/* Test mpz_powm_ui, mpz_mul, mpz_mod.

Copyright 1991, 1993, 1994, 1996, 1997, 2000, 2001, 2002, 2013 Free Software
Foundation, Inc.

This file is part of the GNU MP Library test suite.

The GNU MP Library test suite is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 3 of the License,
or (at your option) any later version.

The GNU MP Library test suite 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 General
Public License for more details.

You should have received a copy of the GNU General Public License along with
the GNU MP Library test suite.  If not, see http://www.gnu.org/licenses/.  */

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

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

void debug_mp (mpz_t, int);

int
main (int argc, char **argv)
{
  mpz_t base, exp, mod;
  mpz_t r1, r2, base2;
  mp_size_t base_size, exp_size, mod_size;
  unsigned long int exp2;
  int i;
  int reps = 100;
  gmp_randstate_ptr rands;
  mpz_t bs;
  unsigned long bsi, size_range;

  tests_start ();
  rands = RANDS;

  mpz_init (bs);

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

  mpz_init (base);
  mpz_init (exp);
  mpz_init (mod);
  mpz_init (r1);
  mpz_init (r2);
  mpz_init (base2);

  for (i = 0; i < reps; i++)
    {
      mpz_urandomb (bs, rands, 32);
      size_range = mpz_get_ui (bs) % 18 + 2;

      do  /* Loop until mathematically well-defined.  */
	{
	  mpz_urandomb (bs, rands, size_range);
	  base_size = mpz_get_ui (bs);
	  mpz_rrandomb (base, rands, base_size);

	  mpz_urandomb (bs, rands, 6L);
	  exp_size = mpz_get_ui (bs);
	  mpz_rrandomb (exp, rands, exp_size);
	  exp2 = mpz_getlimbn (exp, (mp_size_t) 0);
	}
      while (mpz_cmp_ui (base, 0) == 0 && exp2 == 0);

      do
        {
	  mpz_urandomb (bs, rands, size_range);
	  mod_size = mpz_get_ui (bs);
	  mpz_rrandomb (mod, rands, mod_size);
	}
      while (mpz_cmp_ui (mod, 0) == 0);

      mpz_urandomb (bs, rands, 2);
      bsi = mpz_get_ui (bs);
      if ((bsi & 1) != 0)
	mpz_neg (base, base);

      /* printf ("%ld %ld\n", SIZ (base), SIZ (mod)); */

#if 0
      putc ('\n', stderr);
      debug_mp (base, -16);
      debug_mp (mod, -16);
#endif

      mpz_powm_ui (r1, base, exp2, mod);
      MPZ_CHECK_FORMAT (r1);

      mpz_set_ui (r2, 1);
      mpz_set (base2, base);

      mpz_mod (r2, r2, mod);	/* needed when exp==0 and mod==1 */
      while (exp2 != 0)
	{
	  if (exp2 % 2 != 0)
	    {
	      mpz_mul (r2, r2, base2);
	      mpz_mod (r2, r2, mod);
	    }
	  mpz_mul (base2, base2, base2);
	  mpz_mod (base2, base2, mod);
	  exp2 = exp2 / 2;
	}

#if 0
      debug_mp (r1, -16);
      debug_mp (r2, -16);
#endif

      if (mpz_cmp (r1, r2) != 0)
	{
	  fprintf (stderr, "\ntest %d: Incorrect results for operands:\n", i);
	  debug_mp (base, -16);
	  debug_mp (exp, -16);
	  debug_mp (mod, -16);
	  fprintf (stderr, "mpz_powm_ui result:\n");
	  debug_mp (r1, -16);
	  fprintf (stderr, "reference result:\n");
	  debug_mp (r2, -16);
	  abort ();
	}
    }

  mpz_clear (bs);
  mpz_clear (base);
  mpz_clear (exp);
  mpz_clear (mod);
  mpz_clear (r1);
  mpz_clear (r2);
  mpz_clear (base2);

  tests_end ();
  exit (0);
}

void
debug_mp (mpz_t x, int base)
{
  mpz_out_str (stderr, base, x); fputc ('\n', stderr);
}