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First commit. VS2013, Codeblocks and Mac OSX configuration
author Geogaddi\David <d.m.ronan@qmul.ac.uk>
date Thu, 09 Jul 2015 01:12:16 +0100
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+<title>Basic distributed-transpose interface - FFTW 3.2alpha3</title>
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+<a name="Basic-distributed-transpose-interface"></a>
+<a name="Basic-distributed_002dtranspose-interface"></a>
+Next:&nbsp;<a rel="next" accesskey="n" href="Advanced-distributed_002dtranspose-interface.html#Advanced-distributed_002dtranspose-interface">Advanced distributed-transpose interface</a>,
+Previous:&nbsp;<a rel="previous" accesskey="p" href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>,
+Up:&nbsp;<a rel="up" accesskey="u" href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>
+<hr>
+</div>
+
+<h4 class="subsection">6.7.1 Basic distributed-transpose interface</h4>
+
+<p>In particular, suppose that we have an <code>n0</code> by <code>n1</code> array in
+row-major order, block-distributed across the <code>n0</code> dimension.  To
+transpose this into an <code>n1</code> by <code>n0</code> array block-distributed
+across the <code>n1</code> dimension, we would create a plan by calling the
+following function:
+
+<pre class="example">     fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1,
+                                       double *in, double *out,
+                                       MPI_Comm comm, unsigned flags);
+</pre>
+   <p><a name="index-fftw_005fmpi_005fplan_005ftranspose-367"></a>
+The input and output arrays (<code>in</code> and <code>out</code>) can be the
+same.  The transpose is actually executed by calling
+<code>fftw_execute</code> on the plan, as usual. 
+<a name="index-fftw_005fexecute-368"></a>
+The <code>flags</code> are the usual FFTW planner flags, but support
+two additional flags: <code>FFTW_MPI_TRANSPOSED_OUT</code> and/or
+<code>FFTW_MPI_TRANSPOSED_IN</code>.  What these flags indicate, for
+transpose plans, is that the output and/or input, respectively, are
+<em>locally</em> transposed.  That is, on each process input data is
+normally stored as a <code>local_n0</code> by <code>n1</code> array in row-major
+order, but for an <code>FFTW_MPI_TRANSPOSED_IN</code> plan the input data is
+stored as <code>n1</code> by <code>local_n0</code> in row-major order.  Similarly,
+<code>FFTW_MPI_TRANSPOSED_OUT</code> means that the output is <code>n0</code> by
+<code>local_n1</code> instead of <code>local_n1</code> by <code>n0</code>. 
+<a name="index-FFTW_005fMPI_005fTRANSPOSED_005fOUT-369"></a><a name="index-FFTW_005fMPI_005fTRANSPOSED_005fIN-370"></a>
+To determine the local size of the array on each process before and
+after the transpose, as well as the amount of storage that must be
+allocated, one should call <code>fftw_mpi_local_size_2d_transposed</code>,
+just as for a 2d DFT as described in the previous section:
+<a name="index-data-distribution-371"></a>
+<pre class="example">     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);
+</pre>
+   <p><a name="index-fftw_005fmpi_005flocal_005fsize_005f2d_005ftransposed-372"></a>
+
+   </body></html>
+