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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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+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
+<html>
+<!-- This manual is for FFTW
+(version 3.3.5, 30 July 2016).
+
+Copyright (C) 2003 Matteo Frigo.
+
+Copyright (C) 2003 Massachusetts Institute of Technology.
+
+Permission is granted to make and distribute verbatim copies of this
+manual provided the copyright notice and this permission notice are
+preserved on all copies.
+
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided that the
+entire resulting derived work is distributed under the terms of a
+permission notice identical to this one.
+
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions,
+except that this permission notice may be stated in a translation
+approved by the Free Software Foundation. -->
+<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
+<head>
+<title>FFTW 3.3.5: Avoiding MPI Deadlocks</title>
+
+<meta name="description" content="FFTW 3.3.5: Avoiding MPI Deadlocks">
+<meta name="keywords" content="FFTW 3.3.5: Avoiding MPI Deadlocks">
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+<link href="index.html#Top" rel="start" title="Top">
+<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
+<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
+<link href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" rel="up" title="Distributed-memory FFTW with MPI">
+<link href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips" rel="next" title="FFTW MPI Performance Tips">
+<link href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom" rel="prev" title="FFTW MPI Wisdom">
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+</head>
+
+<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
+<a name="Avoiding-MPI-Deadlocks"></a>
+<div class="header">
+<p>
+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>
+</div>
+<hr>
+<a name="Avoiding-MPI-Deadlocks-1"></a>
+<h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
+<a name="index-deadlock"></a>
+
+<p>An MPI program can <em>deadlock</em> if one process is waiting for a
+message from another process that never gets sent.  To avoid deadlocks
+when using FFTW&rsquo;s MPI routines, it is important to know which
+functions are <em>collective</em>: that is, which functions must
+<em>always</em> be called in the <em>same order</em> from <em>every</em>
+process in a given communicator.  (For example, <code>MPI_Barrier</code> is
+the canonical example of a collective function in the MPI standard.)
+<a name="index-collective-function-2"></a>
+<a name="index-MPI_005fBarrier"></a>
+</p>
+
+<p>The functions in FFTW that are <em>always</em> collective are: every
+function beginning with &lsquo;<samp>fftw_mpi_plan</samp>&rsquo;, as well as
+<code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
+Also, the following functions from the ordinary FFTW interface are
+collective when they are applied to a plan created by an
+&lsquo;<samp>fftw_mpi_plan</samp>&rsquo; function: <code>fftw_execute</code>,
+<code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
+<a name="index-fftw_005fexecute-4"></a>
+<a name="index-fftw_005fdestroy_005fplan-2"></a>
+<a name="index-fftw_005fflops-1"></a>
+</p>
+
+
+
+</body>
+</html>