This works yes. However it still leaves open what is going on with disconnected graphs and what is the problem with the proposed is_edge_transitive method!
Do you (or anyone) happens to see a bug or a bizarre mistake in the implementation? On Monday, 29 October 2012 20:02:40 UTC+1, Tom wrote: > > Sorry, I meant n=8. > > sage: print [ec(n) for n in range(9)] > [1, 1, 1, 2, 3, 4, 6, 5, 8] > > On Mon, Oct 29, 2012 at 11:41 AM, Tom Boothby > <tomas....@gmail.com<javascript:>> > wrote: > > Wanna run that on connected graphs? I get the correct sequence out to > n=9 for > > > > def ec(n) > > c = 0 > > for g in graphs(n): > > if g.is_connected() and g.line_graph().is_vertex_transitive(): > > c+= 1 > > return c > > > > > > > > On Mon, Oct 29, 2012 at 11:37 AM, Jernej Azarija > > <azi.s...@gmail.com<javascript:>> > wrote: > >> Hello! > >> > >> Yes but this appears to be even more bogus. Consider this: > >> > >> == > >> def ec(n): > >> c = 0 > >> for el in graphs.nauty_geng(str(n)): > >> if (el.line_graph()).is_vertex_transitive(): > >> c+=1 > >> return c > >> == > >> > >> sage: ec(7) > >> 27 > >> sage: ec(8) > >> 39 > >> > >> But there are 26 and 40 edge-transitive graphs on 7 and 8 nodes > >> respectively. It appears as if something is wrong with the computation > of > >> the automorphism group of a graph. > >> > >> Can someone comment on that? > >> > >> > >> > >> > >> > >> > >> > >> > >> On Monday, 29 October 2012 19:29:56 UTC+1, Tom wrote: > >>> > >>> I use G.line_graph().is_vertex_transitive() > >>> > >>> On Mon, Oct 29, 2012 at 7:12 AM, Jernej Azarija <azi.s...@gmail.com> > >>> wrote: > >>> > Hello! > >>> > > >>> > I am slowly implementing a patch that will provide some features for > >>> > symmetry testing of graphs. > >>> > > >>> > However I am already puzzled by the following attempt at testing for > >>> > edge-transitive graphs. Here is a straightforward textbook > >>> > implementation > >>> > (the presented code omits the exceptional treatment of the singleton > >>> > graph) > >>> > > >>> > === > >>> > def is_edge_transitive(self): > >>> > > >>> > A,T = self.automorphism_group(translation=True) > >>> > for (x,y,_) in self.edges(): > >>> > acts = set([]) > >>> > for g in A: > >>> > a,b = g(T[x]),g(T[y]) > >>> > acts.add((a,b) if a < b else (b,a)) > >>> > if len(acts) == self.size(): > >>> > return True > >>> > return False > >>> > === > >>> > > >>> > Testing the code (Petersen, Gray and path graph) it appears as if > the > >>> > results are correct. But considering the following function > computing > >>> > the > >>> > number connected edge transitive graphs of given order > >>> > > >>> > === > >>> > def ecc(n): > >>> > c = 0 > >>> > for el in graphs.nauty_geng(str(n)+ " -c "): > >>> > if el.is_edge_transitive(): > >>> > c+=1 > >>> > return c > >>> > === > >>> > > >>> > we observe that > >>> > > >>> > sage: [ecc(i) for i in xrange(2,9)] > >>> > [1, 2, 3, 4, 6, 5, 8] > >>> > > >>> > which does not coincide with the data provided at oeis: > >>> > http://oeis.org/A095424/list . The difference gets even bigger if > we > >>> > count > >>> > all edge-transitive graphs instead of just connected. > >>> > > >>> > Anyone happens to see the flaw in the is_edge_transitive method? > >>> > > >>> > Best, > >>> > > >>> > Jernej > >>> > > >>> > -- > >>> > You received this message because you are subscribed to the Google > >>> > Groups > >>> > "sage-devel" group. > >>> > To post to this group, send email to sage-...@googlegroups.com. > >>> > To unsubscribe from this group, send email to > >>> > sage-devel+...@googlegroups.com. > >>> > Visit this group at http://groups.google.com/group/sage-devel?hl=en. > > >>> > > >>> > > >> > >> -- > >> You received this message because you are subscribed to the Google > Groups > >> "sage-devel" group. > >> To post to this group, send email to > >> sage-...@googlegroups.com<javascript:>. > > >> To unsubscribe from this group, send email to > >> sage-devel+...@googlegroups.com <javascript:>. > >> Visit this group at http://groups.google.com/group/sage-devel?hl=en. > >> > >> > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To post to this group, send email to sage-devel@googlegroups.com. To unsubscribe from this group, send email to sage-devel+unsubscr...@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel?hl=en.
