From 8893408c30662713e7ea2664634880b8e053753b Mon Sep 17 00:00:00 2001
From: Josh Stone <cuviper@gmail.com>
Date: Wed, 7 Feb 2018 21:56:28 -0800
Subject: [PATCH] add a gcd benchmark

---
 Cargo.toml     |  3 ++
 benches/gcd.rs | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100755 benches/gcd.rs

diff --git a/Cargo.toml b/Cargo.toml
index 9eff655..241e6af 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,9 @@ readme = "README.md"
 [[bench]]
 name = "bigint"
 
+[[bench]]
+name = "gcd"
+
 [[bench]]
 harness = false
 name = "shootout-pidigits"
diff --git a/benches/gcd.rs b/benches/gcd.rs
new file mode 100755
index 0000000..695aee8
--- /dev/null
+++ b/benches/gcd.rs
@@ -0,0 +1,84 @@
+#![feature(test)]
+
+extern crate test;
+extern crate num_bigint;
+extern crate num_integer;
+extern crate num_traits;
+extern crate rand;
+
+use test::Bencher;
+use num_bigint::{BigUint, RandBigInt};
+use num_integer::Integer;
+use num_traits::Zero;
+use rand::{SeedableRng, StdRng};
+
+fn get_rng() -> StdRng {
+    let seed: &[_] = &[1, 2, 3, 4];
+    SeedableRng::from_seed(seed)
+}
+
+fn bench(b: &mut Bencher, bits: usize, gcd: fn(&BigUint, &BigUint) -> BigUint) {
+    let mut rng = get_rng();
+    let x = rng.gen_biguint(bits);
+    let y = rng.gen_biguint(bits);
+
+    assert_eq!(euclid(&x, &y), x.gcd(&y));
+
+    b.iter(|| gcd(&x, &y));
+}
+
+
+fn euclid(x: &BigUint, y: &BigUint) -> BigUint {
+    // Use Euclid's algorithm
+    let mut m = x.clone();
+    let mut n = y.clone();
+    while !m.is_zero() {
+        let temp = m;
+        m = n % &temp;
+        n = temp;
+    }
+    return n;
+}
+
+#[bench]
+fn gcd_euclid_0064(b: &mut Bencher) {
+    bench(b, 64, euclid);
+}
+
+#[bench]
+fn gcd_euclid_0256(b: &mut Bencher) {
+    bench(b, 256, euclid);
+}
+
+#[bench]
+fn gcd_euclid_1024(b: &mut Bencher) {
+    bench(b, 1024, euclid);
+}
+
+#[bench]
+fn gcd_euclid_4096(b: &mut Bencher) {
+    bench(b, 4096, euclid);
+}
+
+
+// Integer for BigUint now uses Stein for gcd
+
+#[bench]
+fn gcd_stein_0064(b: &mut Bencher) {
+    bench(b, 64, BigUint::gcd);
+}
+
+#[bench]
+fn gcd_stein_0256(b: &mut Bencher) {
+    bench(b, 256, BigUint::gcd);
+}
+
+#[bench]
+fn gcd_stein_1024(b: &mut Bencher) {
+    bench(b, 1024, BigUint::gcd);
+}
+
+#[bench]
+fn gcd_stein_4096(b: &mut Bencher) {
+    bench(b, 4096, BigUint::gcd);
+}