gcd-gmp.c

/* 
 * http://gmplib.org/
 *
 * gcc gcd-gmp.c -o gcd-gmp -lgmp
 *
 */

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

void
gcd2 (mpz_t r, mpz_t a1, mpz_t b1)
{
  mpz_t a, b;
  mpz_init_set (a, a1);
  mpz_init_set (b, b1);
  while (mpz_sgn (b) != 0)
    {
      mpz_set (r, b);           /* r = b; */
      mpz_mod (b, a, b);        /* b = a % b; */
      mpz_set (a, r);           /* a = r; */
    }
  mpz_set (r, a);
  mpz_clear (a);
  mpz_clear (b);
}

void
gcdn (mpz_t r, mpz_t a[], size_t n)
{
  size_t i;
  mpz_set (r, a[0]);
  for (i = 1; i < n; i++)
    gcd2 (r, r, a[i]);          /* mpz_gcd ;-) */
}


int
main (int argc, char *argv[])
{
  mpz_t *a, g;
  int i, n;

  if (argc > 1)
    {
      n = argc - 1;
      a = (mpz_t *) malloc (n * sizeof (mpz_t));
      if (!a)
        return EXIT_FAILURE;

      for (i = 1; i <= n; i++)
        mpz_init_set_str (a[i - 1], argv[i], 10);

      mpz_init (g);
      gcdn (g, a, n);
      mpz_out_str (NULL, 10, g);
      printf ("\n");

      mpz_clear (g);
      for (i = 1; i <= n; i++)
        mpz_clear (a[i - 1]);
      free (a);
    }
  return EXIT_SUCCESS;
}