[sage-devel] problem with graph.is_isomorphic

2010-05-24 Thread Chris Godsil
The issue is that we have two vertex-transitive graphs on 156 vertices, coming from two constructions of a generalized quadrangle over GF(5). According to sage these graphs are not isomorphic, but the graphs we obtain by deleting one vertex from each are isomorphic. One of these claims has to be f

Re: [sage-devel] problem with graph.is_isomorphic

2010-05-24 Thread Robert Miller
On it. -- Robert L. Miller http://www.rlmiller.org/ -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel UR

Re: [sage-devel] problem with graph.is_isomorphic

2010-05-25 Thread Robert Miller
Ok, in case I get hit by lightning in the next twelve hours, I've at least figured out what the bug is, but fixing it will take some effort. Essentially, the bug is in double_coset.pyx, when we do the first set of refinements to get the left partition stack and the first partition stack set up. The