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| author | Chris Cannam |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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| 9:c0fb53affa76 | 10:37bf6b4a2645 |
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| 1 <html lang="en"> | |
| 2 <head> | |
| 3 <title>Avoiding MPI Deadlocks - FFTW 3.3.3</title> | |
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| 5 <meta name="description" content="FFTW 3.3.3"> | |
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| 8 <link rel="up" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" title="Distributed-memory FFTW with MPI"> | |
| 9 <link rel="prev" href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom" title="FFTW MPI Wisdom"> | |
| 10 <link rel="next" href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips" title="FFTW MPI Performance Tips"> | |
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| 12 <!-- | |
| 13 This manual is for FFTW | |
| 14 (version 3.3.3, 25 November 2012). | |
| 15 | |
| 16 Copyright (C) 2003 Matteo Frigo. | |
| 17 | |
| 18 Copyright (C) 2003 Massachusetts Institute of Technology. | |
| 19 | |
| 20 Permission is granted to make and distribute verbatim copies of | |
| 21 this manual provided the copyright notice and this permission | |
| 22 notice are preserved on all copies. | |
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| 25 this manual under the conditions for verbatim copying, provided | |
| 26 that the entire resulting derived work is distributed under the | |
| 27 terms of a permission notice identical to this one. | |
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| 29 Permission is granted to copy and distribute translations of this | |
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| 49 <a name="Avoiding-MPI-Deadlocks"></a> | |
| 50 <p> | |
| 51 Next: <a rel="next" accesskey="n" href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips">FFTW MPI Performance Tips</a>, | |
| 52 Previous: <a rel="previous" accesskey="p" href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom">FFTW MPI Wisdom</a>, | |
| 53 Up: <a rel="up" accesskey="u" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI">Distributed-memory FFTW with MPI</a> | |
| 54 <hr> | |
| 55 </div> | |
| 56 | |
| 57 <h3 class="section">6.9 Avoiding MPI Deadlocks</h3> | |
| 58 | |
| 59 <p><a name="index-deadlock-417"></a> | |
| 60 An MPI program can <em>deadlock</em> if one process is waiting for a | |
| 61 message from another process that never gets sent. To avoid deadlocks | |
| 62 when using FFTW's MPI routines, it is important to know which | |
| 63 functions are <em>collective</em>: that is, which functions must | |
| 64 <em>always</em> be called in the <em>same order</em> from <em>every</em> | |
| 65 process in a given communicator. (For example, <code>MPI_Barrier</code> is | |
| 66 the canonical example of a collective function in the MPI standard.) | |
| 67 <a name="index-collective-function-418"></a><a name="index-MPI_005fBarrier-419"></a> | |
| 68 | |
| 69 <p>The functions in FFTW that are <em>always</em> collective are: every | |
| 70 function beginning with ‘<samp><span class="samp">fftw_mpi_plan</span></samp>’, as well as | |
| 71 <code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>. | |
| 72 Also, the following functions from the ordinary FFTW interface are | |
| 73 collective when they are applied to a plan created by an | |
| 74 ‘<samp><span class="samp">fftw_mpi_plan</span></samp>’ function: <code>fftw_execute</code>, | |
| 75 <code>fftw_destroy_plan</code>, and <code>fftw_flops</code>. | |
| 76 <a name="index-fftw_005fexecute-420"></a><a name="index-fftw_005fdestroy_005fplan-421"></a><a name="index-fftw_005fflops-422"></a> | |
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