#18972: twographs and Seidel switching
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Reporter: dimpase | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.9
Component: graph theory | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/dimpase/seidelsw | b76c9a0369a5babc98481d6b96125c9b86f1adc9
Dependencies: | Stopgaps:
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Comment (by dimpase):
Replying to [comment:1 ncohen]:
> Hellooooooo,
>
> 1) The docstring must begin with a one-line sentence
(http://doc.sagemath.org/html/en/developer/coding_basics.html#the-
docstring-of-a-function-content)
>
> 2) small case (e.g.: `Graph.tutte_polynomial`)
why, why... Tutte won't complain from the grave, but, you know, to me this
feels like dancing on his tombstone... And I actually happened to know
Jaap Seidel; I was a postdoc in Eindhoven, and he (and Jack van Lint,
whose name just popped up on your 2-weights code ticket) were still
there...
>
> 3) If your methods only apply to undirected graphs, they should be in
graph.py
>
ok, I will fix it.
> 4) Add doctests for your new constructor
>
> 5) This line is an insult to computer science: {{{idx =
frozenset([self.vertices().index(v) for v in s])}}}It builds a list `n`
times to compute the index of an element with a linear search.
that's what you write as an 1:30am prototype, you know; thanks for
pointing this out :-)
> And I don't think that you need a `.Seydel_adjacency_matrix` or a new
input type for this function.
Seidel adj.mat. has interesting spectral properties, and that's why it is
there.
(one gets srgs out of it if it has just 2 distinct eigenvalues; as well,
it is a means to construct cospectral graphs, by switching---which is
matrix conjugation, and this is why you preserve the spectrum...)
So it is very useful on its own right.
>
> 6) A new method must be added to the index at the top of the file.
OK; should there also be something done in src/doc ?
Dima
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Ticket URL: <http://trac.sagemath.org/ticket/18972#comment:2>
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