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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.

-- .- .-. - .. -. .-.. --- ...- . ... .- -. -. .. -.- .- 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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