1-D: FFTW on vector of size 10 
DIM: 1, N 10, Ny 12

 2-D: FFTW on vector of size 100 
DIM: 2, N 100, Ny 120

 3-D: FFTW on vector of size 1000 
DIM: 3, N 1000, Ny 1200

 4-D: FFTW on vector of size 10000 
DIM: 4, N 10000, Ny 12000