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
_fmod(double x,double y)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
fmodf(float x,float y)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
doit(double x,double y)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
main(int argc,char ** argv)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 */
168