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1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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3 <!-- This manual is for FFTW
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4 (version 3.3.5, 30 July 2016).
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5
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6 Copyright (C) 2003 Matteo Frigo.
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7
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8 Copyright (C) 2003 Massachusetts Institute of Technology.
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9
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10 Permission is granted to make and distribute verbatim copies of this
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11 manual provided the copyright notice and this permission notice are
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15 manual under the conditions for verbatim copying, provided that the
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16 entire resulting derived work is distributed under the terms of a
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17 permission notice identical to this one.
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24 <head>
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25 <title>FFTW 3.3.5: MPI Plan Creation</title>
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26
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27 <meta name="description" content="FFTW 3.3.5: MPI Plan Creation">
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34 <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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36 <link href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" rel="up" title="FFTW MPI Reference">
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37 <link href="MPI-Wisdom-Communication.html#MPI-Wisdom-Communication" rel="next" title="MPI Wisdom Communication">
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66 </style>
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69 </head>
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70
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71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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72 <a name="MPI-Plan-Creation"></a>
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73 <div class="header">
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74 <p>
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75 Next: <a href="MPI-Wisdom-Communication.html#MPI-Wisdom-Communication" accesskey="n" rel="next">MPI Wisdom Communication</a>, Previous: <a href="MPI-Data-Distribution-Functions.html#MPI-Data-Distribution-Functions" accesskey="p" rel="prev">MPI Data Distribution Functions</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</a> [<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>
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76 </div>
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77 <hr>
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78 <a name="MPI-Plan-Creation-1"></a>
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79 <h4 class="subsection">6.12.5 MPI Plan Creation</h4>
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80
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81 <a name="Complex_002ddata-MPI-DFTs"></a>
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82 <h4 class="subsubheading">Complex-data MPI DFTs</h4>
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83
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84 <p>Plans for complex-data DFTs (see <a href="2d-MPI-example.html#g_t2d-MPI-example">2d MPI example</a>) are created by:
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85 </p>
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86 <a name="index-fftw_005fmpi_005fplan_005fdft_005f1d"></a>
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87 <a name="index-fftw_005fmpi_005fplan_005fdft_005f2d-1"></a>
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88 <a name="index-fftw_005fmpi_005fplan_005fdft_005f3d"></a>
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89 <a name="index-fftw_005fmpi_005fplan_005fdft"></a>
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90 <a name="index-fftw_005fmpi_005fplan_005fmany_005fdft"></a>
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91 <div class="example">
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92 <pre class="example">fftw_plan fftw_mpi_plan_dft_1d(ptrdiff_t n0, fftw_complex *in, fftw_complex *out,
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93 MPI_Comm comm, int sign, unsigned flags);
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94 fftw_plan fftw_mpi_plan_dft_2d(ptrdiff_t n0, ptrdiff_t n1,
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95 fftw_complex *in, fftw_complex *out,
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96 MPI_Comm comm, int sign, unsigned flags);
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97 fftw_plan fftw_mpi_plan_dft_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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98 fftw_complex *in, fftw_complex *out,
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99 MPI_Comm comm, int sign, unsigned flags);
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100 fftw_plan fftw_mpi_plan_dft(int rnk, const ptrdiff_t *n,
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101 fftw_complex *in, fftw_complex *out,
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102 MPI_Comm comm, int sign, unsigned flags);
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103 fftw_plan fftw_mpi_plan_many_dft(int rnk, const ptrdiff_t *n,
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104 ptrdiff_t howmany, ptrdiff_t block, ptrdiff_t tblock,
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105 fftw_complex *in, fftw_complex *out,
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106 MPI_Comm comm, int sign, unsigned flags);
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107 </pre></div>
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108
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109 <a name="index-MPI-communicator-2"></a>
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110 <a name="index-collective-function-4"></a>
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111 <p>These are similar to their serial counterparts (see <a href="Complex-DFTs.html#Complex-DFTs">Complex DFTs</a>)
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112 in specifying the dimensions, sign, and flags of the transform. The
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113 <code>comm</code> argument gives an MPI communicator that specifies the set
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114 of processes to participate in the transform; plan creation is a
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115 collective function that must be called for all processes in the
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116 communicator. The <code>in</code> and <code>out</code> pointers refer only to a
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117 portion of the overall transform data (see <a href="MPI-Data-Distribution.html#MPI-Data-Distribution">MPI Data Distribution</a>)
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118 as specified by the ‘<samp>local_size</samp>’ functions in the previous
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119 section. Unless <code>flags</code> contains <code>FFTW_ESTIMATE</code>, these
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120 arrays are overwritten during plan creation as for the serial
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121 interface. For multi-dimensional transforms, any dimensions <code>>
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122 1</code> are supported; for one-dimensional transforms, only composite
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123 (non-prime) <code>n0</code> are currently supported (unlike the serial
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124 FFTW). Requesting an unsupported transform size will yield a
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125 <code>NULL</code> plan. (As in the serial interface, highly composite sizes
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126 generally yield the best performance.)
