neurons/
random.rs

1// Copyright (C) 2024 Hallvard Høyland Lavik
2
3/// A linear congruential generator. [Source.](https://en.wikipedia.org/wiki/Linear_congruential_generator)
4///
5/// # Formula
6///
7/// * `X_{n+1} = (multiplier * X_n + increment) % modulus`
8/// * `value = (X_{n+1} / (modulus - 1)) * (min - max) + min`
9///
10/// # Attributes
11///
12/// * `seed` - The initial value.
13/// * `modulus` - The modulus.
14/// * `multiplier` - The multiplier.
15/// * `increment` - The increment.
16/// * `current` - The current value.
17pub struct Generator {
18    modulus: u64,
19    multiplier: u64,
20    increment: u64,
21
22    current: u64,
23}
24
25impl Generator {
26    /// Creates a new linear congruential generator using C++11's `minstd_rand` parameters.
27    ///
28    /// # Arguments
29    ///
30    /// * `seed` - The initial value.
31    /// * `modulus` - The modulus.
32    /// * `multiplier` - The multiplier.
33    /// * `increment` - The increment.
34    /// * `current` - The current value.
35    ///
36    /// # Returns
37    ///
38    /// A new linear congruential generator.
39    pub fn create(seed: u64) -> Self {
40        Self {
41            modulus: 2u64.pow(31) - 1,
42            multiplier: 48271,
43            increment: 0,
44            current: seed,
45        }
46    }
47
48    /// Generates the next random number.
49    ///
50    /// # Formula
51    ///
52    /// * `X_{n+1} = (aX_n + c) mod m`
53    /// * `value = X_{n+1} / (m - 1) * (min - max) + min`
54    ///
55    /// # Returns
56    ///
57    /// The next random number (`value`).
58    pub fn generate(&mut self, min: f32, max: f32) -> f32 {
59        self.current = (self.multiplier * self.current + self.increment) % self.modulus;
60
61        (self.current as f32 / (self.modulus - 1) as f32) * (max - min) + min
62    }
63
64    /// Shuffles the given values inplace.
65    ///
66    /// # Arguments
67    ///
68    /// * `values` - The values to shuffle.
69    ///
70    /// # Example
71    ///
72    /// ```
73    /// use neurons::random;
74    ///
75    /// let mut generator = random::Generator::create(12345);
76    /// let mut values = vec![1, 2, 3, 4, 5];
77    /// generator.shuffle(&mut values);
78    /// println!("{:?}", values);
79    /// ```
80    pub fn shuffle(&mut self, values: &mut Vec<usize>) {
81        for i in 0..values.len() {
82            let j = self.generate(0.0, values.len() as f32) as usize;
83            values.swap(i, j);
84        }
85    }
86}
neurons/random.rs

neurons/
random.rs
