent, newRowInfo, member) );
         break;
      }
      case SPQR_MEMBERTYPE_SERIES:
      {
         SCIP_CALL( splitAndMergeSeries(dec, newRow, smallMember, largeIsParent, newRowInfo, member) );
         break;
      }
      case SPQR_MEMBERTYPE_LOOP:
      case SPQR_MEMBERTYPE_UNASSIGNED:
      default:
      {
         newRow->remainsNetwork = FALSE;
         SCIPABORT();
         return SCIP_ERROR;
      }
   }
   return SCIP_OKAY;
}
 
/** Update an SPQR tree with multiple members to reflect the addition of a new row,
 * merging it into one big rigid node.
 */
static
SCIP_RETCODE mergeTree(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   reduced_member_id     root,               /**< The root node of the SPQR tree that is to be merged */
   NewRowInformation* const newRowInfo       /**< Stores the information on how to add the new row */
   )
{
   //We use the same ordering as when finding
   //go to a leaf. We need to start in a leaf to avoid the ambiguity of choosing an orientation
   //in members which have no cut arcs; otherwise, we might choose the wrong one
   reduced_member_id leaf = root;
   while( newRow->reducedMembers[leaf].numChildren != newRow->reducedMembers[leaf].numPropagatedChildren )
   {
      for( int i = 0; i < newRow->reducedMembers[leaf].numChildren; ++i )
      {
         children_idx idx = newRow->reducedMembers[leaf].firstChild + i;
         reduced_member_id child = newRow->childrenStorage[idx];
         if( newRow->reducedMembers[child].type != TYPE_PROPAGATED )
         {
            leaf = child;
            break;
         }
      }
   }
   SCIP_CALL( splitFirstLeaf(dec, newRow, leaf, newRowInfo) );
 
   reduced_member_id baseNode = leaf;
   reduced_member_id nextNode = newRow->reducedMembers[baseNode].parent;
 
   while( reducedMemberIsValid(nextNode) )
   {
      //check this node
      SCIP_CALL( splitAndMerge(dec, newRow, nextNode, FALSE, newRowInfo) );
 
      //Recursively merge the children
      //use a while loop to avoid recursion; we may get stack overflows for large graphs
      MergeTreeCallData * data = newRow->mergeTreeCallData;
 
      data[0].id = nextNode;
      data[0].currentChild = newRow->reducedMembers[nextNode].firstChild ;
      int depth = 0;
      while( depth >= 0 )
      {
         reduced_member_id id = data[depth].id;
         children_idx childidx = data[depth].currentChild;
         if( childidx == newRow->reducedMembers[id].firstChild + newRow->reducedMembers[id].numChildren )
         {
            --depth;
            continue;
         }
         reduced_member_id currentchild = newRow->childrenStorage[childidx];
         data[depth].currentChild += 1;
         //skip this child if we already processed it or it is not merged
         if( currentchild == baseNode || newRow->reducedMembers[currentchild].type == TYPE_PROPAGATED )
         {
            continue;
         }
         SCIP_CALL( splitAndMerge(dec, newRow, currentchild, TRUE, newRowInfo) );
 
         //recursively process the child
         depth += 1;
         assert(depth < newRow->memMergeTreeCallData);
         data[depth].id = currentchild;
         data[depth].currentChild = newRow->reducedMembers[currentchild].firstChild;
      }
      //Move up one layer
      baseNode = nextNode;
      nextNode = newRow->reducedMembers[nextNode].parent;
   }
 
   return SCIP_OKAY;
}
 
/** Update an SPQR tree (a single component of the SPQR forest) to reflect addition of a new row. */
static
SCIP_RETCODE transformComponentRowAddition(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       newRow,             /**< The network matrix row addition data structure */
   SPQRRowReducedComponent* component,       /**< The component to transform */
   NewRowInformation* const newRowInfo       /**< Stores the information on how to add the new row */
   )
{
   assert(component);
   if( newRow->reducedMembers[component->root].numChildren ==
       newRow->reducedMembers[component->root].numPropagatedChildren )
   {
      //No merging necessary, only a single component
      reduced_member_id reducedMember = component->root;
      assert(reducedMemberIsValid(reducedMember));
      spqr_member member = newRow->reducedMembers[reducedMember].member;
      SPQRMemberType type = getMemberType(dec, member);
 
