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| author | Chris Cannam <cannam@all-day-breakfast.com> |
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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/MPI-Data-Distribution-Functions.html Wed Mar 20 15:35:50 2013 +0000 @@ -0,0 +1,149 @@ +<html lang="en"> +<head> +<title>MPI Data Distribution Functions - 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="FFTW-MPI-Reference.html#FFTW-MPI-Reference" title="FFTW MPI Reference"> +<link rel="prev" href="Using-MPI-Plans.html#Using-MPI-Plans" title="Using MPI Plans"> +<link rel="next" href="MPI-Plan-Creation.html#MPI-Plan-Creation" title="MPI Plan Creation"> +<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="MPI-Data-Distribution-Functions"></a> +<p> +Next: <a rel="next" accesskey="n" href="MPI-Plan-Creation.html#MPI-Plan-Creation">MPI Plan Creation</a>, +Previous: <a rel="previous" accesskey="p" href="Using-MPI-Plans.html#Using-MPI-Plans">Using MPI Plans</a>, +Up: <a rel="up" accesskey="u" href="FFTW-MPI-Reference.html#FFTW-MPI-Reference">FFTW MPI Reference</a> +<hr> +</div> + +<h4 class="subsection">6.12.4 MPI Data Distribution Functions</h4> + +<p><a name="index-data-distribution-447"></a>As described above (see <a href="MPI-Data-Distribution.html#MPI-Data-Distribution">MPI Data Distribution</a>), in order to +allocate your arrays, <em>before</em> creating a plan, you must first +call one of the following routines to determine the required +allocation size and the portion of the array locally stored on a given +process. The <code>MPI_Comm</code> communicator passed here must be +equivalent to the communicator used below for plan creation. + + <p>The basic interface for multidimensional transforms consists of the +functions: + + <p><a name="index-fftw_005fmpi_005flocal_005fsize_005f2d-448"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005f3d-449"></a><a name="index-fftw_005fmpi_005flocal_005fsize-450"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005f2d_005ftransposed-451"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005f3d_005ftransposed-452"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005ftransposed-453"></a> +<pre class="example"> ptrdiff_t fftw_mpi_local_size_2d(ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start); + ptrdiff_t fftw_mpi_local_size_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, + MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start); + ptrdiff_t fftw_mpi_local_size(int rnk, const ptrdiff_t *n, MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start); + + ptrdiff_t fftw_mpi_local_size_2d_transposed(ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start, + ptrdiff_t *local_n1, ptrdiff_t *local_1_start); + ptrdiff_t fftw_mpi_local_size_3d_transposed(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, + MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start, + ptrdiff_t *local_n1, ptrdiff_t *local_1_start); + ptrdiff_t fftw_mpi_local_size_transposed(int rnk, const ptrdiff_t *n, MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start, + ptrdiff_t *local_n1, ptrdiff_t *local_1_start); +</pre> + <p>These functions return the number of elements to allocate (complex +numbers for DFT/r2c/c2r plans, real numbers for r2r plans), whereas +the <code>local_n0</code> and <code>local_0_start</code> return the portion +(<code>local_0_start</code> to <code>local_0_start + local_n0 - 1</code>) of the +first dimension of an n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub> array that is stored on the local +process. See <a href="Basic-and-advanced-distribution-interfaces.html#Basic-and-advanced-distribution-interfaces">Basic and advanced distribution interfaces</a>. For +<code>FFTW_MPI_TRANSPOSED_OUT</code> plans, the ‘<samp><span class="samp">_transposed</span></samp>’ variants +are useful in order to also return the local portion of the first +dimension in the n<sub>1</sub> × n<sub>0</sub> × n<sub>2</sub> ×…× n<sub>d-1</sub> transposed output. See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>. The advanced interface for multidimensional +transforms is: + + <p><a name="index-advanced-interface-454"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005fmany-455"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005ftransposed-456"></a> +<pre class="example"> ptrdiff_t fftw_mpi_local_size_many(int rnk, const ptrdiff_t *n, ptrdiff_t howmany, + ptrdiff_t block0, MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start); + ptrdiff_t fftw_mpi_local_size_many_transposed(int rnk, const ptrdiff_t *n, ptrdiff_t howmany, + ptrdiff_t block0, ptrdiff_t block1, MPI_Comm comm, + ptrdiff_t *local_n0, ptrdiff_t *local_0_start, + ptrdiff_t *local_n1, ptrdiff_t *local_1_start); +</pre> + <p>These differ from the basic interface in only two ways. First, they +allow you to specify block sizes <code>block0</code> and <code>block1</code> (the +latter for the transposed output); you can pass +<code>FFTW_MPI_DEFAULT_BLOCK</code> to use FFTW's default block size as in +the basic interface. Second, you can pass a <code>howmany</code> parameter, +corresponding to the advanced planning interface below: this is for +transforms of contiguous <code>howmany</code>-tuples of numbers +(<code>howmany = 1</code> in the basic interface). + + <p>The corresponding basic and advanced routines for one-dimensional +transforms (currently only complex DFTs) are: + + <p><a name="index-fftw_005fmpi_005flocal_005fsize_005f1d-457"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005f1d-458"></a> +<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); + ptrdiff_t fftw_mpi_local_size_many_1d( + ptrdiff_t n0, ptrdiff_t howmany, + 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> + <p><a name="index-FFTW_005fMPI_005fSCRAMBLED_005fOUT-459"></a><a name="index-FFTW_005fMPI_005fSCRAMBLED_005fIN-460"></a>As above, the return value is the number of elements to allocate +(complex numbers, for complex DFTs). The <code>local_ni</code> and +<code>local_i_start</code> arguments return the portion +(<code>local_i_start</code> to <code>local_i_start + local_ni - 1</code>) of the +1d array that is stored on this process for the transform +<em>input</em>, and <code>local_no</code> and <code>local_o_start</code> are the +corresponding quantities for the input. The <code>sign</code> +(<code>FFTW_FORWARD</code> or <code>FFTW_BACKWARD</code>) and <code>flags</code> must +match the arguments passed when creating a plan. Although the inputs +and outputs have different data distributions in general, it is +guaranteed that the <em>output</em> data distribution of an +<code>FFTW_FORWARD</code> plan will match the <em>input</em> data distribution +of an <code>FFTW_BACKWARD</code> plan and vice versa; similarly for the +<code>FFTW_MPI_SCRAMBLED_OUT</code> and <code>FFTW_MPI_SCRAMBLED_IN</code> flags. +See <a href="One_002ddimensional-distributions.html#One_002ddimensional-distributions">One-dimensional distributions</a>. + + </body></html> +