n_fmod.c revision 1.8 
1/*	$NetBSD: n_fmod.c,v 1.8 2016/01/16 19:44:05 christos 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#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
77static double
78_fmod(double x, double y)
79#else	/* TEST_FMOD */
80double
81fmod(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
105float
106fmodf(float x, float y)
107{
108	return fmod(x, y);
109}
110
111#ifdef TEST_FMOD
112extern long random();
113extern double fmod();
114
115#define	NTEST	10000
116#define	NCASES	3
117
118static int nfail = 0;
119static void
120prf(const char *s, double d)
121{
122	union {
123		double d;
124		unsigned long long u;
125	} x;
126	x.d = d;
127	printf("%s = %#016.16llx (%24.16e)\n:, s, x.u, x.d);
128}
129
130static void
131doit(double x, double y)
132{
133	double ro = fmod(x,y),rn = _fmod(x,y);
134	if (ro != rn) {
135		prf(" x   ", x);
136		prf(" y   ", y);
137		prf(" fmod", ro);
138		prf("_fmod", rn);
139		(void)printf("\n");
140	}
141}
142
143int
144main(int argc, char **argv)
145{
146	int i,cases;
147	double x,y;
148
149	srandom(12345);
150	for (i = 0; i < NTEST; i++) {
151		x = (double)random();
152		y = (double)random();
153		for (cases = 0; cases < NCASES; cases++) {
154			switch (cases) {
155			case 0:
156				break;
157			case 1:
158				y = (double)1/y; break;
159			case 2:
160				x = (double)1/x; break;
161			default:
162				abort(); break;
163			}
164			doit(x,y);
165			doit(x,-y);
166			doit(-x,y);
167			doit(-x,-y);
168		}
169	}
170	if (nfail)
171		(void)printf("Number of failures: %d (out of a total of %d)\n",
172			nfail,NTEST*NCASES*4);
173	else
174		(void)printf("No discrepancies were found\n");
175	exit(0);
176}
177#endif	/* TEST_FMOD */
178