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math: cosh cleanup

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do fabs by hand, don't check for nan and inf separately
This commit is contained in:
Szabolcs Nagy
2012-12-12 01:39:23 +01:00
parent 9c6b1de0fb
commit 14cc9c7f38
3 changed files with 63 additions and 70 deletions
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41
src/math/cosh.c
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@ -23,7 +23,7 @@
* 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)
* ln2ovft < x : cosh(x) := inf (overflow)
*
* Special cases:
* cosh(x) is |x| if x is +INF, -INF, or NaN.
@ -32,43 +32,40 @@
#include "libm.h"
static const double huge = 1.0e300;
double cosh(double x)
{
double t, w;
int32_t ix;
union {double f; uint64_t i;} u = {.f = x};
uint32_t ix;
double t;
GET_HIGH_WORD(ix, x);
ix &= 0x7fffffff;
/* x is INF or NaN */
if (ix >= 0x7ff00000)
return x*x;
/* |x| */
u.i &= (uint64_t)-1/2;
x = u.f;
ix = u.i >> 32;
/* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
if (ix < 0x3fd62e43) {
t = expm1(fabs(x));
w = 1.0+t;
t = expm1(x);
if (ix < 0x3c800000)
return w; /* cosh(tiny) = 1 */
return 1.0 + (t*t)/(w+w);
return 1;
return 1 + t*t/(2*(1+t));
}
/* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|))/2; */
if (ix < 0x40360000) {
t = exp(fabs(x));
t = exp(x);
return 0.5*t + 0.5/t;
}
/* |x| in [22, log(maxdouble)] return 0.5*exp(|x|) */
if (ix < 0x40862E42)
return 0.5*exp(fabs(x));
if (ix < 0x40862e42)
return 0.5*exp(x);
/* |x| in [log(maxdouble), overflowthresold] */
if (ix <= 0x408633CE)
return __expo2(fabs(x));
if (ix <= 0x408633ce)
return __expo2(x);
/* |x| > overflowthresold, cosh(x) overflow */
return huge*huge;
/* overflow (or nan) */
x *= 0x1p1023;
return x;
}