mpir/tests/mpz/t-perfsqr.c

/* Test mpz_perfect_square_p.

Copyright 2000, 2001, 2002 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.

The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA. */

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

#include "mpir.h"
#include "gmp-impl.h"
#include "tests.h"

/* check_modulo() exercises mpz_perfect_square_p on squares which cover each
   possible quadratic residue to each divisor used within
   mpn_perfect_square_p, ensuring those residues aren't incorrectly claimed
   to be non-residues.

   Each divisor is taken separately.  It's arranged that n is congruent to 0
   modulo the other divisors, 0 of course being a quadratic residue to any
   modulus.

   The values "(j*others)^2" cover all quadratic residues mod divisor[i],
   but in no particular order.  j is run from 1<=j<=divisor[i] so that zero
   is excluded.  A literal n==0 doesn't reach the residue tests.  */

void
check_modulo (void)
{
  static const unsigned long  divisor[] = PERFSQR_DIVISORS;
  unsigned long  i, j;

  mpz_t  alldiv, others, n;

  mpz_init (alldiv);
  mpz_init (others);
  mpz_init (n);

  /* product of all divisors */
  mpz_set_ui (alldiv, 1L);
  for (i = 0; i < numberof (divisor); i++)
    mpz_mul_ui (alldiv, alldiv, divisor[i]);

  for (i = 0; i < numberof (divisor); i++)
    {
      /* product of all divisors except i */
      mpz_set_ui (others, 1L);
      for (j = 0; j < numberof (divisor); j++)
        if (i != j)
          mpz_mul_ui (others, others, divisor[j]);

      for (j = 1; j <= divisor[i]; j++)
        {
          /* square */
          mpz_mul_ui (n, others, j);
          mpz_mul (n, n, n);
          if (! mpz_perfect_square_p (n))
            {
              printf ("mpz_perfect_square_p got 0, want 1\n");
              mpz_trace ("  n", n);
              abort ();
            }
        }
    }

  mpz_clear (alldiv);
  mpz_clear (others);
  mpz_clear (n);
}


/* Exercise mpz_perfect_square_p compared to what mpz_sqrt says. */
void
check_sqrt (int reps)
{
  mpz_t x2, x2t, x;
  mp_size_t x2n;
  int res;
  int i;
  /* int cnt = 0; */
  gmp_randstate_t rands;
  mpz_t bs;

  mpz_init (bs);

  mpz_init (x2);
  mpz_init (x);
  mpz_init (x2t);
  gmp_randinit_default(rands);

  for (i = 0; i < reps; i++)
    {
      mpz_urandomb (bs, rands, 9);
      x2n = mpz_get_ui (bs);
      mpz_rrandomb (x2, rands, x2n);
      /* mpz_out_str (stdout, -16, x2); puts (""); */

      res = mpz_perfect_square_p (x2);
      mpz_sqrt (x, x2);
      mpz_mul (x2t, x, x);

      if (res != (mpz_cmp (x2, x2t) == 0))
        {
          printf    ("mpz_perfect_square_p and mpz_sqrt differ\n");
          mpz_trace ("   x  ", x);
          mpz_trace ("   x2 ", x2);
          mpz_trace ("   x2t", x2t);
          printf    ("   mpz_perfect_square_p %d\n", res);
          printf    ("   mpz_sqrt             %d\n", mpz_cmp (x2, x2t) == 0);
          abort ();
        }

      /* cnt += res != 0; */
    }
  /* printf ("%d/%d perfect squares\n", cnt, reps); */

  mpz_clear (bs);
  mpz_clear (x2);
  mpz_clear (x);
  mpz_clear (x2t);
  gmp_randclear(rands);
}


int
main (int argc, char **argv)
{
  int reps = 100000;

  tests_start ();
  mp_trace_base = -16;

  if (argc == 2)
     reps = atoi (argv[1]);

  check_modulo ();
  check_sqrt (reps);

  tests_end ();
  exit (0);
}