|
d@0
|
1 <html lang="en">
|
|
d@0
|
2 <head>
|
|
d@0
|
3 <title>FFTW MPI Performance Tips - FFTW 3.2alpha3</title>
|
|
d@0
|
4 <meta http-equiv="Content-Type" content="text/html">
|
|
d@0
|
5 <meta name="description" content="FFTW 3.2alpha3">
|
|
d@0
|
6 <meta name="generator" content="makeinfo 4.8">
|
|
d@0
|
7 <link title="Top" rel="start" href="index.html#Top">
|
|
d@0
|
8 <link rel="up" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" title="Distributed-memory FFTW with MPI">
|
|
d@0
|
9 <link rel="prev" href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks" title="Avoiding MPI Deadlocks">
|
|
d@0
|
10 <link rel="next" href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads" title="Combining MPI and Threads">
|
|
d@0
|
11 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
d@0
|
12 <!--
|
|
d@0
|
13 This manual is for FFTW
|
|
d@0
|
14 (version 3.2alpha3, 14 August 2007).
|
|
d@0
|
15
|
|
d@0
|
16 Copyright (C) 2003 Matteo Frigo.
|
|
d@0
|
17
|
|
d@0
|
18 Copyright (C) 2003 Massachusetts Institute of Technology.
|
|
d@0
|
19
|
|
d@0
|
20 Permission is granted to make and distribute verbatim copies of
|
|
d@0
|
21 this manual provided the copyright notice and this permission
|
|
d@0
|
22 notice are preserved on all copies.
|
|
d@0
|
23
|
|
d@0
|
24 Permission is granted to copy and distribute modified versions of
|
|
d@0
|
25 this manual under the conditions for verbatim copying, provided
|
|
d@0
|
26 that the entire resulting derived work is distributed under the
|
|
d@0
|
27 terms of a permission notice identical to this one.
|
|
d@0
|
28
|
|
d@0
|
29 Permission is granted to copy and distribute translations of this
|
|
d@0
|
30 manual into another language, under the above conditions for
|
|
d@0
|
31 modified versions, except that this permission notice may be
|
|
d@0
|
32 stated in a translation approved by the Free Software Foundation.
|
|
d@0
|
33 -->
|
|
d@0
|
34 <meta http-equiv="Content-Style-Type" content="text/css">
|
|
d@0
|
35 <style type="text/css"><!--
|
|
d@0
|
36 pre.display { font-family:inherit }
|
|
d@0
|
37 pre.format { font-family:inherit }
|
|
d@0
|
38 pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
d@0
|
39 pre.smallformat { font-family:inherit; font-size:smaller }
|
|
d@0
|
40 pre.smallexample { font-size:smaller }
|
|
d@0
|
41 pre.smalllisp { font-size:smaller }
|
|
d@0
|
42 span.sc { font-variant:small-caps }
|
|
d@0
|
43 span.roman { font-family:serif; font-weight:normal; }
|
|
d@0
|
44 span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
d@0
|
45 --></style>
|
|
d@0
|
46 </head>
|
|
d@0
|
47 <body>
|
|
d@0
|
48 <div class="node">
|
|
d@0
|
49 <p>
|
|
d@0
|
50 <a name="FFTW-MPI-Performance-Tips"></a>
|
|
d@0
|
51 Next: <a rel="next" accesskey="n" href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads">Combining MPI and Threads</a>,
|
|
d@0
|
52 Previous: <a rel="previous" accesskey="p" href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks">Avoiding MPI Deadlocks</a>,
|
|
d@0
|
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>
|
|
d@0
|
54 <hr>
|
|
d@0
|
55 </div>
|
|
d@0
|
56
|
|
d@0
|
57 <h3 class="section">6.10 FFTW MPI Performance Tips</h3>
|
|
d@0
|
58
|
|
d@0
|
59 <p>In this section, we collect a few tips on getting the best performance
|
|
d@0
|
60 out of FFTW's MPI transforms.
|
|
d@0
|
61
|
|
d@0
|
62 <p>First, because of the 1d block distribution, FFTW's parallelization is
|
|
d@0
|
63 currently limited by the size of the first dimension.
|
|
d@0
|
64 (Multidimensional block distributions may be supported by a future
|
|
d@0
|
65 version.) More generally, you should ideally arrange the dimensions so
|
|
d@0
|
66 that FFTW can divide them equally among the processes. See <a href="Load-balancing.html#Load-balancing">Load balancing</a>.
|
|
d@0
|
67 <a name="index-block-distribution-394"></a><a name="index-load-balancing-395"></a>
|
|
d@0
|
68 Second, if it is not too inconvenient, you should consider working
|
|
d@0
|
69 with transposed output for multidimensional plans, as this saves a
|
|
d@0
|
70 considerable amount of communications. See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>.
|
|
d@0
|
71 <a name="index-transpose-396"></a>
|
|
d@0
|
72 Third, the fastest choices are generally either an in-place transform
|
|
d@0
|
73 or an out-of-place transform with the <code>FFTW_DESTROY_INPUT</code> flag
|
|
d@0
|
74 (which allows the input array to be used as scratch space). In-place
|
|
d@0
|
75 is especially beneficial if the amount of data per process is large.
|
|
d@0
|
76 <a name="index-FFTW_005fDESTROY_005fINPUT-397"></a>
|
|
d@0
|
77 Fourth, if you have multiple arrays to transform at once, rather than
|
|
d@0
|
78 calling FFTW's MPI transforms several times it usually seems to be
|
|
d@0
|
79 faster to interleave the data and use the advanced interface. (This
|
|
d@0
|
80 groups the communications together instead of requiring separate
|
|
d@0
|
81 messages for each transform.)
|
|
d@0
|
82
|
|
d@0
|
83 <!-- -->
|
|
d@0
|
84 </body></html>
|
|
d@0
|
85
|
