#19586: Add is_cayley_graph
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Reporter: jaanos | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.10
Component: graph theory | Resolution:
Keywords: Cayley graphs | Merged in:
groups | Reviewers: Nathann Cohen
Authors: Janoš Vidali | Work issues:
Report Upstream: N/A | Commit:
Branch: | 8685628455d2364bbb1896bf28e18c637bfab50c
u/jaanos/add_is_cayley_graph | Stopgaps:
Dependencies: |
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Comment (by ncohen):
> Yes, I was a bit worried about that. Anyway, this was intended more as a
demonstration that the method works on non-simple graphs, so maybe it
should be moved to the Examples section. Instead of printing out the
generating set, maybe we should just print its length and the number of
distinct elements, and maybe check that it contains the identity element.
If you meant it as a 'pedagogical' doctest, then there is an easy way out:
just add a '# random' flag to the doctest.
file:///home/ncohen/.Sage/src/doc/output/html/en/developer/coding_basics.html
#special-markup-to-influence-tests
> Yes, because the generating set of a Cayley graph is not the same as the
set of generators of a group.
Arg... Sorry. Not only I am an idiot, but I already asked the same
question and you gave me the very same answer `>_<`
> This reminds me that I should probably add a further optimization: if a
(simple) graph is connected and dense (say, vertex degree more than half
the order), then it may be more efficient to check for Cayleyness of its
complement (in case it is disconnected it will be more efficient,
otherwise the same).
The .density() and .complement() method raise exceptions on non-simple
graphs. I think that it is better to not care about this, unless you
really need those cases and the speedup is obvious.
> No, because we are not guaranteed that a tuple will be returned.
Weird. I thought you said in the doctest that a tuple will always be
returned, whether the graph is a cayley graph or not, and that the
additional values would be set to `None` if necessary.
> True, but other methods returning multiple data also return tuples, so I
think it should stay (IMO lists should be used when the size of the output
is not predetermined, and its members have the same type).
`O_o`
Okay. Well. Tastes `:-P`
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/19586#comment:64>
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