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Fix IsomorphismPermGroupOrFailFpGroup to honor its second argument, which limits the coset table size that gets used before it gives up #5900

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merged 1 commit into from
Jan 9, 2025
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Fix IsomorphismPermGroupOrFailFpGroup to honor its second argument, which limits the coset table size that gets used before it gives up #5900

merged 1 commit into from
Jan 9, 2025

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fingolfin
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This examples works fine in GAP 4.13.1:

gap> F:=FreeGroup(2);;G:=F/[F.1^2, F.2^2];;
gap> IsomorphismPermGroupOrFailFpGroup(G, 100);
fail
gap> time;
1

But in GAP 4.14.0 is does not terminate.

This is a regression introduced in PR #5770.

I also added in a test case that verifies that the issue addressed by PR #5770 stays fixed.

CC @lgoettgens

@fingolfin fingolfin added kind: bug Issues describing general bugs, and PRs fixing them topic: library release notes: use title For PRs: the title of this PR is suitable for direct use in the release notes labels Jan 9, 2025
@fingolfin fingolfin mentioned this pull request Jan 9, 2025
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@fingolfin
Fix IsomorphismPermGroupOrFailFpGroup(G,max)
1932c3d 
... to honor its second argument, which limits the coset table size
that gets used before it gives up.
@fingolfin fingolfin force-pushed the mh/IsomorphismPermGroupOrFailFpGroup branch from f1a8d2d to 1932c3d Compare January 9, 2025 01:11
ThomasBreuer
ThomasBreuer approved these changes Jan 9, 2025
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Very nice. Thanks.

@fingolfin fingolfin merged commit eb4ca9b into gap-system:master Jan 9, 2025
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@fingolfin fingolfin deleted the mh/IsomorphismPermGroupOrFailFpGroup branch January 9, 2025 07:32
fingolfin added a commit that referenced this pull request Jan 9, 2025
@fingolfin
Fix IsomorphismPermGroupOrFailFpGroup(G,max) (#5900)
f885d71 
... to honor its second argument, which limits the coset table size
that gets used before it gives up.
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Backported to stable-4.14 in commit f885d71

@lgoettgens lgoettgens mentioned this pull request Jan 9, 2025
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@ThomasBreuer ThomasBreuer ThomasBreuer approved these changes

@hulpke hulpke hulpke approved these changes

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