Re: weird error in thueinit

[Max Alekseyev <maxale@gmail.com>]

Karim,

Replacing thueinit(p) by thueinit(simplify(p)) does not help.
Moreover, this particular place is successfully executed multiple
times (with different p) before the error occurs.
Each time the error occur on the same p and that does not depend on
random seeds (I have tried various setrand() before running the
computation).

I'll send you my script in private email.

Regards,
Max

On Sun, Jun 2, 2013 at 9:13 AM, Karim Belabas
<Karim.Belabas@math.u-bordeaux1.fr> wrote:
> * Max Alekseyev [2013-06-02 13:31]:
>> In my lengthy computations involving many thueinit() / thue() calls, I
>> suddenly get the following error:
>>
>>   *** thueinit: incorrect priority in nfroots: variable x >= x
>>
>> in the call "thueinit(p)" with apperently innocent p = -29*x^4 +
>> 184*x^3 - 294*x^2 + 184*x - 29.
>> Right after this, calling thueinit(p) causes the same error, while
>> explicit calling thueinit(-29*x^4 + 184*x^3 - 294*x^2 + 184*x - 29)
>> works fine.
>
> This is apparently generated when calling
>   thueinit(t_POL with automorphisms)
>   -> bnfinit
>   -> nfroots (to compute automorphisms in order to speed up bnfinit)
>
> The "incorrect priority" is either
> 1) a programming mistake on your side. Try to
>
>   - replace thueinit(p) by thueinit(simplify(p))
>
>   - add write("some_logfile", getrand()) statements at various places
>     Maybe resetting the random seed to this know value will help
>     reproduce the problem.
>
> 2) the result of internal data corruption somewhere, which will be very
> hard to track down unless you can supply a script that generates the
> problem from scratch. Can you experiment and try to generate such a script ?
>
> Cheers,
>
>     K.B.
> --
> Karim Belabas, IMB (UMR 5251)  Tel: (+33) (0)5 40 00 26 17
> Universite Bordeaux 1          Fax: (+33) (0)5 40 00 69 50
> 351, cours de la Liberation    http://www.math.u-bordeaux1.fr/~kbelabas/
> F-33405 Talence (France)       http://pari.math.u-bordeaux1.fr/  [PARI/GP]
> `