implement xorshift128+

Author: arthurprs

benches/bench.rs

@@ -3,64 +3,52 @@
 extern crate test;
 extern crate rand;
 
-const RAND_BENCH_N: u64 = 100;
-
 mod distributions;
 
-use std::mem::size_of;
-use test::{black_box, Bencher};
-use rand::{XorShiftRng, StdRng, IsaacRng, Isaac64Rng, Rng};
-use rand::{OsRng, weak_rng};
+use test::Bencher;
+use rand::{weak_rng, Rng};
 
-#[bench]
-fn rand_xorshift(b: &mut Bencher) {
-    let mut rng: XorShiftRng = OsRng::new().unwrap().gen();
-    b.iter(|| {
-        for _ in 0..RAND_BENCH_N {
-            black_box(rng.gen::<usize>());
-        }
-    });
-    b.bytes = size_of::<usize>() as u64 * RAND_BENCH_N;
-}
-
-#[bench]
-fn rand_isaac(b: &mut Bencher) {
-    let mut rng: IsaacRng = OsRng::new().unwrap().gen();
-    b.iter(|| {
-        for _ in 0..RAND_BENCH_N {
-            black_box(rng.gen::<usize>());
-        }
-    });
-    b.bytes = size_of::<usize>() as u64 * RAND_BENCH_N;
-}
-
-#[bench]
-fn rand_isaac64(b: &mut Bencher) {
-    let mut rng: Isaac64Rng = OsRng::new().unwrap().gen();
-    b.iter(|| {
-        for _ in 0..RAND_BENCH_N {
-            black_box(rng.gen::<usize>());
-        }
-    });
-    b.bytes = size_of::<usize>() as u64 * RAND_BENCH_N;
-}
-
-#[bench]
-fn rand_std(b: &mut Bencher) {
-    let mut rng = StdRng::new().unwrap();
-    b.iter(|| {
-        for _ in 0..RAND_BENCH_N {
-            black_box(rng.gen::<usize>());
-        }
-    });
-    b.bytes = size_of::<usize>() as u64 * RAND_BENCH_N;
-}
+pub const RAND_BENCH_N: u64 = 100;
 
 #[bench]
 fn rand_shuffle_100(b: &mut Bencher) {
     let mut rng = weak_rng();
     let x : &mut [usize] = &mut [1; 100];
     b.iter(|| {
-        rng.shuffle(x);
+        rng.shuffle(x)
     })
 }
+
+mod algorithms {
+    use test::{black_box, Bencher};
+    use std::mem::size_of;
+    use rand::{OsRng, XorShift64Rng, XorShift128PRng, IsaacRng, Isaac64Rng, Rng, ChaChaRng};
+
+    use super::*;
+
+    macro_rules! impl_bench {
+        ($result_ty: ty: $fn_name: ident, $hasher: ident) => (
+            #[bench]
+            fn $fn_name(b: &mut Bencher) {
+                let mut rng: $hasher = OsRng::new().unwrap().gen();
+                b.iter(|| {
+                    for _ in 0..RAND_BENCH_N {
+                        black_box(rng.gen::<$result_ty>());
+                    }
+                });
+                b.bytes = size_of::<$result_ty>() as u64 * RAND_BENCH_N;
+            }
+        )
+    }
+
+    impl_bench!(u32: xorshift_u32, XorShift64Rng);
+    impl_bench!(u64: xorshift_u64, XorShift64Rng);
+    impl_bench!(u32: xorshiftp_u32, XorShift128PRng);
+    impl_bench!(u64: xorshiftp_u64, XorShift128PRng);
+    impl_bench!(u32: isaac_u32, IsaacRng);
+    impl_bench!(u64: isaac_u64, IsaacRng);
+    impl_bench!(u32: isaac64_u32, Isaac64Rng);
+    impl_bench!(u64: isaac64_u64, Isaac64Rng);
+    impl_bench!(u32: chacha_u32, ChaChaRng);
+    impl_bench!(u64: chacha_u64, ChaChaRng);
+}

src/lib.rs

@@ -254,18 +254,25 @@ pub use os::OsRng;
 
 pub use isaac::{IsaacRng, Isaac64Rng};
 pub use chacha::ChaChaRng;
+pub use xorshift::{XorShift64Rng, XorShift128PRng};
 
 #[cfg(target_pointer_width = "32")]
 use IsaacRng as IsaacWordRng;
 #[cfg(target_pointer_width = "64")]
 use Isaac64Rng as IsaacWordRng;
 
