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Current fftw source
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 18 Oct 2016 13:40:26 +0100
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cannam@127 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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cannam@127 3 <!-- This manual is for FFTW
cannam@127 4 (version 3.3.5, 30 July 2016).
cannam@127 5
cannam@127 6 Copyright (C) 2003 Matteo Frigo.
cannam@127 7
cannam@127 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@127 24 <head>
cannam@127 25 <title>FFTW 3.3.5: Avoiding MPI Deadlocks</title>
cannam@127 26
cannam@127 27 <meta name="description" content="FFTW 3.3.5: Avoiding MPI Deadlocks">
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cannam@127 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
cannam@127 36 <link href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" rel="up" title="Distributed-memory FFTW with MPI">
cannam@127 37 <link href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips" rel="next" title="FFTW MPI Performance Tips">
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cannam@127 69 </head>
cannam@127 70
cannam@127 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
cannam@127 72 <a name="Avoiding-MPI-Deadlocks"></a>
cannam@127 73 <div class="header">
cannam@127 74 <p>
cannam@127 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>
cannam@127 76 </div>
cannam@127 77 <hr>
cannam@127 78 <a name="Avoiding-MPI-Deadlocks-1"></a>
cannam@127 79 <h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
cannam@127 80 <a name="index-deadlock"></a>
cannam@127 81
cannam@127 82 <p>An MPI program can <em>deadlock</em> if one process is waiting for a
cannam@127 83 message from another process that never gets sent. To avoid deadlocks
cannam@127 84 when using FFTW&rsquo;s MPI routines, it is important to know which
cannam@127 85 functions are <em>collective</em>: that is, which functions must
cannam@127 86 <em>always</em> be called in the <em>same order</em> from <em>every</em>
cannam@127 87 process in a given communicator. (For example, <code>MPI_Barrier</code> is
cannam@127 88 the canonical example of a collective function in the MPI standard.)
cannam@127 89 <a name="index-collective-function-2"></a>
cannam@127 90 <a name="index-MPI_005fBarrier"></a>
cannam@127 91 </p>
cannam@127 92
cannam@127 93 <p>The functions in FFTW that are <em>always</em> collective are: every
cannam@127 94 function beginning with &lsquo;<samp>fftw_mpi_plan</samp>&rsquo;, as well as
cannam@127 95 <code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
cannam@127 96 Also, the following functions from the ordinary FFTW interface are
cannam@127 97 collective when they are applied to a plan created by an
cannam@127 98 &lsquo;<samp>fftw_mpi_plan</samp>&rsquo; function: <code>fftw_execute</code>,
cannam@127 99 <code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
cannam@127 100 <a name="index-fftw_005fexecute-4"></a>
cannam@127 101 <a name="index-fftw_005fdestroy_005fplan-2"></a>
cannam@127 102 <a name="index-fftw_005fflops-1"></a>
cannam@127 103 </p>
cannam@127 104
cannam@127 105
cannam@127 106
cannam@127 107 </body>
cannam@127 108 </html>