      switch( type )
      {
         case SPQR_MEMBERTYPE_RIGID:
            SCIP_CALL( transformSingleRigid(dec, newRow, reducedMember, member, newRowInfo) );
            break;
         case SPQR_MEMBERTYPE_PARALLEL:
         {
            SCIP_CALL( transformSingleParallel(dec, newRow, reducedMember, member, newRowInfo) );
            break;
         }
         case SPQR_MEMBERTYPE_LOOP:
         case SPQR_MEMBERTYPE_SERIES:
         {
            newRowInfo->member = member;
            cut_arc_id cutArc = newRow->reducedMembers[reducedMember].firstCutArc;
            spqr_arc arc = newRow->cutArcs[cutArc].arc;
            newRowInfo->reversed = arcIsReversedNonRigid(dec, arc) == newRow->cutArcs[cutArc].arcReversed;
            if( type == SPQR_MEMBERTYPE_LOOP )
            {
               if( getNumMemberArcs(dec, member) == 2 )
               {
                  changeLoopToSeries(dec, member);
               }
            }
            break;
         }
         case SPQR_MEMBERTYPE_UNASSIGNED:
         default:
         {
            SCIPABORT();
            return SCIP_ERROR;
         }
      }
 
      return SCIP_OKAY;
   }
 
   SCIP_CALL( mergeTree(dec, newRow, component->root, newRowInfo) );
 
   return SCIP_OKAY;
}
 
/** Create the network row addition data structure. */
static
SCIP_RETCODE netrowaddCreate(
   BMS_BLKMEM*           blkmem,             /**< Block memory */
   SCIP_NETROWADD**      prowadd             /**< Pointer to store the new row addition struct at */
   )
{
   assert(blkmem);
   SCIP_ALLOC( BMSallocBlockMemory(blkmem, prowadd) );
   SCIP_NETROWADD* newRow = *prowadd;
 
   newRow->remainsNetwork = TRUE;
 
   newRow->reducedMembers = NULL;
   newRow->memReducedMembers = 0;
   newRow->numReducedMembers = 0;
 
   newRow->reducedComponents = NULL;
   newRow->memReducedComponents = 0;
   newRow->numReducedComponents = 0;
 
   newRow->memberInformation = NULL;
   newRow->memMemberInformation = 0;
   newRow->numMemberInformation = 0;
 
   newRow->cutArcs = NULL;
   newRow->memCutArcs = 0;
   newRow->numCutArcs = 0;
   newRow->firstOverallCutArc = INVALID_CUT_ARC;
 
   newRow->childrenStorage = NULL;
   newRow->memChildrenStorage = 0;
   newRow->numChildrenStorage = 0;
 
   newRow->newRowIndex = SPQR_INVALID_ROW;
 
   newRow->newColumnArcs = NULL;
   newRow->newColumnReversed = NULL;
   newRow->memColumnArcs = 0;
   newRow->numColumnArcs = 0;
 
   newRow->leafMembers = NULL;
   newRow->numLeafMembers = 0;
   newRow->memLeafMembers = 0;
 
   newRow->decompositionColumnArcs = NULL;
   newRow->decompositionColumnArcReversed = NULL;
   newRow->memDecompositionColumnArcs = 0;
   newRow->numDecompositionColumnArcs = 0;
 
   newRow->isArcCut = NULL;
   newRow->isArcCutReversed = NULL;
   newRow->memIsArcCut = 0;
 
   newRow->nodeColors = NULL;
   newRow->memNodeColors = 0;
 
   newRow->articulationNodes = NULL;
   newRow->memArticulationNodes = 0;
   newRow->numArticulationNodes = 0;
 
   newRow->articulationNodeSearchInfo = NULL;
   newRow->memNodeSearchInfo = 0;
 
   newRow->crossingPathCount = NULL;
   newRow->memCrossingPathCount = 0;
 
   newRow->intersectionDFSData = NULL;
   newRow->memIntersectionDFSData = 0;
 
   newRow->colorDFSData = NULL;
   newRow->memColorDFSData = 0;
 
   newRow->artDFSData = NULL;
   newRow->memArtDFSData = 0;
 
   newRow->createReducedMembersCallstack = NULL;
   newRow->memCreateReducedMembersCallstack = 0;
 
   newRow->intersectionPathDepth = NULL;
   newRow->memIntersectionPathDepth = 0;
 
   newRow->intersectionPathParent = NULL;
   newRow->memIntersectionPathParent = 0;
 
   newRow->mergeTreeCallData = NULL;
   newRow->memMergeTreeCallData = 0;
 
   newRow->temporaryColorArray = NULL;
   newRow->memTemporaryColorArray = 0;
 
   return SCIP_OKAY;
}
 
/** Frees the network row addition data structure. */
static
void netrowaddFree(
   BMS_BLKMEM*           blkmem,             /**< Block memory */
   SCIP_NETROWADD**      prowadd             /**< Pointer to row addition struct to be freed */
   )
{
   assert(*prowadd);
 
