Mercurial > hg > sv-dependency-builds

<html lang="en">
<head>
<title>FFTW MPI Performance Tips - FFTW 3.3.3</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="FFTW 3.3.3">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Distributed_002dmemory-FFTW-with-MPI.html#Distributed_002dmemory-FFTW-with-MPI" title="Distributed-memory FFTW with MPI">
<link rel="prev" href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks" title="Avoiding MPI Deadlocks">
<link rel="next" href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads" title="Combining MPI and Threads">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
This manual is for FFTW
(version 3.3.3, 25 November 2012).

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.
   -->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
  pre.display { font-family:inherit }
  pre.format  { font-family:inherit }
  pre.smalldisplay { font-family:inherit; font-size:smaller }
  pre.smallformat  { font-family:inherit; font-size:smaller }
  pre.smallexample { font-size:smaller }
  pre.smalllisp    { font-size:smaller }
  span.sc    { font-variant:small-caps }
  span.roman { font-family:serif; font-weight:normal; }
  span.sansserif { font-family:sans-serif; font-weight:normal; }
--></style>
</head>
<body>
<div class="node">
<a name="FFTW-MPI-Performance-Tips"></a>
<p>
Next:&nbsp;<a rel="next" accesskey="n" href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads">Combining MPI and Threads</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks">Avoiding MPI Deadlocks</a>,
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>
<hr>
</div>

<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>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">Load balancing</a>.
<a name="index-block-distribution-423"></a><a name="index-load-balancing-424"></a>

   <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">Transposed distributions</a>.
<a name="index-transpose-425"></a>

   <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.
<a name="index-FFTW_005fDESTROY_005fINPUT-426"></a>

   <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.)

<!--  -->
   </body></html>
author	Chris Cannam <cannam@all-day-breakfast.com>
date	Wed, 20 Mar 2013 15:35:50 +0000
parents
children