#20155: Graph Generators: Add Turan Graph
-------------------------------------+-------------------------------------
Reporter: mcognetta | Owner:
Type: enhancement | Status: needs_review
Priority: minor | Milestone: sage-7.1
Component: graph theory | Resolution:
Keywords: graphs | Merged in:
Authors: Marco Cognetta | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/mcognetta/graph_generators__add_turan_graph|
718ad7841a15352bc482f904ce8be89ff198086b
Dependencies: | Stopgaps:
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Comment (by mcognetta):
Replying to [comment:3 dcoudert]:
> Hello,
>
> If the method for assigning positions to vertices is also valid for
multipartite complete graphs, you could instead add it to the
`CompleteMultipartiteGraph` method and then just call this method with
appropriate parameters. This would thus improve both methods. Your method
could thus be reduced to:
> {{{
> if n < r:
> raise ValueError('n should be at least r')
> if n < 1:
> raise ValueError('n should be at least 1')
> if r < 1:
> raise ValueError('r should be at least 1')
>
> name = "Turan Graph with n: {}, r: {}".format(n,r)
>
> if r == 1:
> g = Graph(name=name)
> g.add_vertices(range(n))
> return g
>
> if r == 2:
> g = graphs.CompleteBipartiteGraph(floor(n/2),ceil(n/2))
> g.name(name)
> return g
>
> sizes = [ceil(n/r) for i in range(n%r)]
> sizes += [floor(n/r) for i in range(r-(n%r))]
> g = graphs.CompleteMultipartiteGraph(sizes)
> g.name(name)
> return g
> }}}
> I'm not sure the case `r==2` is actually needed.
>
> Also, I don't understand the need for method `calculate_positions` since
it is called only once. You could simply add the code in the method.
>
> I think there is no need for importing `math`. You should try calling
`floor` and `ceil` directly.
>
> There are several typos in the method descriptions: `wih`, `properity`,
etc.
>
> You must add some `TESTS` to ilustrate the errors when calling the
method with wrong parameters.
>
> Thanks for your first patch.
>
> David.
Yes, I think that I will end up doing this. I wrote the code before really
thinking about just using the CompleteMultipartiteGraph code.
I originally tried to just use ceil() and floor() but I got an error that
I couldn't fix.
I will edit this patch and reupload it.
Thanks.
--
Ticket URL: <http://trac.sagemath.org/ticket/20155#comment:5>
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