   SCIP_NETROWADD* newRow = *prowadd;
 
   BMSfreeBlockMemoryArray(blkmem, &newRow->temporaryColorArray, newRow->memTemporaryColorArray);
   BMSfreeBlockMemoryArray(blkmem, &newRow->createReducedMembersCallstack, newRow->memCreateReducedMembersCallstack);
   BMSfreeBlockMemoryArray(blkmem, &newRow->artDFSData, newRow->memArtDFSData);
   BMSfreeBlockMemoryArray(blkmem, &newRow->colorDFSData, newRow->memColorDFSData);
   BMSfreeBlockMemoryArray(blkmem, &newRow->mergeTreeCallData, newRow->memMergeTreeCallData);
   BMSfreeBlockMemoryArray(blkmem, &newRow->intersectionDFSData, newRow->memIntersectionDFSData);
   BMSfreeBlockMemoryArray(blkmem, &newRow->intersectionPathParent, newRow->memIntersectionPathParent);
   BMSfreeBlockMemoryArray(blkmem, &newRow->intersectionPathDepth, newRow->memIntersectionPathDepth);
   BMSfreeBlockMemoryArray(blkmem, &newRow->crossingPathCount, newRow->memCrossingPathCount);
   BMSfreeBlockMemoryArray(blkmem, &newRow->articulationNodeSearchInfo, newRow->memNodeSearchInfo);
   BMSfreeBlockMemoryArray(blkmem, &newRow->articulationNodes, newRow->memArticulationNodes);
   BMSfreeBlockMemoryArray(blkmem, &newRow->nodeColors, newRow->memNodeColors);
   BMSfreeBlockMemoryArray(blkmem, &newRow->isArcCut, newRow->memIsArcCut);
   BMSfreeBlockMemoryArray(blkmem, &newRow->isArcCutReversed, newRow->memIsArcCut);
   BMSfreeBlockMemoryArray(blkmem, &newRow->decompositionColumnArcs, newRow->memDecompositionColumnArcs);
   BMSfreeBlockMemoryArray(blkmem, &newRow->decompositionColumnArcReversed, newRow->memDecompositionColumnArcs);
   BMSfreeBlockMemoryArray(blkmem, &newRow->newColumnArcs, newRow->memColumnArcs);
   BMSfreeBlockMemoryArray(blkmem, &newRow->newColumnReversed, newRow->memColumnArcs);
   BMSfreeBlockMemoryArray(blkmem, &newRow->childrenStorage, newRow->memChildrenStorage);
   BMSfreeBlockMemoryArray(blkmem, &newRow->cutArcs, newRow->memCutArcs);
   BMSfreeBlockMemoryArray(blkmem, &newRow->memberInformation, newRow->memMemberInformation);
   BMSfreeBlockMemoryArray(blkmem, &newRow->reducedComponents, newRow->memReducedComponents);
   BMSfreeBlockMemoryArray(blkmem, &newRow->reducedMembers, newRow->memReducedMembers);
   BMSfreeBlockMemoryArray(blkmem, &newRow->leafMembers, newRow->memLeafMembers);
   BMSfreeBlockMemory(blkmem, prowadd);
}
 
/** Checks if the given row can be added to the network decomposition. */
static
SCIP_RETCODE netrowaddCheck(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       rowadd,             /**< The network matrix row addition data structure */
   int                   row,                /**< The row to be checked */
   const int*            nonzcols,           /**< The column indices of the row's nonzero values */
   const double*         nonzvals,           /**< The matrix entries of the row's nonzeroes */
   int                   nnonzs              /**< The number of nonzeroes in the row */
   )
{
   assert(dec);
   assert(rowadd);
   assert(nnonzs == 0 || nonzcols);
 
   /* A row can only be added once */
   if( netMatDecDataContainsRow(dec,row) )
   {
      return SCIP_INVALIDDATA;
   }
 
   rowadd->remainsNetwork = TRUE;
   cleanUpPreviousIteration(dec, rowadd);
 
   SCIP_CALL( newRowUpdateRowInformation(dec, rowadd, row, nonzcols, nonzvals, nnonzs) );
   SCIP_CALL( constructRowReducedDecomposition(dec, rowadd) );
   SCIP_CALL( createReducedDecompositionCutArcs(dec, rowadd) );
 
