Karim Belabas on Mon, 11 Dec 2006 16:59:33 +0100


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Re: pari bug 

* William Stein [2006-12-11 10:34]:
> I found a bug in PARI's polynomial factorization over finite fields
> in pari-2.3.1 and in pari-2.4.0.alpha:
> 
> ?  f = Mod(Mod(1, 100003), Mod(1, 100003)*a^2 + Mod(78244, 100003)*a  
> + Mod(99957, 100003))*x^2 + Mod(Mod(92725, 100003)*a + Mod(69647, 100003),  
> Mod(1, 100003)*a^2 + Mod(78244, 100003)*a + Mod(99957, 100003))*x  
> + Mod(Mod(80881, 100003)*a + Mod(93268, 100003), Mod(1, 100003)*a^2  
> + Mod(78244, 100003)*a + Mod(99957, 100003))
> %1 = Mod(Mod(1, 100003), Mod(1, 100003)*a^2 + Mod(78244, 100003)*a  
> + Mod(99957, 100003))*x^2 + Mod(Mod(92725, 100003)*a + Mod(69647, 100003),  
> Mod(1, 100003)*a^2 + Mod(78244, 100003)*a + Mod(99957, 100003))*x  
> + Mod(Mod(80881, 100003)*a + Mod(93268, 100003), Mod(1, 100003)*a^2  
> + Mod(78244, 100003)*a + Mod(99957, 100003))
> ?
> ? factor(f)
> 
> Program received signal EXC_BAD_ACCESS, Could not access memory.

This affected all archs & mp kernels: factor() over non-prime finite field
assumed a given temp polynomial could not be a constant. This was wrong
for some "pure-power" inputs.

Fixed in CVS.

Cheers,

    K.B.
-- 
Karim Belabas                  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]