tests/test-ceil2.c

   1 /* Test of rounding towards positive infinity.
   2    Copyright (C) 2007-2024 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 /* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
  18
  19 /* When this test fails on some platform, build it together with the gnulib
  20    module 'fprintf-posix' for optimal debugging output.  */
  21
  22 #include <config.h>
  23
  24 #include <math.h>
  25
  26 #include <float.h>
  27 #include <stdint.h>
  28 #include <stdio.h>
  29
  30 #include "isnand-nolibm.h"
  31 #include "minus-zero.h"
  32 #include "macros.h"
  33
  34 /* MSVC with option -fp:strict refuses to compile constant initializers that
  35    contain floating-point operations.  Pacify this compiler.  */
  36 #if defined _MSC_VER && !defined __clang__
  37 # pragma fenv_access (off)
  38 #endif
  39
  40
  41 /* The reference implementation, taken from lib/ceil.c.  */
  42
  43 #define DOUBLE double
  44 #define MANT_DIG DBL_MANT_DIG
  45 #define L_(literal) literal
  46
  47 /* -0.0.  See minus-zero.h.  */
  48 #define MINUS_ZERO minus_zerod
  49
  50 /* 2^(MANT_DIG-1).  */
  51 static const DOUBLE TWO_MANT_DIG =
  52   /* Assume MANT_DIG <= 5 * 31.
  53      Use the identity
  54        n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
  55   (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
  56   * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
  57   * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
  58   * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
  59   * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
  60
  61 DOUBLE
  62 ceil_reference (DOUBLE x)
  63 {
  64   /* The use of 'volatile' guarantees that excess precision bits are dropped
  65      at each addition step and before the following comparison at the caller's
  66      site.  It is necessary on x86 systems where double-floats are not IEEE
  67      compliant by default, to avoid that the results become platform and compiler
  68      option dependent.  'volatile' is a portable alternative to gcc's
  69      -ffloat-store option.  */
  70   volatile DOUBLE y = x;
  71   volatile DOUBLE z = y;
  72
  73   if (z > L_(0.0))
  74     {
  75       /* Work around ICC's desire to optimize denormal floats to 0.  */
  76       if (z < DBL_MIN)
  77         return L_(1.0);
  78       /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1.  */
  79       if (z < TWO_MANT_DIG)
  80         {
  81           /* Round to the next integer (nearest or up or down, doesn't matter).  */
  82           z += TWO_MANT_DIG;
  83           z -= TWO_MANT_DIG;
  84           /* Enforce rounding up.  */
  85           if (z < y)
  86             z += L_(1.0);
  87         }
  88     }
  89   else if (z < L_(0.0))
  90     {
  91       /* For -1 < x < 0, return -0.0 regardless of the current rounding
  92          mode.  */
  93       if (z > L_(-1.0))
  94         z = MINUS_ZERO;
  95       /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1.  */
  96       else if (z > - TWO_MANT_DIG)
  97         {
  98           /* Round to the next integer (nearest or up or down, doesn't matter).  */
  99           z -= TWO_MANT_DIG;
 100           z += TWO_MANT_DIG;
 101           /* Enforce rounding up.  */
 102           if (z < y)
 103             z += L_(1.0);
 104         }
 105     }
 106   return z;
 107 }
 108
 109
 110 /* Test for equality.  */
 111 static int
 112 equal (DOUBLE x, DOUBLE y)
 113 {
 114   return (isnand (x) ? isnand (y) : x == y);
 115 }
 116
 117 /* Test whether the result for a given argument is correct.  */
 118 static bool
 119 correct_result_p (DOUBLE x, DOUBLE result)
 120 {
 121   return
 122     (x > 0 && x <= 1 ? result == L_(1.0) :
 123      x + 1 > x ? result >= x && result <= x + 1 && result - x < 1 :
 124      equal (result, x));
 125 }
 126
 127 /* Test the function for a given argument.  */
 128 static int
 129 check (double x)
 130 {
 131   /* If the reference implementation is incorrect, bail out immediately.  */
 132   double reference = ceil_reference (x);
 133   ASSERT (correct_result_p (x, reference));
 134   /* If the actual implementation is wrong, return an error code.  */
 135   {
 136     double result = ceil (x);
 137     if (correct_result_p (x, result))
 138       return 0;
 139     else
 140       {
 141 #if GNULIB_TEST_FPRINTF_POSIX
 142         fprintf (stderr, "ceil %g(%a) = %g(%a) or %g(%a)?\n",
 143                  x, x, reference, reference, result, result);
 144 #endif
 145         return 1;
 146       }
 147   }
 148 }
 149
 150 #define NUM_HIGHBITS 12
 151 #define NUM_LOWBITS 4
 152
 153 int
 154 main ()
 155 {
 156   unsigned int highbits;
 157   unsigned int lowbits;
 158   int error = 0;
 159   for (highbits = 0; highbits < (1 << NUM_HIGHBITS); highbits++)
 160     for (lowbits = 0; lowbits < (1 << NUM_LOWBITS); lowbits++)
 161       {
 162         /* Combine highbits and lowbits into a floating-point number,
 163            sign-extending the lowbits to 64-NUM_HIGHBITS bits.  */
 164         union { double f; uint64_t i; } janus;
 165         janus.i = ((uint64_t) highbits << (64 - NUM_HIGHBITS))
 166                   | ((uint64_t) ((int64_t) ((uint64_t) lowbits << (64 - NUM_LOWBITS))
 167                                  >> (64 - NUM_LOWBITS - NUM_HIGHBITS))
 168                      >> NUM_HIGHBITS);
 169         error |= check (janus.f);
 170       }
 171   return (error ? 1 : test_exit_status);
 172 }