Hi Dillon, I think the problem is your definition of N: > N=Matroid(reduced_matrix=matrix(GF(2),[[1,1,0,0,1,0],[1,0,1,0,1,0],[1,0,0,1,1,0],[1,1,0,0,0,1],[1,0,1,0,0,1],[1,0,0,1,0,1]]))
This produces a LinearMatroid over GF(2), whereas the matroids in your Regular[12] are all RegularMatroids. The following should solve the problem, since it creates N as a RegularMatroid: N=Matroid(reduced_matrix=matrix(GF(2),[[1,1,0,0,1,0],[1,0,1,0,1,0],[1,0,0,1,1,0],[1,1,0,0,0,1],[1,0,1,0,0,1],[1,0,0,1,0,1]]), regular=True) Sage can only test isomorphism directly if the matroids are stored in the same type. Of course a RegularMatroids can easily be turned into a LinearMatroid over GF(2), I know, but Sage does not know. We chose this as standard behaviour (M, N not same type => M.isomorphic(N) returns False), since here appears to be no proper way to automatically handle this in general without investing significant cpu time. I mean, how to resolve regular and GF(2) is clear, but there are many other combinations and we also did not want to silently resolve the problem in some cases and not in others, since that is even more confusing. But now that you bring it up, we could consider a different answer (e.g. no answer, ‘None’ rather than False) or an error message when someone attempts to test isomorphism between types, because I can see how the current behaviour may lead to silent errors. Cheers, Rudi -- --- You received this message because you are subscribed to the Google Groups "sage-matroid" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
