[GAP Forum] Finding certain subgroups from very large group

[Kher Sham Lim]

Dear Stephen,

Thanks, the command IsomorphicSubgroups(G,H) does exactly what I need.

Best regards,

Kher Sham


On 02/01/2013 01:09 PM, Stephen Linton wrote:
> Dear Kher Sham Lim,
>
> I assume you actually want to know if G has a subgroup isomorphic to H.
> If so, the command you want is IsomorphicSubgroups(G,H).
>
> This is enormously more efficient than simply listing all [conjugacy classes of] subgroups of G in most cases.
>
> It might also be helpful to first replace G by an isomorphic permutation group (using IsomorphismPermGroup).
>
> All of these commands are documented in the reference manual (equivalently in the on-line help).
>
> 	Steve
>
> On 1 Feb 2013, at 11:33, Kher Sham Lim <khersham.lim at mpi-hd.mpg.de> wrote:
>
>> Dear GAP forum
>>
>> I have a very large group to study, say G (it is an automorphism group
>> of a small group). G has order of 10 million and I am interested in
>> knowing whether a certain known group, say H is a subgroup in G. To find
>> H is impossible in GAP, as GAP tries to calculate all the subgroups and
>> this process exceeds my computer's memory. Is there another command or
>> algorithm in GAP to compute subgroup of specific order only, or at least
>> limit the subgroup order? I used SONATA to obtain the subgroups by the
>> way. Thanks in advanced.
>>
>> Sincerely
>>
>> Kher Sham Lim
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