   SCIP_CALL( determineLeafReducedMembers(dec, rowadd) );
   SCIP_CALL( allocateRigidSearchMemory(dec, rowadd) );
   SCIP_CALL( allocateTreeSearchMemory(dec, rowadd) );
   //Check for each component if the cut arcs propagate through a row tree marker to a cut arc in another component
   //From the leafs inward.
   propagateComponents(dec, rowadd);
   //It can happen that we are not graphic by some of the checked components.
   //In that case, further checking may lead to errors as some invariants that the code assumes will be broken.
   if( rowadd->remainsNetwork )
   {
      for( int i = 0; i < rowadd->numReducedComponents; ++i )
      {
         determineMergeableTypes(dec, rowadd, rowadd->reducedComponents[i].root);
         //exit early if one is not graphic
         if( !rowadd->remainsNetwork )
         {
            break;
         }
      }
   }
 
   cleanUpRowMemberInformation(rowadd);
 
   return SCIP_OKAY;
}
 
/** Adds the last checked row to the network decomposition. */
static
SCIP_RETCODE netrowaddAdd(
   SCIP_NETMATDECDATA*   dec,                /**< The network matrix decomposition */
   SCIP_NETROWADD*       rowadd              /**< The network matrix row addition data structure */
   )
{
   assert(rowadd->remainsNetwork);
   if( rowadd->numReducedComponents == 0 )
   {
      spqr_member newMember = SPQR_INVALID_MEMBER;
      SCIP_CALL( createStandaloneParallel(dec, rowadd->newColumnArcs, rowadd->newColumnReversed,
                                          rowadd->numColumnArcs, rowadd->newRowIndex, &newMember) );
   }
   else if( rowadd->numReducedComponents == 1 )
   {
      NewRowInformation information = NEWROWINFORMATION_EMPTY;
      SCIP_CALL( transformComponentRowAddition(dec, rowadd, &rowadd->reducedComponents[0], &information) );
 
      if( rowadd->numColumnArcs == 0 )
      {
         spqr_arc rowArc = SPQR_INVALID_ARC;
         SCIP_CALL( createRowArc(dec, information.member, &rowArc, rowadd->newRowIndex, information.reversed) );
         if( SPQRnodeIsValid(information.head))
         {
            assert(SPQRnodeIsValid(information.tail));
            assert(SPQRarcIsValid(information.representative));
            setArcHeadAndTail(dec, rowArc, findNode(dec, information.head), findNode(dec, information.tail));
            arcSetRepresentative(dec, rowArc, information.representative);
            arcSetReversed(dec, rowArc, information.reversed != arcIsReversedNonRigid(dec, information.representative));
         }
      }
      else
      {
         spqr_member new_row_parallel = SPQR_INVALID_MEMBER;
         SCIP_CALL( createConnectedParallel(dec, rowadd->newColumnArcs, rowadd->newColumnReversed, rowadd->numColumnArcs,
                                            rowadd->newRowIndex, &new_row_parallel) );
         spqr_arc markerArc = SPQR_INVALID_ARC;
         spqr_arc ignore = SPQR_INVALID_ARC;
         SCIP_CALL( createMarkerPairWithReferences(dec, information.member, new_row_parallel, TRUE,
                                                   information.reversed, FALSE,
                                                   &markerArc, &ignore) );
         if( SPQRnodeIsValid(information.head))
         {
            assert(SPQRnodeIsValid(information.tail));
            assert(SPQRarcIsValid(information.representative));
            setArcHeadAndTail(dec, markerArc, findNode(dec, information.head), findNode(dec, information.tail));
            arcSetRepresentative(dec, markerArc, information.representative);
            arcSetReversed(dec, markerArc,
                           information.reversed != arcIsReversedNonRigid(dec, information.representative));
         }
      }
      if( getMemberType(dec, information.member) == SPQR_MEMBERTYPE_LOOP )
      {
         assert(getNumMemberArcs(dec, information.member) == 2 || getNumMemberArcs(dec, information.member) == 3);
         if( getNumMemberArcs(dec, information.member) == 3 )
         {
            changeLoopToSeries(dec, information.member);
         }
      }
   }
   else
   {
#ifndef NDEBUG
      int numDecComponentsBefore = numConnectedComponents(dec);
#endif
      spqr_member new_row_parallel = SPQR_INVALID_MEMBER;
      SCIP_CALL( createConnectedParallel(dec, rowadd->newColumnArcs, rowadd->newColumnReversed, rowadd->numColumnArcs,
                                         rowadd->newRowIndex, &new_row_parallel) );
      for( int i = 0; i < rowadd->numReducedComponents; ++i )
      {
         NewRowInformation information = NEWROWINFORMATION_EMPTY;
 
