Re: thue() wants more than 4GB stack

[Karim Belabas <Karim.Belabas@math.u-bordeaux1.fr>]

* Max Alekseyev [2010-02-05 19:27]:
> I wonder whether this behavior is intended?
> 
> ? thue(thueinit(-3711916*x^4 - 161330*x^3 + 178491*x^2 - 365*x - 19),344622096)
>   *** thue: Warning: Non trivial conditional class group.
>   *** The result returned by 'thue' is conditional on the GRH.
>   ***   at top-level: thue(thueinit(-37119
>   ***                 ^--------------------
>   *** thue: the PARI stack overflows !
>   current stack size: 4294967296 (4096.000 Mbytes)
>   [hint] you can increase GP stack with allocatemem()

Intended, no. Expected, yes :-)

> This is rather unusual example since many other thue() computations I
> performed were not so eager for memory.

After a simple change of variable, the algorithm needs to solve

  K = bnfinit(x^4+365*x^3-3391329*x^2+58240130*x+25460031844);
  a = -461794186226632896;
  bnfisintnorm(K, a)

Unfortunately, 'a' has many prime divisors (with moderately large
valuations), in fact 18 prime ideal divisors, producing a huge number of
potential solutions, about half of which should yield actual solutions
since the class number of K is 2.

It is not clean whether these solutions can actually fit in physical
memory (I'll double check this, maybe there is some simple obstruction
and no solution after all...).

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-bordeaux.fr/~belabas/
F-33405 Talence (France)       http://pari.math.u-bordeaux.fr/  [PARI/GP]
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