1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
/*
* // Copyright (c) Radzivon Bartoshyk 4/2025. All rights reserved.
* //
* // Redistribution and use in source and binary forms, with or without modification,
* // are permitted provided that the following conditions are met:
* //
* // 1. Redistributions of source code must retain the above copyright notice, this
* // list of conditions and the following disclaimer.
* //
* // 2. Redistributions in binary form must reproduce the above copyright notice,
* // this list of conditions and the following disclaimer in the documentation
* // and/or other materials provided with the distribution.
* //
* // 3. Neither the name of the copyright holder nor the names of its
* // contributors may be used to endorse or promote products derived from
* // this software without specific prior written permission.
* //
* // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/// Computes Square root.
/// Most of CPU have built-in instruction with higher precision,
/// prefer use this only for const contexts.
#[inline]
pub const fn sqrtf(d: f32) -> f32 {
let mut q = 0.5f32;
let mut d = if d < 0f32 { f32::NAN } else { d };
if d < 5.2939559203393770e-23f32 {
d *= 1.8889465931478580e+22f32;
q = 7.2759576141834260e-12f32;
}
if d > 1.8446744073709552e+19f32 {
d *= 5.4210108624275220e-20f32;
q = 4294967296.0f32;
}
// http://en.wikipedia.org/wiki/Fast_inverse_square_root
let mut x = f32::from_bits(0x5f375a86 - ((d + 1e-45).to_bits() >> 1)) as f64;
x = x * (1.5 - 0.5 * (d as f64) * x * x);
x = x * (1.5 - 0.5 * (d as f64) * x * x);
x = x * (1.5 - 0.5 * (d as f64) * x * x) * (d as f64);
let d2 = ((d as f64) + x * x) * (1. / x);
if d.is_infinite() {
return f32::INFINITY;
}
(d2 * q as f64) as f32
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn sqrtf_test() {
assert!(
(sqrtf(4f32) - 2f32).abs() < 1e-6,
"Invalid result {}",
sqrtf(4f32)
);
assert!(
(sqrtf(9f32) - 3f32).abs() < 1e-6,
"Invalid result {}",
sqrtf(9f32)
);
println!("{}", sqrtf(4f32));
println!("{}", sqrtf(9f32));
println!("{}", sqrtf(12f32));
println!("{}", sqrtf(25f32));
}
}