Merge pull request #892 from hulpke/newmtc

Performance improvement and fix of generators. This fixes the bugs reported in #887
gap-system · Aug 23, 2016 · 8f5e7f4 · 8f5e7f4
2 parents da0416e + 06a79e7
commit 8f5e7f4
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Showing 3 changed files with 24 additions and 7 deletions.
diff --git a/lib/ghomfp.gi b/lib/ghomfp.gi
@@ -858,17 +858,17 @@ local aug,w,p,pres,f,fam,G;
   w:=FamilyObj(u)!.wholeGroup;
   aug:=NEWTC_CosetEnumerator(FreeGeneratorsOfFpGroup(w),
 	RelatorsOfFpGroup(w),
-	List(GeneratorsOfGroup(u),UnderlyingElement),
+	List(gens,UnderlyingElement),
 	true);
 
-  pres:=NEWTC_PresentationMTC(aug,1,"%");
+  pres:=NEWTC_PresentationMTC(aug,1,nam);
   if Length(GeneratorsOfPresentation(pres))>Length(gens) then
     aug:=NEWTC_CosetEnumerator(FreeGeneratorsOfFpGroup(w),
 	  RelatorsOfFpGroup(w),
-	  List(GeneratorsOfGroup(u),UnderlyingElement),
+	  List(gens,UnderlyingElement),
 	  true,false);
 
-    pres:=NEWTC_PresentationMTC(aug,0,"%");
+    pres:=NEWTC_PresentationMTC(aug,0,nam);
   fi;
   Assert(0,Length(GeneratorsOfPresentation(pres))=Length(gens));
 

diff --git a/lib/sgpres.gi b/lib/sgpres.gi
@@ -2731,7 +2731,7 @@ local c,offset,f,b,r,i,j;
   r:=Length(w);
   f:=alpha;i:=1;
   b:=alpha;j:=r;
-  while true do
+  while i<=j do
     # forward scan
     while i<=r and c[w[i]+offset][f]<>0 do
       f:=c[w[i]+offset][f];
@@ -2750,12 +2750,14 @@ local c,offset,f,b,r,i,j;
       j:=j-1;
     od;
     if j<i then 
+
       NEWTC_Coincidence(DATA,f,b);
     elif j=i then 
       # deduction
       c[w[i]+offset][f]:=b;
       c[-w[i]+offset][b]:=f;
       Add(DATA.deductions,[f,w[i]]);
+      return;
     else
       NEWTC_Define(DATA,f,w[i]);
     fi;
@@ -2771,7 +2773,7 @@ local c,offset,f,b,r,i,j,fp,bp;
   r:=Length(w);
   b:=alpha;j:=r; 
   bp:=y;
-  while true do #N
+  while i<=j do #N
     # forward scan
     while i<=r and c[w[i]+offset][f]<>0 do
       if DATA.useAddition then
@@ -2817,6 +2819,7 @@ local c,offset,f,b,r,i,j,fp,bp;
 	DATA.aug[-w[i]+offset][b]:=WordProductLetterRep(-Reversed(bp),fp);
       fi;
       Add(DATA.deductions,[f,w[i]]);
+      return;
     else
       NEWTC_Define(DATA,f,w[i]);
     fi;
@@ -2966,6 +2969,7 @@ local m,offset,rels,ri,ccr,i,r,ct,A,a,w,n,DATA,p,ds,dr,
       NEWTC_ScanAndFill(DATA,1,DATA.subgword[w]);
     fi;
   od;
+
   NEWTC_ProcessDeductions(DATA);
 
   # words we want to trace early (as they might reduce the number of
@@ -3383,6 +3387,8 @@ local DATA,rels,i,j,w,f,r,s,fam,new,ri,a,offset,p,rset,re,start,stack,pres,
     CompletionBar(InfoFpGroup,2,"Coset Loop: ",i/DATA.n);
     for w in DATA.rels do
       r:=NEWTC_Rewrite(DATA,i,w);
+      MakeCanonical(r);
+
       # reduce with others
       for j in rels do
 	r:=NEWTC_ReplacedStringCyclic(r,j);
@@ -3488,7 +3494,7 @@ local DATA,rels,i,j,w,f,r,s,fam,new,ri,a,offset,p,rset,re,start,stack,pres,
       TzSearch(pres);
       TzEliminate(pres,i);
     od;
-    Assert(1,Length(GeneratorsOfPresentation)=subnum);
+    Assert(1,Length(GeneratorsOfPresentation(pres))=subnum);
 
   fi;
   r:=List(GeneratorsOfPresentation(pres){

diff --git a/tst/teststandard/bugfix.tst b/tst/teststandard/bugfix.tst
@@ -3135,6 +3135,17 @@ gap> rels:=[x_1^2+x_2,x_1*x_2+x_3,x_1*x_3+x_4, x_1*x_4+x_1,x_2^2+x_4,
 gap> Size(r1/Ideal(r1,rels));
 32
 
+# 2016/8/18 (AH)
+gap> src := FreeGroup(3);;
+gap> src := src / [src.3*src.1];;
+gap> SetReducedMultiplication(src);
+gap> f1:=src.1;;f2:=src.2;;f3:=src.3;;
+gap> gens := [ f1, f2, f2^-1*f3*f2 ];;
+gap> fp := IsomorphismFpGroupByGeneratorsNC(src,gens,"F");;
+gap> dst := Image(fp);;wrd:=RelatorsOfFpGroup(dst)[1];;
+gap> m:=MappedWord(wrd,GeneratorsOfGroup(FreeGroupOfFpGroup(dst)),gens);       
+<identity ...>
+
 #############################################################################
 gap> STOP_TEST( "bugfix.tst", 831990000);