[GAP Forum] Error in NormalSubgroups

[David Roe]

I managed to install GAP and this command is functional in the latest
version of GAP.  I've written to sage-devel to try to address the problem
there.  Sorry for the noise!
David

On Thu, Feb 15, 2018 at 2:16 AM, David Roe <roed at mit.edu> wrote:

> In my version of GAP (4.8.6 included in Sage, with the SmallGroups library
> added), the following command produces an error:
>
> gap> NormalSubgroups(SmallGroup(1458,1180));
> Error, List Element: <list>[4] must have an assigned value in
>   if map[d] > max  then
>     elm := id;
> else
>     if not IsBound( map[d] )  then
>         Error( "<elm> lies not in group defined by <pcgs>" );
>     fi;
>     ll := LeadingExponentOfPcElement( pa, elm );
>     lr := lc[d];
>     exp[map[d]] := ll / lr mod ros[d];
>     elm := LeftQuotientPowerPcgsElement( pcgs, map[d], exp[map[d]], elm );
> fi; at /home/roed/sage/local/gap/latest/lib/pcgsind.gi:1411 called from
> ExponentsOfPcElement( NumeratorOfModuloPcgs( pcgs ), elm, pcgs!.depthMap )
> at /home/roed/sage/local/gap/latest/lib/pcgsmodu.gi:931 called from
> ExponentsOfPcElement( ocr.modulePcgs, x ) at /home/roed/sage/local/gap/
> latest/lib/onecohom.gi:264 called from
> ocr.moduleMap( n ) at /home/roed/sage/local/gap/latest/lib/onecohom.gi:339
> called from
> ocr.listToCocycle( lc ) at /home/roed/sage/local/gap/latest/lib/
> grplatt.gi:1926 called from
> opr( Zero( vs ), k ) at /home/roed/sage/local/gap/latest/lib/
> grplatt.gi:1932 called from
> ...  at line 1 of *stdin*
>
> I tried installing the most recent version of GAP from source to see if
> the error was also present there, but ran into a build error:
>
> checking for GAP architecture... x86_64-apple-darwin16.7.0-gcc-default64
>
> ********************************************************************
>   ERROR
>
>   Found a GAP installation at /Users/roed/sage/gap4r8 but could not find
>   information about GAP's architecture in the
>   file /Users/roed/sage/gap4r8/sysinfo.gap or did not find the directory
>   /Users/roed/sage/gap4r8/bin/x86_64-apple-darwin16.7.0-gcc-default64.
>   This file and directory should be present: please check your
>   GAP installation.
> ********************************************************************
>
> configure: error: Unable to find plausible GAParch information.
> = Failed to build xgap-4.26
>
>
> Does anyone else see this error in finding the normal subgroups of
> SmallGroup(1458, 1180)?  I'm able to successfully execute this command for
> many other groups in the table of small groups....
>
> Thanks,
> David
>