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96 lines
4.3 KiB
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<!-- This manual is for FFTW
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(version 3.3.10, 10 December 2020).
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Copyright (C) 2003 Matteo Frigo.
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Copyright (C) 2003 Massachusetts Institute of Technology.
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Permission is granted to make and distribute verbatim copies of this
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manual provided the copyright notice and this permission notice are
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preserved on all copies.
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, provided that the
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entire resulting derived work is distributed under the terms of a
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permission notice identical to this one.
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Permission is granted to copy and distribute translations of this manual
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approved by the Free Software Foundation. -->
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<head>
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<title>Avoiding MPI Deadlocks (FFTW 3.3.10)</title>
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<meta name="description" content="Avoiding MPI Deadlocks (FFTW 3.3.10)">
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Distributed_002dmemory-FFTW-with-MPI.html" rel="up" title="Distributed-memory FFTW with MPI">
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<link href="FFTW-MPI-Performance-Tips.html" rel="next" title="FFTW MPI Performance Tips">
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<link href="FFTW-MPI-Wisdom.html" rel="prev" title="FFTW MPI Wisdom">
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<span id="Avoiding-MPI-Deadlocks"></span><div class="header">
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<p>
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Next: <a href="FFTW-MPI-Performance-Tips.html" accesskey="n" rel="next">FFTW MPI Performance Tips</a>, Previous: <a href="FFTW-MPI-Wisdom.html" accesskey="p" rel="prev">FFTW MPI Wisdom</a>, Up: <a href="Distributed_002dmemory-FFTW-with-MPI.html" 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" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<span id="Avoiding-MPI-Deadlocks-1"></span><h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
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<span id="index-deadlock"></span>
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<p>An MPI program can <em>deadlock</em> if one process is waiting for a
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message from another process that never gets sent. To avoid deadlocks
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when using FFTW’s MPI routines, it is important to know which
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functions are <em>collective</em>: that is, which functions must
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<em>always</em> be called in the <em>same order</em> from <em>every</em>
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process in a given communicator. (For example, <code>MPI_Barrier</code> is
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the canonical example of a collective function in the MPI standard.)
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<span id="index-collective-function-2"></span>
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<span id="index-MPI_005fBarrier"></span>
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</p>
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<p>The functions in FFTW that are <em>always</em> collective are: every
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function beginning with ‘<samp>fftw_mpi_plan</samp>’, as well as
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<code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
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Also, the following functions from the ordinary FFTW interface are
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collective when they are applied to a plan created by an
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‘<samp>fftw_mpi_plan</samp>’ function: <code>fftw_execute</code>,
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<code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
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<span id="index-fftw_005fexecute-4"></span>
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<span id="index-fftw_005fdestroy_005fplan-2"></span>
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<span id="index-fftw_005fflops-1"></span>
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</p>
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</body>
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</html>
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