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This manual is for FFTW
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(version 3.1.1, 4 March 2006).
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Copyright (C) 2003 Matteo Frigo.
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Copyright (C) 2003 Massachusetts Institute of Technology.
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this manual provided the copyright notice and this permission
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notice are preserved on all copies.
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<h3 class="section">6.4 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_002dSaving-Plans">Words of Wisdom-Saving Plans</a>.
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<p><a name="index-portability-336"></a>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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<a name="index-dfftw_005fimport_005fsystem_005fwisdom-337"></a><a name="index-dfftw_005fimport_005fwisdom-338"></a><a name="index-dfftw_005fexport_005fwisdom-339"></a><a name="index-dfftw_005fforget_005fwisdom-340"></a>
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So, for example, to import the system-wide wisdom, you would do:
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<pre class="example"> integer isuccess
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call dfftw_import_system_wisdom(isuccess)
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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>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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