ray 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-404"></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 *