| 0,0 → 1,28 |
|---|
| #include <math.h> |
| #include <errno.h> |
| #include "fastmath.h" |
| |
| /* asinh(x) = copysign(log(fabs(x) + sqrt(x * x + 1.0)), x) */ |
| double asinh(double x) |
| { |
| double z; |
| if (!isfinite (x)) |
| return x; |
| z = fabs (x); |
| |
| /* Avoid setting FPU underflow exception flag in x * x. */ |
| #if 0 |
| if ( z < 0x1p-32) |
| return x; |
| #endif |
| |
| /* Use log1p to avoid cancellation with small x. Put |
| x * x in denom, so overflow is harmless. |
| asinh(x) = log1p (x + sqrt (x * x + 1.0) - 1.0) |
| = log1p (x + x * x / (sqrt (x * x + 1.0) + 1.0)) */ |
| |
| z = __fast_log1p (z + z * z / (__fast_sqrt (z * z + 1.0) + 1.0)); |
| |
| return ( x > 0.0 ? z : -z); |
| } |
| |