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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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Chris@82 3 <!-- This manual is for FFTW
Chris@82 4 (version 3.3.8, 24 May 2018).
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Chris@82 6 Copyright (C) 2003 Matteo Frigo.
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Chris@82 24 <head>
Chris@82 25 <title>FFTW 3.3.8: Wisdom Generic Export/Import from Fortran</title>
Chris@82 26
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Chris@82 36 <link href="Accessing-the-wisdom-API-from-Fortran.html#Accessing-the-wisdom-API-from-Fortran" rel="up" title="Accessing the wisdom API from Fortran">
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Chris@82 68 </head>
Chris@82 69
Chris@82 70 <body lang="en">
Chris@82 71 <a name="Wisdom-Generic-Export_002fImport-from-Fortran"></a>
Chris@82 72 <div class="header">
Chris@82 73 <p>
Chris@82 74 Previous: <a href="Wisdom-String-Export_002fImport-from-Fortran.html#Wisdom-String-Export_002fImport-from-Fortran" accesskey="p" rel="prev">Wisdom String Export/Import from Fortran</a>, Up: <a href="Accessing-the-wisdom-API-from-Fortran.html#Accessing-the-wisdom-API-from-Fortran" accesskey="u" rel="up">Accessing the wisdom API from Fortran</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>
Chris@82 75 </div>
Chris@82 76 <hr>
Chris@82 77 <a name="Wisdom-Generic-Export_002fImport-from-Fortran-1"></a>
Chris@82 78 <h4 class="subsection">7.6.3 Wisdom Generic Export/Import from Fortran</h4>
Chris@82 79
Chris@82 80 <p>The most generic wisdom export/import functions allow you to provide
Chris@82 81 an arbitrary callback function to read/write one character at a time
Chris@82 82 in any way you want. However, your callback function must be written
Chris@82 83 in a special way, using the <code>bind(C)</code> attribute to be passed to a
Chris@82 84 C interface.
Chris@82 85 </p>
Chris@82 86 <a name="index-fftw_005fexport_005fwisdom-1"></a>
Chris@82 87 <p>In particular, to call the generic wisdom export function
Chris@82 88 <code>fftw_export_wisdom</code>, you would write a callback subroutine of the form:
Chris@82 89 </p>
Chris@82 90 <div class="example">
Chris@82 91 <pre class="example"> subroutine my_write_char(c, p) bind(C)
Chris@82 92 use, intrinsic :: iso_c_binding
Chris@82 93 character(C_CHAR), value :: c
Chris@82 94 type(C_PTR), value :: p
Chris@82 95 <em>...write c...</em>
Chris@82 96 end subroutine my_write_char
Chris@82 97 </pre></div>
Chris@82 98
Chris@82 99 <p>Given such a subroutine (along with the corresponding interface definition), you could then export wisdom using:
Chris@82 100 </p>
Chris@82 101 <a name="index-c_005ffunloc"></a>
Chris@82 102 <div class="example">
Chris@82 103 <pre class="example"> call fftw_export_wisdom(c_funloc(my_write_char), p)
Chris@82 104 </pre></div>
Chris@82 105
Chris@82 106 <a name="index-c_005floc"></a>
Chris@82 107 <a name="index-c_005ff_005fpointer-4"></a>
Chris@82 108 <p>The standard <code>c_funloc</code> intrinsic converts a Fortran
Chris@82 109 <code>bind(C)</code> subroutine into a C function pointer. The parameter
Chris@82 110 <code>p</code> is a <code>type(C_PTR)</code> to any arbitrary data that you want
Chris@82 111 to pass to <code>my_write_char</code> (or <code>C_NULL_PTR</code> if none). (Note
Chris@82 112 that you can get a C pointer to Fortran data using the intrinsic
Chris@82 113 <code>c_loc</code>, and convert it back to a Fortran pointer in
Chris@82 114 <code>my_write_char</code> using <code>c_f_pointer</code>.)
Chris@82 115 </p>
Chris@82 116 <p>Similarly, to use the generic <code>fftw_import_wisdom</code>, you would
Chris@82 117 define a callback function of the form:
Chris@82 118 </p>
Chris@82 119 <a name="index-fftw_005fimport_005fwisdom-1"></a>
Chris@82 120 <div class="example">
Chris@82 121 <pre class="example"> integer(C_INT) function my_read_char(p) bind(C)
Chris@82 122 use, intrinsic :: iso_c_binding
Chris@82 123 type(C_PTR), value :: p
Chris@82 124 character :: c
Chris@82 125 <em>...read a character c...</em>
Chris@82 126 my_read_char = ichar(c, C_INT)
Chris@82 127 end function my_read_char
Chris@82 128
Chris@82 129 ....
Chris@82 130
Chris@82 131 integer(C_INT) :: ret
Chris@82 132 ret = fftw_import_wisdom(c_funloc(my_read_char), p)
Chris@82 133 if (ret .eq. 0) stop 'error importing wisdom'
Chris@82 134 </pre></div>
Chris@82 135
Chris@82 136 <p>Your function can return <code>-1</code> if the end of the input is reached.
Chris@82 137 Again, <code>p</code> is an arbitrary <code>type(C_PTR</code> that is passed
Chris@82 138 through to your function. <code>fftw_import_wisdom</code> returns <code>0</code>
Chris@82 139 if an error occurred and nonzero otherwise.
Chris@82 140 </p>
Chris@82 141 <hr>
Chris@82 142 <div class="header">
Chris@82 143 <p>
Chris@82 144 Previous: <a href="Wisdom-String-Export_002fImport-from-Fortran.html#Wisdom-String-Export_002fImport-from-Fortran" accesskey="p" rel="prev">Wisdom String Export/Import from Fortran</a>, Up: <a href="Accessing-the-wisdom-API-from-Fortran.html#Accessing-the-wisdom-API-from-Fortran" accesskey="u" rel="up">Accessing the wisdom API from Fortran</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>
Chris@82 145 </div>
Chris@82 146
Chris@82 147
Chris@82 148
Chris@82 149 </body>
Chris@82 150 </html>