1 /* $NetBSD: n_fmod.c,v 1.11 2018/11/09 10:19:47 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 __weak_alias(modfl, fmod);
74 #endif
75 #endif
76
77 #ifdef TEST_FMOD
78 static double
_fmod(double x,double y)79 _fmod(double x, double y)
80 #else /* TEST_FMOD */
81 double
82 fmod(double x, double y)
83 #endif /* TEST_FMOD */
84 {
85 int ir,iy;
86 double r,w;
87
88 if (y == (double)0
89 #if !defined(__vax__) && !defined(tahoe) /* per "fmod" manual entry, SunOS 4.0 */
90 || isnan(y) || !finite(x)
91 #endif /* !defined(__vax__) && !defined(tahoe) */
92 )
93 return (x*y)/(x*y);
94
95 r = fabs(x);
96 y = fabs(y);
97 (void)frexp(y,&iy);
98 while (r >= y) {
99 (void)frexp(r,&ir);
100 w = ldexp(y,ir-iy);
101 r -= w <= r ? w : w*(double)0.5;
102 }
103 return x >= (double)0 ? r : -r;
104 }
105
106 float
fmodf(float x,float y)107 fmodf(float x, float y)
108 {
109 return fmod(x, y);
110 }
111
112 #ifdef TEST_FMOD
113 #include <math.h>
114 #include <stdio.h>
115 #include <stdlib.h>
116
117 #define NTEST 10000
118 #define NCASES 3
119
120 static int nfail = 0;
121 static void
prf(const char * s,double d)122 prf(const char *s, double d)
123 {
124 union {
125 double d;
126 unsigned long long u;
127 } x;
128 x.d = d;
129 printf("%s = %#016.16llx (%24.16e)\n", s, x.u, x.d);
130 }
131
132 static void
doit(double x,double y)133 doit(double x, double y)
134 {
135 double ro = fmod(x,y),rn = _fmod(x,y);
136 if (ro != rn) {
137 prf(" x ", x);
138 prf(" y ", y);
139 prf(" fmod", ro);
140 prf("_fmod", rn);
141 (void)printf("\n");
142 }
143 }
144
145 int
main(int argc,char ** argv)146 main(int argc, char **argv)
147 {
148 int i,cases;
149 double x,y;
150
151 srandom(12345);
152 for (i = 0; i < NTEST; i++) {
153 x = (double)random();
154 y = (double)random();
155 for (cases = 0; cases < NCASES; cases++) {
156 switch (cases) {
157 case 0:
158 break;
159 case 1:
160 y = (double)1/y; break;
161 case 2:
162 x = (double)1/x; break;
163 default:
164 abort(); break;
165 }
166 doit(x,y);
167 doit(x,-y);
168 doit(-x,y);
169 doit(-x,-y);
170 }
171 }
172 if (nfail)
173 (void)printf("Number of failures: %d (out of a total of %d)\n",
174 nfail,NTEST*NCASES*4);
175 else
176 (void)printf("No discrepancies were found\n");
177 exit(0);
178 }
179 #endif /* TEST_FMOD */
180