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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
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Chris@10 1 <html lang="en">
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Chris@10 3 <title>FFTW MPI Performance Tips - FFTW 3.3.3</title>
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Chris@10 13 This manual is for FFTW
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Chris@10 48 <div class="node">
Chris@10 49 <a name="FFTW-MPI-Performance-Tips"></a>
Chris@10 50 <p>
Chris@10 51 Next:&nbsp;<a rel="next" accesskey="n" href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads">Combining MPI and Threads</a>,
Chris@10 52 Previous:&nbsp;<a rel="previous" accesskey="p" href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks">Avoiding MPI Deadlocks</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">6.10 FFTW MPI Performance Tips</h3>
Chris@10 58
Chris@10 59 <p>In this section, we collect a few tips on getting the best performance
Chris@10 60 out of FFTW's MPI transforms.
Chris@10 61
Chris@10 62 <p>First, because of the 1d block distribution, FFTW's parallelization is
Chris@10 63 currently limited by the size of the first dimension.
Chris@10 64 (Multidimensional block distributions may be supported by a future
Chris@10 65 version.) More generally, you should ideally arrange the dimensions so
Chris@10 66 that FFTW can divide them equally among the processes. See <a href="Load-balancing.html#Load-balancing">Load balancing</a>.
Chris@10 67 <a name="index-block-distribution-423"></a><a name="index-load-balancing-424"></a>
Chris@10 68
Chris@10 69 <p>Second, if it is not too inconvenient, you should consider working
Chris@10 70 with transposed output for multidimensional plans, as this saves a
Chris@10 71 considerable amount of communications. See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>.
Chris@10 72 <a name="index-transpose-425"></a>
Chris@10 73
Chris@10 74 <p>Third, the fastest choices are generally either an in-place transform
Chris@10 75 or an out-of-place transform with the <code>FFTW_DESTROY_INPUT</code> flag
Chris@10 76 (which allows the input array to be used as scratch space). In-place
Chris@10 77 is especially beneficial if the amount of data per process is large.
Chris@10 78 <a name="index-FFTW_005fDESTROY_005fINPUT-426"></a>
Chris@10 79
Chris@10 80 <p>Fourth, if you have multiple arrays to transform at once, rather than
Chris@10 81 calling FFTW's MPI transforms several times it usually seems to be
Chris@10 82 faster to interleave the data and use the advanced interface. (This
Chris@10 83 groups the communications together instead of requiring separate
Chris@10 84 messages for each transform.)
Chris@10 85
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