986
|
1 |
|
|
2 |
/* @(#)e_remainder.c 1.3 95/01/18 */
|
|
3 |
/*
|
|
4 |
* ====================================================
|
|
5 |
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
6 |
*
|
|
7 |
* Developed at SunSoft, a Sun Microsystems, Inc. business.
|
|
8 |
* Permission to use, copy, modify, and distribute this
|
|
9 |
* software is freely granted, provided that this notice
|
|
10 |
* is preserved.
|
|
11 |
* ====================================================
|
|
12 |
*/
|
|
13 |
|
|
14 |
/* __ieee754_remainder(x,p)
|
|
15 |
* Return :
|
|
16 |
* returns x REM p = x - [x/p]*p as if in infinite
|
|
17 |
* precise arithmetic, where [x/p] is the (infinite bit)
|
|
18 |
* integer nearest x/p (in half way case choose the even one).
|
|
19 |
* Method :
|
|
20 |
* Based on fmod() return x-[x/p]chopped*p exactlp.
|
|
21 |
*/
|
|
22 |
|
|
23 |
#include "fdlibm.h"
|
|
24 |
|
|
25 |
#ifdef __STDC__
|
|
26 |
static const double zero = 0.0;
|
|
27 |
#else
|
|
28 |
static double zero = 0.0;
|
|
29 |
#endif
|
|
30 |
|
|
31 |
|
|
32 |
#ifdef __STDC__
|
|
33 |
double __ieee754_remainder(double x, double p)
|
|
34 |
#else
|
|
35 |
double __ieee754_remainder(x,p)
|
|
36 |
double x,p;
|
|
37 |
#endif
|
|
38 |
{
|
|
39 |
int hx,hp;
|
|
40 |
unsigned sx,lx,lp;
|
|
41 |
double p_half;
|
|
42 |
|
|
43 |
hx = __HI(x); /* high word of x */
|
|
44 |
lx = __LO(x); /* low word of x */
|
|
45 |
hp = __HI(p); /* high word of p */
|
|
46 |
lp = __LO(p); /* low word of p */
|
|
47 |
sx = hx&0x80000000;
|
|
48 |
hp &= 0x7fffffff;
|
|
49 |
hx &= 0x7fffffff;
|
|
50 |
|
|
51 |
/* purge off exception values */
|
|
52 |
if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */
|
|
53 |
if((hx>=0x7ff00000)|| /* x not finite */
|
|
54 |
((hp>=0x7ff00000)&& /* p is NaN */
|
|
55 |
(((hp-0x7ff00000)|lp)!=0)))
|
|
56 |
return (x*p)/(x*p);
|
|
57 |
|
|
58 |
|
|
59 |
if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p); /* now x < 2p */
|
|
60 |
if (((hx-hp)|(lx-lp))==0) return zero*x;
|
|
61 |
x = fabs(x);
|
|
62 |
p = fabs(p);
|
|
63 |
if (hp<0x00200000) {
|
|
64 |
if(x+x>p) {
|
|
65 |
x-=p;
|
|
66 |
if(x+x>=p) x -= p;
|
|
67 |
}
|
|
68 |
} else {
|
|
69 |
p_half = 0.5*p;
|
|
70 |
if(x>p_half) {
|
|
71 |
x-=p;
|
|
72 |
if(x>=p_half) x -= p;
|
|
73 |
}
|
|
74 |
}
|
|
75 |
__HI(x) ^= sx;
|
|
76 |
return x;
|
|
77 |
}
|