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Current fftw source
author Chris Cannam
date Tue, 18 Oct 2016 13:40:26 +0100
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3 <!-- This manual is for FFTW
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35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
36 <link href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" rel="up" title="Distributed-memory FFTW with MPI">
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72 <a name="Avoiding-MPI-Deadlocks"></a>
73 <div class="header">
74 <p>
75 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> &nbsp; [<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>
76 </div>
77 <hr>
78 <a name="Avoiding-MPI-Deadlocks-1"></a>
79 <h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
80 <a name="index-deadlock"></a>
81
82 <p>An MPI program can <em>deadlock</em> if one process is waiting for a
83 message from another process that never gets sent. To avoid deadlocks
84 when using FFTW&rsquo;s MPI routines, it is important to know which
85 functions are <em>collective</em>: that is, which functions must
86 <em>always</em> be called in the <em>same order</em> from <em>every</em>
87 process in a given communicator. (For example, <code>MPI_Barrier</code> is
88 the canonical example of a collective function in the MPI standard.)
89 <a name="index-collective-function-2"></a>
90 <a name="index-MPI_005fBarrier"></a>
91 </p>
92
93 <p>The functions in FFTW that are <em>always</em> collective are: every
94 function beginning with &lsquo;<samp>fftw_mpi_plan</samp>&rsquo;, as well as
95 <code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
96 Also, the following functions from the ordinary FFTW interface are
97 collective when they are applied to a plan created by an
98 &lsquo;<samp>fftw_mpi_plan</samp>&rsquo; function: <code>fftw_execute</code>,
99 <code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
100 <a name="index-fftw_005fexecute-4"></a>
101 <a name="index-fftw_005fdestroy_005fplan-2"></a>
102 <a name="index-fftw_005fflops-1"></a>
103 </p>
104
105
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