added comments

Author: Christopher Hojny

src/scip/prop_symmetry.c

@@ -199,8 +199,11 @@
 /* other defines */
 #define MAXGENNUMERATOR          64000000    /**< determine maximal number of generators by dividing this number by the number of variables */
 #define COMPRESSNVARSLB             25000    /**< lower bound on the number of variables above which compression could be performed */
-#define DEFAULT_NAUTYMAXNCELLS     100000    /**< terminate symmetry detection using Nauty when number of cells in color refinment is at least this number */
+#define DEFAULT_NAUTYMAXNCELLS     100000    /**< terminate symmetry detection using Nauty when number of cells in color refinment is at least this number
+                                              *   (avoids segfaults due to Nauty for large graphs) */
 #define DEFAULT_NAUTYMAXNNODES   10000000    /**< terminate symmetry detection using Nauty when its search tree has at least this number of nodes */
+/*@todo investigate why the Nauty works well for some large instances (miplib2010/mspp16.mps) but not for PB instances (e.g., normalized-celar6-sub0_wcsp.wbo) */
+
 
 /* macros for getting activeness of symmetry handling methods */
 #define ISSYMRETOPESACTIVE(x)      (((unsigned) x & SYM_HANDLETYPE_SYMBREAK) != 0)