dfs: attempt to fix x 2

Author: james-d-mitchell

Makefile.am

@@ -23,6 +23,7 @@ lib_LTLIBRARIES = digraphs.la
 
 pkginclude_HEADERS =  src/bitarray.h
 pkginclude_HEADERS += src/conditions.h
+pkginclude_HEADERS += src/dfs.h
 pkginclude_HEADERS += src/digraphs-debug.h
 pkginclude_HEADERS += src/digraphs.h
 pkginclude_HEADERS += src/homos-graphs.h
@@ -31,7 +32,6 @@ pkginclude_HEADERS += src/cliques.h
 pkginclude_HEADERS += src/perms.h
 pkginclude_HEADERS += src/planar.h
 pkginclude_HEADERS += src/schreier-sims.h
-pkginclude_HEADERS += src/dfs.h
 
 if WITH_INCLUDED_BLISS
   pkginclude_HEADERS += extern/bliss-0.73/bignum.hh
@@ -49,6 +49,7 @@ if WITH_INCLUDED_BLISS
 endif
 
 digraphs_la_SOURCES =  src/digraphs.c
+digraphs_la_SOURCES += src/dfs.c
 digraphs_la_SOURCES += src/bitarray.c
 digraphs_la_SOURCES += src/conditions.c
 digraphs_la_SOURCES += src/homos.c
@@ -57,7 +58,6 @@ digraphs_la_SOURCES += src/homos-graphs.c
 digraphs_la_SOURCES += src/perms.c
 digraphs_la_SOURCES += src/planar.c
 digraphs_la_SOURCES += src/schreier-sims.c
-digraphs_la_SOURCES += src/dfs.c
 
 if WITH_INCLUDED_BLISS
   digraphs_la_SOURCES += extern/bliss-0.73/defs.cc

gap/attr.gi

@@ -684,35 +684,40 @@ end);
 InstallMethod(DigraphTopologicalSort, "for a digraph by out-neighbours",
 [IsDigraphByOutNeighboursRep],
 function(D)
-  local i, record, num_vertices, data, AncestorFunc, PostOrderFunc;
-  if DigraphNrVertices(D) = 0 then
+  local N, record, count, out, PostOrderFunc, AncestorFunc, i;
+
+  N := DigraphNrVertices(D);
+  if N = 0 then
     return [];
   fi;
   record := NewDFSRecord(D);
-  num_vertices := DigraphNrVertices(D);
-  data := rec(count := 0,
-              out := ListWithIdenticalEntries(num_vertices, 0));
+  count := 0;
+  out := [];
+  PostOrderFunc := function(record, data)
+    count := count + 1;
+    out[count] := record.child;
+  end;
   AncestorFunc := function(record, data)
     if record.current <> record.child then
       record.stop := true;
     fi;
   end;
-  PostOrderFunc := function(record, data)
-    data.count := data.count + 1;
-    data.out[data.count] := record.child;
-  end;
   for i in DigraphVertices(D) do
-    if not IsBound(record.preorder[i]) then
+    if IsBound(record.preorder[i]) then
       continue;
     fi;
-    ExecuteDFS(record, data, i, DFSDefault,
-                PostOrderFunc, AncestorFunc,
-                DFSDefault);
+    ExecuteDFS(record, 
+               fail, 
+               i, 
+               DFSDefault,
+               PostOrderFunc, 
+               AncestorFunc,
+               DFSDefault);
     if record.stop then
       return fail;
     fi;
   od;
-  return data.out;
+  return out;
 end);
 
 InstallMethod(DigraphStronglyConnectedComponents,

gap/oper.gi

@@ -2273,10 +2273,10 @@ function(graph)
   record.child := -1;
   record.current := -1;
   record.stop := false;
-  record.parent := [fail];
-  record.preorder := [fail];
-  record.postorder := [fail];
-  record.edge := [fail];
+  record.parent := [];
+  record.preorder := [];
+  record.postorder := [];
+  record.edge := [];
   return record;
 end);
 

src/dfs.c

@@ -64,12 +64,14 @@ Obj ExecuteDFS(Obj self, Obj args) {
   Obj preorder  = ElmPRec(record, RNamName("preorder"));
   Obj edge      = ElmPRec(record, RNamName("edge"));
 
