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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam
date Tue, 19 Nov 2019 14:52:55 +0000
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3 <!-- This manual is for FFTW
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25 <title>FFTW 3.3.8: MPI Data Distribution Functions</title>
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71 <a name="MPI-Data-Distribution-Functions"></a>
72 <div class="header">
73 <p>
74 Next: <a href="MPI-Plan-Creation.html#MPI-Plan-Creation" accesskey="n" rel="next">MPI Plan Creation</a>, Previous: <a href="Using-MPI-Plans.html#Using-MPI-Plans" accesskey="p" rel="prev">Using MPI Plans</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
75 </div>
76 <hr>
77 <a name="MPI-Data-Distribution-Functions-1"></a>
78 <h4 class="subsection">6.12.4 MPI Data Distribution Functions</h4>
79
80 <a name="index-data-distribution-5"></a>
81 <p>As described above (see <a href="MPI-Data-Distribution.html#MPI-Data-Distribution">MPI Data Distribution</a>), in order to
82 allocate your arrays, <em>before</em> creating a plan, you must first
83 call one of the following routines to determine the required
84 allocation size and the portion of the array locally stored on a given
85 process. The <code>MPI_Comm</code> communicator passed here must be
86 equivalent to the communicator used below for plan creation.
87 </p>
88 <p>The basic interface for multidimensional transforms consists of the
89 functions:
90 </p>
91 <a name="index-fftw_005fmpi_005flocal_005fsize_005f2d-2"></a>
92 <a name="index-fftw_005fmpi_005flocal_005fsize_005f3d"></a>
93 <a name="index-fftw_005fmpi_005flocal_005fsize"></a>
94 <a name="index-fftw_005fmpi_005flocal_005fsize_005f2d_005ftransposed-1"></a>
95 <a name="index-fftw_005fmpi_005flocal_005fsize_005f3d_005ftransposed-1"></a>
96 <a name="index-fftw_005fmpi_005flocal_005fsize_005ftransposed"></a>
97 <div class="example">
98 <pre class="example">ptrdiff_t fftw_mpi_local_size_2d(ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm,
99 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
100 ptrdiff_t fftw_mpi_local_size_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
101 MPI_Comm comm,
102 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
103 ptrdiff_t fftw_mpi_local_size(int rnk, const ptrdiff_t *n, MPI_Comm comm,
104 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
105
106 ptrdiff_t fftw_mpi_local_size_2d_transposed(ptrdiff_t n0, ptrdiff_t n1, MPI_Comm comm,
107 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
108 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
109 ptrdiff_t fftw_mpi_local_size_3d_transposed(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
110 MPI_Comm comm,
111 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
112 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
113 ptrdiff_t fftw_mpi_local_size_transposed(int rnk, const ptrdiff_t *n, MPI_Comm comm,
114 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
115 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
116 </pre></div>
117
118 <p>These functions return the number of elements to allocate (complex
119 numbers for DFT/r2c/c2r plans, real numbers for r2r plans), whereas
120 the <code>local_n0</code> and <code>local_0_start</code> return the portion
121 (<code>local_0_start</code> to <code>local_0_start + local_n0 - 1</code>) of the
122 first dimension 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>
123 array that is stored on the local
124 process. See <a href="Basic-and-advanced-distribution-interfaces.html#Basic-and-advanced-distribution-interfaces">Basic and advanced distribution interfaces</a>. For
125 <code>FFTW_MPI_TRANSPOSED_OUT</code> plans, the &lsquo;<samp>_transposed</samp>&rsquo; variants
126 are useful in order to also return the local portion of the first
127 dimension in 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>
128 transposed output.
