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d@0: An MPI program can deadlock if one process is waiting for a
d@0: message from another process that never gets sent. To avoid deadlocks
d@0: when using FFTW's MPI routines, it is important to know which
d@0: functions are collective: that is, which functions must
d@0: always be called in the same order from every
d@0: process in a given communicator. (For example, MPI_Barrier
is
d@0: the canonical example of a collective function in the MPI standard.)
d@0:
d@0: The functions in FFTW that are always collective are: every
d@0: function beginning with `fftw_mpi_plan', as well as
d@0: fftw_mpi_broadcast_wisdom
and fftw_mpi_gather_wisdom
.
d@0: Also, the following functions from the ordinary FFTW interface are
d@0: collective when they are applied to a plan created by an
d@0: `fftw_mpi_plan' function: fftw_execute
,
d@0: fftw_destroy_plan
, and fftw_flops
.
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