         SCIP_CALL( transformComponentRowAddition(dec, rowadd, &rowadd->reducedComponents[i], &information) );
         if( getMemberType(dec, information.member) == SPQR_MEMBERTYPE_LOOP )
         {
            assert(getNumMemberArcs(dec, information.member) == 1);
            spqr_arc arc = getFirstMemberArc(dec, information.member);
            assert(rowadd->isArcCut[arc]);
            moveArcToNewMember(dec, arc, information.member, new_row_parallel);
            arcSetReversed(dec, arc, rowadd->isArcCutReversed[arc]);
            dec->members[information.member].type = SPQR_MEMBERTYPE_UNASSIGNED;
         }
         else
         {
            reorderComponent(dec, information.member);//Make sure the new component is the root of the local decomposition tree
            spqr_arc markerArc = SPQR_INVALID_ARC;
            spqr_arc ignore = SPQR_INVALID_ARC;
            SCIP_CALL( createMarkerPairWithReferences(dec, new_row_parallel, information.member, FALSE,
                                                      FALSE, information.reversed,
                                                      &ignore, &markerArc) );
            if( SPQRnodeIsValid(information.head))
            {
               assert(SPQRnodeIsValid(information.tail));
               assert(SPQRarcIsValid(information.representative));
               setArcHeadAndTail(dec, markerArc, findNode(dec, information.head), findNode(dec, information.tail));
               arcSetRepresentative(dec, markerArc, information.representative);
               arcSetReversed(dec, markerArc,
                              information.reversed != arcIsReversedNonRigid(dec, information.representative));
            }
         }
      }
      decreaseNumConnectedComponents(dec, rowadd->numReducedComponents - 1);
      assert(numConnectedComponents(dec) == ( numDecComponentsBefore - rowadd->numReducedComponents + 1 ));
   }
 
   return SCIP_OKAY;
}
 
/** Returns whether the last checked row can be added to the network decomposition. */
static
SCIP_Bool netrowaddRemainsNetwork(
   const SCIP_NETROWADD* rowadd              /**< The network matrix row addition data structure */
   )
{
   return rowadd->remainsNetwork;
}
 
/** A generic data structure that stores a decomposition and can perform both column and row additions. */
struct SCIP_Netmatdec
{
   SCIP_NETMATDECDATA*   dec;
   SCIP_NETROWADD*       rowadd;
   SCIP_NETCOLADD*       coladd;
};
 
SCIP_RETCODE SCIPnetmatdecCreate(
   BMS_BLKMEM*           blkmem,             /**< Block memory */
   SCIP_NETMATDEC**      pdec,               /**< buffer to store pointer to created decomposition */
   int                   nrows,              /**< The maximal number of rows that the decomposition can expect */
   int                   ncols               /**< The maximal number of columns that the decomposition can expect */
   )
{
   SCIP_ALLOC( BMSallocBlockMemory(blkmem,pdec) );
   SCIP_NETMATDEC* dec = *pdec;
 
   dec->dec = NULL;
   SCIP_CALL( netMatDecDataCreate(blkmem, &dec->dec, nrows, ncols) );
   dec->rowadd = NULL;
   dec->coladd = NULL;
 
   return SCIP_OKAY;
}
 
void SCIPnetmatdecFree(
   SCIP_NETMATDEC**      pdec                /**< pointer to the network matrix decomposition to freed */
   )
{
   SCIP_NETMATDEC* dec = *pdec;
   BMS_BLKMEM* blkmem = dec->dec->env;
 
   if( dec->coladd != NULL )
   {
      netcoladdFree(blkmem, &dec->coladd);
   }
   if( dec->rowadd != NULL )
   {
      netrowaddFree(blkmem, &dec->rowadd);
   }
   netMatDecDataFree(&dec->dec);
   BMSfreeBlockMemory(blkmem,pdec);
}
 
SCIP_RETCODE SCIPnetmatdecTryAddCol(
   SCIP_NETMATDEC*       dec,                /**< Network matrix decomposition */
   int                   column,             /**< The column to add */
   int*                  nonzrows,           /**< The column's nonzero row indices */
   double*               nonzvals,           /**< The column's nonzero entries */
   int                   nnonzs,             /**< The number of nonzeros in the column */
   SCIP_Bool*            success             /**< Buffer to store whether the column was added */
   )
{
   if( dec->coladd == NULL )
   {
      SCIP_CALL( netcoladdCreate(dec->dec->env, &dec->coladd) );
   }
 
