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<html>
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<!-- This manual is for FFTW
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(version 3.3.10, 10 December 2020).
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Copyright (C) 2003 Matteo Frigo.
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Copyright (C) 2003 Massachusetts Institute of Technology.
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Permission is granted to make and distribute verbatim copies of this
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<title>MPI Plan Creation (FFTW 3.3.10)</title>
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="FFTW-MPI-Reference.html" rel="up" title="FFTW MPI Reference">
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<link href="MPI-Wisdom-Communication.html" rel="next" title="MPI Wisdom Communication">
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</head>
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<span id="MPI-Plan-Creation"></span><div class="header">
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<p>
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Next: <a href="MPI-Wisdom-Communication.html" accesskey="n" rel="next">MPI Wisdom Communication</a>, Previous: <a href="MPI-Data-Distribution-Functions.html" accesskey="p" rel="prev">MPI Data Distribution Functions</a>, Up: <a href="FFTW-MPI-Reference.html" accesskey="u" rel="up">FFTW MPI Reference</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>
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</div>
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<hr>
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<span id="MPI-Plan-Creation-1"></span><h4 class="subsection">6.12.5 MPI Plan Creation</h4>
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<span id="Complex_002ddata-MPI-DFTs"></span><h4 class="subsubheading">Complex-data MPI DFTs</h4>
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<p>Plans for complex-data DFTs (see <a href="2d-MPI-example.html">2d MPI example</a>) are created by:
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</p>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005f1d"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005f2d-1"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005f3d"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft"></span>
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<span id="index-fftw_005fmpi_005fplan_005fmany_005fdft"></span>
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<div class="example">
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<pre class="example">fftw_plan fftw_mpi_plan_dft_1d(ptrdiff_t n0, fftw_complex *in, fftw_complex *out,
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MPI_Comm comm, int sign, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_2d(ptrdiff_t n0, ptrdiff_t n1,
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fftw_complex *in, fftw_complex *out,
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MPI_Comm comm, int sign, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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fftw_complex *in, fftw_complex *out,
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MPI_Comm comm, int sign, unsigned flags);
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fftw_plan fftw_mpi_plan_dft(int rnk, const ptrdiff_t *n,
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fftw_complex *in, fftw_complex *out,
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MPI_Comm comm, int sign, unsigned flags);
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fftw_plan fftw_mpi_plan_many_dft(int rnk, const ptrdiff_t *n,
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ptrdiff_t howmany, ptrdiff_t block, ptrdiff_t tblock,
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fftw_complex *in, fftw_complex *out,
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MPI_Comm comm, int sign, unsigned flags);
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</pre></div>
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<span id="index-MPI-communicator-2"></span>
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<span id="index-collective-function-4"></span>
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<p>These are similar to their serial counterparts (see <a href="Complex-DFTs.html">Complex DFTs</a>)
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in specifying the dimensions, sign, and flags of the transform. The
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<code>comm</code> argument gives an MPI communicator that specifies the set
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of processes to participate in the transform; plan creation is a
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collective function that must be called for all processes in the
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communicator. The <code>in</code> and <code>out</code> pointers refer only to a
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portion of the overall transform data (see <a href="MPI-Data-Distribution.html">MPI Data Distribution</a>)
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as specified by the ‘<samp>local_size</samp>’ functions in the previous
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section. Unless <code>flags</code> contains <code>FFTW_ESTIMATE</code>, these
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arrays are overwritten during plan creation as for the serial
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interface. For multi-dimensional transforms, any dimensions <code>>
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1</code> are supported; for one-dimensional transforms, only composite
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(non-prime) <code>n0</code> are currently supported (unlike the serial
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FFTW). Requesting an unsupported transform size will yield a
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<code>NULL</code> plan. (As in the serial interface, highly composite sizes
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generally yield the best performance.)
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</p>
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<span id="index-advanced-interface-6"></span>
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<span id="index-FFTW_005fMPI_005fDEFAULT_005fBLOCK-2"></span>
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<span id="index-stride-3"></span>
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<p>The advanced-interface <code>fftw_mpi_plan_many_dft</code> additionally
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allows you to specify the block sizes for the first dimension
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(<code>block</code>) of the n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub>
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input data and the first dimension
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(<code>tblock</code>) of the n<sub>1</sub> × n<sub>0</sub> × n<sub>2</sub> ×…× n<sub>d-1</sub>
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transposed data (at intermediate
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steps of the transform, and for the output if
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<code>FFTW_TRANSPOSED_OUT</code> is specified in <code>flags</code>). These must
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be the same block sizes as were passed to the corresponding
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‘<samp>local_size</samp>’ function; you can pass <code>FFTW_MPI_DEFAULT_BLOCK</code>
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to use FFTW’s default block size as in the basic interface. Also, the
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<code>howmany</code> parameter specifies that the transform is of contiguous
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<code>howmany</code>-tuples rather than individual complex numbers; this
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corresponds to the same parameter in the serial advanced interface
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(see <a href="Advanced-Complex-DFTs.html">Advanced Complex DFTs</a>) with <code>stride = howmany</code> and
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<code>dist = 1</code>.
