dist/tests/trandom.c

/* Test file for mpfr_urandomb

Copyright 1999-2004, 2006-2020 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR 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 3 of the License, or (at your
option) any later version.

The GNU MPFR 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 MPFR Library; see the file COPYING.LESSER.  If not, see
https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */

#include "mpfr-test.h"

static void
test_urandomb (long nbtests, mpfr_prec_t prec, int verbose)
{
  mpfr_t x;
  int *tab, size_tab, k, sh, xn;
  double d, av = 0, var = 0, chi2 = 0, th;
  mpfr_exp_t emin;

  size_tab = (nbtests >= 1000 ? nbtests / 50 : 20);
  tab = (int *) tests_allocate (size_tab * sizeof (int));
  for (k = 0; k < size_tab; k++)
    tab[k] = 0;

  mpfr_init2 (x, prec);
  xn = 1 + (prec - 1) / mp_bits_per_limb;
  sh = xn * mp_bits_per_limb - prec;

  for (k = 0; k < nbtests; k++)
    {
      mpfr_urandomb (x, RANDS);
      MPFR_ASSERTN (MPFR_IS_FP (x));
      /* check that lower bits are zero */
      if (MPFR_NOTZERO(x) && (MPFR_MANT(x)[0] & MPFR_LIMB_MASK(sh)))
        {
          printf ("Error: mpfr_urandomb() returns invalid numbers:\n");
          mpfr_dump (x);
          exit (1);
        }
      d = mpfr_get_d1 (x); av += d; var += d*d;
      tab[(int)(size_tab * d)]++;
    }

  /* coverage test */
  emin = mpfr_get_emin ();
  set_emin (1); /* the generated number in [0,1[ is not in the exponent
                        range, except if it is zero */
  k = mpfr_urandomb (x, RANDS);
  if (MPFR_IS_ZERO(x) == 0 && (k == 0 || mpfr_nan_p (x) == 0))
    {
      printf ("Error in mpfr_urandomb, expected NaN, got ");
      mpfr_dump (x);
      exit (1);
    }
  set_emin (emin);

  mpfr_clear (x);

  if (verbose)
    {
      av /= nbtests;
      var = (var / nbtests) - av * av;

      th = (double) nbtests / size_tab;
      printf ("Average = %.5f\nVariance = %.5f\n", av, var);
      printf ("Repartition for urandomb. Each integer should be close to"
              " %d.\n", (int) th);

      for (k = 0; k < size_tab; k++)
        {
          chi2 += (tab[k] - th) * (tab[k] - th) / th;
          printf ("%d ", tab[k]);
          if (((unsigned int) (k+1) & 7) == 0)
            printf ("\n");
        }

      printf ("\nChi2 statistics value (with %d degrees of freedom) :"
              " %.5f\n\n", size_tab - 1, chi2);
    }

  tests_free (tab, size_tab * sizeof (int));
  return;
}

#ifndef MPFR_USE_MINI_GMP
/* Problem reported by Carl Witty: check mpfr_urandomb give similar results
   on 32-bit and 64-bit machines.
   We assume the default GMP random generator does not depend on the machine
   word size, not on the GMP version.
*/
static void
bug20100914 (void)
{
  mpfr_t x;
  gmp_randstate_t s;

#if __MPFR_GMP(4,2,0)
# define C1 "0.895943"
# define C2 "0.848824"
#else
# define C1 "0.479652"
# define C2 "0.648529"
#endif

  gmp_randinit_default (s);
  gmp_randseed_ui (s, 42);
  mpfr_init2 (x, 17);
  mpfr_urandomb (x, s);
  if (mpfr_cmp_str1 (x, C1) != 0)
    {
      printf ("Error in bug20100914, expected " C1 ", got ");
      mpfr_out_str (stdout, 10, 0, x, MPFR_RNDN);
      printf ("\n");
      exit (1);
    }
  mpfr_urandomb (x, s);
  if (mpfr_cmp_str1 (x, C2) != 0)
    {
      printf ("Error in bug20100914, expected " C2 ", got ");
      mpfr_out_str (stdout, 10, 0, x, MPFR_RNDN);
      printf ("\n");
      exit (1);
    }
  mpfr_clear (x);
  gmp_randclear (s);
}
#endif

int
main (int argc, char *argv[])
{
  long nbtests;
  mpfr_prec_t prec;
  int verbose = 0;

  tests_start_mpfr ();

  if (argc > 1)
    verbose = 1;

  nbtests = 10000;
  if (argc > 1)
    {
      long a = atol (argv[1]);
      if (a != 0)
        nbtests = a;
    }

  if (argc <= 2)
    prec = 1000;
  else
    prec = atol (argv[2]);

  test_urandomb (nbtests, prec, verbose);

  if (argc == 1)  /* check also small precision */
    {
      test_urandomb (nbtests, 2, 0);
    }

#ifndef MPFR_USE_MINI_GMP

  /* Since these tests assume a deterministic random generator, and this
     is not implemented in mini-gmp, we omit them with mini-gmp. */

  bug20100914 ();

#if __MPFR_GMP(4,2,0)
  /* Get a non-zero fixed-point number whose first 32 bits are 0 with the
     default GMP PRNG. This corresponds to the case cnt == 0 && k != 0 in
     src/urandomb.c (fixed in r8762) with the 32-bit ABI. */
  {
    gmp_randstate_t s;
    mpfr_t x;
    const char *str = "0.1010111100000000000000000000000000000000E-32";
    int k;

    gmp_randinit_default (s);
    gmp_randseed_ui (s, 4518);
    mpfr_init2 (x, 40);

    for (k = 0; k < 575123; k++)
      {
        mpfr_urandomb (x, s);
        MPFR_ASSERTN (MPFR_IS_FP (x));
      }

    if (mpfr_cmp_str (x, str, 2, MPFR_RNDN) != 0)
      {
        printf ("Error in test_urandomb:\n");
        printf ("Expected %s\n", str);
        printf ("Got      ");
        mpfr_dump (x);
        exit (1);
      }

    mpfr_clear (x);
    gmp_randclear (s);
  }
#endif

#endif

  tests_end_mpfr ();
  return 0;
}