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....@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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