| #include "libm.h" |
| |
| #if FLT_EVAL_METHOD==2 |
| #undef sqrtf |
| #define sqrtf sqrtl |
| #elif FLT_EVAL_METHOD==1 |
| #undef sqrtf |
| #define sqrtf sqrt |
| #endif |
| |
| /* acosh(x) = log(x + sqrt(x*x-1)) */ |
| float acoshf(float x) |
| { |
| union {float f; uint32_t i;} u = {x}; |
| uint32_t a = u.i & 0x7fffffff; |
| |
| if (a < 0x3f800000+(1<<23)) |
| /* |x| < 2, invalid if x < 1 or nan */ |
| /* up to 2ulp error in [1,1.125] */ |
| return log1pf(x-1 + sqrtf((x-1)*(x-1)+2*(x-1))); |
| if (a < 0x3f800000+(12<<23)) |
| /* |x| < 0x1p12 */ |
| return logf(2*x - 1/(x+sqrtf(x*x-1))); |
| /* x >= 0x1p12 */ |
| return logf(x) + 0.693147180559945309417232121458176568f; |
| } |
