Canon uniform benches

Cargo.toml

@@ -54,6 +54,11 @@ small_rng = []
 # using min-const-generics
 min_const_gen = []
 
+# Option: use unbiased sampling. By default, bias affecting no more than one in
+# 2^48 samples (for uniform distributions) is accepted.
+# Note: enabling this option is expected to affect reproducibility of results.
+unbiased = []
+
 [workspace]
 members = [
     "rand_core",
@@ -80,6 +85,12 @@ features = ["into_bits"]
 libc = { version = "0.2.22", optional = true, default-features = false }
 
 [dev-dependencies]
+criterion = "0.4.0"
+num-traits = "0.2.14"
 rand_pcg = { path = "rand_pcg", version = "0.3.0" }
 # Only to test serde1
 bincode = "1.2.1"
+
+[[bench]]
+name = "uniform"
+harness = false

benches/uniform.rs

@@ -0,0 +1,78 @@
+// Copyright 2021 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.
+
+//! Implement benchmarks for uniform distributions over integer types
+
+use core::time::Duration;
+use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
+use rand::distributions::uniform::{SampleRange, Uniform};
+use rand::prelude::*;
+use rand_chacha::ChaCha8Rng;
+use rand_pcg::{Pcg32, Pcg64};
+
+const WARM_UP_TIME: Duration = Duration::from_millis(1000);
+const MEASUREMENT_TIME: Duration = Duration::from_secs(3);
+const SAMPLE_SIZE: usize = 100_000;
+const N_RESAMPLES: usize = 10_000;
+
+macro_rules! sample {
+    ($R:ty, $T:ty, $U:ty, $g:expr) => {
+        $g.bench_function(BenchmarkId::new(stringify!($R), "single"), |b| {
+            let mut rng = <$R>::from_entropy();
+            let x = rng.gen::<$U>();
+            let bits = (<$T>::BITS / 2);
+            let mask = (1 as $U).wrapping_neg() >> bits;
+            let range = (x >> bits) * (x & mask);
+            let low = <$T>::MIN;
+            let high = low.wrapping_add(range as $T);
+
+            b.iter(|| (low..=high).sample_single(&mut rng));
+        });
+
+        $g.bench_function(BenchmarkId::new(stringify!($R), "distr"), |b| {
+            let mut rng = <$R>::from_entropy();
+            let x = rng.gen::<$U>();
+            let bits = (<$T>::BITS / 2);
+            let mask = (1 as $U).wrapping_neg() >> bits;
+            let range = (x >> bits) * (x & mask);
+            let low = <$T>::MIN;
+            let high = low.wrapping_add(range as $T);
+            let dist = Uniform::<$T>::new_inclusive(<$T>::MIN, high);
+
+            b.iter(|| dist.sample(&mut rng));
+        });
+    };
+
+    ($c:expr, $T:ty, $U:ty) => {{
+        let mut g = $c.benchmark_group(concat!("sample", stringify!($T)));
+        g.sample_size(SAMPLE_SIZE);
+        g.warm_up_time(WARM_UP_TIME);
+        g.measurement_time(MEASUREMENT_TIME);
+        g.nresamples(N_RESAMPLES);
+        sample!(SmallRng, $T, $U, g);
+        sample!(ChaCha8Rng, $T, $U, g);
+        sample!(Pcg32, $T, $U, g);
+        sample!(Pcg64, $T, $U, g);
+        g.finish();
+    }};
+}
+
+fn sample(c: &mut Criterion) {
+    sample!(c, i8, u8);
+    sample!(c, i16, u16);
+    sample!(c, i32, u32);
+    sample!(c, i64, u64);
+    sample!(c, i128, u128);
+}
+
+criterion_group! {
+    name = benches;
+    config = Criterion::default();
+    targets = sample
+}
+criterion_main!(benches);