## nightly framp

Fork of James Miller's Ramp, a high-performance multiple-precision arithmetic library

### 4 releases

Uses old Rust 2015

 0.3.7 Jun 6, 2017 Jan 17, 2017 Jan 17, 2017 Jan 17, 2017

#1106 in Algorithms

Used in paillier

Apache-2.0

320KB
8K SLoC

# RAMP - Rust Arithmetic in Multiple Precision

Documentation

Ramp is a high-performance mulitple-precision (aka "BigNum") library for working with numbers bigger than can normally be handled. Usage is very easy, you can almost use them as regular numbers.

## Example

``````
extern crate framp as ramp;
use ramp::Int;

// Calculates n!
fn factorial(n: usize) -> Int {
let mut a = Int::from(1);

for i in 2..n {
a *= i;
}

return a * n;
}
``````

As you can see, it is very easy to work with these numbers.

Operator overloads have been provided for by-value, which consumes the operand(s) and by-reference, which does not. The by-value overloads will attempt to re-use the space for the result (this isn't always possible).

Operator overloads have also been provided for `i32` and `usize`, allowing easy (and efficient) operations when you have smaller numbers. The above example actually uses the `usize` overload, meaning only one `Int` is ever allocated.

NOTE Due to use of unstable features (notably inline assembly), Ramp can only be compiled with a nightly build of `rustc`.

## Why another library?

The `num` crate provides some bignum types that can be used, so why use Ramp? Well, Ramp is specifically focussed on multiple-precision arithmetic, while `num` is a general-purpose numerics library that happens to provide some multiple-precision arithmetic.

You should `num` if you aren't able to use unstable Rust features or just want a small amount of functionality. Ramp should be used when you need high-performance and extra functionality.

## Overall Design

Ramp is split into two main parts: high-level code and low-level code. The high-level code is what you should be using, however the low-level code is where the real work is done.

The low-level routines (in `ll`) are predominately unsafe functions that work with raw pointers, and some of the routines are implemented using inline assembly to gain access to processor-specific functionality.

### Limbs

The term "Limb" is used frequently in Ramp. It's a term borrowed from GMP and is a single "digit" for the base that Ramp works in. Since the base is equal to 2^word_size, these are very large "digits", hence the use of the word "Limb" instead.

## Future Work

Ramp is currently very rough and incomplete. Broadly, there are three types Ramp aims to provide: integers, rationals, and floats. Integers (`Int`) are present and mostly complete, Rationals are present and have a basic implementation. Floats are not yet implemented.

In the low-level routines, there are a few operations, notably multiplication and division, that are currently implemented using the simplest working algorithm. While this is sufficient for relatively small numbers, larger numbers should be using better algorithms.

~0.7–1MB
~15K SLoC