#13391: WeylCharacterRing improvement
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Reporter: bump | Owner: bump
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.4
Component: combinatorics | Resolution:
Keywords: WeylCharacterRing, Lie | Work issues:
Report Upstream: N/A | Reviewers: Anne Schilling
Authors: Daniel Bump | Merged in:
Dependencies: | Stopgaps:
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Description changed by bump:
Old description:
> The multiplication algorithm for {{{WeylCharacterRings}}} is changed by
> this patch to an algorithm based on the Brauer-Klimyk formula. This
> algorithm is asymmetric, so that a*b and b*a are equal but computed
> differently. It gives a modest speedup for sage -t weyl_characters.py but
> for tasks it is a dramatic improvement. As an example, create the spin
> character of Spin(9):
>
> {{{
> sage: B4=WeylCharacterRing("B4",style="coroots")
> sage: spin=B4(0,0,0,1)
> }}}
>
> Now try raising this to different powers before and after the patch.
New description:
The multiplication algorithm for {{{WeylCharacterRings}}} is changed by
this patch to an algorithm based on the Brauer-Klimyk formula. This
algorithm is asymmetric, so that a*b and b*a are equal but computed
differently. They are sometimes interchanged in an attempt to give the
most efficient evaluation. This patch gives a modest speedup for {{{sage
-t --long weyl_characters.py}}} but in certain cases it is a dramatic
improvement. As an example, create the spin character of Spin(9):
{{{
sage: B4=WeylCharacterRing("B4",style="coroots")
sage: spin=B4(0,0,0,1)
}}}
Now try raising this to different powers before and after the patch.
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13391#comment:18>
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