gmp_randseed()

bom brill bombrill_gmp@yahoo.fr
Wed, 18 Dec 2002 19:57:03 +0100 (CET)


I have a real problem understanding the role of the
gmp_randseed(), and its implementation. 
In order to understand how does that function works, I
want to create a program that generates some random
numbers.

So here is what I did : 

#include <stdio.h>
#include <gmp.h>
#include <unistd.h>

/* le but de ce programme est de pondre un nombre
aleatoire */

int main(int argc, char **argv)
{
  gmp_randstate_t state;
  mpz_t nbre1, nbre2, seed;

  while(1)
    {
      /* Initialisation */
      mpz_init(nbre1);
      mpz_init(nbre2);
      mpz_init(seed);
      gmp_randinit_default(state);
      
      mpz_init_set_str(seed, "2^256", 10);
      gmp_randseed(state, seed);
      
      mpz_urandomb(nbre1, state, 256);
      mpz_urandomb(nbre2, state, 256);
      
      /* Affichage */
      gmp_printf(" nbre1 : %Zd \n nbre2 : %Zd\n",
nbre1, nbre2);
      printf(" ---------------------- \n");

      /* Nettoyage */
      gmp_randclear(state);
      mpz_clear(nbre1);
      mpz_clear(nbre2);
      mpz_clear(seed);
    }
  
  return 0;
}


But it doesn t work as I expected. In fact, the
numbers are always the same !
So, if there is someone who wants to explain me,
first, what is the concept behind the "state", what is
the role of the seed fuction, and eventually, what do
I have to do, to make my program run as I want to.

Really thx for your help, and sorry for my english..
but I m french.

Jeremie

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