tests/test-ceil2.c

   1 /* Test of rounding towards positive infinity.
   2    Copyright (C) 2007-2020 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 <stdbool.h>
  28 #include <stdint.h>
  29 #include <stdio.h>
  30
  31 #include "isnand-nolibm.h"
  32 #include "minus-zero.h"
  33 #include "macros.h"
  34
  35 /* MSVC with option -fp:strict refuses to compile constant initializers that
  36    contain floating-point operations.  Pacify this compiler.  */
  37 #if defined _MSC_VER && !defined __clang__
  38 # pragma fenv_access (off)
  39 #endif
  40
  41
  42 /* The reference implementation, taken from lib/ceil.c.  */
  43
  44 #define DOUBLE double
  45 #define MANT_DIG DBL_MANT_DIG
  46 #define L_(literal) literal
  47
  48 /* -0.0.  See minus-zero.h.  */
  49 #define MINUS_ZERO minus_zerod
  50
  51 /* 2^(MANT_DIG-1).  */
  52 static const DOUBLE TWO_MANT_DIG =
  53   /* Assume MANT_DIG <= 5 * 31.
  54      Use the identity
  55        n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
  56   (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
  57   * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
  58   * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
  59   * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
  60   * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
  61
  62 DOUBLE
  63 ceil_reference (DOUBLE x)
  64 {
  65   /* The use of 'volatile' guarantees that excess precision bits are dropped
  66      at each addition step and before the following comparison at the caller's
  67      site.  It is necessary on x86 systems where double-floats are not IEEE
  68      compliant by default, to avoid that the results become platform and compiler
  69      option dependent.  'volatile' is a portable alternative to gcc's
  70      -ffloat-store option.  */
  71   volatile DOUBLE y = x;
  72   volatile DOUBLE z = y;
  73
  74   if (z > L_(0.0))
  75     {
  76       /* Work around ICC's desire to optimize denormal floats to 0.  */
  77       if (z < DBL_MIN)
  78         return L_(1.0);
  79       /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1.  */
  80       if (z < TWO_MANT_DIG)
  81         {
  82           /* Round to the next integer (nearest or up or down, doesn't matter).  */
  83           z += TWO_MANT_DIG;
  84           z -= TWO_MANT_DIG;
  85           /* Enforce rounding up.  */
  86           if (z < y)
  87             z += L_(1.0);
  88         }
  89     }
  90   else if (z < L_(0.0))
  91     {
  92       /* For -1 < x < 0, return -0.0 regardless of the current rounding
  93          mode.  */
  94       if (z > L_(-1.0))
  95         z = MINUS_ZERO;
  96       /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1.  */
  97       else if (z > - TWO_MANT_DIG)
  98         {
  99           /* Round to the next integer (nearest or up or down, doesn't matter).  */
 100           z -= TWO_MANT_DIG;
 101           z += TWO_MANT_DIG;
 102           /* Enforce rounding up.  */
 103           if (z < y)
 104             z += L_(1.0);
 105         }
 106     }
 107   return z;
 108 }
 109
 110
 111 /* Test for equality.  */
 112 static int
 113 equal (DOUBLE x, DOUBLE y)
 114 {
 115   return (isnand (x) ? isnand (y) : x == y);
 116 }
 117
 118 /* Test whether the result for a given argument is correct.  */
 119 static bool
 120 correct_result_p (DOUBLE x, DOUBLE result)
 121 {
 122   return
 123     (x > 0 && x <= 1 ? result == L_(1.0) :
 124      x + 1 > x ? result >= x && result <= x + 1 && result - x < 1 :
 125      equal (result, x));
 126 }
 127
 128 /* Test the function for a given argument.  */
 129 static int
 130 check (double x)
 131 {
 132   /* If the reference implementation is incorrect, bail out immediately.  */
 133   double reference = ceil_reference (x);
 134   ASSERT (correct_result_p (x, reference));
 135   /* If the actual implementation is wrong, return an error code.  */
 136   {
 137     double result = ceil (x);
 138     if (correct_result_p (x, result))
 139       return 0;
 140     else
 141       {
 142 #if GNULIB_TEST_FPRINTF_POSIX
 143         fprintf (stderr, "ceil %g(%a) = %g(%a) or %g(%a)?\n",
 144                  x, x, reference, reference, result, result);
 145 #endif
 146         return 1;
 147       }
 148   }
 149 }
 150
 151 #define NUM_HIGHBITS 12
 152 #define NUM_LOWBITS 4
 153
 154 int
 155 main ()
 156 {
 157   unsigned int highbits;
 158   unsigned int lowbits;
 159   int error = 0;
 160   for (highbits = 0; highbits < (1 << NUM_HIGHBITS); highbits++)
 161     for (lowbits = 0; lowbits < (1 << NUM_LOWBITS); lowbits++)
 162       {
 163         /* Combine highbits and lowbits into a floating-point number,
 164            sign-extending the lowbits to 64-NUM_HIGHBITS bits.  */
 165         union { double f; uint64_t i; } janus;
 166         janus.i = ((uint64_t) highbits << (64 - NUM_HIGHBITS))
 167                   | ((uint64_t) ((int64_t) ((uint64_t) lowbits << (64 - NUM_LOWBITS))
 168                                  >> (64 - NUM_LOWBITS - NUM_HIGHBITS))
 169                      >> NUM_HIGHBITS);
 170         error |= check (janus.f);
 171       }
 172   return (error ? 1 : 0);
 173 }