On Mon, Apr 26, 2010 at 4:59 PM, Dima Pasechnik <dimp...@gmail.com> wrote: > I work a lot with (large, say, 5000 vertices) (di)graphs having large > automorphism groups (often vertex-transitive, etc).
You should post up some examples somewhere, so I can get a sense of Sage's performance with these kinds of graphs. > Such graphs are very efficiently represented in GAP (via GRAPE) > package. > (one needs to keep representatives of arc orbits, and few other > things, to be able to check adjacency of vertices, say) > These kinds of graphs often arise in e.g. coding theory. > Is there anything like this in Sage? Everything you've described can be done in Sage, but I think that's not quite the question. There aren't any specialized data structures for keeping track of these things, just the usual digraph objects and permutation group objects. > My primary use of Sage is an interface between GAP and cvxopt, so e.g. > I can compute such graph invariants as > Lovasz theta-function. The size of graphs makes it mandatory to use a > compact representation, and > "collapsed" adjacency matrices, that carry enough information about > underlying algebra (e.g. graph eigenvalues). It would be helpful if you could explain these in a bit more detail. E.g. are these graphs highly sparse? > I wonder if Sage should get its own "graph with symmetries" class > (unless there is already one...) There isn't one. Right now even the automorphism group itself could be better, since the vertices and the points that get permuted aren't even the same. There is plenty of room for improvement... > Dima -- 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 URL: http://www.sagemath.org
