#9343: Upgrade PARI to svn snapshot 12577 - a pre-release of PARI 2.4.3.
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Reporter: was
| Owner: jdemeyer
Type: enhancement
| Status: needs_review
Priority: major
| Milestone: sage-4.6
Component: packages
| Keywords:
Author: Robert Bradshaw, John Cremona, Jeroen Demeyer, William Stein,
David Kirkby | Upstream: N/A
Reviewer:
| Merged:
Work_issues:
|
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Changes (by jdemeyer):
* status: needs_work => needs_review
Comment:
Replying to [comment:243 drkirkby]:
> Whilst the doctest can be changed to make this pass, is a real bug being
covered up?
I would rather say on the contrary. The problem was that we were
computing the roots of a polynomial with complex non-exact roots. I.e.:
instead of computing the roots of x^5+x-17, we were computing the roots of
(1.0 + 0.0*I)*x^5 + ... I changed that in my patch.
> Can anyone explain why a calculation performed with integers should
differ depending on whether the program is compiled 32-bit or 64-bit?
Since to me, of the arbitrary precision maths is implemented correctly,
they should give the same result.
This is not always true because the precisions might be different. In
PARI, the precision is always a multiple of the machine word size. If you
try to compute with 90 bits of precision, you will get 96 bits of
precision on a 32-bit machine but you will get 128 bits of precision on a
64-bit machine.
If might be possible to change this such that PARI always uses a multiple
of 64 bits of precision (I have been thinking about this), but it's not so
easy.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9343#comment:244>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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