some core features are broken for bipartite graphs

[Max Alekseyev]

Hello,

I'd like to bring your attention to two bugs related to handling bipartite graphs:

https://trac.sagemath.org/ticket/33246

https://trac.sagemath.org/ticket/33249

The first one is especially severe as it produces an inconsistent object and can easily propagate errors. I have already identified a few errors in my earlier computational results caused by this bug.

And while we are on this page, I was not able to find a complement function for a given bipartite graph G in K_{p,q}, where p and q are sizes of the partite sets of G. The existing .complement() method seems to treat G as a generic graph and thus complements it in K_{p+q} and results in a non-bipartite graph. Do I miss something here?

Regards,

Max

[Max Alekseyev]

... and here is one more bug, which is truly weird: https://trac.sagemath.org/ticket/33255 (distinct graphs have equals hashes)

Bipartite graphs routines are totally unreliable ;-(

Regards,

Max