Function parallel_fft

pub fn parallel_fft<F: PrimeField>(
    a: &mut [F],
    worker: &Worker,
    omega: &F,
    log_n: u32,
    log_threads: u32,
)

Calculate the Fast Fourier Transform on the CPU (multithreaded).

The result is is written to the input a. The number of threads used will be 2^log_threads. There must be more items to process than threads.