You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
34 lines
926 B
34 lines
926 B
/*****************************************************************************/
|
|
/*****************************************************************************/
|
|
// atanhf from musl-0.9.15
|
|
/*****************************************************************************/
|
|
/*****************************************************************************/
|
|
|
|
#include "libm.h"
|
|
|
|
/* atanh(x) = log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2 ~= x + x^3/3 + o(x^5) */
|
|
float atanhf(float x)
|
|
{
|
|
union {float f; uint32_t i;} u = {.f = x};
|
|
unsigned s = u.i >> 31;
|
|
float_t y;
|
|
|
|
/* |x| */
|
|
u.i &= 0x7fffffff;
|
|
y = u.f;
|
|
|
|
if (u.i < 0x3f800000 - (1<<23)) {
|
|
if (u.i < 0x3f800000 - (32<<23)) {
|
|
/* handle underflow */
|
|
if (u.i < (1<<23))
|
|
FORCE_EVAL((float)(y*y));
|
|
} else {
|
|
/* |x| < 0.5, up to 1.7ulp error */
|
|
y = 0.5f*log1pf(2*y + 2*y*y/(1-y));
|
|
}
|
|
} else {
|
|
/* avoid overflow */
|
|
y = 0.5f*log1pf(2*(y/(1-y)));
|
|
}
|
|
return s ? -y : y;
|
|
}
|
|
|