Karim BELABAS on Thu, 6 Feb 2003 01:59:31 +0100 (MET) |
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Re: qflll() bug |
On Tue, 21 Jan 2003, Igor Schein wrote: > ? m=[x^2-x+2,x^2-2*x-1,x^2+x+1;x^2-2*x+2,x^2+2,x^2-x-1;x^2-2*x+2,x^2+x+2,x^2-2*x-1]; > ? qflllgram(m,5) > [[;], [3, -1, 23; 0, 1, 13; 1, 0, -1]] This result is meaningless, m is not even symmetric. > ? qflll(m,5) > *** incorrect type in euclidean division (poldivres). Funny, this already didn't work in release 1.39 ! Actually, I don't see how it could possibly work over characteristic 0 domains, except in very degenerate circonstances [ in each reduction, we replace an entry by its primitive part, but don't update properly all data ]. Fixed by not taking the primitive part. If inefficiency of rational polynomial arithmetic in this LLL variant becomes a concern in a genuine application, I shall try to find a better way [ the only application I see for this routine is over finite fields, to compute in the divisor class group ]. 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 Email: Karim.Belabas@math.u-psud.fr F-91405 Orsay (France) http://www.math.u-psud.fr/~belabas/ -- PARI/GP Home Page: http://www.parigp-home.de/