1 files changed, 124 insertions, 0 deletions
diff --git a/rand/rand_xoshiro/src/xoshiro512plus.rs b/rand/rand_xoshiro/src/xoshiro512plus.rs
new file mode 100644
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+++ b/rand/rand_xoshiro/src/xoshiro512plus.rs
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+// 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 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)]
+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.
+    ///
+    /// ```
+    /// # extern crate rand;
+    /// # extern crate rand_xoshiro;
+    /// # fn main() {
+    /// use rand::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
+        ]);
+    }
+}
+
+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);
+        }
+    }
+}