tests/test-log10.h

   1 /* Test of log10*() function family.
   2    Copyright (C) 2012-2024 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 static void
  18 test_function (void)
  19 {
  20   int i;
  21   int j;
  22   const DOUBLE TWO_MANT_DIG =
  23     /* Assume MANT_DIG <= 5 * 31.
  24        Use the identity
  25          n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
  26     (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
  27     * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
  28     * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
  29     * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
  30     * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
  31
  32   /* Pole.  */
  33   {
  34     DOUBLE z = LOG10 (L_(0.0));
  35     ASSERT (z == - HUGEVAL);
  36   }
  37   {
  38     DOUBLE z = LOG10 (MINUS_ZERO);
  39     ASSERT (z == - HUGEVAL);
  40   }
  41
  42   /* Randomized tests.  */
  43   {
  44     /* Error bound, in ulps.  */
  45     const DOUBLE err_bound =
  46       (sizeof (DOUBLE) > sizeof (double) ?
  47 #if defined __i386__ && defined __FreeBSD__
  48        /* On FreeBSD/x86 6.4, the 'long double' type really has only 53 bits of
  49           precision in the compiler but 64 bits of precision at runtime.  See
  50           <https://lists.gnu.org/r/bug-gnulib/2008-07/msg00063.html>.
  51           The compiler has truncated all 'long double' literals in log10l.c to
  52           53 bits of precision.  */
  53        L_(18.0)
  54 #else
  55        L_(3.0)
  56 #endif
  57        : L_(3.0));
  58
  59     for (i = 0; i < SIZEOF (RANDOM); i++)
  60       {
  61         DOUBLE x = L_(16.0) * RANDOM[i] + L_(1.0); /* 1.0 <= x <= 17.0 */
  62         DOUBLE y = LOG10 (x);
  63         DOUBLE z = LOG10 (L_(1.0) / x);
  64         DOUBLE err = y + z;
  65         ASSERT (y >= L_(0.0));
  66         ASSERT (z <= L_(0.0));
  67         ASSERT (err > - err_bound / TWO_MANT_DIG
  68                 && err < err_bound / TWO_MANT_DIG);
  69       }
  70   }
  71
  72   {
  73     /* Error bound, in ulps.  */
  74     const DOUBLE err_bound =
  75       (sizeof (DOUBLE) > sizeof (double) ?
  76 #if defined __i386__ && defined __FreeBSD__
  77        /* On FreeBSD/x86 6.4, the 'long double' type really has only 53 bits of
  78           precision in the compiler but 64 bits of precision at runtime.  See
  79           <https://lists.gnu.org/r/bug-gnulib/2008-07/msg00063.html>.
  80           The compiler has truncated all 'long double' literals in log10l.c to
  81           53 bits of precision.  */
  82        L_(38.0)
  83 #else
  84        L_(5.0)
  85 #endif
  86        : L_(5.0));
  87
  88     for (i = 0; i < SIZEOF (RANDOM) / 5; i++)
  89       for (j = 0; j < SIZEOF (RANDOM) / 5; j++)
  90         {
  91           DOUBLE x = L_(17.0) / (L_(16.0) - L_(15.0) * RANDOM[i]) - L_(1.0);
  92           DOUBLE y = L_(17.0) / (L_(16.0) - L_(15.0) * RANDOM[j]) - L_(1.0);
  93           /* 1/16 <= x,y <= 16 */
  94           DOUBLE z = L_(1.0) / (x * y);
  95           /* Approximately  x * y * z = 1.  */
  96           DOUBLE err = LOG10 (x) + LOG10 (y) + LOG10 (z);
  97           ASSERT (err > - err_bound / TWO_MANT_DIG
  98                   && err < err_bound / TWO_MANT_DIG);
  99         }
 100   }
 101 }
 102
 103 volatile DOUBLE x;
 104 DOUBLE y;