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127 </p>
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128 <a name="index-advanced-interface-6"></a>
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129 <a name="index-FFTW_005fMPI_005fDEFAULT_005fBLOCK-2"></a>
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130 <a name="index-stride-3"></a>
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131 <p>The advanced-interface <code>fftw_mpi_plan_many_dft</code> additionally
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132 allows you to specify the block sizes for the first dimension
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133 (<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
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134 (<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
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135 steps of the transform, and for the output if
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136 <code>FFTW_TRANSPOSED_OUT</code> is specified in <code>flags</code>). These must
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137 be the same block sizes as were passed to the corresponding
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138 ‘<samp>local_size</samp>’ function; you can pass <code>FFTW_MPI_DEFAULT_BLOCK</code>
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139 to use FFTW’s default block size as in the basic interface. Also, the
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140 <code>howmany</code> parameter specifies that the transform is of contiguous
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141 <code>howmany</code>-tuples rather than individual complex numbers; this
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142 corresponds to the same parameter in the serial advanced interface
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143 (see <a href="Advanced-Complex-DFTs.html#Advanced-Complex-DFTs">Advanced Complex DFTs</a>) with <code>stride = howmany</code> and
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144 <code>dist = 1</code>.
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145 </p>
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146 <a name="MPI-flags"></a>
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147 <h4 class="subsubheading">MPI flags</h4>
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148
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149 <p>The <code>flags</code> can be any of those for the serial FFTW
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150 (see <a href="Planner-Flags.html#Planner-Flags">Planner Flags</a>), and in addition may include one or more of
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151 the following MPI-specific flags, which improve performance at the
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152 cost of changing the output or input data formats.
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153 </p>
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154 <ul>
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155 <li> <a name="index-FFTW_005fMPI_005fSCRAMBLED_005fOUT-2"></a>
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156 <a name="index-FFTW_005fMPI_005fSCRAMBLED_005fIN-2"></a>
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157 <code>FFTW_MPI_SCRAMBLED_OUT</code>, <code>FFTW_MPI_SCRAMBLED_IN</code>: valid for
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158 1d transforms only, these flags indicate that the output/input of the
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159 transform are in an undocumented “scrambled” order. A forward
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160 <code>FFTW_MPI_SCRAMBLED_OUT</code> transform can be inverted by a backward
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161 <code>FFTW_MPI_SCRAMBLED_IN</code> (times the usual 1/<i>N</i> normalization).
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162 See <a href="One_002ddimensional-distributions.html#One_002ddimensional-distributions">One-dimensional distributions</a>.
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163
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164 </li><li> <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fOUT-2"></a>
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165 <a name="index-FFTW_005fMPI_005fTRANSPOSED_005fIN-2"></a>
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166 <code>FFTW_MPI_TRANSPOSED_OUT</code>, <code>FFTW_MPI_TRANSPOSED_IN</code>: valid
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167 for multidimensional (<code>rnk > 1</code>) transforms only, these flags
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168 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
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169 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>.
