/rust/registry/src/index.crates.io-1949cf8c6b5b557f/pxfm-0.1.29/src/logs/logitf.rs
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1 | | /* |
2 | | * // Copyright (c) Radzivon Bartoshyk 9/2025. All rights reserved. |
3 | | * // |
4 | | * // Redistribution and use in source and binary forms, with or without modification, |
5 | | * // are permitted provided that the following conditions are met: |
6 | | * // |
7 | | * // 1. Redistributions of source code must retain the above copyright notice, this |
8 | | * // list of conditions and the following disclaimer. |
9 | | * // |
10 | | * // 2. Redistributions in binary form must reproduce the above copyright notice, |
11 | | * // this list of conditions and the following disclaimer in the documentation |
12 | | * // and/or other materials provided with the distribution. |
13 | | * // |
14 | | * // 3. Neither the name of the copyright holder nor the names of its |
15 | | * // contributors may be used to endorse or promote products derived from |
16 | | * // this software without specific prior written permission. |
17 | | * // |
18 | | * // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
19 | | * // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
20 | | * // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
21 | | * // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE |
22 | | * // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
23 | | * // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
24 | | * // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
25 | | * // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
26 | | * // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
27 | | * // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
28 | | */ |
29 | | use crate::logs::log1pf::{core_log1pf, core_logf}; |
30 | | |
31 | | /// Inverse logistic function |
32 | 0 | pub fn f_logitf(x: f32) -> f32 { |
33 | 0 | let ux = x.to_bits(); |
34 | 0 | if ux >= 0x3f80_0000u32 || ux == 0 { |
35 | | // |x| == 0, |x| == inf, |x| == NaN, x < 0, x >= 1 |
36 | 0 | if ux.wrapping_shl(1) == 0 { |
37 | 0 | return 0.; |
38 | 0 | } |
39 | 0 | if ux == 0x3f80_0000u32 { |
40 | | // x == 1 |
41 | 0 | return f32::INFINITY; |
42 | 0 | } |
43 | 0 | return f32::NAN; |
44 | 0 | } |
45 | | // logit(x) = log(x/(1-p)) = log(x) - log(1-p) |
46 | 0 | let v0 = core_logf(x as f64); |
47 | 0 | let v1 = core_log1pf(-x); |
48 | 0 | (v0 - v1) as f32 |
49 | 0 | } |
50 | | |
51 | | #[cfg(test)] |
52 | | mod tests { |
53 | | use super::*; |
54 | | |
55 | | #[test] |
56 | | fn test_logit() { |
57 | | assert_eq!(f_logitf(0.234), -1.1858611); |
58 | | assert_eq!(f_logitf(0.142112), -1.7978581); |
59 | | assert_eq!(f_logitf(0.86543), 1.8611419); |
60 | | assert_eq!(f_logitf(0.21312), -1.3062204); |
61 | | assert_eq!(f_logitf(0.128765), -1.9119227); |
62 | | assert_eq!(f_logitf(1.), f32::INFINITY); |
63 | | assert!(f_logitf(-0.00123).is_nan()); |
64 | | assert!(f_logitf(f32::NAN).is_nan()); |
65 | | } |
66 | | } |