README.md

@@ -43,7 +43,6 @@ Usage: ./SOCgen -n <order> [-r <num>] [--graphviz] [FILTER ...]
        -c             ... that are cyclic (i.e., not DAGs)
        --no-sink      ... without sink nodes (this logically implies -c)
        --no-source    ... without source nodes (also this logically implies -c)
-       --chordless    ... without cycles that have chords (this is incompatible with --no-source, see paper)
 
 This program prints the found SOCs as adjacency matrices to stdout, unless --graphviz has been specified.
 To exclude (some) of the isomorphic SOCs, it uses a degree-order filter, unless --all is specified.

src/SOCgen.c

@@ -324,65 +324,6 @@ int find_cycles(int *cycles, int *cyclescnt, int n, const int *children, \
   return found;
 }
 
-/***
- * gischordless tests wheter the graph provided has chordless cycles only
- * Parameter `n':            Number of nodes
- * Parameter `parents':      Pointer to list of parents per node
- * Parameter `parentslen':   Pointer to list of number of parents per node
- * Parameter `children':     Pointer to list of children per node
- * Parameter `childrenlen':  Pointer to list of number of children per node
- * Parameter `cycles':       Pointer to list of cycles in the graph
- * Parameter `cyclescnt':    Pointer to list of cycles count
- * Parameter `num_cycles'    Total number of cycles
- *
- * This function retruns 0 if the graph has a directed cycle with a chord, and
- * 1 otherwise.
- *
- * If there is no cycle, then the graph trivially satisfy this condition.
- * Cycles of length two are trivially chordless.
- * If there is a k-cycle, then a chord implies the existance of an l-cycle
- * with l < k.
- ***/
-int gischordless(int n, const int *parents, const int *parentslen, \
-    const int *children, const int *childrenlen, const int *cycles, \
-    const int *cyclescnt, int num_cycles) {
-  if (!num_cycles) return 1;
-  for (int clen=n; clen>2; clen--) {
-    if (!cyclescnt[clen]) continue;
-    // A chord can only exist if there is a cycle of length < clen
-    int shortercycleexists = 0;
-    for (int sclen = 2; sclen < clen; sclen++) {
-      if (cyclescnt[sclen]) {
-        shortercycleexists = 1;
-        break;
-      }
-    }
-    if (!shortercycleexists) return 1;
-    for (int i=0; i<cyclescnt[clen]; i++) {
-      const int bs = blocksize(n);
-      const int startidx = clen*bs + i*clen;  // Cycle starts here
-      int v = cycles[startidx+clen-1];
-      for (int pos=0; pos<clen; pos++) {
-        const int u = v;
-        v = cycles[startidx+pos];
-        // Cycle has arc u -> v
-        // Is there a chord, i.e., A) reverse arc u <- v or B) u -> v' for v'
-        // on the cycle? We test only B), but for all vertices on the cycle.
-        for (int cidx=0; cidx<childrenlen[u]; cidx++) {
-          const int child = children[n*u+cidx];
-          if (child == v) continue;
-          // Is `child` on the cycle?
-          for (int j=0; j<clen; j++) {
-            const int w = cycles[startidx+j];
-            if (child == w) return 0;
-          }
-        }
-      }
-    }
-  }
-  return 1;
-}
-
 /***
  * gissoc tests wheter the graph provided is a SOC or not.
  * Parameter `n':            Number of nodes
@@ -544,7 +485,6 @@ int main(int argc, char *argv[]) {
   int RANDOM = 0;
   int GRAPHVIZ = 0;
   int VECTOR = 0;
-  int CHORDLESS = 0;
   int UNKOPTION = 0;
   int ALL = 0;
   for (int i = 1; i < argc; i++) {
@@ -566,8 +506,6 @@ int main(int argc, char *argv[]) {
       ALL = 1;
     } else if (strcmp(argv[i], "--vector") == 0) {
       VECTOR = 1;
-    } else if (strcmp(argv[i], "--chordless") == 0) {
-      CHORDLESS = 1;
     } else {
       UNKOPTION = 1;
       break;
@@ -585,7 +523,6 @@ int main(int argc, char *argv[]) {
     fprintf(stderr, "       -c             ... that are cyclic (i.e., not DAGs)\n");
     fprintf(stderr, "       --no-sink      ... without sink nodes (this logically implies -c)\n");
     fprintf(stderr, "       --no-source    ... without source nodes (also this logically implies -c)\n");
-    fprintf(stderr, "       --chordless    ... without cycles that have chords (this is incompatible with --no-source, see paper)\n");
     fprintf(stderr, "\n");
     fprintf(stderr, "This program prints the found SOCs as adjacency matrices to stdout, unless --graphviz has been specified.\n");
     fprintf(stderr, "To exclude (some) of the isomorphic SOCs, it uses a degree-order filter, unless --all is specified.\n");
@@ -629,8 +566,6 @@ int main(int argc, char *argv[]) {
     fprintf(stderr, "  Filter: Omitting graphs with sink nodes\n");
   if (NOSOURCE)
     fprintf(stderr, "  Filter: Omitting graphs with source nodes\n");
-  if (CHORDLESS)
-    fprintf(stderr, "  Filter: Omitting graphs with chords in directed cycles\n");
   // We will always omit the graph with `graphnumber' 0;
   // it is unintersting anyway
   unsigned long long graphnumber = 0;
@@ -695,9 +630,6 @@ int main(int argc, char *argv[]) {
     if (num_cycles > 0 && !gissoc(n, parents, parentslen, children, \
         childrenlen, cycles, cyclescnt)) continue;
     // We have found a SOC
-    // If enabled, test chordless property
-    if (CHORDLESS && !gischordless(n, parents, parentslen, children, \
-        childrenlen, cycles, cyclescnt, num_cycles)) continue;
     len++;
     if (GRAPHVIZ)
       dumpgv(n, graphnumber, children, childrenlen);