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			106 lines
		
	
	
		
			5.1 KiB
		
	
	
	
		
			HTML
		
	
	
	
	
	
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!-- This manual is for FFTW
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(version 3.3.10, 10 December 2020).
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Copyright (C) 2003 Matteo Frigo.
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Copyright (C) 2003 Massachusetts Institute of Technology.
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Permission is granted to make and distribute verbatim copies of this
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manual provided the copyright notice and this permission notice are
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preserved on all copies.
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Permission is granted to copy and distribute modified versions of this
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<title>Wisdom File Export/Import from Fortran (FFTW 3.3.10)</title>
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<span id="Wisdom-File-Export_002fImport-from-Fortran"></span><div class="header">
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<p>
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Next: <a href="Wisdom-String-Export_002fImport-from-Fortran.html" accesskey="n" rel="next">Wisdom String Export/Import from Fortran</a>, Previous: <a href="Accessing-the-wisdom-API-from-Fortran.html" accesskey="p" rel="prev">Accessing the wisdom API from Fortran</a>, Up: <a href="Accessing-the-wisdom-API-from-Fortran.html" accesskey="u" rel="up">Accessing the wisdom API from Fortran</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
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<span id="Wisdom-File-Export_002fImport-from-Fortran-1"></span><h4 class="subsection">7.6.1 Wisdom File Export/Import from Fortran</h4>
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<span id="index-fftw_005fimport-wisdom_005ffrom_005ffilename"></span>
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<span id="index-fftw_005fexport_005fwisdom_005fto_005ffilename-2"></span>
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<p>The easiest way to export and import wisdom is to do so using
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<code>fftw_export_wisdom_to_filename</code> and
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<code>fftw_wisdom_from_filename</code>.  The only trick is that these
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require you to pass a C string, which is an array of type
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<code>CHARACTER(C_CHAR)</code> that is terminated by <code>C_NULL_CHAR</code>.
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You can call them like this:
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</p>
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<div class="example">
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<pre class="example">  integer(C_INT) :: ret
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  ret = fftw_export_wisdom_to_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
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  if (ret .eq. 0) stop 'error exporting wisdom to file'
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  ret = fftw_import_wisdom_from_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
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  if (ret .eq. 0) stop 'error importing wisdom from file'
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</pre></div>
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<p>Note that prepending ‘<samp>C_CHAR_</samp>’ is needed to specify that the
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literal string is of kind <code>C_CHAR</code>, and we null-terminate the
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string by appending ‘<samp>// C_NULL_CHAR</samp>’.  These functions return an
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<code>integer(C_INT)</code> (<code>ret</code>) which is <code>0</code> if an error
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occurred during export/import and nonzero otherwise.
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</p>
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<p>It is also possible to use the lower-level routines
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<code>fftw_export_wisdom_to_file</code> and
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<code>fftw_import_wisdom_from_file</code>, which accept parameters of the C
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type <code>FILE*</code>, expressed in Fortran as <code>type(C_PTR)</code>.
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However, you are then responsible for creating the <code>FILE*</code>
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yourself.  You can do this by using <code>iso_c_binding</code> to define
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Fortran intefaces for the C library functions <code>fopen</code> and
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<code>fclose</code>, which is a bit strange in Fortran but workable.
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</p>
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