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
|
// 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.
use rand_core::impls::fill_bytes_via_next;
use rand_core::le::read_u64_into;
use rand_core::{SeedableRng, RngCore, Error};
use Seed512;
/// A xoshiro512** random number generator.
///
/// The xoshiro512** algorithm is not suitable for cryptographic purposes, but
/// is very fast and has excellent statistical properties.
///
/// The algorithm used here is translated from [the `xoshiro512starstar.c`
/// reference source code](http://xoshiro.di.unimi.it/xoshiro512starstar.c) by
/// David Blackman and Sebastiano Vigna.
#[derive(Debug, Clone)]
pub struct Xoshiro512StarStar {
s: [u64; 8],
}
impl Xoshiro512StarStar {
/// Jump forward, equivalently to 2^256 calls to `next_u64()`.
///
/// This can be used to generate 2^256 non-overlapping subsequences for
/// parallel computations.
///
/// ```
/// # extern crate rand;
/// # extern crate rand_xoshiro;
/// # fn main() {
/// use rand::SeedableRng;
/// use rand_xoshiro::Xoshiro512StarStar;
///
/// let rng1 = Xoshiro512StarStar::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, [
0x33ed89b6e7a353f9, 0x760083d7955323be, 0x2837f2fbb5f22fae,
0x4b8c5674d309511c, 0xb11ac47a7ba28c25, 0xf1be7667092bcc1c,
0x53851efdb6df0aaf, 0x1ebbc8b23eaf25db
]);
}
}
impl SeedableRng for Xoshiro512StarStar {
type Seed = Seed512;
/// Create a new `Xoshiro512StarStar`. If `seed` is entirely 0, it will be
/// mapped to a different seed.
#[inline]
fn from_seed(seed: Seed512) -> Xoshiro512StarStar {
deal_with_zero_seed!(seed, Self);
let mut state = [0; 8];
read_u64_into(&seed.0, &mut state);
Xoshiro512StarStar { s: state }
}
/// Seed a `Xoshiro512StarStar` from a `u64` using `SplitMix64`.
fn seed_from_u64(seed: u64) -> Xoshiro512StarStar {
from_splitmix!(seed)
}
}
impl RngCore for Xoshiro512StarStar {
#[inline]
fn next_u32(&mut self) -> u32 {
self.next_u64() as u32
}
#[inline]
fn next_u64(&mut self) -> u64 {
let result_starstar = starstar_u64!(self.s[1]);
impl_xoshiro_large!(self);
result_starstar
}
#[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<(), Error> {
self.fill_bytes(dest);
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn reference() {
let mut rng = Xoshiro512StarStar::from_seed(Seed512(
[1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0,
3, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0,
5, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0,
7, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0]));
// These values were produced with the reference implementation:
// http://xoshiro.di.unimi.it/xoshiro512starstar.c
let expected = [
11520, 0, 23040, 23667840, 144955163520, 303992986974289920,
25332796375735680, 296904390158016, 13911081092387501979,
15304787717237593024,
];
for &e in &expected {
assert_eq!(rng.next_u64(), e);
}
}
}
|
