Multiple loops and edges are lost upon pickling

[nthiery]

Title says it all:

sage: H = DiGraph(loops=True, multiedges=True)
sage: H.add_vertex(0)
sage: H.add_edge((0,0,0))
sage: H.add_edge((0,0,1))
sage: H.add_edge((0,1,0))
sage: H.add_edge((0,1,1))
sage: H.edges()
[(0, 0, 0), (0, 0, 1), (0, 1, 0), (0, 1, 1)]

sage: HH = loads(dumps(H))
sage: HH.edges()
sage: [(0, 0, 1), (0, 1, 1)]

CC: @sagetrac-sage-combinat @nathanncohen @sagetrac-brunellus

Component: graph theory

Author: Lukáš Lánský

Reviewer: Nathann Cohen

Merged: sage-5.0.beta3

Issue created by migration from https://trac.sagemath.org/ticket/10916

[nathanncohen]

comment:3

Attachment: trac_10916_pickling_repair.patch.gz

Hellooooooooooo !!

Well, this fixes the bug but it also means that the object that is pickled does not necessarily correspond to the original one, as the new one admits multiple edges ^^;

What about setting multiple_edges = self._multiple_edges as it seems to be defined ? And there is an allow_loops() method for the other argument.

Nathann

[sagetrac-brunellus]

comment:4

Hi! I think this is not the case because the DiGraph object is not used in the resulting tuple -- it is just a device to get all arcs. Maybe I don't understand it correctly, but I assume that allow_multiedges is pickled one level higher, in the SparseGraphBackend object.

sage: loads(dumps(Graph({0: [1]})))
Graph on 2 vertices
sage: loads(dumps(Graph({0: [1,1]})))
Multi-graph on 2 vertices

What do you think?

[nathanncohen]

comment:5

What do you think?

Quite obviously that I said something stupid :-)

Give me a few seconds to give it a more attentive look :-p

Nathann

[nathanncohen]

comment:7

Hmmmm... You are totally right, your patch is good and sound. I do not explain why Sage's source code is written like that, but....
I really need to rewrite a lot of stuff there O_O;;

Thank you for this patch, and sorry for my stupid remark :-)

Nathann

[sagetrac-brunellus]

comment:8

Thanks for the fast review! The fix really looks like something everyone would try without any thinking. :-)

Lukáš

[jdemeyer]

Reviewer: Nathann Cohen

[jdemeyer]

Author: Lukáš Lánský

[jdemeyer]

Merged: sage-5.0.beta3