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
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
|
// Copyright 2018 Developers of the Rand project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#[cfg(feature="serde1")] use serde::{Serialize, Deserialize};
use rand_core::le::read_u64_into;
use rand_core::impls::fill_bytes_via_next;
use rand_core::{RngCore, SeedableRng};
/// A xoroshiro128++ random number generator.
///
/// The xoroshiro128++ algorithm is not suitable for cryptographic purposes, but
/// is very fast and has excellent statistical properties.
///
/// The algorithm used here is translated from [the `xoroshiro128plusplus.c`
/// reference source code](http://xoshiro.di.unimi.it/xoroshiro128plusplus.c) by
/// David Blackman and Sebastiano Vigna.
#[allow(missing_copy_implementations)]
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
pub struct Xoroshiro128PlusPlus {
s0: u64,
s1: u64,
}
impl Xoroshiro128PlusPlus {
/// Jump forward, equivalently to 2^64 calls to `next_u64()`.
///
/// This can be used to generate 2^64 non-overlapping subsequences for
/// parallel computations.
///
/// ```
/// use rand_xoshiro::rand_core::SeedableRng;
/// use rand_xoshiro::Xoroshiro128PlusPlus;
///
/// let rng1 = Xoroshiro128PlusPlus::seed_from_u64(0);
/// let mut rng2 = rng1.clone();
/// rng2.jump();
/// let mut rng3 = rng2.clone();
/// rng3.jump();
/// ```
pub fn jump(&mut self) {
impl_jump!(u64, self, [0x2bd7a6a6e99c2ddc, 0x0992ccaf6a6fca05]);
}
/// Jump forward, equivalently to 2^96 calls to `next_u64()`.
///
/// This can be used to generate 2^32 starting points, from each of which
/// `jump()` will generate 2^32 non-overlapping subsequences for parallel
/// distributed computations.
pub fn long_jump(&mut self) {
impl_jump!(u64, self, [0x360fd5f2cf8d5d99, 0x9c6e6877736c46e3]);
}
}
impl RngCore for Xoroshiro128PlusPlus {
#[inline]
fn next_u32(&mut self) -> u32 {
self.next_u64() as u32
}
#[inline]
fn next_u64(&mut self) -> u64 {
let r = plusplus_u64!(self.s0, self.s1, 17);
impl_xoroshiro_u64_plusplus!(self);
r
}
#[inline]
fn fill_bytes(&mut self, dest: &mut [u8]) {
fill_bytes_via_next(self, dest);
}
#[inline]
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand_core::Error> {
self.fill_bytes(dest);
Ok(())
}
}
impl SeedableRng for Xoroshiro128PlusPlus {
type Seed = [u8; 16];
/// Create a new `Xoroshiro128PlusPlus`. If `seed` is entirely 0, it will be
/// mapped to a different seed.
fn from_seed(seed: [u8; 16]) -> Xoroshiro128PlusPlus {
deal_with_zero_seed!(seed, Self);
let mut s = [0; 2];
read_u64_into(&seed, &mut s);
Xoroshiro128PlusPlus {
s0: s[0],
s1: s[1],
}
}
/// Seed a `Xoroshiro128PlusPlus` from a `u64` using `SplitMix64`.
fn seed_from_u64(seed: u64) -> Xoroshiro128PlusPlus {
from_splitmix!(seed)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn reference() {
let mut rng = Xoroshiro128PlusPlus::from_seed(
[1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0]);
// These values were produced with the reference implementation:
// http://xoshiro.di.unimi.it/xoshiro128plusplus.c
let expected = [
393217, 669327710093319, 1732421326133921491, 11394790081659126983,
9555452776773192676, 3586421180005889563, 1691397964866707553,
10735626796753111697, 15216282715349408991, 14247243556711267923,
];
for &e in &expected {
assert_eq!(rng.next_u64(), e);
}
}
}
|
