rand_xoshiro/
xoshiro128plusplus.rs

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1// Copyright 2018 Developers of the Rand project.
2//
3// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
6// option. This file may not be copied, modified, or distributed
7// except according to those terms.
8
9#[cfg(feature="serde1")] use serde::{Serialize, Deserialize};
10use rand_core::impls::{next_u64_via_u32, fill_bytes_via_next};
11use rand_core::le::read_u32_into;
12use rand_core::{SeedableRng, RngCore, Error};
13
14/// A xoshiro128++ random number generator.
15///
16/// The xoshiro128++ algorithm is not suitable for cryptographic purposes, but
17/// is very fast and has excellent statistical properties.
18///
19/// The algorithm used here is translated from [the `xoshiro128plusplus.c`
20/// reference source code](http://xoshiro.di.unimi.it/xoshiro128plusplus.c) by
21/// David Blackman and Sebastiano Vigna.
22#[derive(Debug, Clone, PartialEq, Eq)]
23#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
24pub struct Xoshiro128PlusPlus {
25    s: [u32; 4],
26}
27
28impl Xoshiro128PlusPlus {
29    /// Jump forward, equivalently to 2^64 calls to `next_u32()`.
30    ///
31    /// This can be used to generate 2^64 non-overlapping subsequences for
32    /// parallel computations.
33    ///
34    /// ```
35    /// use rand_xoshiro::rand_core::SeedableRng;
36    /// use rand_xoshiro::Xoroshiro128PlusPlus;
37    ///
38    /// let rng1 = Xoroshiro128PlusPlus::seed_from_u64(0);
39    /// let mut rng2 = rng1.clone();
40    /// rng2.jump();
41    /// let mut rng3 = rng2.clone();
42    /// rng3.jump();
43    /// ```
44    pub fn jump(&mut self) {
45        impl_jump!(u32, self, [0x8764000b, 0xf542d2d3, 0x6fa035c3, 0x77f2db5b]);
46    }
47
48    /// Jump forward, equivalently to 2^96 calls to `next_u32()`.
49    ///
50    /// This can be used to generate 2^32 starting points, from each of which
51    /// `jump()` will generate 2^32 non-overlapping subsequences for parallel
52    /// distributed computations.
53    pub fn long_jump(&mut self) {
54        impl_jump!(u32, self, [0xb523952e, 0x0b6f099f, 0xccf5a0ef, 0x1c580662]);
55    }
56}
57
58impl SeedableRng for Xoshiro128PlusPlus {
59    type Seed = [u8; 16];
60
61    /// Create a new `Xoshiro128PlusPlus`.  If `seed` is entirely 0, it will be
62    /// mapped to a different seed.
63    #[inline]
64    fn from_seed(seed: [u8; 16]) -> Xoshiro128PlusPlus {
65        deal_with_zero_seed!(seed, Self);
66        let mut state = [0; 4];
67        read_u32_into(&seed, &mut state);
68        Xoshiro128PlusPlus { s: state }
69    }
70
71    /// Seed a `Xoshiro128PlusPlus` from a `u64` using `SplitMix64`.
72    fn seed_from_u64(seed: u64) -> Xoshiro128PlusPlus {
73        from_splitmix!(seed)
74    }
75}
76
77impl RngCore for Xoshiro128PlusPlus {
78    #[inline]
79    fn next_u32(&mut self) -> u32 {
80        let result_starstar = plusplus_u32!(self.s[0], self.s[3]);
81        impl_xoshiro_u32!(self);
82        result_starstar
83    }
84
85    #[inline]
86    fn next_u64(&mut self) -> u64 {
87        next_u64_via_u32(self)
88    }
89
90    #[inline]
91    fn fill_bytes(&mut self, dest: &mut [u8]) {
92        fill_bytes_via_next(self, dest);
93    }
94
95    #[inline]
96    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
97        self.fill_bytes(dest);
98        Ok(())
99    }
100}
101
102#[cfg(test)]
103mod tests {
104    use super::*;
105
106    #[test]
107    fn reference() {
108        let mut rng = Xoshiro128PlusPlus::from_seed(
109            [1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0]);
110        // These values were produced with the reference implementation:
111        // http://xoshiro.di.unimi.it/xoshiro128plusplus.c
112        let expected = [
113            641, 1573767, 3222811527, 3517856514, 836907274, 4247214768,
114            3867114732, 1355841295, 495546011, 621204420,
115        ];
116        for &e in &expected {
117            assert_eq!(rng.next_u32(), e);
118        }
119    }
120}
rand_xoshiro/xoshiro128plusplus.rs

rand_xoshiro/
xoshiro128plusplus.rs
