test-suite/standalone/test-round.c

   1 /* Copyright (C) 2004, 2006 Free Software Foundation, Inc.
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 #include "config.h"
  19
  20 #include <assert.h>
  21 #include <math.h>
  22 #include <stdio.h>
  23
  24 #if HAVE_FENV_H
  25 #include <fenv.h>
  26 #endif
  27
  28 #include "libguile.h"
  29
  30
  31 #define numberof(x)  (sizeof (x) / sizeof ((x)[0]))
  32
  33 static void
  34 test_scm_c_round ()
  35 {
  36   /* FE constants are defined only where supported, in particular for
  37      instance some ARM systems have been seen with only a couple of modes */
  38   static const int modes[] = {
  39     0,
  40 #ifdef FE_TONEAREST
  41     FE_TONEAREST,
  42 #endif
  43 #ifdef FE_UPWARD
  44     FE_UPWARD,
  45 #endif
  46 #ifdef FE_DOWNWARD
  47     FE_DOWNWARD,
  48 #endif
  49 #ifdef FE_TOWARDZERO
  50     FE_TOWARDZERO,
  51 #endif
  52   };
  53
  54   double  x, want;
  55   int  i;
  56
  57   for (i = 0; i < numberof (modes); i++)
  58     {
  59       /* First iteration is the default rounding mode, ie. no call to
  60          fesetround.  Subsequent iterations are the FE modes from the
  61          table.  */
  62       if (i != 0)
  63         {
  64 #if HAVE_FESETROUND
  65           fesetround (modes[i]);
  66 #endif
  67         }
  68
  69       assert (scm_c_round (0.0) == 0.0);
  70       assert (scm_c_round (1.0) == 1.0);
  71       assert (scm_c_round (-1.0) == -1.0);
  72
  73       assert (scm_c_round (0.5) == 0.0);
  74       assert (scm_c_round (1.5) == 2.0);
  75       assert (scm_c_round (-1.5) == -2.0);
  76       assert (scm_c_round (2.5) == 2.0);
  77       assert (scm_c_round (-2.5) == -2.0);
  78       assert (scm_c_round (3.5) == 4.0);
  79       assert (scm_c_round (-3.5) == -4.0);
  80
  81       /* 2^(DBL_MANT_DIG-1)-1+0.5 */
  82       x = ldexp (1.0, DBL_MANT_DIG - 1) - 1.0 + 0.5;
  83       want = ldexp (1.0, DBL_MANT_DIG - 1);
  84       assert (scm_c_round (x) == want);
  85
  86       /* -(2^(DBL_MANT_DIG-1)-1+0.5) */
  87       x = - (ldexp (1.0, DBL_MANT_DIG - 1) - 1.0 + 0.5);
  88       want = - ldexp (1.0, DBL_MANT_DIG - 1);
  89       assert (scm_c_round (x) == want);
  90
  91       /* 2^DBL_MANT_DIG-1
  92          In the past scm_c_round had incorrectly incremented this value, due
  93          to the way that x+0.5 would round upwards (in the usual default
  94          nearest-even mode on most systems).  */
  95       x = ldexp (1.0, DBL_MANT_DIG) - 1.0;
  96       assert (x == floor (x));      /* should be an integer already */
  97       assert (scm_c_round (x) == x);  /* scm_c_round should return it unchanged */
  98
  99       /* -(2^DBL_MANT_DIG-1) */
 100       x = - (ldexp (1.0, DBL_MANT_DIG) - 1.0);
 101       assert (x == floor (x));      /* should be an integer already */
 102       assert (scm_c_round (x) == x);  /* scm_c_round should return it unchanged */
 103
 104       /* 2^64 */
 105       x = ldexp (1.0, 64);
 106       assert (scm_c_round (x) == x);
 107
 108       /* -2^64
 109          In the past scm_c_round had incorrectely gone to the next highest
 110          representable value in FE_UPWARD, due to x+0.5 rounding.  */
 111       x = - ldexp (1.0, 64);
 112       assert (scm_c_round (x) == x);
 113     }
 114 }
 115
 116 static void
 117 tests (void *data, int argc, char **argv)
 118 {
 119   test_scm_c_round ();
 120 }
 121
 122 int
 123 main (int argc, char *argv[])
 124 {
 125   scm_boot_guile (argc, argv, tests, NULL);
 126   return 0;
 127 }