From 64c698567c27707f322d5130732eac1ee13ef7f6 Mon Sep 17 00:00:00 2001
From: Paul Dicker <pitdicker@gmail.com>
Date: Wed, 18 Apr 2018 06:54:15 +0200
Subject: [PATCH] Benchmark options

---
 benches/rayon.rs           | 61 ++++++++++++++++++++++++++++++++++++++
 src/distributions/rayon.rs |  5 +++-
 src/thread_rng.rs          | 16 ++++------
 3 files changed, 70 insertions(+), 12 deletions(-)
 create mode 100644 benches/rayon.rs

diff --git a/benches/rayon.rs b/benches/rayon.rs
new file mode 100644
index 00000000000..5195aafe8aa
--- /dev/null
+++ b/benches/rayon.rs
@@ -0,0 +1,61 @@
+#![feature(test)]
+
+extern crate test;
+extern crate rand;
+extern crate rayon;
+
+use test::{black_box, Bencher};
+
+use rand::{Rng, NewRng, XorShiftRng, thread_rng};
+use rand::distributions::*;
+
+use rayon::iter::{ParallelIterator, IntoParallelIterator};
+
+#[bench]
+fn gen_100_000_sequential(b: &mut Bencher) {
+    let mut rng = XorShiftRng::new();
+
+    b.iter(|| {
+        let vec: Vec<u32> = (0..100_000)
+            .into_iter()
+            .map(|_| { rng.gen::<u32>() })
+            .collect();
+        black_box(vec[0]);
+    });
+    b.bytes = 100_000 * 4;
+}
+
+#[bench]
+fn gen_100_000_sample_iter(b: &mut Bencher) {
+    let mut rng = XorShiftRng::new();
+
+    b.iter(|| {
+        let vec: Vec<u32> = rng.sample_iter(&Standard).take(100_000).collect();
+        black_box(vec[0]);
+    });
+    b.bytes = 100_000 * 4;
+}
+
+#[bench]
+fn gen_100_000_parallel(b: &mut Bencher) {
+    let mut rng = XorShiftRng::new();
+
+    b.iter(|| {
+        let vec: Vec<u32> = Standard.sample_par_iter(&mut rng, 100_000).collect();
+        black_box(vec[0]);
+    });
+    b.bytes = 100_000 * 4;
+}
+
+#[bench]
+fn gen_100_000_thread_local(b: &mut Bencher) {
+    b.iter(|| {
+
+        let vec: Vec<u32> = (0..100_000)
+            .into_par_iter()
+            .map(|_| { thread_rng().gen::<u32>() })
+            .collect();
+        black_box(vec[0]);
+    });
+    b.bytes = 100_000 * 4;
+}
diff --git a/src/distributions/rayon.rs b/src/distributions/rayon.rs
index 21f0ba05c0d..b4a9330be5d 100644
--- a/src/distributions/rayon.rs
+++ b/src/distributions/rayon.rs
@@ -145,13 +145,16 @@ impl<'a, D, R, T> Producer for DistProducer<'a, D, R, T>
         assert!(index <= self.amount);
         // Create a new PRNG of the same type, by seeding it with this PRNG.
         // `from_rng` should never fail.
-        let new = DistProducer {
+        let mut new = DistProducer {
             distr: self.distr,
             amount: self.amount - index,
             rng: R::from_rng(&mut self.rng).unwrap(),
             phantom: ::core::marker::PhantomData,
         };
         self.amount = index;
+
+        // emulate an expensive jump operation
+        for _ in 0..150 { let _ = new.rng.next_u32(); }
         (self, new)
     }
 
diff --git a/src/thread_rng.rs b/src/thread_rng.rs
index 1b93a8c2107..93f5426785b 100644
--- a/src/thread_rng.rs
+++ b/src/thread_rng.rs
@@ -13,8 +13,8 @@
 use std::cell::UnsafeCell;
 use std::rc::Rc;
 
-use {RngCore, CryptoRng, SeedableRng, EntropyRng};
-use prng::hc128::Hc128Core;
+use {RngCore, CryptoRng, SeedableRng, EntropyRng, NewRng};
+use prng::XorShiftRng;
 use {Distribution, Standard, Rng, Error};
 use reseeding::ReseedingRng;
 
@@ -53,18 +53,12 @@ const THREAD_RNG_RESEED_THRESHOLD: u64 = 32*1024*1024; // 32 MiB
 /// [`thread_rng`]: fn.thread_rng.html
 #[derive(Clone, Debug)]
 pub struct ThreadRng {
-    rng: Rc<UnsafeCell<ReseedingRng<Hc128Core, EntropyRng>>>,
+    rng: Rc<UnsafeCell<XorShiftRng>>,
 }
 
 thread_local!(
-    static THREAD_RNG_KEY: Rc<UnsafeCell<ReseedingRng<Hc128Core, EntropyRng>>> = {
-        let mut entropy_source = EntropyRng::new();
-        let r = Hc128Core::from_rng(&mut entropy_source).unwrap_or_else(|err|
-                panic!("could not initialize thread_rng: {}", err));
-        let rng = ReseedingRng::new(r,
-                                    THREAD_RNG_RESEED_THRESHOLD,
-                                    entropy_source);
-        Rc::new(UnsafeCell::new(rng))
+    static THREAD_RNG_KEY: Rc<UnsafeCell<XorShiftRng>> = {
+        Rc::new(UnsafeCell::new(XorShiftRng::new()))
     }
 );