twibint

Rust crate for arbitrarily big integers, signed or unsigned.

This crate does not need any dependency, and relies only on the standard library. Some dependencies are optional, depending on a specific feature (see list of features below).

The main API of this crate is to export 2 types: BigUint and BigInt, meant to represent unsigned or signed integers of arbitrarily large absolute value. They are meant to be used in almost any way a regular integer can be used, though they don't implement the Copy trait.

Build, documentation, benchmarks and tests are available the usual way calling the following:

cargo build
cargo docs
cargo bench --features=rand
cargo test

For benchmarks specifically, you might want to call only some of these:

cargo bench mul --features=rand
cargo bench add --features=rand
cargo bench sub --features=rand

Benchmarks won't compile/run without the rand feature enabled.

Performance

The ambitious and naive goal of this project is to be as performant or better than any state of the art crate on these methods.

I choose to compare myself to num-bigint first, as it's quite standard at this point.

Today, on x86, twibint is faster than num-bigint v0.4 for addition, above around 10000 bits. It is on par for multiplication, starting 1000 bits.

List of features

• rand: enables the possibility to generate a random integer with a specific number of bits. Uses rand crate as a dependency.
• pyo3: Only used to generate python bindings, it's only meant to be used indirectly via the pip install . command. Uses pyo3 crate as a dependency.
• unsafe: Enables accelerations that use unsafe Rust. Enabled by default. Disabled via the flag --no-default-features for pure safe Rust (compile time enforced).

Install as a Python package

Simply use from the base directory

python3 -m pip install .

This crate seems faster than the default Python integers for addition and multiplication above a certain numbers of bits (between 1000 and 10000 bits).

Python tests are available to be run in the pytest framework. They are located in the tests folder and should provide ample example usage.

Changelog for version 0.2

This new version contains extensive accelerations for addition, subtraction, and multiplication on x86_64 machines. I used no modern extensions of x86, so these acceleration should be portable accross this family of mahcines. These will probably also have performance repercussions on many other features.

These acceleration are mostly due to dropping inline assembly for core loops, and are based on unsafe Rust. Other unsafe features used include smartly swapping between &[u32] and &[u64] slices via pointers (when alignment is lucky).

To disable any unsafe code, use with the flag --no-default-features for a slower experience, but fully compiled in safe Rust.