129 See <a href="Transposed-distributions.html#Transposed-distributions">Transposed distributions</a>.
130 The advanced interface for multidimensional transforms is:
131 </p>
132 <a name="index-advanced-interface-5"></a>
133 <a name="index-fftw_005fmpi_005flocal_005fsize_005fmany-1"></a>
134 <a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005ftransposed-1"></a>
135 <div class="example">
136 <pre class="example">ptrdiff_t fftw_mpi_local_size_many(int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
137 ptrdiff_t block0, MPI_Comm comm,
138 ptrdiff_t *local_n0, ptrdiff_t *local_0_start);
139 ptrdiff_t fftw_mpi_local_size_many_transposed(int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
140 ptrdiff_t block0, ptrdiff_t block1, MPI_Comm comm,
141 ptrdiff_t *local_n0, ptrdiff_t *local_0_start,
142 ptrdiff_t *local_n1, ptrdiff_t *local_1_start);
143 </pre></div>
144
145 <p>These differ from the basic interface in only two ways. First, they
146 allow you to specify block sizes <code>block0</code> and <code>block1</code> (the
147 latter for the transposed output); you can pass
148 <code>FFTW_MPI_DEFAULT_BLOCK</code> to use FFTW&rsquo;s default block size as in
149 the basic interface. Second, you can pass a <code>howmany</code> parameter,
150 corresponding to the advanced planning interface below: this is for
151 transforms of contiguous <code>howmany</code>-tuples of numbers
152 (<code>howmany = 1</code> in the basic interface).
153 </p>
154 <p>The corresponding basic and advanced routines for one-dimensional
155 transforms (currently only complex DFTs) are:
156 </p>
157 <a name="index-fftw_005fmpi_005flocal_005fsize_005f1d-1"></a>
158 <a name="index-fftw_005fmpi_005flocal_005fsize_005fmany_005f1d"></a>
159 <div class="example">
160 <pre class="example">ptrdiff_t fftw_mpi_local_size_1d(
161 ptrdiff_t n0, MPI_Comm comm, int sign, unsigned flags,
162 ptrdiff_t *local_ni, ptrdiff_t *local_i_start,
163 ptrdiff_t *local_no, ptrdiff_t *local_o_start);
164 ptrdiff_t fftw_mpi_local_size_many_1d(
165 ptrdiff_t n0, ptrdiff_t howmany,
166 MPI_Comm comm, int sign, unsigned flags,
167 ptrdiff_t *local_ni, ptrdiff_t *local_i_start,
168 ptrdiff_t *local_no, ptrdiff_t *local_o_start);
169 </pre></div>
170
171 <a name="index-FFTW_005fMPI_005fSCRAMBLED_005fOUT-1"></a>
172 <a name="index-FFTW_005fMPI_005fSCRAMBLED_005fIN-1"></a>
173 <p>As above, the return value is the number of elements to allocate
174 (complex numbers, for complex DFTs). The <code>local_ni</code> and
175 <code>local_i_start</code> arguments return the portion
176 (<code>local_i_start</code> to <code>local_i_start + local_ni - 1</code>) of the
177 1d array that is stored on this process for the transform
178 <em>input</em>, and <code>local_no</code> and <code>local_o_start</code> are the
179 corresponding quantities for the input. The <code>sign</code>
180 (<code>FFTW_FORWARD</code> or <code>FFTW_BACKWARD</code>) and <code>flags</code> must
181 match the arguments passed when creating a plan. Although the inputs
182 and outputs have different data distributions in general, it is
183 guaranteed that the <em>output</em> data distribution of an
184 <code>FFTW_FORWARD</code> plan will match the <em>input</em> data distribution
185 of an <code>FFTW_BACKWARD</code> plan and vice versa; similarly for the
186 <code>FFTW_MPI_SCRAMBLED_OUT</code> and <code>FFTW_MPI_SCRAMBLED_IN</code> flags.
187 See <a href="One_002ddimensional-distributions.html#One_002ddimensional-distributions">One-dimensional distributions</a>.
188 </p>
189 <hr>
190 <div class="header">
191 <p>
192 Next: <a href="MPI-Plan-Creation.html#MPI-Plan-Creation" accesskey="n" rel="next">MPI Plan Creation</a>, Previous: <a href="Using-MPI-Plans.html#Using-MPI-Plans" accesskey="p" rel="prev">Using MPI Plans</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
193 </div>
194
195
196
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