BigNum
A library that allows the creation of incredibly large numbers, but with a low memory/runtime footprint (relative to arbitrary-precision libraries). It accomplishes this by only storing up to 64 bits in the significand (similar to the floating point standard).
Usage
Bases 2, 8, 10, and 16 are all pre-defined, and aliased to
BigNumBin, BigNumOct, BigNumDec, BigNumHex. As an example, to create a binary BigNum
to represent the formula 1234123223468 * 2^123422235, do
BigNumBin::new(1234123223468, 123422235). Then you can freely apply any of the 4 standard
math operations between this value and a u64 or another BigNumBin. For more examples
check the page on docs.rs and the test code.
Performance
Here are a couple of results from benchmarking the current version. TL;DR it's probably fast enough for anything but performance-critical applications.
Each test involved running 10k of the listed operations, code is in benches/multi.rs
| Test | Time(us) |
|---|---|
| Binary Add | 21.540 |
| Binary Sub | 17.002 |
| Binary Mul | 35.191 |
| Binary Div | 43.534 |
| Base300 Add | 26.034 |
| Base300 Sub | 68.320 |
| Base300 Mul | 107.33 |
| Base300 Div | 180.44 |
| The results are not perfectly descriptive but I think give a general sense of efficiency. |
Features
Random
I've added an implementation to generate random-ish BigNum values for testing. It is not actually correct (values won't appear at the frequency you'd expect and the bounds are not expected). But it will do for peformance testing and whatnot.