#13202: conversion problems in BooleanPolynomialRing with degrevlex order
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Reporter: Bouillaguet | Owner: malb
Type: defect | Status: new
Priority: major | Milestone: sage-5.2
Component: commutative algebra | Resolution:
Keywords: conversion | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by Bouillaguet):
Replying to [comment:2 AlexanderDreyer]:
> in `pbori.pyx`'s function `get_var_mapping`, indices are used to
represent the variables, but the reversing of the internal variable order
is not obeyed here (`PolyBoRi` does not support degrevlex directly, but a
variant with revered variable order.). I attach a quick fix for that
problem, but one can probably do better by using the the indexed
reordering from the ring (I'm not so familiar with that part of
pbori.pyx).
Wow ! Your patch seems to do it. I tried to patch the function myself but
I couldn't. It would be great if some comments in the file explained
what's going on. For instance, I somehow convinced myself that I wouldn't
be able to solve the problem without accessing the `pbind` array.
So, I discussed this off-list with malb, and we kind of agreed to
deprecate degreglex for boolean polynomials (after all, it is exactly the
same as deglex with variables in reverse order). How do you feel about
this? I suppose that with your patch it is not necessary anymore...
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13202#comment:3>
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