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
>
> Martin
>
>
> >
>
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