tests/test-logb.h

   1 /* Test of logb*() 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 DOUBLE
  18 my_ldexp (DOUBLE x, int d)
  19 {
  20   for (; d > 0; d--)
  21     x *= L_(2.0);
  22   for (; d < 0; d++)
  23     x *= L_(0.5);
  24   return x;
  25 }
  26
  27 static void
  28 test_function (void)
  29 {
  30   int i;
  31   VOLATILE DOUBLE x;
  32   DOUBLE y;
  33
  34   /* Some particular values.  */
  35   x = L_(0.6);
  36   y = LOGB (x);
  37   ASSERT (y == - L_(1.0));
  38
  39   x = L_(1.2);
  40   y = LOGB (x);
  41   ASSERT (y == L_(0.0));
  42
  43   x = L_(2.1);
  44   y = LOGB (x);
  45   ASSERT (y == L_(1.0));
  46
  47   x = L_(3.9);
  48   y = LOGB (x);
  49   ASSERT (y == L_(1.0));
  50
  51   x = L_(4.0);
  52   y = LOGB (x);
  53   ASSERT (y == (FLT_RADIX == 2 ? L_(2.0) : L_(1.0)));
  54
  55   x = L_(0.25);
  56   y = LOGB (x);
  57   ASSERT (y == (FLT_RADIX == 2 ? - L_(2.0) : - L_(1.0)));
  58
  59   /* Zero.  */
  60   ASSERT (LOGB (L_(0.0)) == - HUGEVAL);
  61   ASSERT (LOGB (MINUS_ZERO) == - HUGEVAL);
  62
  63   /* From here on, this test assumes FLT_RADIX == 2.  */
  64
  65   for (i = 1, x = L_(1.0); i <= MAX_EXP; i++, x *= L_(2.0))
  66     {
  67       y = LOGB (x);
  68       ASSERT (y == (DOUBLE)(i - 1));
  69     }
  70   for (i = 1, x = L_(1.0); i >= MIN_NORMAL_EXP; i--, x *= L_(0.5))
  71     {
  72       y = LOGB (x);
  73       ASSERT (y == (DOUBLE)(i - 1));
  74     }
  75   for (; i >= MIN_EXP - 100 && x > L_(0.0); i--, x *= L_(0.5))
  76     {
  77       y = LOGB (x);
  78       ASSERT (y == (DOUBLE)(i - 1));
  79     }
  80
  81   for (i = 1, x = - L_(1.0); i <= MAX_EXP; i++, x *= L_(2.0))
  82     {
  83       y = LOGB (x);
  84       ASSERT (y == (DOUBLE)(i - 1));
  85     }
  86   for (i = 1, x = - L_(1.0); i >= MIN_NORMAL_EXP; i--, x *= L_(0.5))
  87     {
  88       y = LOGB (x);
  89       ASSERT (y == (DOUBLE)(i - 1));
  90     }
  91   for (; i >= MIN_EXP - 100 && x < L_(0.0); i--, x *= L_(0.5))
  92     {
  93       y = LOGB (x);
  94       ASSERT (y == (DOUBLE)(i - 1));
  95     }
  96
  97   for (i = 1, x = L_(1.01); i <= MAX_EXP; i++, x *= L_(2.0))
  98     {
  99       y = LOGB (x);
 100       ASSERT (y == (DOUBLE)(i - 1));
 101     }
 102   for (i = 1, x = L_(1.01); i >= MIN_NORMAL_EXP; i--, x *= L_(0.5))
 103     {
 104       y = LOGB (x);
 105       ASSERT (y == (DOUBLE)(i - 1));
 106     }
 107   for (; i >= MIN_EXP - 100 && x > L_(0.0); i--, x *= L_(0.5))
 108     {
 109       y = LOGB (x);
 110       ASSERT (y == (DOUBLE)(i - 1));
 111     }
 112
 113   for (i = 1, x = L_(1.73205); i <= MAX_EXP; i++, x *= L_(2.0))
 114     {
 115       y = LOGB (x);
 116       ASSERT (y == (DOUBLE)(i - 1));
 117     }
 118   for (i = 1, x = L_(1.73205); i >= MIN_NORMAL_EXP; i--, x *= L_(0.5))
 119     {
 120       y = LOGB (x);
 121       ASSERT (y == (DOUBLE)(i - 1));
 122     }
 123   for (; i >= MIN_EXP - 100 && x > L_(0.0); i--, x *= L_(0.5))
 124     {
 125       y = LOGB (x);
 126       ASSERT (y == (DOUBLE)(i - 1) || y == (DOUBLE)i);
 127     }
 128
 129   /* Randomized tests.  */
 130   for (i = 0; i < SIZEOF (RANDOM); i++)
 131     {
 132       x = L_(20.0) * RANDOM[i] - L_(10.0); /* -10.0 <= x <= 10.0 */
 133       if (x != L_(0.0))
 134         {
 135           DOUBLE abs_x = (x < L_(0.0) ? - x : x);
 136           y = LOGB (x);
 137           ASSERT (y == (DOUBLE) (int) y);
 138           ASSERT (abs_x >= my_ldexp (L_(1.0), (int) y));
 139           ASSERT (abs_x < my_ldexp (L_(1.0), (int) y + 1));
 140         }
 141     }
 142 }
 143
 144 volatile DOUBLE x;
 145 DOUBLE y;