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1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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2 <html>
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3 <!-- This manual is for FFTW
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4 (version 3.3.5, 30 July 2016).
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5
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6 Copyright (C) 2003 Matteo Frigo.
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7
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8 Copyright (C) 2003 Massachusetts Institute of Technology.
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9
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10 Permission is granted to make and distribute verbatim copies of this
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11 manual provided the copyright notice and this permission notice are
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12 preserved on all copies.
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13
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14 Permission is granted to copy and distribute modified versions of this
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15 manual under the conditions for verbatim copying, provided that the
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16 entire resulting derived work is distributed under the terms of a
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17 permission notice identical to this one.
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18
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19 Permission is granted to copy and distribute translations of this manual
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20 into another language, under the above conditions for modified versions,
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22 approved by the Free Software Foundation. -->
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23 <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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24 <head>
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25 <title>FFTW 3.3.5: Avoiding MPI Deadlocks</title>
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26
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27 <meta name="description" content="FFTW 3.3.5: Avoiding MPI Deadlocks">
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28 <meta name="keywords" content="FFTW 3.3.5: Avoiding MPI Deadlocks">
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33 <link href="index.html#Top" rel="start" title="Top">
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34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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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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37 <link href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips" rel="next" title="FFTW MPI Performance Tips">
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38 <link href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom" rel="prev" title="FFTW MPI Wisdom">
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65 -->
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66 </style>
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67
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68
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69 </head>
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70
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71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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72 <a name="Avoiding-MPI-Deadlocks"></a>
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73 <div class="header">
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74 <p>
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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> [<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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76 </div>
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77 <hr>
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78 <a name="Avoiding-MPI-Deadlocks-1"></a>
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79 <h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
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80 <a name="index-deadlock"></a>
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81
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82 <p>An MPI program can <em>deadlock</em> if one process is waiting for a
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83 message from another process that never gets sent. To avoid deadlocks
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84 when using FFTW’s MPI routines, it is important to know which
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85 functions are <em>collective</em>: that is, which functions must
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86 <em>always</em> be called in the <em>same order</em> from <em>every</em>
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87 process in a given communicator. (For example, <code>MPI_Barrier</code> is
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88 the canonical example of a collective function in the MPI standard.)
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89 <a name="index-collective-function-2"></a>
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90 <a name="index-MPI_005fBarrier"></a>
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91 </p>
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92
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93 <p>The functions in FFTW that are <em>always</em> collective are: every
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94 function beginning with ‘<samp>fftw_mpi_plan</samp>’, as well as
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95 <code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
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96 Also, the following functions from the ordinary FFTW interface are
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97 collective when they are applied to a plan created by an
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98 ‘<samp>fftw_mpi_plan</samp>’ function: <code>fftw_execute</code>,
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99 <code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
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100 <a name="index-fftw_005fexecute-4"></a>
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101 <a name="index-fftw_005fdestroy_005fplan-2"></a>
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102 <a name="index-fftw_005fflops-1"></a>
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103 </p>
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104
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105
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106
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107 </body>
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108 </html>
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