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| author | Chris Cannam |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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| 1 <html lang="en"> | |
| 2 <head> | |
| 3 <title>MPI Plan Creation - FFTW 3.3.3</title> | |
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| 12 <!-- | |
| 13 This manual is for FFTW | |
| 14 (version 3.3.3, 25 November 2012). | |
| 15 | |
| 16 Copyright (C) 2003 Matteo Frigo. | |
| 17 | |
| 18 Copyright (C) 2003 Massachusetts Institute of Technology. | |
| 19 | |
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| 47 <body> | |
| 48 <div class="node"> | |
| 49 <a name="MPI-Plan-Creation"></a> | |
| 50 <p> | |
| 51 Next: <a rel="next" accesskey="n" href="MPI-Wisdom-Communication.html#MPI-Wisdom-Communication">MPI Wisdom Communication</a>, | |
| 52 Previous: <a rel="previous" accesskey="p" href="MPI-Data-Distribution-Functions.html#MPI-Data-Distribution-Functions">MPI Data Distribution Functions</a>, | |
| 53 Up: <a rel="up" accesskey="u" href="FFTW-MPI-Reference.html#FFTW-MPI-Reference">FFTW MPI Reference</a> | |
| 54 <hr> | |
| 55 </div> | |
| 56 | |
| 57 <h4 class="subsection">6.12.5 MPI Plan Creation</h4> | |
| 58 | |
| 59 <h5 class="subsubheading">Complex-data MPI DFTs</h5> | |
| 60 | |
| 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: | |
| 62 | |
| 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> | |
| 64 <pre class="example"> fftw_plan fftw_mpi_plan_dft_1d(ptrdiff_t n0, fftw_complex *in, fftw_complex *out, | |
| 65 MPI_Comm comm, int sign, unsigned flags); | |
| 66 fftw_plan fftw_mpi_plan_dft_2d(ptrdiff_t n0, ptrdiff_t n1, | |
| 67 fftw_complex *in, fftw_complex *out, | |
| 68 MPI_Comm comm, int sign, unsigned flags); | |
| 69 fftw_plan fftw_mpi_plan_dft_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, | |
| 70 fftw_complex *in, fftw_complex *out, | |
| 71 MPI_Comm comm, int sign, unsigned flags); | |
| 72 fftw_plan fftw_mpi_plan_dft(int rnk, const ptrdiff_t *n, | |
| 73 fftw_complex *in, fftw_complex *out, | |
| 74 MPI_Comm comm, int sign, unsigned flags); | |
| 75 fftw_plan fftw_mpi_plan_many_dft(int rnk, const ptrdiff_t *n, | |
| 76 ptrdiff_t howmany, ptrdiff_t block, ptrdiff_t tblock, | |
| 77 fftw_complex *in, fftw_complex *out, | |
| 78 MPI_Comm comm, int sign, unsigned flags); | |
| 79 </pre> | |
| 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>) | |
| 81 in specifying the dimensions, sign, and flags of the transform. The | |
| 82 <code>comm</code> argument gives an MPI communicator that specifies the set | |
| 83 of processes to participate in the transform; plan creation is a | |
| 84 collective function that must be called for all processes in the | |
| 85 communicator. The <code>in</code> and <code>out</code> pointers refer only to a | |
| 86 portion of the overall transform data (see <a href="MPI-Data-Distribution.html#MPI-Data-Distribution">MPI Data Distribution</a>) | |
| 87 as specified by the ‘<samp><span class="samp">local_size</span></samp>’ functions in the previous | |
| 88 section. Unless <code>flags</code> contains <code>FFTW_ESTIMATE</code>, these | |
| 89 arrays are overwritten during plan creation as for the serial | |
| 90 interface. For multi-dimensional transforms, any dimensions <code>> | |
| 91 1</code> are supported; for one-dimensional transforms, only composite | |
| 92 (non-prime) <code>n0</code> are currently supported (unlike the serial | |
| 93 FFTW). Requesting an unsupported transform size will yield a | |
| 94 <code>NULL</code> plan. (As in the serial interface, highly composite sizes | |
| 95 generally yield the best performance.) | |
| 96 | |
| 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 | |
| 98 allows you to specify the block sizes for the first dimension | |
| 99 (<code>block</code>) of the n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub> input data and the first dimension | |
| 100 (<code>tblock</code>) of the n<sub>1</sub> × n<sub>0</sub> × n<sub>2</sub> ×…× n<sub>d-1</sub> transposed data (at intermediate | |
| 101 steps of the transform, and for the output if | |
| 102 <code>FFTW_TRANSPOSED_OUT</code> is specified in <code>flags</code>). These must | |
| 103 be the same block sizes as were passed to the corresponding | |
| 104 ‘<samp><span class="samp">local_size</span></samp>’ function; you can pass <code>FFTW_MPI_DEFAULT_BLOCK</code> | |
| 105 to use FFTW's default block size as in the basic interface. Also, the | |
