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Diffstat (limited to 'vendor/rand_xoshiro/src/xoroshiro128plusplus.rs')
-rw-r--r-- | vendor/rand_xoshiro/src/xoroshiro128plusplus.rs | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/vendor/rand_xoshiro/src/xoroshiro128plusplus.rs b/vendor/rand_xoshiro/src/xoroshiro128plusplus.rs new file mode 100644 index 000000000..fcdd2710c --- /dev/null +++ b/vendor/rand_xoshiro/src/xoroshiro128plusplus.rs @@ -0,0 +1,126 @@ +// 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); + } + } +} |