Opened 13 years ago

Closed 13 years ago

# Coxeter groups: more Bruhat and weak order features

Reported by: Owned by: Nicolas M. Thiéry Nicolas M. Thiéry major sage-4.3.1 combinatorics Bruhat order, Weak order Sage Combinat CC user sage-4.3.1.alpha2 Nicolas M. Thiéry, Daniel Bump Daniel Bump N/A

New methods:

• bruhat_le (code inspired from code by Daniel Bump)
• weak_le
• bruhat_poset (finite Coxeter groups)
• weak_poset (finite Coxeter groups)

Improved doctests for related methods

(Trivially) depends on #7842

### comment:1 Changed 13 years ago by Nicolas M. Thiéry

Status: new → needs_review

### comment:2 follow-up:  3 Changed 13 years ago by Daniel Bump

Status: needs_review → needs_work Coxeter groups: more Bruhat and weak order features → Coxeter groups: more Bruhat and weak order features [with patch, needs work]

This patch implements the bruhat_order as a cached method and is badly needed.

With Sage 4.3, this raises an exception at the test in coxeter_groups.py, line 1010.

The definition of Q could be rewritten:

```W = WeylGroup("B3")
sage: fcn = lambda x,y : x.bruhat_le(y)
sage: Q=Poset((W.list(),fcn))
```

Maybe the `?!?` should be removed from the `# long time` directive a couple of lines later since it is unclear what it means.

### comment:3 in reply to:  2 Changed 13 years ago by Nicolas M. Thiéry

Description: modified (diff) needs_work → needs_review Coxeter groups: more Bruhat and weak order features [with patch, needs work] → Coxeter groups: more Bruhat and weak order features

This patch implements the bruhat_order as a cached method and is badly needed.

With Sage 4.3, this raises an exception at the test in coxeter_groups.py, line 1010.

Oops, I forgot that this depended on another patch; now #7842. As you mention, this dependency is trivial though, so we can also work around it if #7842 is not merged instantly.

Maybe the `?!?` should be removed from the `# long time` directive a couple of lines later since it is unclear what it means.

Fixed, and updated the # long time around that line. I was just surprised by how much time this was taking. We need more Weyl group optimizations!

### Changed 13 years ago by Nicolas M. Thiéry

Updated timings w.r.t. #7754 which is already in Sage

### comment:4 Changed 13 years ago by Daniel Bump

Status: needs_review → positive_review

By now this code is tested a lot, at least for finite Weyl groups, and the previous reviewer comments were addressed. I am changing the status to positive review.

### comment:5 Changed 13 years ago by Robert Miller

Merged in: → 4.3.1.alpha2 → fixed positive_review → closed

### comment:6 Changed 13 years ago by Minh Van Nguyen

Merged in: 4.3.1.alpha2 → sage-4.3.1.alpha2
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