| 106 <code>howmany</code> parameter specifies that the transform is of contiguous | |
| 107 <code>howmany</code>-tuples rather than individual complex numbers; this | |
| 108 corresponds to the same parameter in the serial advanced interface | |
| 109 (see <a href="Advanced-Complex-DFTs.html#Advanced-Complex-DFTs">Advanced Complex DFTs</a>) with <code>stride = howmany</code> and | |
| 110 <code>dist = 1</code>. | |
| 111 | |
| 112 <h5 class="subsubheading">MPI flags</h5> | |
| 113 | |
| 114 <p>The <code>flags</code> can be any of those for the serial FFTW | |
| 115 (see <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>), and in addition may include one or more of | |
| 116 the following MPI-specific flags, which improve performance at the | |
| 117 cost of changing the output or input data formats. | |
| 118 | |
| 119 <ul> | |
| 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 | |
| 121 1d transforms only, these flags indicate that the output/input of the | |
| 122 transform are in an undocumented “scrambled” order. A forward | |
| 123 <code>FFTW_MPI_SCRAMBLED_OUT</code> transform can be inverted by a backward | |
| 124 <code>FFTW_MPI_SCRAMBLED_IN</code> (times the usual 1/<i>N</i> normalization). | |
| 125 See <a href="One_002ddimensional-distributions.html#One_002ddimensional-distributions">One-dimensional distributions</a>. | |
| 126 | |
| 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 | |
| 128 for multidimensional (<code>rnk > 1</code>) transforms only, these flags | |
| 129 specify that the output or input of an n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub> transform is | |
| 130 transposed to n<sub>1</sub> × n<sub>0</sub> × n<sub>2</sub> ×…× n<sub>d-1</sub>. See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>. | |
| 131 | |
| 132 </ul> | |
| 133 | |
| 134 <h5 class="subsubheading">Real-data MPI DFTs</h5> | |
| 135 | |
| 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: | |
| 137 | |
| 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> | |
| 139 <pre class="example"> fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1, | |
| 140 double *in, fftw_complex *out, | |
| 141 MPI_Comm comm, unsigned flags); | |
| 142 fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1, | |
| 143 double *in, fftw_complex *out, | |
| 144 MPI_Comm comm, unsigned flags); | |
| 145 fftw_plan fftw_mpi_plan_dft_r2c_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, | |
| 146 double *in, fftw_complex *out, | |
| 147 MPI_Comm comm, unsigned flags); | |
| 148 fftw_plan fftw_mpi_plan_dft_r2c(int rnk, const ptrdiff_t *n, | |
| 149 double *in, fftw_complex *out, | |
| 150 MPI_Comm comm, unsigned flags); | |
| 151 fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1, | |
| 152 fftw_complex *in, double *out, | |
| 153 MPI_Comm comm, unsigned flags); | |
| 154 fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1, | |
| 155 fftw_complex *in, double *out, | |
| 156 MPI_Comm comm, unsigned flags); | |
| 157 fftw_plan fftw_mpi_plan_dft_c2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, | |
| 158 fftw_complex *in, double *out, | |
| 159 MPI_Comm comm, unsigned flags); | |
| 160 fftw_plan fftw_mpi_plan_dft_c2r(int rnk, const ptrdiff_t *n, | |
| 161 fftw_complex *in, double *out, | |
| 162 MPI_Comm comm, unsigned flags); | |
| 163 </pre> | |
| 164 <p>Similar to the serial interface (see <a href="Real_002ddata-DFTs.html#Real_002ddata-DFTs">Real-data DFTs</a>), these | |
| 165 transform logically n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × n<sub>d-1</sub> real data to/from n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × (n<sub>d-1</sub>/2 + 1) complex | |
| 166 data, representing the non-redundant half of the conjugate-symmetry | |
| 167 output of a real-input DFT (see <a href="Multi_002ddimensional-Transforms.html#Multi_002ddimensional-Transforms">Multi-dimensional Transforms</a>). | |
| 168 However, the real array must be stored within a padded n<sub>0</sub> × n<sub>1</sub> × n<sub>2</sub> × … × [2 (n<sub>d-1</sub>/2 + 1)] | |
| 169 | |
| 170 <p>array (much like the in-place serial r2c transforms, but here for | |
| 171 out-of-place transforms as well). Currently, only multi-dimensional | |
| 172 (<code>rnk > 1</code>) r2c/c2r transforms are supported (requesting a plan | |
| 173 for <code>rnk = 1</code> will yield <code>NULL</code>). As explained above | |
| 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 | |
