#18946: unweighted matroid intersection using blocking flow approach
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Reporter: chaoxu | Owner:
Type: enhancement | Status: needs_review
Priority: minor | Milestone: sage-6.9
Component: matroid theory | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: u/chaoxu/faster- | Commit:
abstract-matroid-intersection | c9fb292e9d2155ddc647e83970204a256ae53b3f
Dependencies: | Stopgaps:
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Comment (by Stefan):
The runtime seems to depend a lot on the type of matroid.
{{{
sage: M1 = Matroid(MatrixSpace(GF(2), 500, 2000).random_element())
sage: M2 = Matroid(MatrixSpace(GF(3), 500, 2000).random_element())
sage: %time X = M1.intersection(M2)
CPU times: user 929 ms, sys: 122 ms, total: 1.05 s
Wall time: 1.05 s
sage: %time X = M1._intersection_unweighted(M2)
CPU times: user 332 ms, sys: 1.68 ms, total: 334 ms
Wall time: 334 ms
sage: M1 = Matroid(MatrixSpace(GF(7), 500, 2000).random_element())
sage: M2 = Matroid(MatrixSpace(GF(3), 500, 2000).random_element())
sage: %time X = M1.intersection(M2)
CPU times: user 37 s, sys: 201 ms, total: 37.2 s
Wall time: 37.2 s
sage: %time X2 = M1._intersection_unweighted(M2)
CPU times: user 5min 1s, sys: 217 ms, total: 5min 1s
Wall time: 5min 2s
}}}
Your method is not accessible to end users; mention it in the
documentation of the intersection method. After adding that documentation
(where you could say something like "a method that might be faster,
depending on the matroids involved"), I would say it's good to go in
--
Ticket URL: <http://trac.sagemath.org/ticket/18946#comment:5>
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