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-rw-r--r-- | vendor/rand_xoshiro/src/xoshiro512plusplus.rs | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/vendor/rand_xoshiro/src/xoshiro512plusplus.rs b/vendor/rand_xoshiro/src/xoshiro512plusplus.rs new file mode 100644 index 000000000..3ae50b121 --- /dev/null +++ b/vendor/rand_xoshiro/src/xoshiro512plusplus.rs @@ -0,0 +1,137 @@ +// 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::fill_bytes_via_next; +use rand_core::le::read_u64_into; +use rand_core::{SeedableRng, RngCore, Error}; + +use crate::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 `xoshiro512plusplus.c` +/// reference source code](http://xoshiro.di.unimi.it/xoshiro512plusplus.c) by +/// David Blackman and Sebastiano Vigna. +#[derive(Debug, Clone, PartialEq, Eq)] +#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] +pub struct Xoshiro512PlusPlus { + s: [u64; 8], +} + +impl Xoshiro512PlusPlus { + /// Jump forward, equivalently to 2^256 calls to `next_u64()`. + /// + /// This can be used to generate 2^256 non-overlapping subsequences for + /// parallel computations. + /// + /// ``` + /// use rand_xoshiro::rand_core::SeedableRng; + /// use rand_xoshiro::Xoshiro512PlusPlus; + /// + /// let rng1 = Xoshiro512PlusPlus::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 + ]); + } + + /// Jump forward, equivalently to 2^384 calls to `next_u64()`. + /// + /// This can be used to generate 2^128 starting points, from each of which + /// `jump()` will generate 2^128 non-overlapping subsequences for parallel + /// distributed computations. + pub fn long_jump(&mut self) { + impl_jump!(u64, self, [ + 0x11467fef8f921d28, 0xa2a819f2e79c8ea8, 0xa8299fc284b3959a, + 0xb4d347340ca63ee1, 0x1cb0940bedbff6ce, 0xd956c5c4fa1f8e17, + 0x915e38fd4eda93bc, 0x5b3ccdfa5d7daca5 + ]); + } +} + + +impl SeedableRng for Xoshiro512PlusPlus { + type Seed = Seed512; + + /// Create a new `Xoshiro512PlusPlus`. If `seed` is entirely 0, it will be + /// mapped to a different seed. + #[inline] + fn from_seed(seed: Seed512) -> Xoshiro512PlusPlus { + deal_with_zero_seed!(seed, Self); + let mut state = [0; 8]; + read_u64_into(&seed.0, &mut state); + Xoshiro512PlusPlus { s: state } + } + + /// Seed a `Xoshiro512PlusPlus` from a `u64` using `SplitMix64`. + fn seed_from_u64(seed: u64) -> Xoshiro512PlusPlus { + from_splitmix!(seed) + } +} + +impl RngCore for Xoshiro512PlusPlus { + #[inline] + fn next_u32(&mut self) -> u32 { + // The lowest bits have some linear dependencies, so we use the + // upper bits instead. + (self.next_u64() >> 32) as u32 + } + + #[inline] + fn next_u64(&mut self) -> u64 { + let result_plusplus = plusplus_u64!(self.s[2], self.s[0], 17); + impl_xoshiro_large!(self); + result_plusplus + } + + #[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 = Xoshiro512PlusPlus::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/xoshiro512plusplus.c + let expected = [ + 524291, 1048578, 539099140, 3299073855497, 6917532603230064654, + 7494048333530275843, 14418333309547923463, 10960079161595355914, + 18279570946505382726, 10209173166699159237, + ]; + for &e in &expected { + assert_eq!(rng.next_u64(), e); + } + } +} |