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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1906 | serge | 1 | #include |
| 2 | #include |
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| 3 | #include "fastmath.h" |
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| 4 | |||
| 5 | /* asinh(x) = copysign(log(fabs(x) + sqrt(x * x + 1.0)), x) */ |
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| 6 | double asinh(double x) |
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| 7 | { |
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| 8 | double z; |
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| 9 | if (!isfinite (x)) |
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| 10 | return x; |
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| 11 | z = fabs (x); |
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| 12 | |||
| 13 | /* Avoid setting FPU underflow exception flag in x * x. */ |
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| 14 | #if 0 |
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| 15 | if ( z < 0x1p-32) |
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| 16 | return x; |
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| 17 | #endif |
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| 18 | |||
| 19 | /* Use log1p to avoid cancellation with small x. Put |
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| 20 | x * x in denom, so overflow is harmless. |
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| 21 | asinh(x) = log1p (x + sqrt (x * x + 1.0) - 1.0) |
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| 22 | = log1p (x + x * x / (sqrt (x * x + 1.0) + 1.0)) */ |
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| 23 | |||
| 24 | z = __fast_log1p (z + z * z / (__fast_sqrt (z * z + 1.0) + 1.0)); |
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| 25 | |||
| 26 | return ( x > 0.0 ? z : -z); |
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| 27 | } |
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| 28 |