mirror of
https://github.com/tildearrow/furnace.git
synced 2024-11-18 18:45:10 +00:00
129 lines
6.2 KiB
HTML
129 lines
6.2 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>One-dimensional distributions (FFTW 3.3.10)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="One-dimensional distributions (FFTW 3.3.10)">
|
||
|
|
<meta name="keywords" content="One-dimensional distributions (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="MPI-Data-Distribution.html" rel="up" title="MPI Data Distribution">
|
||
|
|
<link href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html" rel="next" title="Multi-dimensional MPI DFTs of Real Data">
|
||
|
|
<link href="Transposed-distributions.html" rel="prev" title="Transposed distributions">
|
||
|
|
<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="One_002ddimensional-distributions"></span><div class="header">
|
||
|
|
<p>
|
||
|
|
Previous: <a href="Transposed-distributions.html" accesskey="p" rel="prev">Transposed distributions</a>, Up: <a href="MPI-Data-Distribution.html" accesskey="u" rel="up">MPI Data Distribution</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="One_002ddimensional-distributions-1"></span><h4 class="subsection">6.4.4 One-dimensional distributions</h4>
|
||
|
|
|
||
|
|
<p>For one-dimensional distributed DFTs using FFTW, matters are slightly
|
||
|
|
more complicated because the data distribution is more closely tied to
|
||
|
|
how the algorithm works. In particular, you can no longer pass an
|
||
|
|
arbitrary block size and must accept FFTW’s default; also, the block
|
||
|
|
sizes may be different for input and output. Also, the data
|
||
|
|
distribution depends on the flags and transform direction, in order
|
||
|
|
for forward and backward transforms to work correctly.
|
||
|
|
</p>
|
||
|
|
<div class="example">
|
||
|
|
<pre class="example">ptrdiff_t fftw_mpi_local_size_1d(ptrdiff_t n0, MPI_Comm comm,
|
||
|
|
int sign, unsigned flags,
|
||
|
|
ptrdiff_t *local_ni, ptrdiff_t *local_i_start,
|
||
|
|
ptrdiff_t *local_no, ptrdiff_t *local_o_start);
|
||
|
|
</pre></div>
|
||
|
|
<span id="index-fftw_005fmpi_005flocal_005fsize_005f1d"></span>
|
||
|
|
|
||
|
|
<p>This function computes the data distribution for a 1d transform of
|
||
|
|
size <code>n0</code> with the given transform <code>sign</code> and <code>flags</code>.
|
||
|
|
Both input and output data use block distributions. The input on the
|
||
|
|
current process will consist of <code>local_ni</code> numbers starting at
|
||
|
|
index <code>local_i_start</code>; e.g. if only a single process is used,
|
||
|
|
then <code>local_ni</code> will be <code>n0</code> and <code>local_i_start</code> will
|
||
|
|
be <code>0</code>. Similarly for the output, with <code>local_no</code> numbers
|
||
|
|
starting at index <code>local_o_start</code>. The return value of
|
||
|
|
<code>fftw_mpi_local_size_1d</code> will be the total number of elements to
|
||
|
|
allocate on the current process (which might be slightly larger than
|
||
|
|
the local size due to intermediate steps in the algorithm).
|
||
|
|
</p>
|
||
|
|
<p>As mentioned above (see <a href="Load-balancing.html">Load balancing</a>), the data will be divided
|
||
|
|
equally among the processes if <code>n0</code> is divisible by the
|
||
|
|
<em>square</em> of the number of processes. In this case,
|
||
|
|
<code>local_ni</code> will equal <code>local_no</code>. Otherwise, they may be
|
||
|
|
different.
|
||
|
|
</p>
|
||
|
|
<p>For some applications, such as convolutions, the order of the output
|
||
|
|
data is irrelevant. In this case, performance can be improved by
|
||
|
|
specifying that the output data be stored in an FFTW-defined
|
||
|
|
“scrambled” format. (In particular, this is the analogue of
|
||
|
|
transposed output in the multidimensional case: scrambled output saves
|
||
|
|
a communications step.) If you pass <code>FFTW_MPI_SCRAMBLED_OUT</code> in
|
||
|
|
the flags, then the output is stored in this (undocumented) scrambled
|
||
|
|
order. Conversely, to perform the inverse transform of data in
|
||
|
|
scrambled order, pass the <code>FFTW_MPI_SCRAMBLED_IN</code> flag.
|
||
|
|
<span id="index-FFTW_005fMPI_005fSCRAMBLED_005fOUT"></span>
|
||
|
|
<span id="index-FFTW_005fMPI_005fSCRAMBLED_005fIN"></span>
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>In MPI FFTW, only composite sizes <code>n0</code> can be parallelized; we
|
||
|
|
have not yet implemented a parallel algorithm for large prime sizes.
|
||
|
|
</p>
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Previous: <a href="Transposed-distributions.html" accesskey="p" rel="prev">Transposed distributions</a>, Up: <a href="MPI-Data-Distribution.html" accesskey="u" rel="up">MPI Data Distribution</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>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|