I forgot to precise that I would submit another for undirected cycles. Alex
On 28 fév, 20:32, ablondin <alexandre.blondin.ma...@gmail.com> wrote: > Hello, David ! > As Nathann mentionned, I've already submitted a patch which allows one > to enumerate paths and cycles in directed graphs with a lot of > possible parameters (length, starting and ending vertices, etc.). > Since it has received positive review, I'll submit another one for the > next week, so that it is available in Sage 4.3.4 or, in the worse > case, the next release. I'll keep you posted about that. > Thanks for your interest in the matter ! > Alex > > On 28 fév, 15:35, David Joyner <wdjoy...@gmail.com> wrote: > > > On Sun, Feb 28, 2010 at 8:57 AM, Nathann Cohen <nathann.co...@gmail.com> > > wrote: > > > Hello !!!! > > > > By the fundamental circuits, do you mean a base of the Cycle space ? > > > If so, I have to admit I do not know how to do it... > > > I just posted some code to compute the cycle space > > tohttp://sage.math.washington.edu/home/wdj/research/coding-theory/cycle... > > > > If you want to compute a shortest cycle in a graph, though, I do not > > > think the girth function can do it at the moment, but I agree it would > > > be useful to have for such functions an optional argument > > > "certifitate", giving along with a boolean answer a proof which in > > > this example would be a cycle. > > > > If you only want to find a cycle in a graph when it is unique (a tree > > > + an edge), you can also make use of the "cores" function : > > > > sage: G = graphs.HeawoodGraph() > > > sage: mst = G.min_spanning_tree() > > > sage: TG = G.subgraph(edges=mst) > > > sage: e = G.edges()[-1] > > > sage: e in TG > > > False > > > > sage: TG.add_edge(e) > > > sage: cycle = TG.subgraph([v for v,k in > > > TG.cores(with_labels=True).items() if k>=2]) > > > sage: cycle.is_isomorphic(graphs.CycleGraph(cycle.order())) > > > True > > > This is very clever. Thank you! > > > > I do not know how both methods compare algorithmically, though :-) > > > > By the way, you may be interested in a patch from Alexandre Blondin > > > Massé that just got positively reviewed : > > > >http://trac.sagemath.org/sage_trac/ticket/8273 > > > > (he mentionned he may eventually write the same functions for undirected > > > graphs) > > > I hope he does! > > > > Nathann > > > > -- > > > To post to this group, send email to sage-support@googlegroups.com > > > To unsubscribe from this group, send email to > > > sage-support+unsubscr...@googlegroups.com > > > For more options, visit this group > > > athttp://groups.google.com/group/sage-support > > > URL:http://www.sagemath.org -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
