mirror of
https://github.com/tildearrow/furnace.git
synced 2024-11-05 20:35:06 +00:00
92 lines
4 KiB
HTML
92 lines
4 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>How Many Threads to Use? (FFTW 3.3.10)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="How Many Threads to Use? (FFTW 3.3.10)">
|
||
|
|
<meta name="keywords" content="How Many Threads to Use? (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="Multi_002dthreaded-FFTW.html" rel="up" title="Multi-threaded FFTW">
|
||
|
|
<link href="Thread-safety.html" rel="next" title="Thread safety">
|
||
|
|
<link href="Usage-of-Multi_002dthreaded-FFTW.html" rel="prev" title="Usage of Multi-threaded FFTW">
|
||
|
|
<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="How-Many-Threads-to-Use_003f"></span><div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Thread-safety.html" accesskey="n" rel="next">Thread safety</a>, Previous: <a href="Usage-of-Multi_002dthreaded-FFTW.html" accesskey="p" rel="prev">Usage of Multi-threaded FFTW</a>, Up: <a href="Multi_002dthreaded-FFTW.html" accesskey="u" rel="up">Multi-threaded FFTW</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="How-Many-Threads-to-Use_003f-1"></span><h3 class="section">5.3 How Many Threads to Use?</h3>
|
||
|
|
|
||
|
|
<span id="index-number-of-threads"></span>
|
||
|
|
<p>There is a fair amount of overhead involved in synchronizing threads,
|
||
|
|
so the optimal number of threads to use depends upon the size of the
|
||
|
|
transform as well as on the number of processors you have.
|
||
|
|
</p>
|
||
|
|
<p>As a general rule, you don’t want to use more threads than you have
|
||
|
|
processors. (Using more threads will work, but there will be extra
|
||
|
|
overhead with no benefit.) In fact, if the problem size is too small,
|
||
|
|
you may want to use fewer threads than you have processors.
|
||
|
|
</p>
|
||
|
|
<p>You will have to experiment with your system to see what level of
|
||
|
|
parallelization is best for your problem size. Typically, the problem
|
||
|
|
will have to involve at least a few thousand data points before threads
|
||
|
|
become beneficial. If you plan with <code>FFTW_PATIENT</code>, it will
|
||
|
|
automatically disable threads for sizes that don’t benefit from
|
||
|
|
parallelization.
|
||
|
|
<span id="index-FFTW_005fPATIENT-3"></span>
|
||
|
|
</p>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|