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author Chris Cannam <cannam@all-day-breakfast.com>
date Wed, 20 Mar 2013 15:35:50 +0000
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cannam@95 3 <title>MPI Plan Creation - FFTW 3.3.3</title>
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cannam@95 48 <div class="node">
cannam@95 49 <a name="MPI-Plan-Creation"></a>
cannam@95 50 <p>
cannam@95 51 Next:&nbsp;<a rel="next" accesskey="n" href="MPI-Wisdom-Communication.html#MPI-Wisdom-Communication">MPI Wisdom Communication</a>,
cannam@95 52 Previous:&nbsp;<a rel="previous" accesskey="p" href="MPI-Data-Distribution-Functions.html#MPI-Data-Distribution-Functions">MPI Data Distribution Functions</a>,
cannam@95 53 Up:&nbsp;<a rel="up" accesskey="u" href="FFTW-MPI-Reference.html#FFTW-MPI-Reference">FFTW MPI Reference</a>
cannam@95 54 <hr>
cannam@95 55 </div>
cannam@95 56
cannam@95 57 <h4 class="subsection">6.12.5 MPI Plan Creation</h4>
cannam@95 58
cannam@95 59 <h5 class="subsubheading">Complex-data MPI DFTs</h5>
cannam@95 60
cannam@95 61 <p>Plans for complex-data DFTs (see <a href="2d-MPI-example.html#g_t2d-MPI-example">2d MPI example</a>) are created by:
cannam@95 62
cannam@95 63 <p><a name="index-fftw_005fmpi_005fplan_005fdft_005f1d-461"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005f2d-462"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005f3d-463"></a><a name="index-fftw_005fmpi_005fplan_005fdft-464"></a><a name="index-fftw_005fmpi_005fplan_005fmany_005fdft-465"></a>
cannam@95 64 <pre class="example"> fftw_plan fftw_mpi_plan_dft_1d(ptrdiff_t n0, fftw_complex *in, fftw_complex *out,
cannam@95 65 MPI_Comm comm, int sign, unsigned flags);
cannam@95 66 fftw_plan fftw_mpi_plan_dft_2d(ptrdiff_t n0, ptrdiff_t n1,
cannam@95 67 fftw_complex *in, fftw_complex *out,
cannam@95 68 MPI_Comm comm, int sign, unsigned flags);
cannam@95 69 fftw_plan fftw_mpi_plan_dft_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
cannam@95 70 fftw_complex *in, fftw_complex *out,
cannam@95 71 MPI_Comm comm, int sign, unsigned flags);
cannam@95 72 fftw_plan fftw_mpi_plan_dft(int rnk, const ptrdiff_t *n,
cannam@95 73 fftw_complex *in, fftw_complex *out,
cannam@95 74 MPI_Comm comm, int sign, unsigned flags);
cannam@95 75 fftw_plan fftw_mpi_plan_many_dft(int rnk, const ptrdiff_t *n,
cannam@95 76 ptrdiff_t howmany, ptrdiff_t block, ptrdiff_t tblock,
cannam@95 77 fftw_complex *in, fftw_complex *out,
cannam@95 78 MPI_Comm comm, int sign, unsigned flags);
cannam@95 79 </pre>
cannam@95 80 <p><a name="index-MPI-communicator-466"></a><a name="index-collective-function-467"></a>These are similar to their serial counterparts (see <a href="Complex-DFTs.html#Complex-DFTs">Complex DFTs</a>)
cannam@95 81 in specifying the dimensions, sign, and flags of the transform. The
cannam@95 82 <code>comm</code> argument gives an MPI communicator that specifies the set
cannam@95 83 of processes to participate in the transform; plan creation is a
cannam@95 84 collective function that must be called for all processes in the
cannam@95 85 communicator. The <code>in</code> and <code>out</code> pointers refer only to a
cannam@95 86 portion of the overall transform data (see <a href="MPI-Data-Distribution.html#MPI-Data-Distribution">MPI Data Distribution</a>)
cannam@95 87 as specified by the &lsquo;<samp><span class="samp">local_size</span></samp>&rsquo; functions in the previous
cannam@95 88 section. Unless <code>flags</code> contains <code>FFTW_ESTIMATE</code>, these
cannam@95 89 arrays are overwritten during plan creation as for the serial
cannam@95 90 interface. For multi-dimensional transforms, any dimensions <code>&gt;
cannam@95 91 1</code> are supported; for one-dimensional transforms, only composite
cannam@95 92 (non-prime) <code>n0</code> are currently supported (unlike the serial
cannam@95 93 FFTW). Requesting an unsupported transform size will yield a
cannam@95 94 <code>NULL</code> plan. (As in the serial interface, highly composite sizes
cannam@95 95 generally yield the best performance.)
