add a gcd benchmark

Cargo.toml

@@ -14,6 +14,9 @@ readme = "README.md"
 [[bench]]
 name = "bigint"
 
+[[bench]]
+name = "gcd"
+
 [[bench]]
 harness = false
 name = "shootout-pidigits"

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);
+}