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Current fftw source
author Chris Cannam
date Tue, 18 Oct 2016 13:40:26 +0100
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Chris@42 25 <title>FFTW 3.3.5: Wisdom File Export/Import from Fortran</title>
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Chris@42 74 <p>
Chris@42 75 Next: <a href="Wisdom-String-Export_002fImport-from-Fortran.html#Wisdom-String-Export_002fImport-from-Fortran" accesskey="n" rel="next">Wisdom String Export/Import from Fortran</a>, Previous: <a href="Accessing-the-wisdom-API-from-Fortran.html#Accessing-the-wisdom-API-from-Fortran" accesskey="p" rel="prev">Accessing the wisdom API 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@42 76 </div>
Chris@42 77 <hr>
Chris@42 78 <a name="Wisdom-File-Export_002fImport-from-Fortran-1"></a>
Chris@42 79 <h4 class="subsection">7.6.1 Wisdom File Export/Import from Fortran</h4>
Chris@42 80
Chris@42 81 <a name="index-fftw_005fimport-wisdom_005ffrom_005ffilename"></a>
Chris@42 82 <a name="index-fftw_005fexport_005fwisdom_005fto_005ffilename-2"></a>
Chris@42 83 <p>The easiest way to export and import wisdom is to do so using
Chris@42 84 <code>fftw_export_wisdom_to_filename</code> and
Chris@42 85 <code>fftw_wisdom_from_filename</code>. The only trick is that these
Chris@42 86 require you to pass a C string, which is an array of type
Chris@42 87 <code>CHARACTER(C_CHAR)</code> that is terminated by <code>C_NULL_CHAR</code>.
Chris@42 88 You can call them like this:
Chris@42 89 </p>
Chris@42 90 <div class="example">
Chris@42 91 <pre class="example"> integer(C_INT) :: ret
Chris@42 92 ret = fftw_export_wisdom_to_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
Chris@42 93 if (ret .eq. 0) stop 'error exporting wisdom to file'
Chris@42 94 ret = fftw_import_wisdom_from_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
Chris@42 95 if (ret .eq. 0) stop 'error importing wisdom from file'
Chris@42 96 </pre></div>
Chris@42 97
Chris@42 98 <p>Note that prepending &lsquo;<samp>C_CHAR_</samp>&rsquo; is needed to specify that the
Chris@42 99 literal string is of kind <code>C_CHAR</code>, and we null-terminate the
Chris@42 100 string by appending &lsquo;<samp>// C_NULL_CHAR</samp>&rsquo;. These functions return an
Chris@42 101 <code>integer(C_INT)</code> (<code>ret</code>) which is <code>0</code> if an error
Chris@42 102 occurred during export/import and nonzero otherwise.
Chris@42 103 </p>
Chris@42 104 <p>It is also possible to use the lower-level routines
Chris@42 105 <code>fftw_export_wisdom_to_file</code> and
Chris@42 106 <code>fftw_import_wisdom_from_file</code>, which accept parameters of the C
Chris@42 107 type <code>FILE*</code>, expressed in Fortran as <code>type(C_PTR)</code>.
Chris@42 108 However, you are then responsible for creating the <code>FILE*</code>
Chris@42 109 yourself. You can do this by using <code>iso_c_binding</code> to define
Chris@42 110 Fortran intefaces for the C library functions <code>fopen</code> and
Chris@42 111 <code>fclose</code>, which is a bit strange in Fortran but workable.
Chris@42 112 </p>
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