Opened 9 years ago

Closed 7 years ago

#13248 closed enhancement (fixed)

Coxeter groups: all elements of length N, random elements

Reported by: sdenton Owned by: joyner
Priority: minor Milestone: sage-6.3
Component: group theory Keywords: sd40, coxeter
Cc: nthiery, heglin, tscrim, darij Merged in:
Authors: Tom Denton, Frédéric Chapoton Reviewers: Mike Zabrocki, Travis Scrimshaw
Report Upstream: N/A Work issues:
Branch: a96be6f (Commits) Commit: a96be6f6bbe8a90d811570c5023620955e82cce7
Dependencies: Stopgaps:

Description (last modified by chapoton)

Two commonly desired constructions in a Coxeter group are to: a) Iterate over all elements of a given length - this happens especially in affine or other infinite coxeter groups in order to test hypotheses, construct homogenous elements, etc... b) Choose a random element, possibly with length specified. This often occurs to see if a non-special element has a given property.

Iterating over all elements of a given length in particular has a nice solution (due to N. Thiery) and anecdotally has been implemented (usually in an inelegant fashion) by numerous community members in response to short-term problems.

We provide some code implementing these functions!

Change History (18)

comment:1 Changed 9 years ago by sdenton

  • Keywords sd40 added

comment:2 Changed 7 years ago by jdemeyer

  • Milestone changed from sage-5.11 to sage-5.12

comment:3 Changed 7 years ago by vbraun_spam

  • Milestone changed from sage-6.1 to sage-6.2

comment:4 Changed 7 years ago by chapoton

  • Keywords coxeter added

Where is the code ?

comment:5 Changed 7 years ago by sdenton

That's strange; I'm not sure why it isn't there.

The code should be the same used in the AffinePermutationGroup for the methods elements_of_length and random_element.

Example:

sage: A=AffinePermutationGroup?(['A',4,1])

sage: len(list(A.elements_of_length(1)))

5

sage: A.random_element(4)

Type A affine permutation with window [0, 4, 3, 2, 6]

comment:6 Changed 7 years ago by chapoton

Maybe we should then move the code to Coxeter groups, it it works.

comment:7 Changed 7 years ago by chapoton

  • Branch set to u/chapoton/13248
  • Commit set to c2ce1c2aadf83f0e4e10ec2ac307286ac5ecbd1f

here is a git branch, moving elements_of_length into the category of coxeter groups

New commits:

​c2ce1c2trac #13248 first step : moving elements_of_length to coxeter groups

comment:8 Changed 7 years ago by git

  • Commit changed from c2ce1c2aadf83f0e4e10ec2ac307286ac5ecbd1f to 93faac6d489a6b3a54ff5573e90444290bcced8c

Branch pushed to git repo; I updated commit sha1. New commits:

​93faac6Merge branch 'u/chapoton/13248' of trac.sagemath.org:sage into 13248

comment:9 Changed 7 years ago by chapoton

  • Cc nthiery added; ntiery removed

comment:10 Changed 7 years ago by vbraun_spam

  • Milestone changed from sage-6.2 to sage-6.3

comment:11 Changed 7 years ago by chapoton

  • Description modified (diff)
  • Status changed from new to needs_review
  • Work issues set to random not yet done

comment:12 Changed 7 years ago by git

  • Commit changed from 93faac6d489a6b3a54ff5573e90444290bcced8c to a94f96885688a39006c58fceb041694a2716b372

Branch pushed to git repo; I updated commit sha1. New commits:

​34cb3f9Merge branch 'u/chapoton/13248' of ssh://trac.sagemath.org:22/sage into 13248
​a94f968trac #13248 first step towards random

comment:13 Changed 7 years ago by git

  • Commit changed from a94f96885688a39006c58fceb041694a2716b372 to fb613e237c7fb1785256f33fe115d7890c6120bb

Branch pushed to git repo; I updated commit sha1. New commits:

​fb613e2trac #13248 remove code duplication

comment:14 Changed 7 years ago by chapoton

  • Work issues random not yet done deleted

comment:15 Changed 7 years ago by chapoton

  • Authors changed from sdenton to Tom Denton, Frédéric Chapoton
  • Cc tscrim darij added
  • Reviewers changed from zabrocki to Mike Zabrocki

ping ?

comment:16 Changed 7 years ago by tscrim

  • Branch changed from u/chapoton/13248 to u/tscrim/13248
  • Commit changed from fb613e237c7fb1785256f33fe115d7890c6120bb to 707c9c39ec02ba112f19e614a26c99e430b7bd67
  • Reviewers changed from Mike Zabrocki to Mike Zabrocki, Travis Scrimshaw

Hey Frederic,

I've done some minor tweaks and made it so that random_element chooses the length at random in [0, 1000] (so the word is not too long) if not specified. LGTM otherwise, so if you're happy with my changes, then positive review.

New commits:

​ec5652cMerge branch 'u/chapoton/13248' of trac.sagemath.org:sage into u/tscrim/13248
​707c9c3Some review tweaks.

comment:17 Changed 7 years ago by chapoton

  • Branch changed from u/tscrim/13248 to u/chapoton/13248
  • Commit changed from 707c9c39ec02ba112f19e614a26c99e430b7bd67 to a96be6f6bbe8a90d811570c5023620955e82cce7
  • Status changed from needs_review to positive_review

Hello, and thanks.

I just corrected a typo in "chosen".

I'm setting this to positive review.

New commits:

​a96be6ftrac #13248 just corrected a typo in "chosen"

comment:18 Changed 7 years ago by vbraun

  • Branch changed from u/chapoton/13248 to a96be6f6bbe8a90d811570c5023620955e82cce7
  • Resolution set to fixed
  • Status changed from positive_review to closed
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