n_fmod.c revision 1.4 
1/*	$NetBSD: n_fmod.c,v 1.4 2002/06/15 00:10:17 matt 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. All advertising materials mentioning features or use of this software
15 *    must display the following acknowledgement:
16 *	This product includes software developed by the University of
17 *	California, Berkeley and its contributors.
18 * 4. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#ifndef lint
36#if 0
37static char sccsid[] = "@(#)fmod.c	8.1 (Berkeley) 6/4/93";
38#endif
39#endif /* not lint */
40
41#include "mathimpl.h"
42
43/* fmod.c
44 *
45 * SYNOPSIS
46 *
47 *    #include <math.h>
48 *    double fmod(double x, double y)
49 *
50 * DESCRIPTION
51 *
52 *    The fmod function computes the floating-point remainder of x/y.
53 *
54 * RETURNS
55 *
56 *    The fmod function returns the value x-i*y, for some integer i
57 * such that, if y is nonzero, the result has the same sign as x and
58 * magnitude less than the magnitude of y.
59 *
60 * On a VAX or CCI,
61 *
62 *    fmod(x,0) traps/faults on floating-point divided-by-zero.
63 *
64 * On IEEE-754 conforming machines with "isnan()" primitive,
65 *
66 *    fmod(x,0), fmod(INF,y) are invalid operations and NaN is returned.
67 *
68 */
69#if !defined(__vax__) && !defined(tahoe)
70extern int isnan(),finite();
71#endif	/* !defined(__vax__) && !defined(tahoe) */
72
73#ifdef TEST_FMOD
74static double
75_fmod(double x, double y)
76#else	/* TEST_FMOD */
77double
78fmod(double x, double y)
79#endif	/* TEST_FMOD */
80{
81	int ir,iy;
82	double r,w;
83
84	if (y == (double)0
85#if !defined(__vax__) && !defined(tahoe)	/* per "fmod" manual entry, SunOS 4.0 */
86		|| isnan(y) || !finite(x)
87#endif	/* !defined(__vax__) && !defined(tahoe) */
88	    )
89	    return (x*y)/(x*y);
90
91	r = fabs(x);
92	y = fabs(y);
93	(void)frexp(y,&iy);
94	while (r >= y) {
95		(void)frexp(r,&ir);
96		w = ldexp(y,ir-iy);
97		r -= w <= r ? w : w*(double)0.5;
98	}
99	return x >= (double)0 ? r : -r;
100}
101
102#ifdef TEST_FMOD
103extern long random();
104extern double fmod();
105
106#define	NTEST	10000
107#define	NCASES	3
108
109static int nfail = 0;
110
111static void
112doit(double x, double y)
113{
114	double ro = fmod(x,y),rn = _fmod(x,y);
115	if (ro != rn) {
116		(void)printf(" x    = 0x%08.8x %08.8x (%24.16e)\n",x,x);
117		(void)printf(" y    = 0x%08.8x %08.8x (%24.16e)\n",y,y);
118		(void)printf(" fmod = 0x%08.8x %08.8x (%24.16e)\n",ro,ro);
119		(void)printf("_fmod = 0x%08.8x %08.8x (%24.16e)\n",rn,rn);
120		(void)printf("\n");
121	}
122}
123
124int
125main(int argc, char **argv)
126{
127	int i,cases;
128	double x,y;
129
130	srandom(12345);
131	for (i = 0; i < NTEST; i++) {
132		x = (double)random();
133		y = (double)random();
134		for (cases = 0; cases < NCASES; cases++) {
135			switch (cases) {
136			case 0:
137				break;
138			case 1:
139				y = (double)1/y; break;
140			case 2:
141				x = (double)1/x; break;
142			default:
143				abort(); break;
144			}
145			doit(x,y);
146			doit(x,-y);
147			doit(-x,y);
148			doit(-x,-y);
149		}
150	}
151	if (nfail)
152		(void)printf("Number of failures: %d (out of a total of %d)\n",
153			nfail,NTEST*NCASES*4);
154	else
155		(void)printf("No discrepancies were found\n");
156	exit(0);
157}
158#endif	/* TEST_FMOD */
159