1 /*
2 * Copyright (c) 1989 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #ifndef lint
35 static char sccsid[] = "@(#)fmod.c 5.2 (Berkeley) 6/1/90";
36 #endif /* not lint */
37
38 /* fmod.c
39 *
40 * SYNOPSIS
41 *
42 * #include <math.h>
43 * double fmod(double x, double y)
44 *
45 * DESCRIPTION
46 *
47 * The fmod function computes the floating-point remainder of x/y.
48 *
49 * RETURNS
50 *
51 * The fmod function returns the value x-i*y, for some integer i
52 * such that, if y is nonzero, the result has the same sign as x and
53 * magnitude less than the magnitude of y.
54 *
55 * On a VAX or CCI,
56 *
57 * fmod(x,0) traps/faults on floating-point divided-by-zero.
58 *
59 * On IEEE-754 conforming machines with "isnan()" primitive,
60 *
61 * fmod(x,0), fmod(INF,y) are invalid operations and NaN is returned.
62 *
63 */
64 #if !defined(vax) && !defined(tahoe)
65 extern int isnan(),finite();
66 #endif /* !defined(vax) && !defined(tahoe) */
67 extern double frexp(),ldexp(),fabs();
68
69 #ifdef TEST_FMOD
70 static double
_fmod(x,y)71 _fmod(x,y)
72 #else /* TEST_FMOD */
73 double
74 fmod(x,y)
75 #endif /* TEST_FMOD */
76 double x,y;
77 {
78 int ir,iy;
79 double r,w;
80
81 if (y == (double)0
82 #if !defined(vax) && !defined(tahoe) /* per "fmod" manual entry, SunOS 4.0 */
83 || isnan(y) || !finite(x)
84 #endif /* !defined(vax) && !defined(tahoe) */
85 )
86 return (x*y)/(x*y);
87
88 r = fabs(x);
89 y = fabs(y);
90 (void)frexp(y,&iy);
91 while (r >= y) {
92 (void)frexp(r,&ir);
93 w = ldexp(y,ir-iy);
94 r -= w <= r ? w : w*(double)0.5;
95 }
96 return x >= (double)0 ? r : -r;
97 }
98
99 #ifdef TEST_FMOD
100 extern long random();
101 extern double fmod();
102
103 #define NTEST 10000
104 #define NCASES 3
105
106 static int nfail = 0;
107
108 static void
doit(x,y)109 doit(x,y)
110 double x,y;
111 {
112 double ro = fmod(x,y),rn = _fmod(x,y);
113 if (ro != rn) {
114 (void)printf(" x = 0x%08.8x %08.8x (%24.16e)\n",x,x);
115 (void)printf(" y = 0x%08.8x %08.8x (%24.16e)\n",y,y);
116 (void)printf(" fmod = 0x%08.8x %08.8x (%24.16e)\n",ro,ro);
117 (void)printf("_fmod = 0x%08.8x %08.8x (%24.16e)\n",rn,rn);
118 (void)printf("\n");
119 }
120 }
121
main()122 main()
123 {
124 register int i,cases;
125 double x,y;
126
127 srandom(12345);
128 for (i = 0; i < NTEST; i++) {
129 x = (double)random();
130 y = (double)random();
131 for (cases = 0; cases < NCASES; cases++) {
132 switch (cases) {
133 case 0:
134 break;
135 case 1:
136 y = (double)1/y; break;
137 case 2:
138 x = (double)1/x; break;
139 default:
140 abort(); break;
141 }
142 doit(x,y);
143 doit(x,-y);
144 doit(-x,y);
145 doit(-x,-y);
146 }
147 }
148 if (nfail)
149 (void)printf("Number of failures: %d (out of a total of %d)\n",
150 nfail,NTEST*NCASES*4);
151 else
152 (void)printf("No discrepancies were found\n");
153 exit(0);
154 }
155 #endif /* TEST_FMOD */
156