It was pointed out in the blog post [Big Integers in Zig] that we don't
have a special case in `num-bigint` for single-digit divisors. While
you can already get this optimization by dividing directly by `u32`,
it's easy to make small `BigUint` divisors work like this too.
$ cargo benchcmp baseline single-div
name baseline ns/iter single-div ns/iter diff ns/iter diff % speedup
factorial_div_biguint 5,638,353 1,005,488 -4,632,865 -82.17% x 5.61
`BigInt` will also gain from this, since it uses `BigUint` division
internally.
Running [zig-bn's facdiv-rs] shows a nice improvement too. My i7-7700K
with Rust 1.26 goes from 4.15 seconds to just 0.65 -- a 6.38x speedup!
[Big Integers in Zig]: https://tiehuis.github.io/big-integers-in-zig#division-test-single-limb
[zig-bn's facdiv-rs]: https://github.com/tiehuis/zig-bn/tree/master/bench/facdiv/crate-facdiv-rs
Serde 0.7 dropped it's dependency on num, so this patch moves
the implementations here. For the sake of a better implementation,
this just serializes BigUint as a `Vec<u32>`, `BigInt` as a
`(u8, Vec<u32>)`, `Complex<T>` as a `(T, T)`, and `Ratio<T>`
as a `(T, T)`.
Previously, the `rand` and `rustc-serialize` dependencies were optional
except they were required for the `bigint` feature.
Make the dependency on the `rand` crate optional in all cases.
including when the `bigint` feature is selected. Some of the tests for
the bigint feature are randomized so, while `rand` is now an optional
dependency, it is a non-optional dev-dependency.
Similarly, make the dependency on the `rustc-serialize` crate optional
in all cases, including when the `bigint` feature is selected.
