#15245: Pfaffian of a skew-symmetric matrix
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Reporter: darij | Owner:
Type: enhancement | Status:
Priority: major | positive_review
Component: combinatorics | Milestone: sage-5.13
Keywords: matrix, sage-combinat, | Resolution:
pfaffian | Merged in:
Authors: Darij Grinberg | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: #14117 | Stopgaps:
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Changes (by darij):
* status: needs_review => positive_review
Old description:
> I couldn't believe my eyes when I saw we don't have the Pfaffian
> implemented in Sage.
>
> Attached is an implementation that computes it over any ring in the
> combinatorial way using perfect matchings. This is probably not an
> optimal algorithm (and I feel like a lot could already be gained by
> improving up the PerfectMatchings(n) iterator without even changing the
> algorithm) but it's enough for my combinatorial needs.
>
> Other than this, the patch makes perfect matchings iterable (no, they
> weren't) and improves some docstrings related to rook polynomials. The
> #14117 dependency is because both patches edit matrix2.py and would
> probably cause some fuzz.
New description:
I couldn't believe my eyes when I saw we don't have the Pfaffian
implemented in Sage.
Attached is an implementation that computes it over any ring in the
combinatorial way using perfect matchings. This is probably not an optimal
algorithm (and I feel like a lot could already be gained by improving up
the PerfectMatchings(n) iterator without even changing the algorithm) but
it's enough for my combinatorial needs.
Other than this, the patch makes perfect matchings iterable (no, they
weren't) and improves some docstrings related to rook polynomials. The
#14117 dependency is because both patches edit matrix2.py and would
probably cause some fuzz.
Apply:
* [attachment:trac_15245-pfaffian-dg.patch]
--
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Ticket URL: <http://trac.sagemath.org/ticket/15245#comment:5>
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