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. 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
33static 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)
66extern int isnan(),finite();
67#endif	/* !defined(__vax__) && !defined(tahoe) */
68
69#ifdef TEST_FMOD
70static double
71_fmod(double x, double y)
72#else	/* TEST_FMOD */
73double
74fmod(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
99extern long random();
100extern double fmod();
101
102#define	NTEST	10000
103#define	NCASES	3
104
105static int nfail = 0;
106
107static void
108doit(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
120int
121main(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