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
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text/x-csrc;charset=UTF-8
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File size:
697 bytes
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1 | #include "libm.h"
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2 |
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3 | /* asinh(x) = sign(x)*log(|x|+sqrt(x*x+1)) ~= x - x^3/6 + o(x^5) */
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4 | double asinh(double x)
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5 | {
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6 | union {double f; uint64_t i;} u = {.f = x};
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7 | unsigned e = u.i >> 52 & 0x7ff;
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8 | unsigned s = u.i >> 63;
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9 |
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10 | /* |x| */
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11 | u.i &= (uint64_t)-1/2;
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12 | x = u.f;
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13 |
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14 | if (e >= 0x3ff + 26) {
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15 | /* |x| >= 0x1p26 or inf or nan */
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16 | x = log(x) + 0.693147180559945309417232121458176568;
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17 | } else if (e >= 0x3ff + 1) {
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18 | /* |x| >= 2 */
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19 | x = log(2*x + 1/(sqrt(x*x+1)+x));
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20 | } else if (e >= 0x3ff - 26) {
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21 | /* |x| >= 0x1p-26, up to 1.6ulp error in [0.125,0.5] */
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22 | x = log1p(x + x*x/(sqrt(x*x+1)+1));
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23 | } else {
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24 | /* |x| < 0x1p-26, raise inexact if x != 0 */
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25 | FORCE_EVAL(x + 0x1p120f);
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26 | }
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27 | return s ? -x : x;
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28 | }
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