Last change
on this file since 351 was 337, checked in by coas-nagasima, 6 years ago |
ASP3版ECNLを追加
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-
Property svn:eol-style
set to
native
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Property svn:mime-type
set to
text/x-csrc;charset=UTF-8
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File size:
578 bytes
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Rev | Line | |
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[337] | 1 | #include "libm.h"
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| 2 |
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| 3 | /* atanh(x) = log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2 ~= x + x^3/3 + o(x^5) */
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| 4 | float atanhf(float x)
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| 5 | {
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| 6 | union {float f; uint32_t i;} u = {.f = x};
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| 7 | unsigned s = u.i >> 31;
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| 8 | float_t y;
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| 9 |
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| 10 | /* |x| */
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| 11 | u.i &= 0x7fffffff;
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| 12 | y = u.f;
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| 13 |
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| 14 | if (u.i < 0x3f800000 - (1<<23)) {
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| 15 | if (u.i < 0x3f800000 - (32<<23)) {
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| 16 | /* handle underflow */
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| 17 | if (u.i < (1<<23))
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| 18 | FORCE_EVAL((float)(y*y));
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| 19 | } else {
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| 20 | /* |x| < 0.5, up to 1.7ulp error */
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| 21 | y = 0.5f*log1pf(2*y + 2*y*y/(1-y));
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| 22 | }
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| 23 | } else {
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| 24 | /* avoid overflow */
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| 25 | y = 0.5f*log1pf(2*(y/(1-y)));
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| 26 | }
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| 27 | return s ? -y : y;
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| 28 | }
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