Re: polredabs failure

[Karim BELABAS <Karim.Belabas@math.u-psud.fr>]

On Tue, 14 Oct 2003, Igor Schein wrote:

> On Tue, Oct 14, 2003 at 08:29:29PM +0200, Karim BELABAS wrote:
> > I've changed this part of the algorithm. So this example should be slightly
> > faster than it used to be: the field generated by the first 14 elements
> > of the basis is a strict subfield. Previously, only the first 8 ones were
> > tested since the check was (deemed) too expensive otherwise.
> >
> > Any glitches ?
>
> ? polredabs(x^8-2*x^7-34*x^6+78*x^5+265*x^4-628*x^3-389*x^2+1237*x-449)
> x^8 - 2*x^7 - 34*x^6 + 78*x^5 + 265*x^4 - 628*x^3 - 389*x^2 + 1237*x - 449
>
> Failure to reduce.
>
> The correct answer is
>
> x^8 - 2*x^7 - 22*x^6 + 46*x^5 + 73*x^4 - 102*x^3 - 19*x^2 + 25*x + 5

Fixed. One optimization too many...

I have made extensive tests now, and it looks OK. I'm esp. interested
in tough polynomials of small degree (< 10), or general polynomials requiring
more than say 15 minutes for the reduction.

There are many possible small improvements ( large improvements wrt
stacksize requirements ), but I'd like to be sure there are no remaining
regression cases first.

Thanks!

    Karim.
-- 
Karim Belabas                     Tel: (+33) (0)1 69 15 57 48
Dép. de Mathématiques, Bât. 425   Fax: (+33) (0)1 69 15 60 19
Université Paris-Sud              http://www.math.u-psud.fr/~belabas/
F-91405 Orsay (France)            http://www.parigp-home.de/  [PARI/GP]