Lib.rs

Monarch Butterfly

Experimental FFT library with an emphasis on runtime performance. This currently only works on powers of two. The FFTs are autogenerated with a procedural macro which hand unrolls all the loops with inlined functions to allow the compiler to maximize the SIMD throughput available on the given CPU.

This library implements FFTs for both f32 and f64 for the following sizes:

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048

This library will use all SIMD features your CPU has available including AVX512, assuming you compile with those features (RUSTFLAGS="-C target-cpu=native" cargo build).

The larger the FFT sizes, the larger speed boost this library will give you.

As an example of AVX512 instructions, here is an example on just an FFT of size 128: https://godbolt.org/z/rz48azEsd (Ctrl+F for "zmm" instructions)

If a larger FFT size is needed, just clone the repo and add the needed sizes to the top of crates\monarch-derive\src\lib.rs and larger FFTs will be generated. However, this comes at the cost of a longer compile time.

use monarch_butterfly::*;
use num_complex::Complex;

let input: Vec<_> = (0..8).map(|i| Complex::new(i as f32, 0.0)).collect();
let output_slice = fft8(&input);
let output_vec = fft8(input);