source:
asp3_tinet_ecnl_rx/trunk/musl-1.1.18/src/math/tanhf.c
Last change on this file was 337, checked in by , 6 years ago | |
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File size: 653 bytes |
Rev | Line | |
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[337] | 1 | #include "libm.h" |
2 | ||
3 | float tanhf(float x) | |
4 | { | |
5 | union {float f; uint32_t i;} u = {.f = x}; | |
6 | uint32_t w; | |
7 | int sign; | |
8 | float t; | |
9 | ||
10 | /* x = |x| */ | |
11 | sign = u.i >> 31; | |
12 | u.i &= 0x7fffffff; | |
13 | x = u.f; | |
14 | w = u.i; | |
15 | ||
16 | if (w > 0x3f0c9f54) { | |
17 | /* |x| > log(3)/2 ~= 0.5493 or nan */ | |
18 | if (w > 0x41200000) { | |
19 | /* |x| > 10 */ | |
20 | t = 1 + 0/x; | |
21 | } else { | |
22 | t = expm1f(2*x); | |
23 | t = 1 - 2/(t+2); | |
24 | } | |
25 | } else if (w > 0x3e82c578) { | |
26 | /* |x| > log(5/3)/2 ~= 0.2554 */ | |
27 | t = expm1f(2*x); | |
28 | t = t/(t+2); | |
29 | } else if (w >= 0x00800000) { | |
30 | /* |x| >= 0x1p-126 */ | |
31 | t = expm1f(-2*x); | |
32 | t = -t/(t+2); | |
33 | } else { | |
34 | /* |x| is subnormal */ | |
35 | FORCE_EVAL(x*x); | |
36 | t = x; | |
37 | } | |
38 | return sign ? -t : t; | |
39 | } |
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