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<h4 class="subsection">6.7.2 Advanced distributed-transpose interface</h4>
<p>The above routines are for a transpose of a matrix of numbers (of type
<code>double</code>), using FFTW's default block sizes. More generally, one
can perform transposes of <em>tuples</em> of numbers, with
user-specified block sizes for the input and output:
<pre class="example"> fftw_plan fftw_mpi_plan_many_transpose
(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t howmany,
ptrdiff_t block0, ptrdiff_t block1,
double *in, double *out, MPI_Comm comm, unsigned flags);
</pre>
<p><a name="index-fftw_005fmpi_005fplan_005fmany_005ftranspose-403"></a>
In this case, one is transposing an <code>n0</code> by <code>n1</code> matrix of
<code>howmany</code>-tuples (e.g. <code>howmany = 2</code> for complex numbers).
The input is distributed along the <code>n0</code> dimension with block size
<code>block0</code>, and the <code>n1</code> by <code>n0</code> output is distributed
along the <code>n1</code> dimension with block size <code>block1</code>. If
<code>FFTW_MPI_DEFAULT_BLOCK</code> (0) is passed for a block size then FFTW
uses its default block size. To get the local size of the data on
each process, you should then call <code>fftw_mpi_local_size_many_transposed</code>.
<a name="index-FFTW_005fMPI_005fDEFAULT_005fBLOCK-404"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005ftransposed-405"></a>
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