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</p>
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<span id="MPI-flags"></span><h4 class="subsubheading">MPI flags</h4>
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<p>The <code>flags</code> can be any of those for the serial FFTW
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(see <a href="Planner-Flags.html">Planner Flags</a>), and in addition may include one or more of
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the following MPI-specific flags, which improve performance at the
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cost of changing the output or input data formats.
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</p>
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<ul>
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<li> <span id="index-FFTW_005fMPI_005fSCRAMBLED_005fOUT-2"></span>
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<span id="index-FFTW_005fMPI_005fSCRAMBLED_005fIN-2"></span>
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<code>FFTW_MPI_SCRAMBLED_OUT</code>, <code>FFTW_MPI_SCRAMBLED_IN</code>: valid for
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1d transforms only, these flags indicate that the output/input of the
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transform are in an undocumented “scrambled” order. A forward
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<code>FFTW_MPI_SCRAMBLED_OUT</code> transform can be inverted by a backward
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<code>FFTW_MPI_SCRAMBLED_IN</code> (times the usual 1/<i>N</i> normalization).
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See <a href="One_002ddimensional-distributions.html">One-dimensional distributions</a>.
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</li><li> <span id="index-FFTW_005fMPI_005fTRANSPOSED_005fOUT-2"></span>
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<span id="index-FFTW_005fMPI_005fTRANSPOSED_005fIN-2"></span>
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<code>FFTW_MPI_TRANSPOSED_OUT</code>, <code>FFTW_MPI_TRANSPOSED_IN</code>: valid
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for multidimensional (<code>rnk > 1</code>) transforms only, these flags
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specify that the output or input of an n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub>
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transform is
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transposed to n<sub>1</sub> × n<sub>0</sub> × n<sub>2</sub> ×…× n<sub>d-1</sub>
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. See <a href="Transposed-distributions.html">Transposed distributions</a>.
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</li></ul>
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<span id="Real_002ddata-MPI-DFTs"></span><h4 class="subsubheading">Real-data MPI DFTs</h4>
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<span id="index-r2c-4"></span>
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<p>Plans for real-input/output (r2c/c2r) DFTs (see <a href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html">Multi-dimensional MPI DFTs of Real Data</a>) are created by:
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</p>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f2d"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f2d-1"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f3d"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fr2c"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f2d"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f2d-1"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f3d"></span>
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<span id="index-fftw_005fmpi_005fplan_005fdft_005fc2r"></span>
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<div class="example">
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<pre class="example">fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1,
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double *in, fftw_complex *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1,
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double *in, fftw_complex *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_r2c_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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double *in, fftw_complex *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_r2c(int rnk, const ptrdiff_t *n,
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double *in, fftw_complex *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1,
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fftw_complex *in, double *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1,
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fftw_complex *in, double *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_c2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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fftw_complex *in, double *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_dft_c2r(int rnk, const ptrdiff_t *n,
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fftw_complex *in, double *out,
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MPI_Comm comm, unsigned flags);
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</pre></div>
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<p>Similar to the serial interface (see <a href="Real_002ddata-DFTs.html">Real-data DFTs</a>), these
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transform logically n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub>
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real data to/from n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × (n<sub>d-1</sub>/2 + 1)
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complex
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data, representing the non-redundant half of the conjugate-symmetry
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output of a real-input DFT (see <a href="Multi_002ddimensional-Transforms.html">Multi-dimensional Transforms</a>).
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However, the real array must be stored within a padded n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × [2 (n<sub>d-1</sub>/2 + 1)]
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array (much like the in-place serial r2c transforms, but here for
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out-of-place transforms as well). Currently, only multi-dimensional
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(<code>rnk > 1</code>) r2c/c2r transforms are supported (requesting a plan
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for <code>rnk = 1</code> will yield <code>NULL</code>). As explained above
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(see <a href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html">Multi-dimensional MPI DFTs of Real Data</a>), the data
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distribution of both the real and complex arrays is given by the
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‘<samp>local_size</samp>’ function called for the dimensions of the
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<em>complex</em> array. Similar to the other planning functions, the
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input and output arrays are overwritten when the plan is created
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except in <code>FFTW_ESTIMATE</code> mode.
