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author Chris Cannam
date Wed, 20 Mar 2013 15:35:50 +0000
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1 <html lang="en">
2 <head>
3 <title>Using MPI Plans - FFTW 3.3.3</title>
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49 <a name="Using-MPI-Plans"></a>
50 <p>
51 Next:&nbsp;<a rel="next" accesskey="n" href="MPI-Data-Distribution-Functions.html#MPI-Data-Distribution-Functions">MPI Data Distribution Functions</a>,
52 Previous:&nbsp;<a rel="previous" accesskey="p" href="MPI-Initialization.html#MPI-Initialization">MPI Initialization</a>,
53 Up:&nbsp;<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">6.12.3 Using MPI Plans</h4>
58
59 <p>Once an MPI plan is created, you can execute and destroy it using
60 <code>fftw_execute</code>, <code>fftw_destroy_plan</code>, and the other functions
61 in the serial interface that operate on generic plans (see <a href="Using-Plans.html#Using-Plans">Using Plans</a>).
62
63 <p><a name="index-collective-function-438"></a><a name="index-MPI-communicator-439"></a>The <code>fftw_execute</code> and <code>fftw_destroy_plan</code> functions, applied to
64 MPI plans, are <em>collective</em> calls: they must be called for all processes
65 in the communicator that was used to create the plan.
66
67 <p><a name="index-new_002darray-execution-440"></a>You must <em>not</em> use the serial new-array plan-execution functions
68 <code>fftw_execute_dft</code> and so on (see <a href="New_002darray-Execute-Functions.html#New_002darray-Execute-Functions">New-array Execute Functions</a>) with MPI plans. Such functions are specialized to the
69 problem type, and there are specific new-array execute functions for MPI plans:
70
71 <p><a name="index-fftw_005fmpi_005fexecute_005fdft-441"></a><a name="index-fftw_005fmpi_005fexecute_005fdft_005fr2c-442"></a><a name="index-fftw_005fmpi_005fexecute_005fdft_005fc2r-443"></a><a name="index-fftw_005fmpi_005fexecute_005fr2r-444"></a>
72 <pre class="example"> void fftw_mpi_execute_dft(fftw_plan p, fftw_complex *in, fftw_complex *out);
73 void fftw_mpi_execute_dft_r2c(fftw_plan p, double *in, fftw_complex *out);
74 void fftw_mpi_execute_dft_c2r(fftw_plan p, fftw_complex *in, double *out);
75 void fftw_mpi_execute_r2r(fftw_plan p, double *in, double *out);
76 </pre>
77 <p><a name="index-alignment-445"></a><a name="index-fftw_005fmalloc-446"></a>These functions have the same restrictions as those of the serial
78 new-array execute functions. They are <em>always</em> safe to apply to
79 the <em>same</em> <code>in</code> and <code>out</code> arrays that were used to
80 create the plan. They can only be applied to new arrarys if those
81 arrays have the same types, dimensions, in-placeness, and alignment as
82 the original arrays, where the best way to ensure the same alignment
83 is to use FFTW's <code>fftw_malloc</code> and related allocation functions
84 for all arrays (see <a href="Memory-Allocation.html#Memory-Allocation">Memory Allocation</a>). Note that distributed
85 transposes (see <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>) use
86 <code>fftw_mpi_execute_r2r</code>, since they count as rank-zero r2r plans
87 from FFTW's perspective.
88
89 </body></html>
90