#12135: Multiple loops handling in c_graph -- Cernay2012
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Reporter: brunellus | Owner: jason, ncohen, rlm
Type: defect | Status: positive_review
Priority: major | Milestone: sage-5.0
Component: graph theory | Keywords:
Work_issues: | Upstream: N/A
Reviewer: Nathann Cohen | Author: Lukáš Lánský
Merged: | Dependencies:
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Changes (by newvalueoldvalue):
* reviewer: => Nathann Cohen
* author: => Lukáš Lánský
Old description:
> Sage handles multiple loops on one vertex inconsistently.
>
> {{{
> sage:g=Graph({0:[0,0]}, loops=True, multiedges=True,
> implementation="c_graph")
> sage:g.edges()
> [(0, 0, None), (0, 0, None)]
> sage:g.delete_edge(0,0)
> sage:g.edges()
> []
> }}}
>
> Compare with
>
> {{{
> sage:g=Graph({0:[0,0]}, loops=True, multiedges=True,
> implementation="networkx")
> sage:g.edges()
> [(0, 0, None), (0, 0, None)]
> sage:g.delete_edge(0,0)
> sage:g.edges()
> [(0, 0, None)]
> }}}
>
> and
>
> {{{
> sage:g=Graph({0:[1,1]}, loops=True, multiedges=True,
> implementation="c_graph")
> sage:g.edges()
> [(0, 1, None), (0, 1, None)]
> sage:g.delete_edge(0,1)
> sage:g.edges()
> [(0, 1, None)]
> }}}
New description:
Sage handles multiple loops on one vertex inconsistently.
{{{
sage:g=Graph({0:[0,0]}, loops=True, multiedges=True,
implementation="c_graph")
sage:g.edges()
[(0, 0, None), (0, 0, None)]
sage:g.delete_edge(0,0)
sage:g.edges()
[]
}}}
Compare with
{{{
sage:g=Graph({0:[0,0]}, loops=True, multiedges=True,
implementation="networkx")
sage:g.edges()
[(0, 0, None), (0, 0, None)]
sage:g.delete_edge(0,0)
sage:g.edges()
[(0, 0, None)]
}}}
and
{{{
sage:g=Graph({0:[1,1]}, loops=True, multiedges=True,
implementation="c_graph")
sage:g.edges()
[(0, 1, None), (0, 1, None)]
sage:g.delete_edge(0,1)
sage:g.edges()
[(0, 1, None)]
}}}
Apply:
* [attachment:trac_12135_loop_removal.patch]
* [attachment:trac_12135_review.patch]
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12135#comment:6>
Sage <http://www.sagemath.org>
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