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cannam@127: <title>FFTW 3.3.5: Avoiding MPI Deadlocks</title>
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cannam@127: <a name="Avoiding-MPI-Deadlocks"></a>
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cannam@127: Next: <a href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips" accesskey="n" rel="next">FFTW MPI Performance Tips</a>, Previous: <a href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom" accesskey="p" rel="prev">FFTW MPI Wisdom</a>, Up: <a href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" accesskey="u" rel="up">Distributed-memory FFTW with MPI</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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cannam@127: <a name="Avoiding-MPI-Deadlocks-1"></a>
cannam@127: <h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
cannam@127: <a name="index-deadlock"></a>
cannam@127:
cannam@127: <p>An MPI program can <em>deadlock</em> if one process is waiting for a
cannam@127: message from another process that never gets sent. To avoid deadlocks
cannam@127: when using FFTW’s MPI routines, it is important to know which
cannam@127: functions are <em>collective</em>: that is, which functions must
cannam@127: <em>always</em> be called in the <em>same order</em> from <em>every</em>
cannam@127: process in a given communicator. (For example, <code>MPI_Barrier</code> is
cannam@127: the canonical example of a collective function in the MPI standard.)
cannam@127: <a name="index-collective-function-2"></a>
cannam@127: <a name="index-MPI_005fBarrier"></a>
cannam@127: </p>
cannam@127:
cannam@127: <p>The functions in FFTW that are <em>always</em> collective are: every
cannam@127: function beginning with ‘<samp>fftw_mpi_plan</samp>’, as well as
cannam@127: <code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
cannam@127: Also, the following functions from the ordinary FFTW interface are
cannam@127: collective when they are applied to a plan created by an
cannam@127: ‘<samp>fftw_mpi_plan</samp>’ function: <code>fftw_execute</code>,
cannam@127: <code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
cannam@127: <a name="index-fftw_005fexecute-4"></a>
cannam@127: <a name="index-fftw_005fdestroy_005fplan-2"></a>
cannam@127: <a name="index-fftw_005fflops-1"></a>
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