Merge branch 'num-bigint-0.1.x' into master

Cargo.toml

@@ -15,6 +15,9 @@ readme = "README.md"
 [[bench]]
 name = "bigint"
 
+[[bench]]
+name = "factorial"
+
 [[bench]]
 name = "gcd"
 

RELEASES.md

@@ -9,6 +9,16 @@
 [8]: https://github.com/rust-num/num-bigint/pull/8
 [23]: https://github.com/rust-num/num-bigint/pull/23
 
+# Release 0.1.44
+
+- [Division with single-digit divisors is now much faster.][42]
+- The README now compares [`ramp`, `rug`, `rust-gmp`][20], and [`apint`][21].
+
+**Contributors**: @cuviper, @Robbepop
+
+[20]: https://github.com/rust-num/num-bigint/pull/20
+[21]: https://github.com/rust-num/num-bigint/pull/21
+[42]: https://github.com/rust-num/num-bigint/pull/42
 
 # Release 0.1.43
 

benches/factorial.rs

@@ -0,0 +1,35 @@
+#![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));
+}

src/algorithms.rs

@@ -424,9 +424,13 @@ pub fn div_rem(u: &BigUint, d: &BigUint) -> (BigUint, BigUint) {
     if u.is_zero() {
         return (Zero::zero(), Zero::zero());
     }
-    if *d == One::one() {
+    if d.data == [1] {
         return (u.clone(), Zero::zero());
     }
+    if d.data.len() == 1 {
+        let (div, rem) = div_rem_digit(u.clone(), d.data[0]);
+        return (div, rem.into());
+    }
 
     // Required or the q_len calculation below can underflow:
     match u.cmp(d) {