Karim BELABAS on Mon, 3 Mar 2003 12:48:04 +0100 (MET)


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Re: rnflllgram() regression


On Sun, 2 Mar 2003, Igor Schein wrote:
> ? nf=nfinit(y^9-10*y^8-y^7+7*y^6+y^5-y^4+5*y^2+9*y+4);
> ? pol=x^9-10*x^8-10*x^7+6*x^6-4*x^5+7*x^4+7*x^3+8*x^2-1;
> ? rnflllgram(nf,pol,rnfpseudobasis(nf,pol));
>   ***   not a definite matrix in lllgram
>
> It was broken some time between 2.2.4 and 2.2.5

Precision loss. It occured in 2.2.4 also, but was slightly less acute
(different internal nf format), hence was hidden / disregarded [ and the
result was incorrect: not LLL reduced ].

At \p50 it works.

    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]