/rust/registry/src/index.crates.io-1949cf8c6b5b557f/pxfm-0.1.27/src/err/inverfcf.rs
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1 | | /* |
2 | | * // Copyright (c) Radzivon Bartoshyk 8/2025. 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::err::inverff::erfinv_core; |
30 | | |
31 | | /// Complementary inverse error function |
32 | | /// |
33 | | /// Max ulp 0.5 |
34 | 0 | pub fn f_erfcinvf(x: f32) -> f32 { |
35 | 0 | let ix = x.to_bits(); |
36 | 0 | let ux = ix.wrapping_shl(1); |
37 | 0 | if ix >= 0x4000_0000u32 || ux == 0 { |
38 | 0 | if x.is_infinite() { |
39 | 0 | return f32::INFINITY; |
40 | 0 | } |
41 | 0 | if ux == 0 { |
42 | 0 | return f32::INFINITY; |
43 | 0 | } |
44 | | |
45 | 0 | if ix == 0x3f80_0000u32 { |
46 | 0 | return 0.; |
47 | 0 | } |
48 | | // x > 2 |
49 | 0 | if ix == 0x4000_0000u32 { |
50 | | // x == 2. |
51 | 0 | return f32::NEG_INFINITY; |
52 | 0 | } |
53 | 0 | return f32::NAN; // x == NaN, x < 0 |
54 | 0 | } |
55 | | |
56 | 0 | let z = x as f64; |
57 | | static SIGN: [f32; 2] = [1.0, -1.0]; |
58 | | // inferfc(x) = -inverf(1-x) |
59 | | // ax doesn't need to be extremely accurate, |
60 | | // it's just boundary detection so will do subtraction in f32 |
61 | 0 | erfinv_core(1. - z, (1. - x).abs().to_bits(), SIGN[(x > 1.) as usize]) |
62 | 0 | } |
63 | | |
64 | | #[cfg(test)] |
65 | | mod tests { |
66 | | use super::f_erfcinvf; |
67 | | |
68 | | #[test] |
69 | | fn m_test() { |
70 | | assert_eq!(f_erfcinvf(2.), f32::NEG_INFINITY); |
71 | | assert!(f_erfcinvf(-1.).is_nan()); |
72 | | assert_eq!(f_erfcinvf(0.), f32::INFINITY); |
73 | | assert!(f_erfcinvf(2.1).is_nan()); |
74 | | assert_eq!(f_erfcinvf(0.5), 0.47693628); |
75 | | assert_eq!(f_erfcinvf(1.5), -0.47693628); |
76 | | assert_eq!(f_erfcinvf(0.002), 2.1851242); |
77 | | assert_eq!(f_erfcinvf(1.002), -0.0017724329); |
78 | | assert!(f_erfcinvf(f32::NAN).is_nan()); |
79 | | } |
80 | | } |