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170
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171 </li></ul>
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172
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173 <a name="Real_002ddata-MPI-DFTs"></a>
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174 <h4 class="subsubheading">Real-data MPI DFTs</h4>
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175
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176 <a name="index-r2c-4"></a>
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177 <p>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:
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178 </p>
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179 <a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f2d"></a>
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180 <a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f2d-1"></a>
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181 <a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c_005f3d"></a>
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182 <a name="index-fftw_005fmpi_005fplan_005fdft_005fr2c"></a>
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183 <a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f2d"></a>
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184 <a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f2d-1"></a>
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185 <a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r_005f3d"></a>
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186 <a name="index-fftw_005fmpi_005fplan_005fdft_005fc2r"></a>
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187 <div class="example">
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188 <pre class="example">fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1,
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189 double *in, fftw_complex *out,
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190 MPI_Comm comm, unsigned flags);
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191 fftw_plan fftw_mpi_plan_dft_r2c_2d(ptrdiff_t n0, ptrdiff_t n1,
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192 double *in, fftw_complex *out,
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193 MPI_Comm comm, unsigned flags);
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194 fftw_plan fftw_mpi_plan_dft_r2c_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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195 double *in, fftw_complex *out,
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196 MPI_Comm comm, unsigned flags);
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197 fftw_plan fftw_mpi_plan_dft_r2c(int rnk, const ptrdiff_t *n,
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198 double *in, fftw_complex *out,
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199 MPI_Comm comm, unsigned flags);
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200 fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1,
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201 fftw_complex *in, double *out,
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202 MPI_Comm comm, unsigned flags);
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203 fftw_plan fftw_mpi_plan_dft_c2r_2d(ptrdiff_t n0, ptrdiff_t n1,
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204 fftw_complex *in, double *out,
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205 MPI_Comm comm, unsigned flags);
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206 fftw_plan fftw_mpi_plan_dft_c2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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207 fftw_complex *in, double *out,
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208 MPI_Comm comm, unsigned flags);
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209 fftw_plan fftw_mpi_plan_dft_c2r(int rnk, const ptrdiff_t *n,
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210 fftw_complex *in, double *out,
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211 MPI_Comm comm, unsigned flags);
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212 </pre></div>
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213
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214 <p>Similar to the serial interface (see <a href="Real_002ddata-DFTs.html#Real_002ddata-DFTs">Real-data DFTs</a>), these
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215 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
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216 data, representing the non-redundant half of the conjugate-symmetry
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217 output of a real-input DFT (see <a href="Multi_002ddimensional-Transforms.html#Multi_002ddimensional-Transforms">Multi-dimensional Transforms</a>).
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218 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)]
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219 array (much like the in-place serial r2c transforms, but here for
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220 out-of-place transforms as well). Currently, only multi-dimensional
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221 (<code>rnk > 1</code>) r2c/c2r transforms are supported (requesting a plan
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222 for <code>rnk = 1</code> will yield <code>NULL</code>). As explained above
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223 (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
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224 distribution of both the real and complex arrays is given by the
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225 ‘<samp>local_size</samp>’ function called for the dimensions of the
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226 <em>complex</em> array. Similar to the other planning functions, the
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227 input and output arrays are overwritten when the plan is created
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228 except in <code>FFTW_ESTIMATE</code> mode.
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229 </p>
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230 <p>As for the complex DFTs above, there is an advance interface that
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231 allows you to manually specify block sizes and to transform contiguous
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232 <code>howmany</code>-tuples of real/complex numbers:
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233 </p>
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234 <a name="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fr2c"></a>
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235 <a name="index-fftw_005fmpi_005fplan_005fmany_005fdft_005fc2r"></a>
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236 <div class="example">
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237 <pre class="example">fftw_plan fftw_mpi_plan_many_dft_r2c
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238 (int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
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239 ptrdiff_t iblock, ptrdiff_t oblock,
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240 double *in, fftw_complex *out,
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241 MPI_Comm comm, unsigned flags);
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242 fftw_plan fftw_mpi_plan_many_dft_c2r
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243 (int rnk, const ptrdiff_t *n, ptrdiff_t howmany,
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244 ptrdiff_t iblock, ptrdiff_t oblock,
