#13114: Bug in is_isomorphic for multigraphs !
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Reporter: ncohen | Owner: jason, ncohen, rlm
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.1
Component: graph theory | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Changes (by ncohen):
* cc: dcoudert (added)
* status: new => needs_review
Old description:
> In order to test for isomorphism of multigraphs, multiple edges are
> converted to labeled edges whose label encodes the multiplicity.
> Yeah. But if, on the other side, we chose to ignore edge labels for
> isomorphism then the information of multiplicity vanishes !
>
> The bug has been reported by Stavros Garoufalidis.
>
> Nathann
New description:
In order to test for isomorphism of multigraphs, multiple edges are
converted to labeled edges whose label encodes the multiplicity.
Yeah. But if, on the other side, we chose to ignore edge labels for
isomorphism then the information of multiplicity vanishes !
The bug has been reported by Stavros Garoufalidis.
{{{
sage: g = Graph([(0, 0, 0), (0, 2, 0), (1, 1, 0), (1, 2, 0), (1, 2, 1),
(2, 2, 0)])
sage: gg = Graph([(0, 0, 0), (0, 1, 0), (1, 1, 0), (1, 2, 0), (2, 2, 0),
(2, 2, 1)])
sage: g.is_isomorphic(gg)
True
}}}
Nathann
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13114#comment:1>
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