Karim BELABAS on Wed, 15 Oct 2003 11:34:02 +0200 (MEST) |
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Re: polredabs failure |
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]