Re: Question on ternary quadratic form

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

On Fri, Nov 17, 2023 at 03:01:53PM +0100, hermann@stamm-wilbrandt.de wrote:
> On 2023-11-17 11:39, Bill Allombert wrote:
> > > Your "foursquares()" takes 21ms for M_1279.
> > > But I had to stop it after more than an hour for M_2203 on i7-11850H
> > > CPU.
> > 
> > This is strange, do you have the latest version ?
> > 
> > ? foursquares(2^1279-1)
> > time = 12 ms.
> > ? foursquares(2^2203-1)
> > time = 31 ms.
> > ? foursquares(2^9689-1)
> > time = 684 ms.
> > 
> > Cheers,
> > Bill.
> > 
> I did download again and verified that I had last version.
> I did run "foursquares(M_p)" again, 8ms for 1279, did stop after more than
> 40min for 2203:
> 
> gp version is 2.15.3 on RHEL 8.8 and i7-11850H CPU, that was bad.
> With gp 2.16.1 on Ubuntu 22.04 on AMD 7600X "foursquares()" is much better.

Ah indeed, I tested with gp 2.15.4 (the latest stable release).
Unfortunately 2.15.3 has a nasty bug #2469 
<https://pari.math.u-bordeaux.fr/Bugs/2469>
which is precisely that factor(2^2203-1) enters an infinite loop!
So indeed you could have wited for a long time! Sorry about that!

Cheers,
Bill.