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<h4 class="subsection">6.12.2 MPI Initialization</h4>
<p>Before calling any other FFTW MPI (‘<samp><span class="samp">fftw_mpi_</span></samp>’) function, and
before importing any wisdom for MPI problems, you must call:
<p><a name="index-fftw_005fmpi_005finit-434"></a>
<pre class="example"> void fftw_mpi_init(void);
</pre>
<p><a name="index-fftw_005finit_005fthreads-435"></a>If FFTW threads support is used, however, <code>fftw_mpi_init</code> should
be called <em>after</em> <code>fftw_init_threads</code> (see <a href="Combining-MPI-and-Threads.html#Combining-MPI-and-Threads">Combining MPI and Threads</a>). Calling <code>fftw_mpi_init</code> additional times (before
<code>fftw_mpi_cleanup</code>) has no effect.
<p>If you want to deallocate all persistent data and reset FFTW to the
pristine state it was in when you started your program, you can call:
<p><a name="index-fftw_005fmpi_005fcleanup-436"></a>
<pre class="example"> void fftw_mpi_cleanup(void);
</pre>
<p><a name="index-fftw_005fcleanup-437"></a>(This calls <code>fftw_cleanup</code>, so you need not call the serial
cleanup routine too, although it is safe to do so.) After calling
<code>fftw_mpi_cleanup</code>, all existing plans become undefined, and you
should not attempt to execute or destroy them. You must call
<code>fftw_mpi_init</code> again after <code>fftw_mpi_cleanup</code> if you want
to resume using the MPI FFTW routines.
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