Dear All,

It looks to me as if this could be a version problem, from the header file
the first version is:

GAP4, Version: 4r2 fix6 of 26-January-2001

The second is version:

GAP4,	Version: 4r2 fix3 of 18-May-2000

Perhaps it is an error which has been addded as as a side effect of the
bug fix. I know of simillar problems with other applications.

I have the current version:
 GAP4, Version: 4r2 fix8 of 7-June-2001

Running on my system, and when I try your problem I get:

gap> g:=SmallGroup(144,32);
<pc group of size 144 with 6 generators>
gap> lat:=LatticeSubgroups(g);
<subgroup lattice of <pc group of size 144 with 6 generators>, 25 classes,
142 subgroups>

Which is the expected answer.

In short try installing the latest bug fixes, to get to this current
version, and you may find your problem is solved. These fixes can be found
at:

http://www-gap.dcs.st-and.ac.uk/~gap/Info4/bugfixes.html

Let me know how you get on.

Karen

On Wed, 15 Aug 2001, Kurt Ewald wrote:

Forum

I have tried the same and it worked:

Loading the library. Please be patient, this may take a while.
GAP4, Version: 4r2 fix3 of 18-May-2000, i586-pc-cygwin-gcc
Components: small, small2, small3, small4, small5, small6, small7,
small8, id2, id3, id4, id5, id6, trans, prim, tbl,
tom installed.
gap> g:=SmallGroup(144,32);
<pc group of size 144 with 6 generators>
gap> lat:=LatticeSubgroups(g);
<subgroup lattice of <pc group of size 144 with 6 generators>, 25 classes,
142 subgroups>
gap>

Mit freundlichen Grüßen / best regards

Kurt Ewald

-----Ursprüngliche Nachricht-----
Von: GAP-Forum-Sender@dcs.st-and.ac.uk
[mailto:GAP-Forum-Sender@dcs.st-and.ac.uk]Im Auftrag von Gordon Royle
Gesendet: Mittwoch, 15. August 2001 06:03
An: Multiple recipients of list
Betreff: LatticeSubgroups problem

I am trying to determine if a given graph on 72 vertices is a
Cayley graph; its full automorphism group is "SmallGroup(144,32)" and
so I need to know if this has a subgroup of order 72.

But if I simply ask for the subgroup lattice, then it crashes
with a mysterious error....

---------------------------------------------------------------------

ading the library. Please be patient, this may take a while.
GAP4, Version: 4r2 fix6 of 26-January-2001, i686-pc-linux-gnu-gcc
Components: small, small2, small3, small4, small5, small6, small7,
small8, id2, id3, id4, id5, id6, trans, prim, tbl,

gap> g := SmallGroup(144,32);
<pc group of size 144 with 6 generators>
gap> l := LatticeSubgroups(g);
Error <obj> is not an element of the parent of <G> at
Error( "<obj> is not an element of the parent of <G>" );
ClosureSubgroup( Pu, i ) called from
ActionSubspacesElementaryAbelianGroup( f, n ) called from
SubgroupsSolvableGroup( G, rec(
retnorm := true ) ) called from
<function>( <arguments> ) called from read-eval-loop
Entering break read-eval-print loop, you can 'quit;' to quit to outer loop,
or you can return to continue
brk>