#4326: [with patch, positive review] Root systems improvements
---------------------------+------------------------------------------------
Reporter: nthiery | Owner: nthiery
Type: enhancement | Status: assigned
Priority: major | Milestone: sage-combinat
Component: combinatorics | Keywords: root systems
Reviewer: bump | Author: nthiery with help from schilling,
bump, Nicolas Borie, Qiang Wang, Steve Pon
Merged: |
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Comment(by bump):
Normally I would have waited for the category patches to be merged
before reviewing this patch. However I recieved an email from Tom Boothby
urging me to do the review now, so here it is.
This review is based on the version of the patches in the
combinat queue. This is because it depends on patches that
have not been merged yet.
After qpushing the combinat queue up to this patch but
not beyond, all tests pass. This is with Sage 4.1 and
the last changeset is this one:
{{{
changeset: 1520:188022ff52b9
tag: tip
user: Nicolas M. Thiery <[email protected]>
date: Tue Jul 21 01:13:42 2009 +0200
summary: Update
}}}
The patch adds quite a bit of new functionality for working
with Coxeter groups and affine Weyl groups. The following
new files are added. There are new categories added for
CoxeterGroups and WeylGroups. There is an extensive
ChangeLog in the comments at the beginning of the patch.
Since the patch is over 11,000 lines of code, there could
very well be bugs in it. However it probably does not
introduce significant new bugs in the portion of the
code that deals with classical root systems, since I
used it extensively during the spring of 2009 in
connection with #5794. Every classical Cartan type
and many reducible types have been created and worked
with. What problems I found then were fixed. Moreover
the portion of the code that deals with affine root
systems was similarly very tested by Anne Schilling
in connection with affine crystals.
Therefore the most uncertainty in my is with the new
functionality for Coxeter groups. I will mention one
"wish" in this direction, which is that in addition
to implementing the Bruhat covers, the Bruhat order
be properly implemented. This could be done efficiently
using Proposition 1.1 in Stembridge, A Short
Derivation of the Möbius Function for the Bruhat
Order, Journal of Algebraic Combinatorics 25,
(2007).
This wish is not a reason to hold up merging the
patch. Rather the patch should be merged as soon as
possible and such changes can be made later.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4326#comment:7>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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