+#[cfg(target_pointer_width = "32")]
+use XorShift64Rng as InnerWeakRng;
+#[cfg(target_pointer_width = "64")]
+use XorShift128PRng as InnerWeakRng;
+
 use distributions::{Range, IndependentSample};
 use distributions::range::SampleRange;
 
 pub mod distributions;
 pub mod isaac;
 pub mod chacha;
+pub mod xorshift;
 pub mod reseeding;
 mod rand_impls;
 pub mod os;
@@ -598,93 +605,6 @@ pub trait SeedableRng<Seed>: Rng {
     fn from_seed(seed: Seed) -> Self;
 }
 
-/// An Xorshift[1] random number
-/// generator.
-///
-/// The Xorshift algorithm is not suitable for cryptographic purposes
-/// but is very fast. If you do not know for sure that it fits your
-/// requirements, use a more secure one such as `IsaacRng` or `OsRng`.
-///
-/// [1]: Marsaglia, George (July 2003). ["Xorshift
-/// RNGs"](http://www.jstatsoft.org/v08/i14/paper). *Journal of
-/// Statistical Software*. Vol. 8 (Issue 14).
-#[allow(missing_copy_implementations)]
-#[derive(Clone)]
-pub struct XorShiftRng {
-    x: w32,
-    y: w32,
-    z: w32,
-    w: w32,
-}
-
-impl XorShiftRng {
-    /// Creates a new XorShiftRng instance which is not seeded.
-    ///
-    /// The initial values of this RNG are constants, so all generators created
-    /// by this function will yield the same stream of random numbers. It is
-    /// highly recommended that this is created through `SeedableRng` instead of
-    /// this function
-    pub fn new_unseeded() -> XorShiftRng {
-        XorShiftRng {
-            x: w(0x193a6754),
-            y: w(0xa8a7d469),
-            z: w(0x97830e05),
-            w: w(0x113ba7bb),
-        }
-    }
-}
-
-impl Rng for XorShiftRng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        let x = self.x;
-        let t = x ^ (x << 11);
-        self.x = self.y;
-        self.y = self.z;
-        self.z = self.w;
-        let w_ = self.w;
-        self.w = w_ ^ (w_ >> 19) ^ (t ^ (t >> 8));
-        self.w.0
-    }
-}
-
-impl SeedableRng<[u32; 4]> for XorShiftRng {
-    /// Reseed an XorShiftRng. This will panic if `seed` is entirely 0.
-    fn reseed(&mut self, seed: [u32; 4]) {
-        assert!(!seed.iter().all(|&x| x == 0),
-                "XorShiftRng.reseed called with an all zero seed.");
-
-        self.x = w(seed[0]);
-        self.y = w(seed[1]);
-        self.z = w(seed[2]);
-        self.w = w(seed[3]);
-    }
-
-    /// Create a new XorShiftRng. This will panic if `seed` is entirely 0.
-    fn from_seed(seed: [u32; 4]) -> XorShiftRng {
-        assert!(!seed.iter().all(|&x| x == 0),
-                "XorShiftRng::from_seed called with an all zero seed.");
-
-        XorShiftRng {
-            x: w(seed[0]),
-            y: w(seed[1]),
-            z: w(seed[2]),
-            w: w(seed[3]),
-        }
-    }
-}
-
-impl Rand for XorShiftRng {
-    fn rand<R: Rng>(rng: &mut R) -> XorShiftRng {
-        let mut tuple: (u32, u32, u32, u32) = rng.gen();
-        while tuple == (0, 0, 0, 0) {
-            tuple = rng.gen();
-        }
-        let (x, y, z, w_) = tuple;
-        XorShiftRng { x: w(x), y: w(y), z: w(z), w: w(w_) }
-    }
-}
-
 /// A wrapper for generating floating point numbers uniformly in the
 /// open interval `(0,1)` (not including either endpoint).
 ///
@@ -766,6 +686,25 @@ impl<'a> SeedableRng<&'a [usize]> for StdRng {
     }
 }
 
+/// The standard RNG. This is designed to be efficient on the current
+/// platform.
+#[derive(Copy, Clone)]
+pub struct WeakRng {
+    rng: InnerWeakRng,
+}
+
+impl Rng for WeakRng {
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        self.rng.next_u32()
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        self.rng.next_u64()
+    }
+}
+
 /// Create a weak random number generator with a default algorithm and seed.
 ///
 /// It returns the fastest `Rng` algorithm currently available in Rust without
@@ -775,9 +714,9 @@ impl<'a> SeedableRng<&'a [usize]> for StdRng {
 ///
 /// This will read randomness from the operating system to seed the
 /// generator.
-pub fn weak_rng() -> XorShiftRng {
+pub fn weak_rng() -> WeakRng {
     match OsRng::new() {
-        Ok(mut r) => r.gen(),
+        Ok(mut os_rnd) => WeakRng { rng: os_rnd.gen() },
         Err(e) => panic!("weak_rng: failed to create seeded RNG: {:?}", e)
     }
 }