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 */ 155