Using GAP 4.1, I have found LatticeByCyclicExtension very useful to
construct certain small subgroups of a given group (to test as
possible groups of automorphisms of experimental designs with
certain properties). My problem is that even though the groups I
require are all soluble, I get the following sort of error:
Error the perfect residuum is too large at
Error( "the perfect residuum is too large" );
RepresentativesPerfectSubgroups( G ) 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
One small additional point: it appears that the trivial subgroup is
always included in the lattice computed by LatticeByCyclicExtension(G,f),
whether it satisfies the function f or not (is this correct?).
If so, this "feature" should be documented.