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<title>FFTW 3.3.8: Using MPI Plans</title>

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<a name="Using-MPI-Plans"></a>
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<p>
Next: <a href="MPI-Data-Distribution-Functions.html#MPI-Data-Distribution-Functions" accesskey="n" rel="next">MPI Data Distribution Functions</a>, Previous: <a href="MPI-Initialization.html#MPI-Initialization" accesskey="p" rel="prev">MPI Initialization</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Using-MPI-Plans-1"></a>
<h4 class="subsection">6.12.3 Using MPI Plans</h4>

<p>Once an MPI plan is created, you can execute and destroy it using
<code>fftw_execute</code>, <code>fftw_destroy_plan</code>, and the other functions
in the serial interface that operate on generic plans (see <a href="Using-Plans.html#Using-Plans">Using Plans</a>).
</p>
<a name="index-collective-function-3"></a>
<a name="index-MPI-communicator-1"></a>
<p>The <code>fftw_execute</code> and <code>fftw_destroy_plan</code> functions, applied to
MPI plans, are <em>collective</em> calls: they must be called for all processes
in the communicator that was used to create the plan.
</p>
<a name="index-new_002darray-execution-1"></a>
<p>You must <em>not</em> use the serial new-array plan-execution functions
<code>fftw_execute_dft</code> and so on (see <a href="New_002darray-Execute-Functions.html#New_002darray-Execute-Functions">New-array Execute Functions</a>) with MPI plans.  Such functions are specialized to the
problem type, and there are specific new-array execute functions for MPI plans:
</p>
<a name="index-fftw_005fmpi_005fexecute_005fdft"></a>
<a name="index-fftw_005fmpi_005fexecute_005fdft_005fr2c"></a>
<a name="index-fftw_005fmpi_005fexecute_005fdft_005fc2r"></a>
<a name="index-fftw_005fmpi_005fexecute_005fr2r"></a>
<div class="example">
<pre class="example">void fftw_mpi_execute_dft(fftw_plan p, fftw_complex *in, fftw_complex *out);
void fftw_mpi_execute_dft_r2c(fftw_plan p, double *in, fftw_complex *out);
void fftw_mpi_execute_dft_c2r(fftw_plan p, fftw_complex *in, double *out);
void fftw_mpi_execute_r2r(fftw_plan p, double *in, double *out);
</pre></div>

<a name="index-alignment-3"></a>
<a name="index-fftw_005fmalloc-6"></a>
<p>These functions have the same restrictions as those of the serial
new-array execute functions.  They are <em>always</em> safe to apply to
the <em>same</em> <code>in</code> and <code>out</code> arrays that were used to
create the plan.  They can only be applied to new arrarys if those
arrays have the same types, dimensions, in-placeness, and alignment as
the original arrays, where the best way to ensure the same alignment
is to use FFTW&rsquo;s <code>fftw_malloc</code> and related allocation functions
for all arrays (see <a href="Memory-Allocation.html#Memory-Allocation">Memory Allocation</a>).  Note that distributed
transposes (see <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>) use
<code>fftw_mpi_execute_r2r</code>, since they count as rank-zero r2r plans
from FFTW&rsquo;s perspective.
</p>
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Next: <a href="MPI-Data-Distribution-Functions.html#MPI-Data-Distribution-Functions" accesskey="n" rel="next">MPI Data Distribution Functions</a>, Previous: <a href="MPI-Initialization.html#MPI-Initialization" accesskey="p" rel="prev">MPI Initialization</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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author	Chris Cannam <cannam@all-day-breakfast.com>
date	Mon, 02 Mar 2020 14:03:47 +0000
parents	bd3cc4d1df30
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