| 175 distribution of both the real and complex arrays is given by the | |
| 176 ‘<samp><span class="samp">local_size</span></samp>’ function called for the dimensions of the | |
| 177 <em>complex</em> array. Similar to the other planning functions, the | |
| 178 input and output arrays are overwritten when the plan is created | |
| 179 except in <code>FFTW_ESTIMATE</code> mode. | |
| 180 | |
| 181 <p>As for the complex DFTs above, there is an advance interface that | |
| 182 allows you to manually specify block sizes and to transform contiguous | |
| 183 <code>howmany</code>-tuples of real/complex numbers: | |
| 184 | |
| 185 <p><a name="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fr2c-484"></a><a name="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fc2r-485"></a> | |
| 186 <pre class="example"> fftw_plan fftw_mpi_plan_many_dft_r2c | |
| 187 (int rnk, const ptrdiff_t *n, ptrdiff_t howmany, | |
| 188 ptrdiff_t iblock, ptrdiff_t oblock, | |
| 189 double *in, fftw_complex *out, | |
| 190 MPI_Comm comm, unsigned flags); | |
| 191 fftw_plan fftw_mpi_plan_many_dft_c2r | |
| 192 (int rnk, const ptrdiff_t *n, ptrdiff_t howmany, | |
| 193 ptrdiff_t iblock, ptrdiff_t oblock, | |
| 194 fftw_complex *in, double *out, | |
| 195 MPI_Comm comm, unsigned flags); | |
| 196 </pre> | |
| 197 <h5 class="subsubheading">MPI r2r transforms</h5> | |
| 198 | |
| 199 <p><a name="index-r2r-486"></a>There are corresponding plan-creation routines for r2r | |
| 200 transforms (see <a href="More-DFTs-of-Real-Data.html#More-DFTs-of-Real-Data">More DFTs of Real Data</a>), currently supporting | |
| 201 multidimensional (<code>rnk > 1</code>) transforms only (<code>rnk = 1</code> will | |
| 202 yield a <code>NULL</code> plan): | |
| 203 | |
| 204 <pre class="example"> fftw_plan fftw_mpi_plan_r2r_2d(ptrdiff_t n0, ptrdiff_t n1, | |
| 205 double *in, double *out, | |
| 206 MPI_Comm comm, | |
| 207 fftw_r2r_kind kind0, fftw_r2r_kind kind1, | |
| 208 unsigned flags); | |
| 209 fftw_plan fftw_mpi_plan_r2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2, | |
| 210 double *in, double *out, | |
| 211 MPI_Comm comm, | |
| 212 fftw_r2r_kind kind0, fftw_r2r_kind kind1, fftw_r2r_kind kind2, | |
| 213 unsigned flags); | |
| 214 fftw_plan fftw_mpi_plan_r2r(int rnk, const ptrdiff_t *n, | |
| 215 double *in, double *out, | |
| 216 MPI_Comm comm, const fftw_r2r_kind *kind, | |
| 217 unsigned flags); | |
| 218 fftw_plan fftw_mpi_plan_many_r2r(int rnk, const ptrdiff_t *n, | |
| 219 ptrdiff_t iblock, ptrdiff_t oblock, | |
| 220 double *in, double *out, | |
| 221 MPI_Comm comm, const fftw_r2r_kind *kind, | |
| 222 unsigned flags); | |
| 223 </pre> | |
| 224 <p>The parameters are much the same as for the complex DFTs above, except | |
| 225 that the arrays are of real numbers (and hence the outputs of the | |
| 226 ‘<samp><span class="samp">local_size</span></samp>’ data-distribution functions should be interpreted as | |
| 227 counts of real rather than complex numbers). Also, the <code>kind</code> | |
| 228 parameters specify the r2r kinds along each dimension as for the | |
| 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>. | |
| 230 | |
| 231 <h5 class="subsubheading">MPI transposition</h5> | |
| 232 | |
| 233 <p><a name="index-transpose-487"></a> | |
| 234 FFTW also provides routines to plan a transpose of a distributed | |
| 235 <code>n0</code> by <code>n1</code> array of real numbers, or an array of | |
| 236 <code>howmany</code>-tuples of real numbers with specified block sizes | |
| 237 (see <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>): | |
| 238 | |
| 239 <p><a name="index-fftw_005fmpi_005fplan_005ftranspose-488"></a><a name="index-fftw_005fmpi_005fplan_005fmany_005ftranspose-489"></a> | |
| 240 <pre class="example"> fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1, | |
| 241 double *in, double *out, | |
| 242 MPI_Comm comm, unsigned flags); | |
| 243 fftw_plan fftw_mpi_plan_many_transpose | |
| 244 (ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t howmany, | |
| 245 ptrdiff_t block0, ptrdiff_t block1, | |
| 246 double *in, double *out, MPI_Comm comm, unsigned flags); | |
| 247 </pre> | |
| 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 | |
| 249 execute function (see <a href="Using-MPI-Plans.html#Using-MPI-Plans">Using MPI Plans</a>), since they count as (rank | |
| 250 zero) r2r plans from FFTW's perspective. | |
| 251 | |
| 252 </body></html> | |
| 253 |