#9524: Nasty bug with polynomial arithmetic and NTL contexts
--------------------------------+-------------------------------------------
Reporter: craigcitro | Owner: AlexGhitza
Type: defect | Status: new
Priority: major | Milestone:
Component: basic arithmetic | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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I just ran into the following nasty bug:
{{{
sage: polygen(GF(49, 'a')) ; polygen(GF(9, 'a'))
x
x
sage: x = polygen(GF(49, 'a'))
sage: -x
2*x
sage: x + 0
x
sage: -x
6*x
}}}
This is still present in sage-4.5.
I think I know what the problem is, but I haven't had time to sit down and
fix it. It's an issue with the NTL context being correctly restored when
switching from 7 to 3 and back. There's a very nice note (by David Roe, I
think) in most of the `_p` files in NTL that describes a pattern one must
avoid to get context restoration right; unfortunately, the code generated
by `sage.rings.polynomial.polynomial_zz_pex.pyx` (via
`polynomial_template.pxi`) exactly conforms to this anti-pattern.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9524>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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