   SCIP_CALL( netcoladdCheck(dec->dec, dec->coladd, column, nonzrows, nonzvals, nnonzs) );
   *success = netcoladdRemainsNetwork(dec->coladd);
   if( *success )
   {
      SCIP_CALL( netcoladdAdd(dec->dec, dec->coladd) );
   }
 
   return SCIP_OKAY;
}
 
SCIP_RETCODE SCIPnetmatdecTryAddRow(
   SCIP_NETMATDEC*       dec,                /**< Network matrix decomposition */
   int                   row,                /**< The row to add */
   int*                  nonzcols,           /**< The row's nonzero column indices */
   double*               nonzvals,           /**< The row's nonzero entries */
   int                   nnonzs,             /**< The number of nonzeros in the row */
   SCIP_Bool*            success             /**< Buffer to store whether the row was added */
   )
{
   if( dec->rowadd == NULL )
   {
      SCIP_CALL( netrowaddCreate(dec->dec->env, &dec->rowadd) );
   }
 
   SCIP_CALL( netrowaddCheck(dec->dec, dec->rowadd, row, nonzcols, nonzvals, nnonzs) );
   *success = netrowaddRemainsNetwork(dec->rowadd);
   if( *success )
   {
      SCIP_CALL( netrowaddAdd(dec->dec, dec->rowadd) );
   }
 
   return SCIP_OKAY;
}
 
SCIP_Bool SCIPnetmatdecContainsRow(
   SCIP_NETMATDEC*       dec,                /**< The network matrix decomposition */
   int                   row                 /**< The row index that is checked */
   )
{
   return netMatDecDataContainsRow(dec->dec, row);
}
 
SCIP_Bool SCIPnetmatdecContainsColumn(
   SCIP_NETMATDEC*       dec,                /**< The network matrix decomposition */
   int                   column              /**< The column index that is checked */
   )
{
   return netMatDecDataContainsColumn(dec->dec, column);
}
 
void SCIPnetmatdecRemoveComponent(
   SCIP_NETMATDEC*       dec,                /**< The network matrix decomposition */
   int*                  componentrows,      /**< Pointer to the array of rows to delete */
   int                   nrows,              /**< The number of rows to delete */
   int*                  componentcols,      /**< Pointer to the array of columns to delete */
   int                   ncols               /**< The number of columns to delete */
   )
{
   netMatDecDataRemoveComponent(dec->dec, componentrows, nrows, componentcols, ncols);
}
 
SCIP_Bool SCIPnetmatdecIsMinimal(
   SCIP_NETMATDEC*       dec                 /**< The network matrix decomposition */
   )
{
   return netMatDecDataIsMinimal(dec->dec);
}
 
SCIP_Bool SCIPnetmatdecVerifyCycle(
   BMS_BUFMEM*           bufmem,             /**< Buffer memory */
   SCIP_NETMATDEC*       dec,                /**< The network matrix decomposition */
   int                   column,             /**< The column to check */
   int*                  nonzrowidx,         /**< Array with the column's nonzero row indices */
   double*               nonzvals,           /**< Array with the column's nonzero values */
   int                   nnonzs,             /**< Number of nonzeros in the column */
   int*                  pathrowstorage,     /**< A buffer to hold the computed path's rows. Should have size equal or
                                              *   greater than the number of rows in the decomposition. */
   SCIP_Bool*            pathsignstorage     /**< A buffer to store the computed path's row signs. Should have size
                                              *   equal or greater than the number of rows in the decomposition. */
   )
{
   return netMatDecDataVerifyCycle(bufmem, dec->dec, column, nonzrowidx, nonzvals, nnonzs, pathrowstorage, pathsignstorage);
}
 
SCIP_RETCODE SCIPnetmatdecCreateDiGraph(
   SCIP_NETMATDEC*       dec,                /**< The network matrix decomposition */
   BMS_BLKMEM *          blkmem,             /**< The block memory to use for the created digraph */
   SCIP_DIGRAPH**        pdigraph,           /**< Pointer to the pointer to store the created digraph */
   SCIP_Bool             createrowarcs       /**< Should the row arcs be added to the created digraph? */
   )
{
   return netMatDecDataCreateDiGraph(dec->dec, blkmem, pdigraph, createrowarcs);
}