source:
asp3_tinet_ecnl_rx/trunk/musl-1.1.18/src/math/sinh.c
Last change on this file was 337, checked in by , 6 years ago | |
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File size: 837 bytes |
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[337] | 1 | #include "libm.h" |
2 | ||
3 | /* sinh(x) = (exp(x) - 1/exp(x))/2 | |
4 | * = (exp(x)-1 + (exp(x)-1)/exp(x))/2 | |
5 | * = x + x^3/6 + o(x^5) | |
6 | */ | |
7 | double sinh(double x) | |
8 | { | |
9 | union {double f; uint64_t i;} u = {.f = x}; | |
10 | uint32_t w; | |
11 | double t, h, absx; | |
12 | ||
13 | h = 0.5; | |
14 | if (u.i >> 63) | |
15 | h = -h; | |
16 | /* |x| */ | |
17 | u.i &= (uint64_t)-1/2; | |
18 | absx = u.f; | |
19 | w = u.i >> 32; | |
20 | ||
21 | /* |x| < log(DBL_MAX) */ | |
22 | if (w < 0x40862e42) { | |
23 | t = expm1(absx); | |
24 | if (w < 0x3ff00000) { | |
25 | if (w < 0x3ff00000 - (26<<20)) | |
26 | /* note: inexact and underflow are raised by expm1 */ | |
27 | /* note: this branch avoids spurious underflow */ | |
28 | return x; | |
29 | return h*(2*t - t*t/(t+1)); | |
30 | } | |
31 | /* note: |x|>log(0x1p26)+eps could be just h*exp(x) */ | |
32 | return h*(t + t/(t+1)); | |
33 | } | |
34 | ||
35 | /* |x| > log(DBL_MAX) or nan */ | |
36 | /* note: the result is stored to handle overflow */ | |
37 | t = 2*h*__expo2(absx); | |
38 | return t; | |
39 | } |
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