lib/libm/noieee_src/n_fmod.c

   1 /*      $NetBSD: n_fmod.c,v 1.7 2013/11/22 10:59:31 martin 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 #if DBL_MANT_DIG == LDBL_MANT_DIG && DBL_MIN_EXP == LDBL_MIN_EXP \
  70          && DBL_MIN_EXP == LDBL_MIN_EXP
  71 #ifdef __weak_alias
  72 __weak_alias(fmodl, fmod);
  73 #endif
  74 #endif
  75
  76 #ifdef TEST_FMOD
  77 static double
  78 _fmod(double x, double y)
  79 #else   /* TEST_FMOD */
  80 double
  81 fmod(double x, double y)
  82 #endif  /* TEST_FMOD */
  83 {
  84         int ir,iy;
  85         double r,w;
  86
  87         if (y == (double)0
  88 #if !defined(__vax__) && !defined(tahoe)        /* per "fmod" manual entry, SunOS 4.0 */
  89                 || isnan(y) || !finite(x)
  90 #endif  /* !defined(__vax__) && !defined(tahoe) */
  91             )
  92             return (x*y)/(x*y);
  93
  94         r = fabs(x);
  95         y = fabs(y);
  96         (void)frexp(y,&iy);
  97         while (r >= y) {
  98                 (void)frexp(r,&ir);
  99                 w = ldexp(y,ir-iy);
 100                 r -= w <= r ? w : w*(double)0.5;
 101         }
 102         return x >= (double)0 ? r : -r;
 103 }
 104
 105 float
 106 fmodf(float x, float y)
 107 {
 108         return fmod(x, y);
 109 }
 110
 111 #ifdef TEST_FMOD
 112 extern long random();
 113 extern double fmod();
 114
 115 #define NTEST   10000
 116 #define NCASES  3
 117
 118 static int nfail = 0;
 119
 120 static void
 121 doit(double x, double y)
 122 {
 123         double ro = fmod(x,y),rn = _fmod(x,y);
 124         if (ro != rn) {
 125                 (void)printf(" x    = 0x%08.8x %08.8x (%24.16e)\n",x,x);
 126                 (void)printf(" y    = 0x%08.8x %08.8x (%24.16e)\n",y,y);
 127                 (void)printf(" fmod = 0x%08.8x %08.8x (%24.16e)\n",ro,ro);
 128                 (void)printf("_fmod = 0x%08.8x %08.8x (%24.16e)\n",rn,rn);
 129                 (void)printf("\n");
 130         }
 131 }
 132
 133 int
 134 main(int argc, char **argv)
 135 {
 136         int i,cases;
 137         double x,y;
 138
 139         srandom(12345);
 140         for (i = 0; i < NTEST; i++) {
 141                 x = (double)random();
 142                 y = (double)random();
 143                 for (cases = 0; cases < NCASES; cases++) {
 144                         switch (cases) {
 145                         case 0:
 146                                 break;
 147                         case 1:
 148                                 y = (double)1/y; break;
 149                         case 2:
 150                                 x = (double)1/x; break;
 151                         default:
 152                                 abort(); break;
 153                         }
 154                         doit(x,y);
 155                         doit(x,-y);
 156                         doit(-x,y);
 157                         doit(-x,-y);
 158                 }
 159         }
 160         if (nfail)
 161                 (void)printf("Number of failures: %d (out of a total of %d)\n",
 162                         nfail,NTEST*NCASES*4);
 163         else
 164                 (void)printf("No discrepancies were found\n");
 165         exit(0);
 166 }
 167 #endif  /* TEST_FMOD */