Karim BELABAS on Sat, 22 Jun 2002 18:20:00 +0200 (MEST) |
[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]
Re: Point multiplication on elliptic curves over Q_{p} (fwd) |
On Tue, 18 Jun 2002, Iftikhar Burhanuddin wrote: >> On Fri, 14 Jun 2002, Iftikhar Burhanuddin wrote: >>> Say f is an elliptic curve over Q_{p} and P is a point on the curve, >>> e is the reduced elliptic curve, >>> nump are the number of points on e [nump = p+1-ellap(f,p)], >>> randno1 and randno2 are randomly generated integers. >>> >>> P1 = ellpow(f,P,nump); >>> P2 = ellpow(f,P1,nump); >>> P3 = ellpow(f,P,nump*nump); >>> >>> I would expect P2 and P3 to be equal but they are not. I can't figure out >>> why. Also... >> >> Which version of GP, on which architecture ? I cannot reproduce your problem >> with any of pari-2.2.3, 2.1.2, or 2.1.3 on either Solaris or Linux. > > gp/pari calculator version 2.2.2 (alpha) > cygwin > windows 2000 professional > pentium III Now I can reproduce it. There was a nasty bug in the addition of p-adic and rational numbers, introduced in version 2.2.2.alpha and fixed in the next update 2.2.3. You should upgrade to a more recent development release, for instance from CVS, or use a binary from the stable branch (the 2.1.x series). Cheers, Karim. -- Karim Belabas Tel: (+33) (0)1 69 15 57 48 Dép. de Mathematiques, Bat. 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/