1 dimensions: FFTW on vector of size 5 
  Error norm of |x - z1| 2.77388

 2 dimensions: FFTW on vector of size 25 
  Error norm of |x - z1| 21.1472

 3 dimensions: FFTW on vector of size 125 
  Error norm of |x - z1| 91.4129

 4 dimensions: FFTW on vector of size 625 
  Error norm of |x - z1| 471.544