# FFTW on subarray with MPI

With the guru interfaces of FFTW, I can apply transforms only to parts of a multidimensional array by modifying the fftw_iodim parameter (e.g., with fftw_plan_guru_r2r(...)). Unfortunately, there seems to be no MPI interface with the same arguments (see, e.g., fftw_mpi_plan_r2r(...)). Does anybody know how I could apply one of the transforms of FFTW to only part of a multidimensional array (a subarray) using MPI?

• This would be a question best asked of the FFTW developers. – Wolfgang Bangerth Jul 5 '18 at 16:42