lib/libm/noieee_src/n_fmod.c

   1 /*      $NetBSD: n_fmod.c,v 1.5 2003/08/07 16:44:51 agc Exp $   */
   2 /*
   3  * Copyright (c) 1989, 1993
   4  *      The Regents of the University of California.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 3. Neither the name of the University nor the names of its contributors
  15  *    may be used to endorse or promote products derived from this software
  16  *    without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  */
  30
  31 #ifndef lint
  32 #if 0
  33 static char sccsid[] = "@(#)fmod.c      8.1 (Berkeley) 6/4/93";
  34 #endif
  35 #endif /* not lint */
  36
  37 #include "mathimpl.h"
  38
  39 /* fmod.c
  40  *
  41  * SYNOPSIS
  42  *
  43  *    #include <math.h>
  44  *    double fmod(double x, double y)
  45  *
  46  * DESCRIPTION
  47  *
  48  *    The fmod function computes the floating-point remainder of x/y.
  49  *
  50  * RETURNS
  51  *
  52  *    The fmod function returns the value x-i*y, for some integer i
  53  * such that, if y is nonzero, the result has the same sign as x and
  54  * magnitude less than the magnitude of y.
  55  *
  56  * On a VAX or CCI,
  57  *
  58  *    fmod(x,0) traps/faults on floating-point divided-by-zero.
  59  *
  60  * On IEEE-754 conforming machines with "isnan()" primitive,
  61  *
  62  *    fmod(x,0), fmod(INF,y) are invalid operations and NaN is returned.
  63  *
  64  */
  65 #if !defined(__vax__) && !defined(tahoe)
  66 extern int isnan(),finite();
  67 #endif  /* !defined(__vax__) && !defined(tahoe) */
  68
  69 #ifdef TEST_FMOD
  70 static double
  71 _fmod(double x, double y)
  72 #else   /* TEST_FMOD */
  73 double
  74 fmod(double x, double y)
  75 #endif  /* TEST_FMOD */
  76 {
  77         int ir,iy;
  78         double r,w;
  79
  80         if (y == (double)0
  81 #if !defined(__vax__) && !defined(tahoe)        /* per "fmod" manual entry, SunOS 4.0 */
  82                 || isnan(y) || !finite(x)
  83 #endif  /* !defined(__vax__) && !defined(tahoe) */
  84             )
  85             return (x*y)/(x*y);
  86
  87         r = fabs(x);
  88         y = fabs(y);
  89         (void)frexp(y,&iy);
  90         while (r >= y) {
  91                 (void)frexp(r,&ir);
  92                 w = ldexp(y,ir-iy);
  93                 r -= w <= r ? w : w*(double)0.5;
  94         }
  95         return x >= (double)0 ? r : -r;
  96 }
  97
  98 #ifdef TEST_FMOD
  99 extern long random();
 100 extern double fmod();
 101
 102 #define NTEST   10000
 103 #define NCASES  3
 104
 105 static int nfail = 0;
 106
 107 static void
 108 doit(double x, double y)
 109 {
 110         double ro = fmod(x,y),rn = _fmod(x,y);
 111         if (ro != rn) {
 112                 (void)printf(" x    = 0x%08.8x %08.8x (%24.16e)\n",x,x);
 113                 (void)printf(" y    = 0x%08.8x %08.8x (%24.16e)\n",y,y);
 114                 (void)printf(" fmod = 0x%08.8x %08.8x (%24.16e)\n",ro,ro);
 115                 (void)printf("_fmod = 0x%08.8x %08.8x (%24.16e)\n",rn,rn);
 116                 (void)printf("\n");
 117         }
 118 }
 119
 120 int
 121 main(int argc, char **argv)
 122 {
 123         int i,cases;
 124         double x,y;
 125
 126         srandom(12345);
 127         for (i = 0; i < NTEST; i++) {
 128                 x = (double)random();
 129                 y = (double)random();
 130                 for (cases = 0; cases < NCASES; cases++) {
 131                         switch (cases) {
 132                         case 0:
 133                                 break;
 134                         case 1:
 135                                 y = (double)1/y; break;
 136                         case 2:
 137                                 x = (double)1/x; break;
 138                         default:
 139                                 abort(); break;
 140                         }
 141                         doit(x,y);
 142                         doit(x,-y);
 143                         doit(-x,y);
 144                         doit(-x,-y);
 145                 }
 146         }
 147         if (nfail)
 148                 (void)printf("Number of failures: %d (out of a total of %d)\n",
 149                         nfail,NTEST*NCASES*4);
 150         else
 151                 (void)printf("No discrepancies were found\n");
 152         exit(0);
 153 }
 154 #endif  /* TEST_FMOD */