source:
asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/math/sinh.c@
373
Last change on this file since 373 was 352, checked in by , 6 years ago | |
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File size: 837 bytes |
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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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