Recently there was a question about the limits on graph size for
AutGroupGraph, but I appear to have lost the original email.
The nauty 1.7 package (used by GRAPE 2.1 to calculate the automorphism
group of a graph) requires the maximum number of vertices of a graph to
be set at compile time. The default for GRAPE 2.1 is 1024. You can
change this by editing gap-directory/pkg/grape/nauty17/Makefile and
changing 1024 to 2048 (say), and then completely re-installing the
Regards, Leonard Soicher.