John Cremona on Sat, 17 Dec 2016 16:34:33 +0100


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Re: Ratpoint 

On 17 December 2016 at 14:40, Bill Allombert
<Bill.Allombert@math.u-bordeaux.fr> wrote:
> On Sat, Dec 17, 2016 at 08:11:27AM +0000, Jenn Macleod wrote:
>> Does anybody have a Pari implementation of Michael Stoll's ratpoint.c code?
>>
>> This would be of great use in my doodlings.
>
> Denis Simon descent code include one:
> <http://www.math.unicaen.fr/~simon/ellQ.gp>
> function ratpoint.
>

This is misleading.  Denis Simon's code needs a function to find
solutions to y^2=f(x) where f is integral of degree 3 or 4, and he
provides a function called ratpoint() to do this.  It is *not* the
same as Michael Stoll's independent C program of that name.  Stoll's
program ratpoints.c (which he developed from old code by Elkies) is
more general in several ways (deg(f) essentially arbitrary) and also
probably much faster.

John

> We have plan to port Michael Stoll 'ratlift' code to PARI/GP, but this
> has been delayed.
>
> Cheers,
> Bill.
>