#14888: Make FiniteField_pari_ffelt the default for generic finite fields
-------------------------------------+-------------------------------------
Reporter: pbruin | Owner: cpernet
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.13
Component: finite rings | Resolution:
Keywords: FiniteField | Merged in:
performance | Reviewers: Jean-Pierre Flori,
Authors: Peter Bruin | Jeroen Demeyer
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: #12142, #15124, | Stopgaps:
#15125 |
-------------------------------------+-------------------------------------
Comment (by jdemeyer):
Replying to [comment:26 pbruin]:
> Replying to [comment:24 jdemeyer]:
> > I tracked down the problem to this line in
`devel/sage/sage/libs/singular/singular.pyx`:
> > {{{
> > ret = ret + c
> > }}}
> > where ret is a `pari_ffelt` element equal to zero, `c` is the C `long`
equal to 2. The result is 0, while it should be 2.
> I wondered about the same line yesterday evening when I was looking at
the surrounding function, but thought that it hardly looked like something
that could fail with some small probability.
> Does this line always give the wrong result (and for some reason just
isn't called most of the time)?
No, it ''rarely'' gives the wrong result.
> I noticed that c is defined by `cdef int c` (i.e. C int, not Python
int), but is later used as a long; is that something to be suspicious
about?
It's not the cleanest coding ({{{c = <int>napGetCoeff(z)}}} would be
better), but I don't see how that could make a difference, especially
since this doesn't seem to be a case of overflow.
> it must be the conversion from Python `int` to `pari_ffelt` that is
causing the problem
I also guess that this is the problem.
--
Ticket URL: <http://trac.sagemath.org/ticket/14888#comment:27>
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.
