"John Cremona" <john.crem...@gmail.com> writes:
> 2009/1/5 Martin Rubey <martin.ru...@univie.ac.at>:
> >
> > (not sure whether this belongs to sage-support or sage-devel)
> >
> > I'm preparing class for tomorrow, and ran across something I do not quite
> > understand:
> >
> > sage: f=ZZ[x].random_element(10)
> > sage: g=ZZ[x].random_element(10)
> > sage: timeit('gcd(QQ[x](f),QQ[x](g))')
> > 125 loops, best of 3: 2.96 ms per loop
> > sage: timeit('gcd(f,g)')
> > 625 loops, best of 3: 89.2 µs per loop
> >
> > I would have thought that the gcd over the rationals is no more difficult
> > than
> > over the integers. Am I mistaken?
> >
> > (would be wonderful to have a quick answer, even if not 100% polished...)
> > many
> > many thanks,
>
> This is a known issue. ZZ[x] is handled by Flint and is fast. QQ[x]
> is handled by pari and is slow(er). We all know how to reduce the
> latter to the former, but no-one has done it yet. It is trac ticket
> #4000: see http://trac.sagemath.org/sage_trac/ticket/4000
>
> John Cremona
Superb! many many thanks!
Martin
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