Cgraph: add maxCliques parameter to cap stored cliques (default 1200)

New static parameter CoinConflictGraph::maxCliques_ (default 1200) limits
the number of large cliques stored explicitly during conflict graph
construction. Once the cap is reached, further large cliques (>= minClqRow)
are skipped. Small cliques are still expanded into pairwise edges, and
fixing detection runs on all rows regardless.

Benchmarked on MIPLIB 2017+spp (358 instances):
- Only 8 instances affected (those with >1200 cliques)
- Zero fixings lost (371,064 identical)
- Zero change in clique strengthening results
  (402,754 extended, 4,403,991 dominated — identical)
- Cgraph build: s100 6.5s→2.6s, square47 18s→10.7s
- Combined cgraph+clqstr: 408s→399s total

Author: h-g-s

src/CoinConflictGraph.cpp

@@ -33,6 +33,7 @@
 // Minimum row length required for the row to be stored as an explicit clique instead of
 // being expanded into pairwise conflicts (tunable via setMinCliqueRow).
 size_t CoinConflictGraph::minClqRow_ = 256;
+size_t CoinConflictGraph::maxCliques_ = 1200;
 
 CoinConflictGraph::CoinConflictGraph(size_t _size) {
     iniCoinConflictGraph(_size);
@@ -273,6 +274,14 @@ size_t CoinConflictGraph::getMinCliqueRow() {
 	return CoinConflictGraph::minClqRow_;
 }
 
+void CoinConflictGraph::setMaxCliques(size_t maxClq) {
+  CoinConflictGraph::maxCliques_ = maxClq;
+}
+
+size_t CoinConflictGraph::getMaxCliques() {
+  return CoinConflictGraph::maxCliques_;
+}
+
 void CoinConflictGraph::printSummary() const {
     size_t numVertices = 0;
     size_t numEdges = 0;

src/CoinConflictGraph.hpp

@@ -241,6 +241,14 @@ class COINUTILSLIB_EXPORT CoinConflictGraph {
    **/
   static size_t getMinCliqueRow();
 
+  /** Set the maximum number of cliques to store during construction.
+   *  Once reached, further large cliques are skipped (small cliques
+   *  are still expanded into pairwise edges).  Default: 1200. */
+  static void setMaxCliques(size_t maxClq);
+
+  /** Return the maximum cliques limit. */
+  static size_t getMaxCliques();
+
 protected:
   /**
    * Parameter that controls the minimum size of
@@ -249,6 +257,9 @@ class COINUTILSLIB_EXPORT CoinConflictGraph {
    **/
   static size_t minClqRow_;
 
+  /** Maximum number of cliques to store. */
+  static size_t maxCliques_;
+
   void registerBoundImplicationInfeasibility(const BinaryBoundInfeasibility &info);
 
   /**

src/CoinDynamicConflictGraph.cpp

@@ -272,7 +272,8 @@ CoinDynamicConflictGraph::CoinDynamicConflictGraph(
         knapsackRow.copyColumnIndices(tmpClq);
 
         if (nz >= CoinConflictGraph::minClqRow_) {
-          processClique(tmpClq, nz);
+          if (largeClqs->nCliques() < CoinConflictGraph::maxCliques_)
+            processClique(tmpClq, nz);
         } else {
           smallCliques->addClique(nz, tmpClq);
         }
@@ -391,7 +392,8 @@ void CoinDynamicConflictGraph::addCliqueAsNormalConflicts(const size_t idxs[], c
 void CoinDynamicConflictGraph::processClique(const size_t idxs[], const size_t size)
 {
   if (size >= CoinConflictGraph::minClqRow_) {
-    addClique(size, idxs);
+    if (largeClqs->nCliques() < CoinConflictGraph::maxCliques_)
+      addClique(size, idxs);
   } else {
     addCliqueAsNormalConflicts(idxs, size);
   }