Fix a bug in IsomorphismGroups that could result in it returning fail for two isomorphic groups - #6541
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Fix a bug in IsomorphismGroups that could result in it returning fail for two isomorphic groups#6541fingolfin wants to merge 1 commit into
IsomorphismGroups that could result in it returning fail for two isomorphic groups#6541fingolfin wants to merge 1 commit into
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The search for liftable automorphisms seeds the group of known good elements with automorphisms found by random search. Such elements need not stabilize the normal subgroup classes used to shrink the search space, so the shrunken space could fail to contain the known subgroup. SubgroupProperty was then called outside its specification and returned wrong results, silently losing automorphisms. Depending on the random state, IsomorphismGroups could thus return fail for isomorphic groups. Restore the containment after the class stabilization by closing the search space with the known subgroup. Fixes #6537 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #6541 +/- ##
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+ Coverage 78.98% 79.01% +0.03%
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Files 684 684
Lines 294205 294211 +6
Branches 8647 8670 +23
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+ Hits 232369 232478 +109
+ Misses 60028 59925 -103
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hulpke
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Please do not merge this. I have a broader modification in the works (that happens to fix this bug but also provides crucial speedup) which I had been still testing. I will create a PR today or tomorrow.
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The search for liftable automorphisms seeds the group of known good elements with automorphisms found by random search. Such elements need not stabilize the normal subgroup classes used to shrink the search space, so the shrunken space could fail to contain the known subgroup. SubgroupProperty was then called outside its specification and returned wrong results, silently losing automorphisms. Depending on the random state, IsomorphismGroups could thus return fail for isomorphic groups.
Restore the containment after the class stabilization by closing the search space with the known subgroup.
Fixes #6537
Co-authored-by: Claude Fable 5 noreply@anthropic.com