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			112 lines
		
	
	
		
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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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								<title>Wisdom of Fortran? (FFTW 3.3.10)</title>
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								<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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								<link href="Calling-FFTW-from-Legacy-Fortran.html" rel="up" title="Calling FFTW from Legacy Fortran">
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								<span id="Wisdom-of-Fortran_003f"></span><div class="header">
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								<p>
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								Previous: <a href="Fortran-Examples.html" accesskey="p" rel="prev">Fortran Examples</a>, Up: <a href="Calling-FFTW-from-Legacy-Fortran.html" accesskey="u" rel="up">Calling FFTW from Legacy 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-of-Fortran_003f-1"></span><h3 class="section">8.5 Wisdom of Fortran?</h3>
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								<p>In this section, we discuss how one can import/export FFTW wisdom
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								(saved plans) to/from a Fortran program; we assume that the reader is
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								already familiar with wisdom, as described in <a href="Words-of-Wisdom_002dSaving-Plans.html">Words of Wisdom-Saving Plans</a>.
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								</p>
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								<span id="index-portability-8"></span>
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								<p>The basic problem is that is difficult to (portably) pass files and
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								strings between Fortran and C, so we cannot provide a direct Fortran
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								equivalent to the <code>fftw_export_wisdom_to_file</code>, etcetera,
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								functions.  Fortran interfaces <em>are</em> provided for the functions
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								that do not take file/string arguments, however:
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								<code>dfftw_import_system_wisdom</code>, <code>dfftw_import_wisdom</code>,
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								<code>dfftw_export_wisdom</code>, and <code>dfftw_forget_wisdom</code>.
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								<span id="index-dfftw_005fimport_005fsystem_005fwisdom"></span>
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								<span id="index-dfftw_005fimport_005fwisdom"></span>
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								<span id="index-dfftw_005fexport_005fwisdom"></span>
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								<span id="index-dfftw_005fforget_005fwisdom"></span>
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								</p>
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								<p>So, for example, to import the system-wide wisdom, you would do:
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								</p>
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								<div class="example">
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								<pre class="example">        integer isuccess
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								        call dfftw_import_system_wisdom(isuccess)
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								</pre></div>
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								<p>As usual, the C return value is turned into a first parameter;
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								<code>isuccess</code> is non-zero on success and zero on failure (e.g. if
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								there is no system wisdom installed).
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								</p>
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								<p>If you want to import/export wisdom from/to an arbitrary file or
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								elsewhere, you can employ the generic <code>dfftw_import_wisdom</code> and
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								<code>dfftw_export_wisdom</code> functions, for which you must supply a
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								subroutine to read/write one character at a time.  The FFTW package
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								contains an example file <code>doc/f77_wisdom.f</code> demonstrating how to
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								implement <code>import_wisdom_from_file</code> and
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								<code>export_wisdom_to_file</code> subroutines in this way.  (These routines
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								cannot be compiled into the FFTW library itself, lest all FFTW-using
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								programs be required to link with the Fortran I/O library.)
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								</p>
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