#13461: Another WeylCharacterRing speedup
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Reporter: bump | Owner: bump
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.4
Component: combinatorics | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Daniel Bump | Merged in:
Dependencies: | Stopgaps:
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Changes (by bump):
* status: new => needs_review
* work_issues: needs testing and tweaking =>
Old description:
> After the patch, if a WeylCharacterRing is created with style="coroots",
> characters are computed using not the Freudenthal multiplicity formula,
> but
> rather the Demazure character formula. This can be done using only
> integer
> addition and subtraction. If we run {{{sage -t --long
> weyl_characters.py}}},
> it is more than twice as fast (26 seconds versus 69 seconds) as
> previously.
> If we omit {{{--long}}} it is slightly slower, so there is a speedup for
> big computations and a slight penalty for small ones.
New description:
After the patch, if a WeylCharacterRing is created with style="coroots",
characters are computed using not the Freudenthal multiplicity formula,
but
rather the Demazure character formula. This can be done using only integer
addition and subtraction. If we run {{{sage -t --long
weyl_characters.py}}},
it is more than twice as fast (26 seconds versus 69 seconds) as
previously.
If we omit {{{--long}}} it is slightly slower, so there is a speedup for
big computations and a slight penalty for small ones.
Demazure characters are added as a method of WeylCharacterRing and the
Demazure operators are implemented as methods of WeightRing elements.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13461#comment:1>
Sage <http://www.sagemath.org>
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