| // 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 good statistical properties, besides a low linear |
| /// complexity in the lowest bits. |
| /// |
| /// The algorithm used here is translated from [the `xoshiro512plus.c` |
| /// reference source code](http://xoshiro.di.unimi.it/xoshiro512plus.c) by |
| /// David Blackman and Sebastiano Vigna. |
| #[derive(Debug, Clone)] |
| #[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] |
| pub struct Xoshiro512Plus { |
| s: [u64; 8], |
| } |
| |
| impl Xoshiro512Plus { |
| /// 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::Xoshiro512Plus; |
| /// |
| /// let rng1 = Xoshiro512Plus::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 Xoshiro512Plus { |
| type Seed = Seed512; |
| |
| /// Create a new `Xoshiro512Plus`. If `seed` is entirely 0, it will be |
| /// mapped to a different seed. |
| #[inline] |
| fn from_seed(seed: Seed512) -> Xoshiro512Plus { |
| deal_with_zero_seed!(seed, Self); |
| let mut state = [0; 8]; |
| read_u64_into(&seed.0, &mut state); |
| Xoshiro512Plus { s: state } |
| } |
| |
| /// Seed a `Xoshiro512Plus` from a `u64` using `SplitMix64`. |
| fn seed_from_u64(seed: u64) -> Xoshiro512Plus { |
| from_splitmix!(seed) |
| } |
| } |
| |
| impl RngCore for Xoshiro512Plus { |
| #[inline] |
| fn next_u32(&mut self) -> u32 { |
| self.next_u64() as u32 |
| } |
| |
| #[inline] |
| fn next_u64(&mut self) -> u64 { |
| let result_plus = self.s[0].wrapping_add(self.s[2]); |
| impl_xoshiro_large!(self); |
| result_plus |
| } |
| |
| #[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 = Xoshiro512Plus::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/xoshiro512plus.c |
| let expected = [ |
| 4, 8, 4113, 25169936, 52776585412635, 57174648719367, |
| 9223482039571869716, 9331471677901559830, 9340533895746033672, |
| 14078399799840753678, |
| ]; |
| for &e in &expected { |
| assert_eq!(rng.next_u64(), e); |
| } |
| } |
| } |