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Current fftw source
| author | Chris Cannam <cannam@all-day-breakfast.com> |
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| date | Tue, 18 Oct 2016 13:40:26 +0100 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.5/doc/html/Distributed_002dmemory-FFTW-with-MPI.html Tue Oct 18 13:40:26 2016 +0100 @@ -0,0 +1,162 @@ +<!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 3.3.5, 30 July 2016). + +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 5.2, http://www.gnu.org/software/texinfo/ --> +<head> +<title>FFTW 3.3.5: Distributed-memory FFTW with MPI</title> + +<meta name="description" content="FFTW 3.3.5: Distributed-memory FFTW with MPI"> +<meta name="keywords" content="FFTW 3.3.5: Distributed-memory FFTW with MPI"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="index.html#Top" rel="up" title="Top"> +<link href="FFTW-MPI-Installation.html#FFTW-MPI-Installation" rel="next" title="FFTW MPI Installation"> +<link href="Thread-safety.html#Thread-safety" rel="prev" title="Thread safety"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {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} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Distributed_002dmemory-FFTW-with-MPI"></a> +<div class="header"> +<p> +Next: <a href="Calling-FFTW-from-Modern-Fortran.html#Calling-FFTW-from-Modern-Fortran" accesskey="n" rel="next">Calling FFTW from Modern Fortran</a>, Previous: <a href="Multi_002dthreaded-FFTW.html#Multi_002dthreaded-FFTW" accesskey="p" rel="prev">Multi-threaded FFTW</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Distributed_002dmemory-FFTW-with-MPI-1"></a> +<h2 class="chapter">6 Distributed-memory FFTW with MPI</h2> +<a name="index-MPI"></a> + +<a name="index-parallel-transform-1"></a> +<p>In this chapter we document the parallel FFTW routines for parallel +systems supporting the MPI message-passing interface. Unlike the +shared-memory threads described in the previous chapter, MPI allows +you to use <em>distributed-memory</em> parallelism, where each CPU has +its own separate memory, and which can scale up to clusters of many +thousands of processors. This capability comes at a price, however: +each process only stores a <em>portion</em> of the data to be +transformed, which means that the data structures and +programming-interface are quite different from the serial or threads +versions of FFTW. +<a name="index-data-distribution"></a> +</p> + +<p>Distributed-memory parallelism is especially useful when you are +transforming arrays so large that they do not fit into the memory of a +single processor. The storage per-process required by FFTW’s MPI +routines is proportional to the total array size divided by the number +of processes. Conversely, distributed-memory parallelism can easily +pose an unacceptably high communications overhead for small problems; +the threshold problem size for which parallelism becomes advantageous +will depend on the precise problem you are interested in, your +hardware, and your MPI implementation. +</p> +<p>A note on terminology: in MPI, you divide the data among a set of +“processes” which each run in their own memory address space. +Generally, each process runs on a different physical processor, but +this is not required. A set of processes in MPI is described by an +opaque data structure called a “communicator,” the most common of +which is the predefined communicator <code>MPI_COMM_WORLD</code> which +refers to <em>all</em> processes. For more information on these and +other concepts common to all MPI programs, we refer the reader to the +documentation at <a href="http://www.mcs.anl.gov/research/projects/mpi/">the MPI home +page</a>. +<a name="index-MPI-communicator"></a> +<a name="index-MPI_005fCOMM_005fWORLD"></a> +</p> + +<p>We assume in this chapter that the reader is familiar with the usage +of the serial (uniprocessor) FFTW, and focus only on the concepts new +to the MPI interface. +</p> +<table class="menu" border="0" cellspacing="0"> +<tr><td align="left" valign="top">• <a href="FFTW-MPI-Installation.html#FFTW-MPI-Installation" accesskey="1">FFTW MPI Installation</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="Linking-and-Initializing-MPI-FFTW.html#Linking-and-Initializing-MPI-FFTW" accesskey="2">Linking and Initializing MPI FFTW</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="2d-MPI-example.html#g_t2d-MPI-example" accesskey="3">2d MPI example</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="MPI-Data-Distribution.html#MPI-Data-Distribution" accesskey="4">MPI Data Distribution</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data" accesskey="5">Multi-dimensional MPI DFTs of Real Data</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms.html#Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms" accesskey="6">Other Multi-dimensional Real-data MPI Transforms</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes" accesskey="7">FFTW MPI Transposes</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom" accesskey="8">FFTW MPI Wisdom</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks" accesskey="9">Avoiding MPI Deadlocks</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips">FFTW MPI Performance Tips</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads">Combining MPI and Threads</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference">FFTW MPI Reference</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="FFTW-MPI-Fortran-Interface.html#FFTW-MPI-Fortran-Interface">FFTW MPI Fortran Interface</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +</table> + +<hr> +<div class="header"> +<p> +Next: <a href="Calling-FFTW-from-Modern-Fortran.html#Calling-FFTW-from-Modern-Fortran" accesskey="n" rel="next">Calling FFTW from Modern Fortran</a>, Previous: <a href="Multi_002dthreaded-FFTW.html#Multi_002dthreaded-FFTW" accesskey="p" rel="prev">Multi-threaded FFTW</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html>