> < ^ Date: Fri, 03 Nov 1995 15:26:00 +0100 (MET)
> < ^ From: Martin Schoenert <martin.schoenert@math.rwth-aachen.de >
< ^ Subject: Re: LowIndexSubgroupsFpGroup
Paul Robert Brown wrote in his e-mail message of 1995/11/01

The GAP command "LowIndexSubgroupsFpGroup()" could be improved by adding
an argument for a range of subgroup indices instead of the current
maximum integer n implying a range of [1..n]. (This is a feature of the
equivalent magma command, for instance.)

The time taken by the 'LowIndexSubgroupsFpGroup' function depends mostly
on the largest index considered. That means that excluding smaller
indices will not decrease the time taken. I think the same is true for
the corresponding Magma command, but I have never tried it. Anyhow, that
means that it is just as fast to compute all the subgroups up to the
largest index and throwing out the ones whose index does not lie in the
interesting range afterwards. This is the reason why I never bothered
to add this feature.

He continued

I'm also interested if anyone out there has coset enumeration routines
written in C, as I'm only interested in checking for the existence of
representations of a given degree.

I don't see what the fact that you are only interested in checking for
the existence of representations of a given degree has to do with whether
a program to look for them is written in C or in GAP. Besides what
exactely do you mean by ``coset enumeration routines''? A program to
compute the index for a given subgroup or a program to find all subgroups
up to a given index? Write me and I see whether I can help you.


-- .- .-. - .. -.  .-.. --- ...- . ...  .- -. -. .. -.- .-
Martin Sch"onert,   Martin.Schoenert@Math.RWTH-Aachen.DE,   +49 241 804551
Lehrstuhl D f"ur Mathematik, Templergraben 64, RWTH, 52056 Aachen, Germany

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