#18045: Wrong result returned by is_planar on a given embedding
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Reporter: ncohen | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.6
Component: graph theory | Resolution:
Keywords: | Merged in:
Authors: Nathann Cohen | Reviewers:
Report Upstream: N/A | Work issues:
Branch: public/18045 | Commit:
Dependencies: | Stopgaps:
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Description changed by ncohen:
Old description:
> As reported on `AskSage` [1], the function `.is_planar` can return wrong
> results when given a specific embedding to run its computations on.
>
> This actually comes from a mistake in a `if/else` and variable types, as
> `bool(a_dictionary)` returns `True` when the dictionary is nonempty. The
> original authors did not seem to be aware of that, and once fixed the
> code does not mak the mistake again.
>
> Nathann
>
> [1] http://ask.sagemath.org/question/26301/testing-planarity-on-
> embedding-gives-wrong-result/
New description:
As reported on `AskSage` [1], the function `.is_planar` can return wrong
results when given a specific embedding to run its computations on.
This actually comes from a mistake in a `if/else` and variable types, as
`bool(a_dictionary)` returns `True` when the dictionary is nonempty. The
original authors did not seem to be aware of that, and once fixed the code
does not make the mistake again.
The problem was that the computations were run on the cached embedding
(i.e `_embedding`) instead of the one provided by the user.
Nathann
[1] http://ask.sagemath.org/question/26301/testing-planarity-on-embedding-
gives-wrong-result/
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Ticket URL: <http://trac.sagemath.org/ticket/18045#comment:2>
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