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</p>
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<p>As for the complex DFTs above, there is an advance interface that
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allows you to manually specify block sizes and to transform contiguous
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<code>howmany</code>-tuples of real/complex numbers:
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</p>
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<span id="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fr2c"></span>
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<span id="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fc2r"></span>
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<div class="example">
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<pre class="example">fftw_plan fftw_mpi_plan_many_dft_r2c
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(int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
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ptrdiff_t iblock, ptrdiff_t oblock,
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double *in, fftw_complex *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_many_dft_c2r
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(int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
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ptrdiff_t iblock, ptrdiff_t oblock,
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fftw_complex *in, double *out,
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MPI_Comm comm, unsigned flags);
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</pre></div>
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<span id="MPI-r2r-transforms"></span><h4 class="subsubheading">MPI r2r transforms</h4>
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<span id="index-r2r-4"></span>
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<p>There are corresponding plan-creation routines for r2r
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transforms (see <a href="More-DFTs-of-Real-Data.html">More DFTs of Real Data</a>), currently supporting
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multidimensional (<code>rnk > 1</code>) transforms only (<code>rnk = 1</code> will
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yield a <code>NULL</code> plan):
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</p>
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<div class="example">
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<pre class="example">fftw_plan fftw_mpi_plan_r2r_2d(ptrdiff_t n0, ptrdiff_t n1,
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double *in, double *out,
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MPI_Comm comm,
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fftw_r2r_kind kind0, fftw_r2r_kind kind1,
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unsigned flags);
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fftw_plan fftw_mpi_plan_r2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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double *in, double *out,
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MPI_Comm comm,
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fftw_r2r_kind kind0, fftw_r2r_kind kind1, fftw_r2r_kind kind2,
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unsigned flags);
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fftw_plan fftw_mpi_plan_r2r(int rnk, const ptrdiff_t *n,
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double *in, double *out,
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MPI_Comm comm, const fftw_r2r_kind *kind,
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unsigned flags);
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fftw_plan fftw_mpi_plan_many_r2r(int rnk, const ptrdiff_t *n,
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ptrdiff_t iblock, ptrdiff_t oblock,
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double *in, double *out,
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MPI_Comm comm, const fftw_r2r_kind *kind,
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unsigned flags);
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</pre></div>
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<p>The parameters are much the same as for the complex DFTs above, except
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that the arrays are of real numbers (and hence the outputs of the
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‘<samp>local_size</samp>’ data-distribution functions should be interpreted as
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counts of real rather than complex numbers). Also, the <code>kind</code>
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parameters specify the r2r kinds along each dimension as for the
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serial interface (see <a href="Real_002dto_002dReal-Transform-Kinds.html">Real-to-Real Transform Kinds</a>). See <a href="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms.html">Other Multi-dimensional Real-data MPI Transforms</a>.
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</p>
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<span id="MPI-transposition"></span><h4 class="subsubheading">MPI transposition</h4>
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<span id="index-transpose-5"></span>
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<p>FFTW also provides routines to plan a transpose of a distributed
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<code>n0</code> by <code>n1</code> array of real numbers, or an array of
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<code>howmany</code>-tuples of real numbers with specified block sizes
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(see <a href="FFTW-MPI-Transposes.html">FFTW MPI Transposes</a>):
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</p>
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<span id="index-fftw_005fmpi_005fplan_005ftranspose-1"></span>
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<span id="index-fftw_005fmpi_005fplan_005fmany_005ftranspose-1"></span>
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<div class="example">
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<pre class="example">fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1,
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double *in, double *out,
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MPI_Comm comm, unsigned flags);
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fftw_plan fftw_mpi_plan_many_transpose
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(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t howmany,
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ptrdiff_t block0, ptrdiff_t block1,
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double *in, double *out, MPI_Comm comm, unsigned flags);
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</pre></div>
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<span id="index-new_002darray-execution-2"></span>
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<span id="index-fftw_005fmpi_005fexecute_005fr2r-1"></span>
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<p>These plans are used with the <code>fftw_mpi_execute_r2r</code> new-array
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execute function (see <a href="Using-MPI-Plans.html">Using MPI Plans</a>), since they count as (rank
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zero) r2r plans from FFTW’s perspective.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="MPI-Wisdom-Communication.html" accesskey="n" rel="next">MPI Wisdom Communication</a>, Previous: <a href="MPI-Data-Distribution-Functions.html" accesskey="p" rel="prev">MPI Data Distribution Functions</a>, Up: <a href="FFTW-MPI-Reference.html" accesskey="u" rel="up">FFTW MPI Reference</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>
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</div>
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</body>
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</html>
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