Make HasSolvableFactorGroup more efficient

gap-system · Jan 11, 2017 · 7642e6c · 7642e6c
1 parent 1443b97
commit 7642e6c
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/lib/grp.gi b/lib/grp.gi
@@ -5070,8 +5070,11 @@ end);
 #M  HasSolvableFactorGroup(<G>,<N>)   test whether G/N is solvable
 ##
 InstallGlobalFunction(HasSolvableFactorGroup,function(G,N)
+local s,l;
   Assert(2,IsNormal(G,N) and IsSubgroup(G,N));
-  return ForAny(DerivedSeriesOfGroup(G),x->IsSubset(N,x));
+  s := DerivedSeriesOfGroup(G);
+  l := Length(s);
+  return IsSubgroup(N,s[l]);
 end);
 
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