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Roland McGrath
1995-02-18 01:27:10 +00:00
commit 28f540f45b
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/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
static char sccsid[] = "@(#)fmod.c 8.1 (Berkeley) 6/4/93";
#endif /* not lint */
/* fmod.c
*
* SYNOPSIS
*
* #include <math.h>
* double fmod(double x, double y)
*
* DESCRIPTION
*
* The fmod function computes the floating-point remainder of x/y.
*
* RETURNS
*
* The fmod function returns the value x-i*y, for some integer i
* such that, if y is nonzero, the result has the same sign as x and
* magnitude less than the magnitude of y.
*
* On a VAX or CCI,
*
* fmod(x,0) traps/faults on floating-point divided-by-zero.
*
* On IEEE-754 conforming machines with "isnan()" primitive,
*
* fmod(x,0), fmod(INF,y) are invalid operations and NaN is returned.
*
*/
#if !defined(vax) && !defined(tahoe)
extern int isnan(),finite();
#endif /* !defined(vax) && !defined(tahoe) */
extern double frexp(),ldexp(),fabs();
#ifdef TEST_FMOD
static double
_fmod(x,y)
#else /* TEST_FMOD */
double
fmod(x,y)
#endif /* TEST_FMOD */
double x,y;
{
int ir,iy;
double r,w;
if (y == (double)0
#if !defined(vax) && !defined(tahoe) /* per "fmod" manual entry, SunOS 4.0 */
|| isnan(y) || !finite(x)
#endif /* !defined(vax) && !defined(tahoe) */
)
return (x*y)/(x*y);
r = fabs(x);
y = fabs(y);
(void)frexp(y,&iy);
while (r >= y) {
(void)frexp(r,&ir);
w = ldexp(y,ir-iy);
r -= w <= r ? w : w*(double)0.5;
}
return x >= (double)0 ? r : -r;
}
#ifdef TEST_FMOD
extern long random();
extern double fmod();
#define NTEST 10000
#define NCASES 3
static int nfail = 0;
static void
doit(x,y)
double x,y;
{
double ro = fmod(x,y),rn = _fmod(x,y);
if (ro != rn) {
(void)printf(" x = 0x%08.8x %08.8x (%24.16e)\n",x,x);
(void)printf(" y = 0x%08.8x %08.8x (%24.16e)\n",y,y);
(void)printf(" fmod = 0x%08.8x %08.8x (%24.16e)\n",ro,ro);
(void)printf("_fmod = 0x%08.8x %08.8x (%24.16e)\n",rn,rn);
(void)printf("\n");
}
}
main()
{
register int i,cases;
double x,y;
srandom(12345);
for (i = 0; i < NTEST; i++) {
x = (double)random();
y = (double)random();
for (cases = 0; cases < NCASES; cases++) {
switch (cases) {
case 0:
break;
case 1:
y = (double)1/y; break;
case 2:
x = (double)1/x; break;
default:
abort(); break;
}
doit(x,y);
doit(x,-y);
doit(-x,y);
doit(-x,-y);
}
}
if (nfail)
(void)printf("Number of failures: %d (out of a total of %d)\n",
nfail,NTEST*NCASES*4);
else
(void)printf("No discrepancies were found\n");
exit(0);
}
#endif /* TEST_FMOD */