/rust/registry/src/index.crates.io-6f17d22bba15001f/libm-0.2.11/src/math/tanh.rs
Line | Count | Source (jump to first uncovered line) |
1 | | use super::expm1; |
2 | | |
3 | | /* tanh(x) = (exp(x) - exp(-x))/(exp(x) + exp(-x)) |
4 | | * = (exp(2*x) - 1)/(exp(2*x) - 1 + 2) |
5 | | * = (1 - exp(-2*x))/(exp(-2*x) - 1 + 2) |
6 | | */ |
7 | | |
8 | | /// The hyperbolic tangent of `x` (f64). |
9 | | /// |
10 | | /// `x` is specified in radians. |
11 | | #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
12 | 0 | pub fn tanh(mut x: f64) -> f64 { |
13 | 0 | let mut uf: f64 = x; |
14 | 0 | let mut ui: u64 = f64::to_bits(uf); |
15 | 0 |
|
16 | 0 | let w: u32; |
17 | 0 | let sign: bool; |
18 | 0 | let mut t: f64; |
19 | 0 |
|
20 | 0 | /* x = |x| */ |
21 | 0 | sign = ui >> 63 != 0; |
22 | 0 | ui &= !1 / 2; |
23 | 0 | uf = f64::from_bits(ui); |
24 | 0 | x = uf; |
25 | 0 | w = (ui >> 32) as u32; |
26 | 0 |
|
27 | 0 | if w > 0x3fe193ea { |
28 | | /* |x| > log(3)/2 ~= 0.5493 or nan */ |
29 | 0 | if w > 0x40340000 { |
30 | 0 | /* |x| > 20 or nan */ |
31 | 0 | /* note: this branch avoids raising overflow */ |
32 | 0 | t = 1.0 - 0.0 / x; |
33 | 0 | } else { |
34 | 0 | t = expm1(2.0 * x); |
35 | 0 | t = 1.0 - 2.0 / (t + 2.0); |
36 | 0 | } |
37 | 0 | } else if w > 0x3fd058ae { |
38 | 0 | /* |x| > log(5/3)/2 ~= 0.2554 */ |
39 | 0 | t = expm1(2.0 * x); |
40 | 0 | t = t / (t + 2.0); |
41 | 0 | } else if w >= 0x00100000 { |
42 | 0 | /* |x| >= 0x1p-1022, up to 2ulp error in [0.1,0.2554] */ |
43 | 0 | t = expm1(-2.0 * x); |
44 | 0 | t = -t / (t + 2.0); |
45 | 0 | } else { |
46 | 0 | /* |x| is subnormal */ |
47 | 0 | /* note: the branch above would not raise underflow in [0x1p-1023,0x1p-1022) */ |
48 | 0 | force_eval!(x as f32); |
49 | 0 | t = x; |
50 | 0 | } |
51 | | |
52 | 0 | if sign { -t } else { t } |
53 | 0 | } |