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-rw-r--r--src/math/cosh.c41
1 files changed, 19 insertions, 22 deletions
diff --git a/src/math/cosh.c b/src/math/cosh.c
index a1f7dbc7..2fcdea8f 100644
--- a/src/math/cosh.c
+++ b/src/math/cosh.c
@@ -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;
-
- GET_HIGH_WORD(ix, x);
- ix &= 0x7fffffff;
+ union {double f; uint64_t i;} u = {.f = x};
+ uint32_t ix;
+ double t;
- /* 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;
}