27 lines
672 B
C
27 lines
672 B
C
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#include <math.h>
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#include <errno.h>
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#include "fastmath.h"
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/* acosh(x) = log (x + sqrt(x * x - 1)) */
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double acosh (double x)
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{
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if (isnan (x))
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return x;
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if (x < 1.0)
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{
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errno = EDOM;
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return nan("");
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}
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if (x > 0x1p32)
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/* Avoid overflow (and unnecessary calculation when
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sqrt (x * x - 1) == x). GCC optimizes by replacing
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the long double M_LN2 const with a fldln2 insn. */
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return __fast_log (x) + 6.9314718055994530941723E-1L;
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/* Since x >= 1, the arg to log will always be greater than
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the fyl2xp1 limit (approx 0.29) so just use logl. */
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return __fast_log (x + __fast_sqrt((x + 1.0) * (x - 1.0)));
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}
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