This is now http://trac.sagemath.org/ticket/15656
On Thursday, January 9, 2014 11:00:03 AM UTC-5, kcrisman wrote:
>
>
>
> On Thursday, January 9, 2014 9:44:57 AM UTC-5, Georgi Guninski wrote:
>>
>> Strange results with subgroups of automorphism group of graphs
>>
>> There is an element in the automorphism group of graph
>> which is in no subgroup (though the full group is a subgroup).
>>
>> I suspect the problem is the usage of zero.
>>
>> G1=Graph(':H`ECw@HGXGAGUG`e');G=G1.automorphism_group();sg=G.subgroups()
>> print G.gens()
>> [(0,7)(1,4)(2,3)(6,8)]
>> print sg
>> [Permutation Group with generators [()], Permutation Group with
>> generators [(1,8)(2,5)(3,4)(7,9)]]
>>
>>
> sage: G.gens()
> [(0,7)(1,4)(2,3)(6,8)]
> sage: [s.gens() for s in sg]
> [[()], [(1,8)(2,5)(3,4)(7,9)]]
>
> Yeah, that's a problem. At least we get
>
> sage: G.is_isomorphic(sg[0])
> False
> sage: G.is_isomorphic(sg[1])
> True
>
> which is trivial but I think it confirms your suspicion. We seem to have
> Gap-style numbering in the subgroups and Sage/Python-style numbering in the
> group itself. Here's the code:
>
> all_sg = []
> ccs = self._gap_().ConjugacyClassesSubgroups()
> for cc in ccs:
> for h in cc.Elements():
> all_sg.append(PermutationGroup(gap_group=h))
> return all_sg
>
> So we send self to Gap...
>
> sage: G._gap_()
> Group( [ (1,8)(2,5)(3,4)(7,9) ] )
> sage: G
> Permutation Group with generators [(0,7)(1,4)(2,3)(6,8)]
>
> There we go.
>
> Beezer, you apparently wrote this... how would you recommend fixing this?
>
> I'll open a Trac ticket momentarily.
>
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