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3 <title>Avoiding MPI Deadlocks - FFTW 3.3.3</title>
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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">
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9 <link rel="prev" href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom" title="FFTW MPI Wisdom">
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10 <link rel="next" href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips" title="FFTW MPI Performance Tips">
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12 <!--
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13 This manual is for FFTW
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14 (version 3.3.3, 25 November 2012).
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15
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16 Copyright (C) 2003 Matteo Frigo.
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17
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18 Copyright (C) 2003 Massachusetts Institute of Technology.
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19
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20 Permission is granted to make and distribute verbatim copies of
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22 notice are preserved on all copies.
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24 Permission is granted to copy and distribute modified versions of
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25 this manual under the conditions for verbatim copying, provided
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26 that the entire resulting derived work is distributed under the
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27 terms of a permission notice identical to this one.
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28
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29 Permission is granted to copy and distribute translations of this
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30 manual into another language, under the above conditions for
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31 modified versions, except that this permission notice may be
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32 stated in a translation approved by the Free Software Foundation.
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47 <body>
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48 <div class="node">
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49 <a name="Avoiding-MPI-Deadlocks"></a>
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50 <p>
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51 Next: <a rel="next" accesskey="n" href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips">FFTW MPI Performance Tips</a>,
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52 Previous: <a rel="previous" accesskey="p" href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom">FFTW MPI Wisdom</a>,
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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>
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54 <hr>
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55 </div>
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56
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57 <h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
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58
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59 <p><a name="index-deadlock-417"></a>
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60 An MPI program can <em>deadlock</em> if one process is waiting for a
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61 message from another process that never gets sent. To avoid deadlocks
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62 when using FFTW's MPI routines, it is important to know which
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63 functions are <em>collective</em>: that is, which functions must
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64 <em>always</em> be called in the <em>same order</em> from <em>every</em>
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65 process in a given communicator. (For example, <code>MPI_Barrier</code> is
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66 the canonical example of a collective function in the MPI standard.)
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67 <a name="index-collective-function-418"></a><a name="index-MPI_005fBarrier-419"></a>
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68
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69 <p>The functions in FFTW that are <em>always</em> collective are: every
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70 function beginning with ‘<samp><span class="samp">fftw_mpi_plan</span></samp>’, as well as
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71 <code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
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72 Also, the following functions from the ordinary FFTW interface are
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73 collective when they are applied to a plan created by an
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74 ‘<samp><span class="samp">fftw_mpi_plan</span></samp>’ function: <code>fftw_execute</code>,
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75 <code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
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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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77 <!-- -->
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78
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79 </body></html>
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80
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