1 files changed, 44 insertions, 0 deletions
diff --git a/third_party/rust/num-bigint/benches/factorial.rs b/third_party/rust/num-bigint/benches/factorial.rs
new file mode 100644
index 0000000000..4392df8319
--- /dev/null
+++ b/third_party/rust/num-bigint/benches/factorial.rs
@@ -0,0 +1,44 @@
+#![feature(test)]
+
+extern crate num_bigint;
+extern crate num_traits;
+extern crate test;
+
+use num_bigint::BigUint;
+use num_traits::One;
+use std::ops::{Div, Mul};
+use test::Bencher;
+
+#[bench]
+fn factorial_mul_biguint(b: &mut Bencher) {
+    b.iter(|| {
+        (1u32..1000)
+            .map(BigUint::from)
+            .fold(BigUint::one(), Mul::mul)
+    });
+}
+
+#[bench]
+fn factorial_mul_u32(b: &mut Bencher) {
+    b.iter(|| (1u32..1000).fold(BigUint::one(), Mul::mul));
+}
+
+// The division test is inspired by this blog comparison:
+// <https://tiehuis.github.io/big-integers-in-zig#division-test-single-limb>
+
+#[bench]
+fn factorial_div_biguint(b: &mut Bencher) {
+    let n: BigUint = (1u32..1000).fold(BigUint::one(), Mul::mul);
+    b.iter(|| {
+        (1u32..1000)
+            .rev()
+            .map(BigUint::from)
+            .fold(n.clone(), Div::div)
+    });
+}
+
+#[bench]
+fn factorial_div_u32(b: &mut Bencher) {
+    let n: BigUint = (1u32..1000).fold(BigUint::one(), Mul::mul);
+    b.iter(|| (1u32..1000).rev().fold(n.clone(), Div::div));
+}