Multiple dispatch to use Dask (dask.array and dask.fft) and CUDA (cupy arrays and cuFFT).
*Created by: *
For postprocessing one generally loads data sequentially on smaller machines, and in such scenarios big simulations would not fit in the memory. It would be nice to have the Operator class to support out-of-core fft using dask arrays for KX, KY etc and
dask.array.fft either directly or via pyfftw's interface: