[GAP Forum] Schur Multiplier

D.V.Pasechnik D.V.Pasechnik at uvt.nl
Wed Nov 17 12:28:14 GMT 2004

Dear Forum, 

On Tue, Nov 16, 2004 at 11:30:18AM +0000, Derek Holt wrote:
> On Mon, Nov 15, 2004 at 10:31:22PM -0800, Ahmad Erfanian wrote:
> > I would like to ask that  how we can compute the Schur Multiplier of a given finite group by Gap.
> One possibility is to use the package "cohomolo". But this package involves
> external C programs, and it is only possible to use it under Unix or Linux.
in fact, "cohomolo" also runs seemingly OK on Windows with Cygwin.
There are a couple of very minor changes in the installation procedure
of the package.

I had to 

1) change the line "./Makefile" to "Makefile" in the configure script,
 (taking care that .: is in my PATH)

2) add, after the configuration was complete, the first line
to the file bin/i686-pc-cygwin-gcc/execcmd.gap
(the proper fix is to change the original file that gets
 copied to that place during the installation)
3) in testdata/test.g
change the first line to 
TestDir:= "../testdata/";

As far as the installation of the current GAP version under Cygwin, 
just get the standard Unix distribution and follow the Unix instructions.
At the very end of the procedure you'll see

>( cd bin/i686-pc-cygwin-gcc ; strip gap)
>strip: gap: No such file or directory
>make: *** [strip] Error 1
that you can safely ignore.
(This leaves you with a slightly bigger gap executable, that's all)

Actually, this can be fixed, by changing the configure script 
(or maybe just Makefile.in) so that
it takes notice of the fact that the executable files get suffix .exe
on Windows.
That is to say, that the line
( cd bin/i686-pc-cygwin-gcc ; strip gap)
in the generated Makefile must be
( cd bin/i686-pc-cygwin-gcc ; strip gap.exe)

Hope this is of some help,

PS. For these who do not know, Cygwin is on http://www.cygwin.com

Dr. D.V. Pasechnik
Tilburg University
P.O. Box 90153
5000 LE Tilburg 
The Netherlands
email: d.v.pasechnik at uvt.nl
url: http://center.uvt.nl/staff/pasechnik/

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