Skip to content

Speed up RandomIsomorphismTestUEM #13

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
fingolfin merged 2 commits into from
Jul 11, 2026
Merged

Speed up RandomIsomorphismTestUEM #13

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
6e54ff5
Speed up RandomIsomorphismTestUEM
Jun 29, 2026
b78a62e
Merge branch 'master' into master
fingolfin Jul 7, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 8 additions & 2 deletions gap/upext.gi
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -119,7 +119,7 @@ end );
##
BindGlobal( "RandomIsomorphismTestUEM", function( G, H )
local cocl, cocr, size, ngens, size_inner, elms, poses, pos, qual, i, j,
gens1, gens2, f, tpos, tqual, len_classes;
gens1, gens2, f, tpos, tqual, len_classes,free,frowords,fro;

cocl := List( [ G, H ], CocGroup );
cocr := DiffCocList( cocl, false );
Expand All @@ -130,6 +130,9 @@ BindGlobal( "RandomIsomorphismTestUEM", function( G, H )

size := Size( G );
ngens := Length( SmallGeneratingSet( G ) );
free:=GeneratorsOfGroup(FreeGroup(ngens));
frowords:=MorFroWords(free);

size_inner := size / Size( Center( G ) );

cocl := List( cocl, x -> List( x, Concatenation ) );
Expand Down Expand Up @@ -172,6 +175,7 @@ BindGlobal( "RandomIsomorphismTestUEM", function( G, H )
return fail;
fi;
until Size( Group( gens1 ) ) = size;
fro:=List(frowords,x->Order(MappedWord(x,free,gens1)));
repeat
gens2 := List( cocl[ 2 ], Random );
f := f + 1;
Expand All @@ -180,7 +184,9 @@ BindGlobal( "RandomIsomorphismTestUEM", function( G, H )
"RandomIsomorphismTestUEM failed to decide" );
return fail;
fi;
until Size( Group( gens2 ) ) = size;
# check cheap homomorphism property first, before even testing group order
until fro=List(frowords,x->Order(MappedWord(x,free,gens2)))
and Size( Group( gens2 ) ) = size;
if GroupHomomorphismByImages( G, H, gens1, gens2 ) <> fail then
Info( InfoRandIso, 2, "RandomIsomorphismTestUEM ",
"found isomorphism" );
Expand Down