Function fft_batch_parallel 

pub fn fft_batch_parallel<T: Float, P: ThreadPool>(
    input: &[Complex<T>],
    n: usize,
    howmany: usize,
    pool: &P,
) -> Vec<Complex<T>>

Convenience function for parallel batched 1D forward FFT.

Performs howmany independent 1D FFTs, each of size n, in parallel. Input and output are contiguous: batch i starts at index i * n.