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6.12.2 MPI Initialization

Before calling any other FFTW MPI (‘fftw_mpi_’) function, and before importing any wisdom for MPI problems, you must call:

void fftw_mpi_init(void);

If FFTW threads support is used, however, fftw_mpi_init should be called after fftw_init_threads (see Combining MPI and Threads). Calling fftw_mpi_init additional times (before fftw_mpi_cleanup) has no effect.

If you want to deallocate all persistent data and reset FFTW to the pristine state it was in when you started your program, you can call:

void fftw_mpi_cleanup(void);

(This calls fftw_cleanup, so you need not call the serial cleanup routine too, although it is safe to do so.) After calling fftw_mpi_cleanup, all existing plans become undefined, and you should not attempt to execute or destroy them. You must call fftw_mpi_init again after fftw_mpi_cleanup if you want to resume using the MPI FFTW routines.