#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: Travis
Report Upstream: N/A | Scrimshaw
Branch: | Work issues:
Dependencies: #14117 | Commit:
| Stopgaps:
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Comment (by nbruin):
Oh, a comment that may be worthwhile for future work:
The generic implementations of is_skewsymmetric and is_alternating are
probably horribly slow compared to what one can do on specific classes
(see, e.g. #15104). Since the difference between is_alternating and
is_skewsymmetric only is apparent in characteristic 2, we'd probably get
better performance if one of the two calls the other if required. If the
specific implementation only applies to characteristic not equal to 2, it
only needs to implement one fast method and the generic other one will
call it.
Probably `is_skewsymmetric` is the better choice for being the "main"
method, because it's the more widely used term. We'd get something like:
{{{
def is_alternating(self):
if self.base_ring().characteristic() !=2:
return self.is_skewsymmetric()
<rest of code>
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/15245#comment:19>
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