#17408: Faster transitive_reduction (=> faster Poset creation)
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Reporter: ncohen | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.5
Component: graph theory | Resolution:
Keywords: | Merged in:
Authors: Nathann Cohen | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Changes (by ncohen):
* status: new => needs_review
Old description:
> As reported on #17361, the call to `transitive_reduction` represents a
> non-negligible part of Poset creation.
>
> This branch re-implements it for acyclic graphs.
New description:
As reported on #17361, the call to `transitive_reduction` represents a
non-negligible part of Poset creation.
This branch re-implements it for acyclic graphs.
Before
{{{
sage: g = posets.BooleanLattice(5).hasse_diagram().transitive_closure(); g
= g.cartesian_product(g)
sage: %time Poset(g)
CPU times: user 1.3 s, sys: 8 ms, total: 1.3 s
Wall time: 1.29 s
Finite poset containing 1024 elements
}}}
After
{{{
sage: g = posets.BooleanLattice(5).hasse_diagram().transitive_closure(); g
= g.cartesian_product(g)
sage: %time Poset(g)
CPU times: user 292 ms, sys: 12 ms, total: 304 ms
Wall time: 265 ms
Finite poset containing 1024 elements
}}}
Note that a LOT of time is lost on calls to `__eq__`. If I make no mistake
it is because `Posets` are `UniqueRepresentation`. I would personally be
very very glad if we could get rid of that.
--
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Ticket URL: <http://trac.sagemath.org/ticket/17408#comment:1>
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