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Diffstat (limited to 'vendor/rand_xoshiro/src/xoshiro128starstar.rs')
| -rw-r--r-- | vendor/rand_xoshiro/src/xoshiro128starstar.rs | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/vendor/rand_xoshiro/src/xoshiro128starstar.rs b/vendor/rand_xoshiro/src/xoshiro128starstar.rs new file mode 100644 index 000000000..893d2428f --- /dev/null +++ b/vendor/rand_xoshiro/src/xoshiro128starstar.rs @@ -0,0 +1,120 @@ +// 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::impls::{next_u64_via_u32, fill_bytes_via_next}; +use rand_core::le::read_u32_into; +use rand_core::{SeedableRng, RngCore, Error}; + +/// A xoshiro128** random number generator. +/// +/// The xoshiro128** algorithm is not suitable for cryptographic purposes, but +/// is very fast and has excellent statistical properties. +/// +/// The algorithm used here is translated from [the `xoshiro128starstar.c` +/// reference source code](http://xoshiro.di.unimi.it/xoshiro128starstar.c) by +/// David Blackman and Sebastiano Vigna. +#[derive(Debug, Clone, PartialEq, Eq)] +#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] +pub struct Xoshiro128StarStar { + s: [u32; 4], +} + +impl Xoshiro128StarStar { + /// Jump forward, equivalently to 2^64 calls to `next_u32()`. + /// + /// This can be used to generate 2^64 non-overlapping subsequences for + /// parallel computations. + /// + /// ``` + /// use rand_xoshiro::rand_core::SeedableRng; + /// use rand_xoshiro::Xoroshiro128StarStar; + /// + /// let rng1 = Xoroshiro128StarStar::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!(u32, self, [0x8764000b, 0xf542d2d3, 0x6fa035c3, 0x77f2db5b]); + } + + /// Jump forward, equivalently to 2^96 calls to `next_u32()`. + /// + /// 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!(u32, self, [0xb523952e, 0x0b6f099f, 0xccf5a0ef, 0x1c580662]); + } +} + +impl SeedableRng for Xoshiro128StarStar { + type Seed = [u8; 16]; + + /// Create a new `Xoshiro128StarStar`. If `seed` is entirely 0, it will be + /// mapped to a different seed. + #[inline] + fn from_seed(seed: [u8; 16]) -> Xoshiro128StarStar { + deal_with_zero_seed!(seed, Self); + let mut state = [0; 4]; + read_u32_into(&seed, &mut state); + Xoshiro128StarStar { s: state } + } + + /// Seed a `Xoshiro128StarStar` from a `u64` using `SplitMix64`. + fn seed_from_u64(seed: u64) -> Xoshiro128StarStar { + from_splitmix!(seed) + } +} + +impl RngCore for Xoshiro128StarStar { + #[inline] + fn next_u32(&mut self) -> u32 { + let result_starstar = starstar_u64!(self.s[1]); + impl_xoshiro_u32!(self); + result_starstar + } + + #[inline] + fn next_u64(&mut self) -> u64 { + next_u64_via_u32(self) + } + + #[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 = Xoshiro128StarStar::from_seed( + [1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0]); + // These values were produced with the reference implementation (v1.1): + // http://xoshiro.di.unimi.it/xoshiro128starstar.c + let expected = [ + 11520, 0, 5927040, 70819200, 2031721883, 1637235492, 1287239034, + 3734860849, 3729100597, 4258142804, + ]; + for &e in &expected { + assert_eq!(rng.next_u32(), e); + } + } +} |