Re: Problems in 'make bench' under Cygwin/64 with testing elliptic

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Tue, Jan 06, 2015 at 10:56:32AM +0100, Andreas Kellers wrote:
> I did some further investigation using a failed test from 'Testing compat'.
> As far as I understand, the following statements should give 66:
> 
>   default(compatible, 3)
>   acurve = initell([0,0,1,-1,0])
>   apell(acurve,10007)
> 
> Doing this with the GP debug version (via './Configure -g') yields -1591
> instead.
> 
> Doing this with the GP standard version results in an error:
> 
>   ***   at top-level: apell(acurve,10007)
>   ***                 ^-------------------
>   *** apell: impossible inverse in Fl_inv: mod(11266880367774138369, 10007).

Both are wrong, the correct result is 66.
I assume you get the same result with
ellap(ellinit([0,0,1,-1,0]),10007)

This is a progress from the state where isprime(131) was wrong.

The problem is probably in the function "Fp_ellcard_Shanks" in
src/basemath/FpE.c.

I will investigate.

Thanks for all you have done so far on this!

Cheers,
Bill.