1*c9945492SAndroid Build Coastguard Worker #include "libm.h" 2*c9945492SAndroid Build Coastguard Worker 3*c9945492SAndroid Build Coastguard Worker #if FLT_EVAL_METHOD==2 4*c9945492SAndroid Build Coastguard Worker #undef sqrt 5*c9945492SAndroid Build Coastguard Worker #define sqrt sqrtl 6*c9945492SAndroid Build Coastguard Worker #endif 7*c9945492SAndroid Build Coastguard Worker 8*c9945492SAndroid Build Coastguard Worker /* acosh(x) = log(x + sqrt(x*x-1)) */ acosh(double x)9*c9945492SAndroid Build Coastguard Workerdouble acosh(double x) 10*c9945492SAndroid Build Coastguard Worker { 11*c9945492SAndroid Build Coastguard Worker union {double f; uint64_t i;} u = {.f = x}; 12*c9945492SAndroid Build Coastguard Worker unsigned e = u.i >> 52 & 0x7ff; 13*c9945492SAndroid Build Coastguard Worker 14*c9945492SAndroid Build Coastguard Worker /* x < 1 domain error is handled in the called functions */ 15*c9945492SAndroid Build Coastguard Worker 16*c9945492SAndroid Build Coastguard Worker if (e < 0x3ff + 1) 17*c9945492SAndroid Build Coastguard Worker /* |x| < 2, up to 2ulp error in [1,1.125] */ 18*c9945492SAndroid Build Coastguard Worker return log1p(x-1 + sqrt((x-1)*(x-1)+2*(x-1))); 19*c9945492SAndroid Build Coastguard Worker if (e < 0x3ff + 26) 20*c9945492SAndroid Build Coastguard Worker /* |x| < 0x1p26 */ 21*c9945492SAndroid Build Coastguard Worker return log(2*x - 1/(x+sqrt(x*x-1))); 22*c9945492SAndroid Build Coastguard Worker /* |x| >= 0x1p26 or nan */ 23*c9945492SAndroid Build Coastguard Worker return log(x) + 0.693147180559945309417232121458176568; 24*c9945492SAndroid Build Coastguard Worker } 25