#16370: OA(k,n) strongly regular graphs
-------------------------+-------------------------------------------------
Reporter: | Owner:
ncohen | Status: needs_review
Type: | Milestone: sage-6.3
enhancement | Resolution:
Priority: major | Merged in:
Component: graph | Reviewers:
theory | Work issues:
Keywords: | Commit:
Authors: | 90a72bd39d74c24cb548e5b7dc5995c67ac386f8
Nathann Cohen | Stopgaps:
Report Upstream: N/A |
Branch: |
u/ncohen/16370 |
Dependencies: |
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Comment (by vdelecroix):
Replying to [comment:15 ncohen]:
> > > So, you guys decided against implementing a generic
`graphs.IntersectionGraph` constructor?
> >
> > I did not decide anything. I asked questions to Nathann and he puts
the ticket back in needs review... which might mean that I have to
question his answers to my questions...
>
> Yep yep... Actually creating this constructor can be useful... Right now
you can build such graphs easily but nobody knows the syntax :
>
> {{{
> sage: random_sets = [Subsets(range(15)).random_element() for _ in
range(15)]
> sage: g = Graph([random_sets,lambda x,y : x&y])
> }}}
Hi,
So, what is the point of the ticket if we can already do
{{{
sage: g = Graph([map(Set, designs.transversal_design(3,7)), lambda x,y :
x&y])
}}}
Moreover, the graph you obtain is also strongly regular with BIBD input
{{{
sage: BIBD = designs.BalancedIncompleteBlockDesign(31,6)
sage: V = map(Set, BIBD.blocks())
sage: G = Graph([V, lambda x,y: x&y])
sage: G.is_strongly_regular(parameters=True)
(31, 32, 31, -1)
}}}
I would rather add those examples to the documentation (of both designs
and graphs). We could possibly add them to the documentation of the not
yet existing `graphs.IntersectionGraph`.
Vincent
--
Ticket URL: <http://trac.sagemath.org/ticket/16370#comment:16>
Sage <http://www.sagemath.org>
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