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Replace these with versions built using an older toolset (so as to avoid ABI compatibilities when linking on Ubuntu 14.04 for packaging purposes)
author Chris Cannam
date Fri, 07 Feb 2020 11:51:13 +0000
parents 37bf6b4a2645
children
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Chris@10 1 <html lang="en">
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Chris@10 3 <title>Avoiding MPI Deadlocks - FFTW 3.3.3</title>
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Chris@10 48 <div class="node">
Chris@10 49 <a name="Avoiding-MPI-Deadlocks"></a>
Chris@10 50 <p>
Chris@10 51 Next:&nbsp;<a rel="next" accesskey="n" href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips">FFTW MPI Performance Tips</a>,
Chris@10 52 Previous:&nbsp;<a rel="previous" accesskey="p" href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom">FFTW MPI Wisdom</a>,
Chris@10 53 Up:&nbsp;<a rel="up" accesskey="u" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI">Distributed-memory FFTW with MPI</a>
Chris@10 54 <hr>
Chris@10 55 </div>
Chris@10 56
Chris@10 57 <h3 class="section">6.9 Avoiding MPI Deadlocks</h3>
Chris@10 58
Chris@10 59 <p><a name="index-deadlock-417"></a>
Chris@10 60 An MPI program can <em>deadlock</em> if one process is waiting for a
Chris@10 61 message from another process that never gets sent. To avoid deadlocks
Chris@10 62 when using FFTW's MPI routines, it is important to know which
Chris@10 63 functions are <em>collective</em>: that is, which functions must
Chris@10 64 <em>always</em> be called in the <em>same order</em> from <em>every</em>
Chris@10 65 process in a given communicator. (For example, <code>MPI_Barrier</code> is
Chris@10 66 the canonical example of a collective function in the MPI standard.)
Chris@10 67 <a name="index-collective-function-418"></a><a name="index-MPI_005fBarrier-419"></a>
Chris@10 68
Chris@10 69 <p>The functions in FFTW that are <em>always</em> collective are: every
Chris@10 70 function beginning with &lsquo;<samp><span class="samp">fftw_mpi_plan</span></samp>&rsquo;, as well as
Chris@10 71 <code>fftw_mpi_broadcast_wisdom</code> and <code>fftw_mpi_gather_wisdom</code>.
Chris@10 72 Also, the following functions from the ordinary FFTW interface are
Chris@10 73 collective when they are applied to a plan created by an
Chris@10 74 &lsquo;<samp><span class="samp">fftw_mpi_plan</span></samp>&rsquo; function: <code>fftw_execute</code>,
Chris@10 75 <code>fftw_destroy_plan</code>, and <code>fftw_flops</code>.
Chris@10 76 <a name="index-fftw_005fexecute-420"></a><a name="index-fftw_005fdestroy_005fplan-421"></a><a name="index-fftw_005fflops-422"></a>
Chris@10 77 <!-- -->
Chris@10 78
Chris@10 79 </body></html>
Chris@10 80