tests/test-modf.h

   1 /* Test of modf*() 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   const DOUBLE TWO_MANT_DIG =
  22     /* Assume MANT_DIG <= 5 * 31.
  23        Use the identity
  24          n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
  25     (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
  26     * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
  27     * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
  28     * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
  29     * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
  30
  31   /* Randomized tests.  */
  32   for (i = 0; i < SIZEOF (RANDOM); i++)
  33     {
  34       DOUBLE x = RANDOM[i]; /* 0.0 <= x < 1.0 */
  35       DOUBLE y;
  36       DOUBLE z;
  37
  38       y = MODF (x, &z);
  39       ASSERT (z == L_(0.0));
  40       ASSERT (y == x);
  41
  42       y = MODF (- x, &z);
  43       ASSERT (z == L_(0.0));
  44       ASSERT (y == - x);
  45
  46       y = MODF (L_(1.0) + x, &z);
  47       ASSERT (z == L_(1.0));
  48       y -= x;
  49       ASSERT (y >= - L_(1.0) / TWO_MANT_DIG);
  50       ASSERT (y <= L_(1.0) / TWO_MANT_DIG);
  51
  52       y = MODF (- L_(1.0) - x, &z);
  53       ASSERT (z == - L_(1.0));
  54       y -= - x;
  55       ASSERT (y >= - L_(1.0) / TWO_MANT_DIG);
  56       ASSERT (y <= L_(1.0) / TWO_MANT_DIG);
  57     }
  58 }
  59
  60 volatile DOUBLE x;
  61 DOUBLE y;
  62 DOUBLE z;