Prof. J. E. Cremona on Tue, 25 May 1999 20:20:56 +0100 (BST)

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Re: elltors() bug


Darrin Doud implemented a much faster torsion algorithm in GP which
uses (1) reduction moddulo small primes, (2) Mazur's classification.
It is described in a paper which appeared recently in Manuscripta
Math; he also sent me his code, which is in ~cremona/gp/ in
Bordeaux where you can find it.

Doud's program was so much faster than mine that as soon as I received
it I implemented the same tricks in my own code (before that I had
just been too lazy to do so).  It would be great to have that in GP as
the default -- and I am sure  you can convert it from GP to C+pari
faster than I can!