cannam@95 96
cannam@95 97 <p><a name="index-advanced-interface-468"></a><a name="index-FFTW_005fMPI_005fDEFAULT_005fBLOCK-469"></a><a name="index-stride-470"></a>The advanced-interface <code>fftw_mpi_plan_many_dft</code> additionally
cannam@95 98 allows you to specify the block sizes for the first dimension
cannam@95 99 (<code>block</code>) of the n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&nbsp;&hellip;&nbsp;&times;&nbsp;n<sub>d-1</sub> input data and the first dimension
cannam@95 100 (<code>tblock</code>) of the n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&hellip;&times;&nbsp;n<sub>d-1</sub> transposed data (at intermediate
cannam@95 101 steps of the transform, and for the output if
cannam@95 102 <code>FFTW_TRANSPOSED_OUT</code> is specified in <code>flags</code>). These must
cannam@95 103 be the same block sizes as were passed to the corresponding
cannam@95 104 &lsquo;<samp><span class="samp">local_size</span></samp>&rsquo; function; you can pass <code>FFTW_MPI_DEFAULT_BLOCK</code>
cannam@95 105 to use FFTW's default block size as in the basic interface. Also, the
cannam@95 106 <code>howmany</code> parameter specifies that the transform is of contiguous
cannam@95 107 <code>howmany</code>-tuples rather than individual complex numbers; this
cannam@95 108 corresponds to the same parameter in the serial advanced interface
cannam@95 109 (see <a href="Advanced-Complex-DFTs.html#Advanced-Complex-DFTs">Advanced Complex DFTs</a>) with <code>stride = howmany</code> and
cannam@95 110 <code>dist = 1</code>.
cannam@95 111
cannam@95 112 <h5 class="subsubheading">MPI flags</h5>
cannam@95 113
cannam@95 114 <p>The <code>flags</code> can be any of those for the serial FFTW
cannam@95 115 (see <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>), and in addition may include one or more of
cannam@95 116 the following MPI-specific flags, which improve performance at the
cannam@95 117 cost of changing the output or input data formats.
cannam@95 118
cannam@95 119 <ul>
cannam@95 120 <li><a name="index-FFTW_005fMPI_005fSCRAMBLED_005fOUT-471"></a><a name="index-FFTW_005fMPI_005fSCRAMBLED_005fIN-472"></a><code>FFTW_MPI_SCRAMBLED_OUT</code>, <code>FFTW_MPI_SCRAMBLED_IN</code>: valid for
cannam@95 121 1d transforms only, these flags indicate that the output/input of the
cannam@95 122 transform are in an undocumented &ldquo;scrambled&rdquo; order. A forward
cannam@95 123 <code>FFTW_MPI_SCRAMBLED_OUT</code> transform can be inverted by a backward
cannam@95 124 <code>FFTW_MPI_SCRAMBLED_IN</code> (times the usual 1/<i>N</i> normalization).
cannam@95 125 See <a href="One_002ddimensional-distributions.html#One_002ddimensional-distributions">One-dimensional distributions</a>.
cannam@95 126
cannam@95 127 <li><a name="index-FFTW_005fMPI_005fTRANSPOSED_005fOUT-473"></a><a name="index-FFTW_005fMPI_005fTRANSPOSED_005fIN-474"></a><code>FFTW_MPI_TRANSPOSED_OUT</code>, <code>FFTW_MPI_TRANSPOSED_IN</code>: valid
cannam@95 128 for multidimensional (<code>rnk &gt; 1</code>) transforms only, these flags
cannam@95 129 specify that the output or input of an n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&nbsp;&hellip;&nbsp;&times;&nbsp;n<sub>d-1</sub> transform is
cannam@95 130 transposed to n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&hellip;&times;&nbsp;n<sub>d-1</sub>. See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>.
