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diff src/fftw-3.3.3/doc/html/Distributed_002dmemory-FFTW-with-MPI.html @ 10:37bf6b4a2645
Add FFTW3
| author | Chris Cannam |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fftw-3.3.3/doc/html/Distributed_002dmemory-FFTW-with-MPI.html Wed Mar 20 15:35:50 2013 +0000 @@ -0,0 +1,115 @@ +<html lang="en"> +<head> +<title>Distributed-memory FFTW with MPI - 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="prev" href="Multi_002dthreaded-FFTW.html#Multi_002dthreaded-FFTW" title="Multi-threaded FFTW"> +<link rel="next" href="Calling-FFTW-from-Modern-Fortran.html#Calling-FFTW-from-Modern-Fortran" title="Calling FFTW from Modern Fortran"> +<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="Distributed-memory-FFTW-with-MPI"></a> +<a name="Distributed_002dmemory-FFTW-with-MPI"></a> +<p> +Next: <a rel="next" accesskey="n" href="Calling-FFTW-from-Modern-Fortran.html#Calling-FFTW-from-Modern-Fortran">Calling FFTW from Modern Fortran</a>, +Previous: <a rel="previous" accesskey="p" href="Multi_002dthreaded-FFTW.html#Multi_002dthreaded-FFTW">Multi-threaded FFTW</a>, +Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a> +<hr> +</div> + +<h2 class="chapter">6 Distributed-memory FFTW with MPI</h2> + +<p><a name="index-MPI-344"></a> +<a name="index-parallel-transform-345"></a>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-346"></a> + + <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>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-347"></a><a name="index-MPI_005fCOMM_005fWORLD-348"></a> + + <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. + +<ul class="menu"> +<li><a accesskey="1" href="FFTW-MPI-Installation.html#FFTW-MPI-Installation">FFTW MPI Installation</a> +<li><a accesskey="2" href="Linking-and-Initializing-MPI-FFTW.html#Linking-and-Initializing-MPI-FFTW">Linking and Initializing MPI FFTW</a> +<li><a accesskey="3" href="2d-MPI-example.html#g_t2d-MPI-example">2d MPI example</a> +<li><a accesskey="4" href="MPI-Data-Distribution.html#MPI-Data-Distribution">MPI Data Distribution</a> +<li><a accesskey="5" href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data">Multi-dimensional MPI DFTs of Real Data</a> +<li><a accesskey="6" href="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms.html#Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms">Other Multi-dimensional Real-data MPI Transforms</a> +<li><a accesskey="7" href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a> +<li><a accesskey="8" href="FFTW-MPI-Wisdom.html#FFTW-MPI-Wisdom">FFTW MPI Wisdom</a> +<li><a accesskey="9" href="Avoiding-MPI-Deadlocks.html#Avoiding-MPI-Deadlocks">Avoiding MPI Deadlocks</a> +<li><a href="FFTW-MPI-Performance-Tips.html#FFTW-MPI-Performance-Tips">FFTW MPI Performance Tips</a> +<li><a href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads">Combining MPI and Threads</a> +<li><a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference">FFTW MPI Reference</a> +<li><a href="FFTW-MPI-Fortran-Interface.html#FFTW-MPI-Fortran-Interface">FFTW MPI Fortran Interface</a> +</ul> + +<!-- --> + </body></html> +