#15577: Making braid groups independent on the global option for order of
permutations
-------------------------+-------------------------------------------------
Reporter: darij | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.1
Component: group | Keywords: groups, combinat, braid
theory | group, permutations
Merged in: | Authors: Darij Grinbrg
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
-------------------------+-------------------------------------------------
<boilerplate>
As detailed in #14885, it is not healthy for code to rely on the `__mul__`
operation on permutations, since this operation depends on the
`Permutations().global_options()['mul']` variable which can change at
runtime. It is better to use the `left_action_product` and
`right_action_product` methods introduced in #15174 (formerly known as
`_left_to_right_multiply_on_left` and `_left_to_right_multiply_on_right`).
</boilerplate>
The branch I'll attach later today sets out to solve this issue in
`sage/groups/braid.py`. In all methods whose result depends on the `mult`
global variable, the user can now set a local variable `mult` to override
the global one, and this is explicited in the docstrings. (Also, some
speedups have been achieved, most noticeably in the `permutation()` method
which now runs about 8 times faster since permutations are being composed
by list operations rather than multiplied as permutations.)
**WARNING:** Please read the TODO part I left in the comments to the
sourcecode of the `_left_normal_form_perm_` method. I am not sure of my
fix there and would prefer someone who knows what this method does to look
over it (and document the method while at that).
--
Ticket URL: <http://trac.sagemath.org/ticket/15577>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/groups/opt_out.
