Then would factoring 2*x-2 also reveal the bug? Or maybe factoring
2 ?
It seems to me that for Pari to remove and then ignore the content (in
Z?) is a bug.
It would make some sense to optionally not factor such a content
unless you want to
also do integer factorization.
On Oct 3, 11:51 am, Robert Bradshaw <rober...@math.washington.edu>
wrote:
> On Oct 2, 2009, at 9:30 PM, rjf wrote:
>
> > hey, factoring-testing guys..
> > If you make up factoring problems this way, you are probably not doing
> > much testing of the real factoring algorithms.
>
> Actually, given this bug has been in Sage for so long, the real issue
> is that for several years no one had tested "easy" factorizations
> such as this--everyone was worried about timing and testing the
> "hard" ones.
>
>
>
> > Repeated factors like
> > this of different degree are detected by so-called square-free
> > factorization.
> > The time to factor F in Maxima is, to the resolution of the clock,
> > 0.0000 seconds on
> > a 3GHz Intel machine.
>
> > F can also be entirely factored by the sqfr program, which uses a 5
> > line program involving
> > differentiation, GCD, and division. So the problem is essentially no
> > harder than factoring f and g separately.
>
> > There are papers that show how to construct polynomials that are
> > difficult to factor.
>
> > I dunno about the Sage wrapper problem. If that's the difficulty,
> > maybe the subject line is wrong.
>
> Yes, it was all about the wrapper (pari ignores the content, and
> there was a bug in reconstructing it). The subject perfectly
> describes the symptom, and was helpful in locating the cause.
>
> - Robert
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