E, comm);
</pre></div>

<p>This is completely equivalent to:
</p>
<div class="example">
<pre class="example">MPI_Comm_size(comm, &amp;P);
plan = fftw_mpi_plan_many_transpose(P, P, howmany, 1, 1, in, out, comm, FFTW_ESTIMATE);
fftw_execute(plan);
fftw_destroy_plan(plan);
</pre></div>

<p>That is, computing a P&nbsp;&times;&nbsp;P
 transpose on <code>P</code> processes,
with a block size of 1, is just a standard all-to-all communication.
</p>
<p>However, using the FFTW routine instead of <code>MPI_Alltoall</c