105 lines
4.6 KiB
HTML
105 lines
4.6 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<!-- This manual is for FFTW
|
|
(version 3.3.10, 10 December 2020).
|
|
|
|
Copyright (C) 2003 Matteo Frigo.
|
|
|
|
Copyright (C) 2003 Massachusetts Institute of Technology.
|
|
|
|
Permission is granted to make and distribute verbatim copies of this
|
|
manual provided the copyright notice and this permission notice are
|
|
preserved on all copies.
|
|
|
|
Permission is granted to copy and distribute modified versions of this
|
|
manual under the conditions for verbatim copying, provided that the
|
|
entire resulting derived work is distributed under the terms of a
|
|
permission notice identical to this one.
|
|
|
|
Permission is granted to copy and distribute translations of this manual
|
|
into another language, under the above conditions for modified versions,
|
|
except that this permission notice may be stated in a translation
|
|
approved by the Free Software Foundation. -->
|
|
<!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ -->
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<title>FFTW MPI Performance Tips (FFTW 3.3.10)</title>
|
|
|
|
<meta name="description" content="FFTW MPI Performance Tips (FFTW 3.3.10)">
|
|
<meta name="keywords" content="FFTW MPI Performance Tips (FFTW 3.3.10)">
|
|
<meta name="resource-type" content="document">
|
|
<meta name="distribution" content="global">
|
|
<meta name="Generator" content="makeinfo">
|
|
<link href="index.html" rel="start" title="Top">
|
|
<link href="Concept-Index.html" rel="index" title="Concept Index">
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
|
<link href="Distributed_002dmemory-FFTW-with-MPI.html" rel="up" title="Distributed-memory FFTW with MPI">
|
|
<link href="Combining-MPI-and-Threads.html" rel="next" title="Combining MPI and Threads">
|
|
<link href="Avoiding-MPI-Deadlocks.html" rel="prev" title="Avoiding MPI Deadlocks">
|
|
<style type="text/css">
|
|
<!--
|
|
a.summary-letter {text-decoration: none}
|
|
blockquote.indentedblock {margin-right: 0em}
|
|
div.display {margin-left: 3.2em}
|
|
div.example {margin-left: 3.2em}
|
|
div.lisp {margin-left: 3.2em}
|
|
kbd {font-style: oblique}
|
|
pre.display {font-family: inherit}
|
|
pre.format {font-family: inherit}
|
|
pre.menu-comment {font-family: serif}
|
|
pre.menu-preformatted {font-family: serif}
|
|
span.nolinebreak {white-space: nowrap}
|
|
span.roman {font-family: initial; font-weight: normal}
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
|
ul.no-bullet {list-style: none}
|
|
-->
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
<body lang="en">
|
|
<span id="FFTW-MPI-Performance-Tips"></span><div class="header">
|
|
<p>
|
|
Next: <a href="Combining-MPI-and-Threads.html" accesskey="n" rel="next">Combining MPI and Threads</a>, Previous: <a href="Avoiding-MPI-Deadlocks.html" accesskey="p" rel="prev">Avoiding MPI Deadlocks</a>, Up: <a href="Distributed_002dmemory-FFTW-with-MPI.html" accesskey="u" rel="up">Distributed-memory FFTW with MPI</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
<hr>
|
|
<span id="FFTW-MPI-Performance-Tips-1"></span><h3 class="section">6.10 FFTW MPI Performance Tips</h3>
|
|
|
|
<p>In this section, we collect a few tips on getting the best performance
|
|
out of FFTW’s MPI transforms.
|
|
</p>
|
|
<p>First, because of the 1d block distribution, FFTW’s parallelization is
|
|
currently limited by the size of the first dimension.
|
|
(Multidimensional block distributions may be supported by a future
|
|
version.) More generally, you should ideally arrange the dimensions so
|
|
that FFTW can divide them equally among the processes. See <a href="Load-balancing.html">Load balancing</a>.
|
|
<span id="index-block-distribution-2"></span>
|
|
<span id="index-load-balancing-1"></span>
|
|
</p>
|
|
|
|
<p>Second, if it is not too inconvenient, you should consider working
|
|
with transposed output for multidimensional plans, as this saves a
|
|
considerable amount of communications. See <a href="Transposed-distributions.html">Transposed distributions</a>.
|
|
<span id="index-transpose-3"></span>
|
|
</p>
|
|
|
|
<p>Third, the fastest choices are generally either an in-place transform
|
|
or an out-of-place transform with the <code>FFTW_DESTROY_INPUT</code> flag
|
|
(which allows the input array to be used as scratch space). In-place
|
|
is especially beneficial if the amount of data per process is large.
|
|
<span id="index-FFTW_005fDESTROY_005fINPUT-1"></span>
|
|
</p>
|
|
|
|
<p>Fourth, if you have multiple arrays to transform at once, rather than
|
|
calling FFTW’s MPI transforms several times it usually seems to be
|
|
faster to interleave the data and use the advanced interface. (This
|
|
groups the communications together instead of requiring separate
|
|
messages for each transform.)
|
|
</p>
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|