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