+  // FIXME edge needs to be off by 1, so that the first entry is bound
+
   DIGRAPHS_ASSERT(LEN_PLIST(parent) == 1);
   DIGRAPHS_ASSERT(LEN_PLIST(postorder) == 1);
   DIGRAPHS_ASSERT(LEN_PLIST(preorder) == 1);
   DIGRAPHS_ASSERT(LEN_PLIST(edge) == 1);
 
-  AssPlist(parent, INT_INTOBJ(start), start);
+  ASS_LIST(parent, INT_INTOBJ(start), start);
 
   Obj neighbors = FuncOutNeighbours(self, D);
   DIGRAPHS_ASSERT(IS_PLIST(neighbors));
@@ -89,19 +91,18 @@ Obj ExecuteDFS(Obj self, Obj args) {
       AssPRec(record, RNamChild, INTOBJ_INT(child));
       AssPRec(record, RNamCurrent, ELM_PLIST(parent, child));
       CALL_2ARGS(PostOrderFunc, record, data);
-      AssPlist(postorder, child, INTOBJ_INT(++postorder_num));
+      ASS_LIST(postorder, child, INTOBJ_INT(++postorder_num));
       CHANGED_BAG(record);
       continue;
     } else if (current <= LEN_PLIST(preorder)
-               && ELM_PLIST(preorder, current) != 0
-               && ELM_PLIST(preorder, current) != Fail) {
+               && ELM_PLIST(preorder, current) != 0) {
       continue;
     } else {
       AssPRec(record, RNamCurrent, INTOBJ_INT(current));
       CALL_2ARGS(PreorderFunc, record, data);
-      AssPlist(preorder, current, INTOBJ_INT(++preorder_num));
+      ASS_LIST(preorder, current, INTOBJ_INT(++preorder_num));
       CHANGED_BAG(record);
-      AssPlist(stack, ++top, INTOBJ_INT(-1 * current));
+      ASS_LIST(stack, ++top, INTOBJ_INT(-1 * current));
     }
 
     if (ElmPRec(record, RNamStop) == True) {
@@ -112,15 +113,12 @@ Obj ExecuteDFS(Obj self, Obj args) {
     for (UInt j = 0; j < LEN_LIST(succ); ++j) {
       UInt v = INT_INTOBJ(ELM_LIST(succ, LEN_LIST(succ) - j));
       AssPRec(record, RNamChild, INTOBJ_INT(v));
-      if (v > LEN_PLIST(preorder) || ELM_PLIST(preorder, v) == 0
-          || ELM_PLIST(preorder, v) == Fail) {
-        AssPlist(parent, v, INTOBJ_INT(current));
-        AssPlist(edge, v, INTOBJ_INT(LEN_LIST(succ) - j));
+      if (v > LEN_PLIST(preorder) || ELM_PLIST(preorder, v) == 0) {
+        ASS_LIST(parent, v, INTOBJ_INT(current));
+        ASS_LIST(edge, v, INTOBJ_INT(LEN_LIST(succ) - j));
         CHANGED_BAG(record);
-        AssPlist(stack, ++top, INTOBJ_INT(v));
-      } else if (current > LEN_PLIST(preorder)
-                 || ELM_PLIST(preorder, current) != 0
-                 || ELM_PLIST(preorder, current) != Fail) {
+        ASS_LIST(stack, ++top, INTOBJ_INT(v));
+      } else if (v > LEN_PLIST(postorder) || ELM_PLIST(postorder, v) == 0) {
         CALL_2ARGS(AncestorFunc, record, data);
       } else if (INT_INTOBJ(ELM_PLIST(preorder, v))
                  < INT_INTOBJ(ELM_PLIST(preorder, current))) {