cannam@95 131
cannam@95 132 </ul>
cannam@95 133
cannam@95 134 <h5 class="subsubheading">Real-data MPI DFTs</h5>
cannam@95 135
cannam@95 136 <p><a name="index-r2c-475"></a>Plans for real-input/output (r2c/c2r) DFTs (see <a href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data">Multi-dimensional MPI DFTs of Real Data</a>) are created by:
cannam@95 137
cannam@95 138 <p><a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f2d-476"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f2d-477"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f3d-478"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c-479"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f2d-480"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f2d-481"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f3d-482"></a><a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r-483"></a>
cannam@95 139 <pre class="example"> fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1,
cannam@95 140 double *in, fftw_complex *out,
cannam@95 141 MPI_Comm comm, unsigned flags);
cannam@95 142 fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1,
cannam@95 143 double *in, fftw_complex *out,
cannam@95 144 MPI_Comm comm, unsigned flags);
cannam@95 145 fftw_plan fftw_mpi_plan_dft_r2c_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
cannam@95 146 double *in, fftw_complex *out,
cannam@95 147 MPI_Comm comm, unsigned flags);
cannam@95 148 fftw_plan fftw_mpi_plan_dft_r2c(int rnk, const ptrdiff_t *n,
cannam@95 149 double *in, fftw_complex *out,
cannam@95 150 MPI_Comm comm, unsigned flags);
cannam@95 151 fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1,
cannam@95 152 fftw_complex *in, double *out,
cannam@95 153 MPI_Comm comm, unsigned flags);
cannam@95 154 fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1,
cannam@95 155 fftw_complex *in, double *out,
cannam@95 156 MPI_Comm comm, unsigned flags);
cannam@95 157 fftw_plan fftw_mpi_plan_dft_c2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
cannam@95 158 fftw_complex *in, double *out,
cannam@95 159 MPI_Comm comm, unsigned flags);
cannam@95 160 fftw_plan fftw_mpi_plan_dft_c2r(int rnk, const ptrdiff_t *n,
cannam@95 161 fftw_complex *in, double *out,
cannam@95 162 MPI_Comm comm, unsigned flags);
cannam@95 163 </pre>
cannam@95 164 <p>Similar to the serial interface (see <a href="Real_002ddata-DFTs.html#Real_002ddata-DFTs">Real-data DFTs</a>), these
cannam@95 165 transform logically n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&nbsp;&hellip;&nbsp;&times;&nbsp;n<sub>d-1</sub> real data to/from n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&nbsp;&hellip;&nbsp;&times;&nbsp;(n<sub>d-1</sub>/2 + 1) complex
cannam@95 166 data, representing the non-redundant half of the conjugate-symmetry
cannam@95 167 output of a real-input DFT (see <a href="Multi_002ddimensional-Transforms.html#Multi_002ddimensional-Transforms">Multi-dimensional Transforms</a>).
cannam@95 168 However, the real array must be stored within a padded n<sub>0</sub>&nbsp;&times;&nbsp;n<sub>1</sub>&nbsp;&times;&nbsp;n<sub>2</sub>&nbsp;&times;&nbsp;&hellip;&nbsp;&times;&nbsp;[2&nbsp;(n<sub>d-1</sub>/2 + 1)]
cannam@95 169
cannam@95 170 <p>array (much like the in-place serial r2c transforms, but here for
cannam@95 171 out-of-place transforms as well). Currently, only multi-dimensional
cannam@95 172 (<code>rnk &gt; 1</code>) r2c/c2r transforms are supported (requesting a plan
cannam@95 173 for <code>rnk = 1</code> will yield <code>NULL</code>). As explained above
cannam@95 174 (see <a href="Multi_002ddimensional-MPI-DFTs-of-Real-Data.html#Multi_002ddimensional-MPI-DFTs-of-Real-Data">Multi-dimensional MPI DFTs of Real Data</a>), the data
cannam@95 175 distribution of both the real and complex arrays is given by the
cannam@95 176 &lsquo;<samp><span class="samp">local_size</span></samp>&rsquo; function called for the dimensions of the
cannam@95 177 <em>complex</em> array. Similar to the other planning functions, the
cannam@95 178 input and output arrays are overwritten when the plan is created
cannam@95 179 except in <code>FFTW_ESTIMATE</code> mode.
