mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-27 13:10:29 +00:00
83 lines
2.2 KiB
C
83 lines
2.2 KiB
C
/* Optimized by Ulrich Drepper <drepper@gmail.com>, 2011 */
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunPro, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*/
|
|
|
|
/* __ieee754_cosh(x)
|
|
* Method :
|
|
* mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2
|
|
* 1. Replace x by |x| (cosh(x) = cosh(-x)).
|
|
* 2.
|
|
* [ exp(x) - 1 ]^2
|
|
* 0 <= x <= ln2/2 : cosh(x) := 1 + -------------------
|
|
* 2*exp(x)
|
|
*
|
|
* exp(x) + 1/exp(x)
|
|
* ln2/2 <= x <= 22 : cosh(x) := -------------------
|
|
* 2
|
|
* 22 <= x <= lnovft : cosh(x) := exp(x)/2
|
|
* lnovft <= x <= ln2ovft: cosh(x) := exp(x/2)/2 * exp(x/2)
|
|
* ln2ovft < x : cosh(x) := huge*huge (overflow)
|
|
*
|
|
* Special cases:
|
|
* cosh(x) is |x| if x is +INF, -INF, or NaN.
|
|
* only cosh(0)=1 is exact for finite x.
|
|
*/
|
|
|
|
#include <math.h>
|
|
#include <math_private.h>
|
|
|
|
static const double one = 1.0, half=0.5, huge = 1.0e300;
|
|
|
|
double
|
|
__ieee754_cosh (double x)
|
|
{
|
|
double t,w;
|
|
int32_t ix;
|
|
u_int32_t lx;
|
|
|
|
/* High word of |x|. */
|
|
GET_HIGH_WORD(ix,x);
|
|
ix &= 0x7fffffff;
|
|
|
|
/* |x| in [0,22] */
|
|
if (ix < 0x40360000) {
|
|
/* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
|
|
if(ix<0x3fd62e43) {
|
|
t = __expm1(fabs(x));
|
|
w = one+t;
|
|
if (ix<0x3c800000) return w; /* cosh(tiny) = 1 */
|
|
return one+(t*t)/(w+w);
|
|
}
|
|
|
|
/* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
|
|
t = __ieee754_exp(fabs(x));
|
|
return half*t+half/t;
|
|
}
|
|
|
|
/* |x| in [22, log(maxdouble)] return half*exp(|x|) */
|
|
if (ix < 0x40862e42) return half*__ieee754_exp(fabs(x));
|
|
|
|
/* |x| in [log(maxdouble), overflowthresold] */
|
|
GET_LOW_WORD(lx,x);
|
|
if (ix<0x408633ce || ((ix==0x408633ce)&&(lx<=(u_int32_t)0x8fb9f87d))) {
|
|
w = __ieee754_exp(half*fabs(x));
|
|
t = half*w;
|
|
return t*w;
|
|
}
|
|
|
|
/* x is INF or NaN */
|
|
if(ix>=0x7ff00000) return x*x;
|
|
|
|
/* |x| > overflowthresold, cosh(x) overflow */
|
|
return huge*huge;
|
|
}
|
|
strong_alias (__ieee754_cosh, __cosh_finite)
|