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245 fftw_complex *in, double *out,
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246 MPI_Comm comm, unsigned flags);
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247 </pre></div>
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248
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249 <a name="MPI-r2r-transforms"></a>
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250 <h4 class="subsubheading">MPI r2r transforms</h4>
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251
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252 <a name="index-r2r-4"></a>
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253 <p>There are corresponding plan-creation routines for r2r
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254 transforms (see <a href="More-DFTs-of-Real-Data.html#More-DFTs-of-Real-Data">More DFTs of Real Data</a>), currently supporting
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255 multidimensional (<code>rnk > 1</code>) transforms only (<code>rnk = 1</code> will
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256 yield a <code>NULL</code> plan):
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257 </p>
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258 <div class="example">
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259 <pre class="example">fftw_plan fftw_mpi_plan_r2r_2d(ptrdiff_t n0, ptrdiff_t n1,
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260 double *in, double *out,
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261 MPI_Comm comm,
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262 fftw_r2r_kind kind0, fftw_r2r_kind kind1,
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263 unsigned flags);
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264 fftw_plan fftw_mpi_plan_r2r_3d(ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t n2,
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265 double *in, double *out,
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266 MPI_Comm comm,
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267 fftw_r2r_kind kind0, fftw_r2r_kind kind1, fftw_r2r_kind kind2,
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268 unsigned flags);
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269 fftw_plan fftw_mpi_plan_r2r(int rnk, const ptrdiff_t *n,
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270 double *in, double *out,
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271 MPI_Comm comm, const fftw_r2r_kind *kind,
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272 unsigned flags);
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273 fftw_plan fftw_mpi_plan_many_r2r(int rnk, const ptrdiff_t *n,
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274 ptrdiff_t iblock, ptrdiff_t oblock,
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275 double *in, double *out,
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276 MPI_Comm comm, const fftw_r2r_kind *kind,
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277 unsigned flags);
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278 </pre></div>
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279
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280 <p>The parameters are much the same as for the complex DFTs above, except
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281 that the arrays are of real numbers (and hence the outputs of the
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282 ‘<samp>local_size</samp>’ data-distribution functions should be interpreted as
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283 counts of real rather than complex numbers). Also, the <code>kind</code>
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284 parameters specify the r2r kinds along each dimension as for the
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285 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>.
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286 </p>
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287 <a name="MPI-transposition"></a>
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288 <h4 class="subsubheading">MPI transposition</h4>
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289 <a name="index-transpose-5"></a>
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290
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291 <p>FFTW also provides routines to plan a transpose of a distributed
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292 <code>n0</code> by <code>n1</code> array of real numbers, or an array of
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293 <code>howmany</code>-tuples of real numbers with specified block sizes
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294 (see <a href="FFTW-MPI-Transposes.html#FFTW-MPI-Transposes">FFTW MPI Transposes</a>):
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295 </p>
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296 <a name="index-fftw_005fmpi_005fplan_005ftranspose-1"></a>
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297 <a name="index-fftw_005fmpi_005fplan_005fmany_005ftranspose-1"></a>
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298 <div class="example">
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299 <pre class="example">fftw_plan fftw_mpi_plan_transpose(ptrdiff_t n0, ptrdiff_t n1,
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300 double *in, double *out,
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301 MPI_Comm comm, unsigned flags);
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302 fftw_plan fftw_mpi_plan_many_transpose
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303 (ptrdiff_t n0, ptrdiff_t n1, ptrdiff_t howmany,
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304 ptrdiff_t block0, ptrdiff_t block1,
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305 double *in, double *out, MPI_Comm comm, unsigned flags);
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306 </pre></div>
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307
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308 <a name="index-new_002darray-execution-2"></a>
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309 <a name="index-fftw_005fmpi_005fexecute_005fr2r-1"></a>
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310 <p>These plans are used with the <code>fftw_mpi_execute_r2r</code> new-array
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311 execute function (see <a href="Using-MPI-Plans.html#Using-MPI-Plans">Using MPI Plans</a>), since they count as (rank
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312 zero) r2r plans from FFTW’s perspective.
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313 </p>
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314 <hr>
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315 <div class="header">
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316 <p>
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317 Next: <a href="MPI-Wisdom-Communication.html#MPI-Wisdom-Communication" accesskey="n" rel="next">MPI Wisdom Communication</a>, Previous: <a href="MPI-Data-Distribution-Functions.html#MPI-Data-Distribution-Functions" accesskey="p" rel="prev">MPI Data Distribution Functions</a>, Up: <a href="FFTW-MPI-Reference.html#FFTW-MPI-Reference" accesskey="u" rel="up">FFTW MPI Reference</a> [<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>
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318 </div>
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319
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320
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321
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322 </body>
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323 </html>
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