cannam@95 180
cannam@95 181 <p>As for the complex DFTs above, there is an advance interface that
cannam@95 182 allows you to manually specify block sizes and to transform contiguous
cannam@95 183 <code>howmany</code>-tuples of real/complex numbers:
cannam@95 184
cannam@95 185 <p><a name="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fr2c-484"></a><a name="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fc2r-485"></a>
cannam@95 186 <pre class="example"> fftw_plan fftw_mpi_plan_many_dft_r2c
cannam@95 187 (int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
cannam@95 188 ptrdiff_t iblock, ptrdiff_t oblock,
cannam@95 189 double *in, fftw_complex *out,
cannam@95 190 MPI_Comm comm, unsigned flags);
cannam@95 191 fftw_plan fftw_mpi_plan_many_dft_c2r
cannam@95 192 (int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
cannam@95 193 ptrdiff_t iblock, ptrdiff_t oblock,
cannam@95 194 fftw_complex *in, double *out,
cannam@95 195 MPI_Comm comm, unsigned flags);
cannam@95 196 </pre>
cannam@95 197 <h5 class="subsubheading">MPI r2r transforms</h5>
cannam@95 198
cannam@95 199 <p><a name="index-r2r-486"></a>There are corresponding plan-creation routines for r2r
cannam@95 200 transforms (see <a href="More-DFTs-of-Real-Data.html#More-DFTs-of-Real-Data">More DFTs of Real Data</a>), currently supporting
cannam@95 201 multidimensional (<code>rnk &gt; 1</code>) transforms only (<code>rnk = 1</code> will
cannam@95 202 yield a <code>NULL</code> plan):
cannam@95 203
cannam@95 204 <pre class="example"> fftw_plan fftw_mpi_plan_r2r_2d(ptrdiff_t n0, ptrdiff_t n1,
cannam@95 205 double *in, double *out,
cannam@95 206 MPI_Comm comm,
cannam@95 207 fftw_r2r_kind kind0, fftw_r2r_kind kind1,
cannam@95 208 unsigned flags);
cannam@95 209 fftw_plan fftw_mpi_plan_r2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
cannam@95 210 double *in, double *out,
cannam@95 211 MPI_Comm comm,
cannam@95 212 fftw_r2r_kind kind0, fftw_r2r_kind kind1, fftw_r2r_kind kind2,
cannam@95 213 unsigned flags);
cannam@95 214 fftw_plan fftw_mpi_plan_r2r(int rnk, const ptrdiff_t *n,
cannam@95 215 double *in, double *out,
cannam@95 216 MPI_Comm comm, const fftw_r2r_kind *kind,
cannam@95 217 unsigned flags);
cannam@95 218 fftw_plan fftw_mpi_plan_many_r2r(int rnk, const ptrdiff_t *n,
cannam@95 219 ptrdiff_t iblock, ptrdiff_t oblock,
cannam@95 220 double *in, double *out,
cannam@95 221 MPI_Comm comm, const fftw_r2r_kind *kind,
cannam@95 222 unsigned flags);
cannam@95 223 </pre>
cannam@95 224 <p>The parameters are much the same as for the complex DFTs above, except
cannam@95 225 that the arrays are of real numbers (and hence the outputs of the
cannam@95 226 &lsquo;<samp><span class="samp">local_size</span></samp>&rsquo; data-distribution functions should be interpreted as
cannam@95 227 counts of real rather than complex numbers). Also, the <code>kind</code>
cannam@95 228 parameters specify the r2r kinds along each dimension as for the
cannam@95 229 serial interface (see <a href="Real_002dto_002dReal-Transform-Kinds.html#Real_002dto_002dReal-Transform-Kinds">Real-to-Real Transform Kinds</a>). See <a href="Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms.html#Other-Multi_002ddimensional-Real_002ddata-MPI-Transforms">Other Multi-dimensional Real-data MPI Transforms</a>.
cannam@95 230
cannam@95 231 <h5 class="subsubheading">MPI transposition</h5>
cannam@95 232
cannam@95 233 <p><a name="index-transpose-487"></a>
cannam@95 234 FFTW also provides routines to plan a transpose of a distributed
cannam@95 235 <code>n0</code> by <code>n1</code> array of real numbers, or an array of
cannam@95 236 <code>howmany</code>-tuples of real numbers with specified block sizes
cannam@95 237 (see <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>):
cannam@95 238
cannam@95 239 <p><a name="index-fftw_005fmpi_005fplan_005ftranspose-488"></a><a name="index-fftw_005fmpi_005fplan_005fmany_005ftranspose-489"></a>
cannam@95 240 <pre class="example"> fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1,
cannam@95 241 double *in, double *out,
cannam@95 242 MPI_Comm comm, unsigned flags);
cannam@95 243 fftw_plan fftw_mpi_plan_many_transpose
cannam@95 244 (ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t howmany,
cannam@95 245 ptrdiff_t block0, ptrdiff_t block1,
cannam@95 246 double *in, double *out, MPI_Comm comm, unsigned flags);
cannam@95 247 </pre>
cannam@95 248 <p><a name="index-new_002darray-execution-490"></a><a name="index-fftw_005fmpi_005fexecute_005fr2r-491"></a>These plans are used with the <code>fftw_mpi_execute_r2r</code> new-array
cannam@95 249 execute function (see <a href="Using-MPI-Plans.html#Using-MPI-Plans">Using MPI Plans</a>), since they count as (rank
cannam@95 250 zero) r2r plans from FFTW's perspective.
cannam@95 251
cannam@95 252 </body></html>
cannam@95 253