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Add FFTW3
author Chris Cannam
date Wed, 20 Mar 2013 15:35:50 +0000
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3 <title>Advanced distributed-transpose interface - FFTW 3.3.3</title>
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51 <p>
52 Next:&nbsp;<a rel="next" accesskey="n" href="An-improved-replacement-for-MPI_005fAlltoall.html#An-improved-replacement-for-MPI_005fAlltoall">An improved replacement for MPI_Alltoall</a>,
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57
58 <h4 class="subsection">6.7.2 Advanced distributed-transpose interface</h4>
59
60 <p>The above routines are for a transpose of a matrix of numbers (of type
61 <code>double</code>), using FFTW's default block sizes. More generally, one
62 can perform transposes of <em>tuples</em> of numbers, with
63 user-specified block sizes for the input and output:
64
65 <pre class="example"> fftw_plan fftw_mpi_plan_many_transpose
66 (ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t howmany,
67 ptrdiff_t block0, ptrdiff_t block1,
68 double *in, double *out, MPI_Comm comm, unsigned flags);
69 </pre>
70 <p><a name="index-fftw_005fmpi_005fplan_005fmany_005ftranspose-403"></a>
71 In this case, one is transposing an <code>n0</code> by <code>n1</code> matrix of
72 <code>howmany</code>-tuples (e.g. <code>howmany = 2</code> for complex numbers).
73 The input is distributed along the <code>n0</code> dimension with block size
74 <code>block0</code>, and the <code>n1</code> by <code>n0</code> output is distributed
75 along the <code>n1</code> dimension with block size <code>block1</code>. If
76 <code>FFTW_MPI_DEFAULT_BLOCK</code> (0) is passed for a block size then FFTW
77 uses its default block size. To get the local size of the data on
78 each process, you should then call <code>fftw_mpi_local_size_many_transposed</code>.
79 <a name="index-FFTW_005fMPI_005fDEFAULT_005fBLOCK-404"></a><a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005ftransposed-405"></a>
80
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82