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| author | Chris Cannam <cannam@all-day-breakfast.com> |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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| 94:d278df1123f9 | 95:89f5e221ed7b |
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| 1 <html lang="en"> | |
| 2 <head> | |
| 3 <title>FFTW MPI Performance Tips - FFTW 3.3.3</title> | |
| 4 <meta http-equiv="Content-Type" content="text/html"> | |
| 5 <meta name="description" content="FFTW 3.3.3"> | |
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| 7 <link title="Top" rel="start" href="index.html#Top"> | |
| 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="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks" title="Avoiding MPI Deadlocks"> | |
| 10 <link rel="next" href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads" title="Combining MPI and Threads"> | |
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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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| 24 Permission is granted to copy and distribute modified versions of | |
| 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. | |
| 28 | |
| 29 Permission is granted to copy and distribute translations of this | |
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| 46 </head> | |
| 47 <body> | |
| 48 <div class="node"> | |
| 49 <a name="FFTW-MPI-Performance-Tips"></a> | |
| 50 <p> | |
| 51 Next: <a rel="next" accesskey="n" href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads">Combining MPI and Threads</a>, | |
| 52 Previous: <a rel="previous" accesskey="p" href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks">Avoiding MPI Deadlocks</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">6.10 FFTW MPI Performance Tips</h3> | |
| 58 | |
| 59 <p>In this section, we collect a few tips on getting the best performance | |
| 60 out of FFTW's MPI transforms. | |
| 61 | |
| 62 <p>First, because of the 1d block distribution, FFTW's parallelization is | |
| 63 currently limited by the size of the first dimension. | |
| 64 (Multidimensional block distributions may be supported by a future | |
| 65 version.) More generally, you should ideally arrange the dimensions so | |
| 66 that FFTW can divide them equally among the processes. See <a href="Load-balancing.html#Load-balancing">Load balancing</a>. | |
| 67 <a name="index-block-distribution-423"></a><a name="index-load-balancing-424"></a> | |
| 68 | |
| 69 <p>Second, if it is not too inconvenient, you should consider working | |
| 70 with transposed output for multidimensional plans, as this saves a | |
| 71 considerable amount of communications. See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>. | |
| 72 <a name="index-transpose-425"></a> | |
| 73 | |
| 74 <p>Third, the fastest choices are generally either an in-place transform | |
| 75 or an out-of-place transform with the <code>FFTW_DESTROY_INPUT</code> flag | |
| 76 (which allows the input array to be used as scratch space). In-place | |
| 77 is especially beneficial if the amount of data per process is large. | |
| 78 <a name="index-FFTW_005fDESTROY_005fINPUT-426"></a> | |
| 79 | |
| 80 <p>Fourth, if you have multiple arrays to transform at once, rather than | |
| 81 calling FFTW's MPI transforms several times it usually seems to be | |
| 82 faster to interleave the data and use the advanced interface. (This | |
| 83 groups the communications together instead of requiring separate | |
| 84 messages for each transform.) | |
| 85 | |
| 86 <!-- --> | |
| 87 </body></html> | |
| 88 |