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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 3 <!-- This manual is for FFTW
Chris@42 4 (version 3.3.5, 30 July 2016).
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Chris@42 6 Copyright (C) 2003 Matteo Frigo.
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Chris@42 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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Chris@42 24 <head>
Chris@42 25 <title>FFTW 3.3.5: Extended and quadruple precision in Fortran</title>
Chris@42 26
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Chris@42 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
Chris@42 36 <link href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface" rel="up" title="Overview of Fortran interface">
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Chris@42 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
Chris@42 72 <a name="Extended-and-quadruple-precision-in-Fortran"></a>
Chris@42 73 <div class="header">
Chris@42 74 <p>
Chris@42 75 Previous: <a href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface" accesskey="p" rel="prev">Overview of Fortran interface</a>, Up: <a href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface" accesskey="u" rel="up">Overview of Fortran interface</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="Extended-and-quadruple-precision-in-Fortran-1"></a>
Chris@42 79 <h4 class="subsection">7.1.1 Extended and quadruple precision in Fortran</h4>
Chris@42 80 <a name="index-precision-7"></a>
Chris@42 81
Chris@42 82 <p>If FFTW is compiled in <code>long double</code> (extended) precision
Chris@42 83 (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>), you may be able to call the
Chris@42 84 resulting <code>fftwl_</code> routines (see <a href="Precision.html#Precision">Precision</a>) from Fortran if
Chris@42 85 your compiler supports the <code>C_LONG_DOUBLE_COMPLEX</code> type code.
Chris@42 86 </p>
Chris@42 87 <p>Because some Fortran compilers do not support
Chris@42 88 <code>C_LONG_DOUBLE_COMPLEX</code>, the <code>fftwl_</code> declarations are
Chris@42 89 segregated into a separate interface file <code>fftw3l.f03</code>, which you
Chris@42 90 should include <em>in addition</em> to <code>fftw3.f03</code> (which declares
Chris@42 91 precision-independent &lsquo;<samp>FFTW_</samp>&rsquo; constants):
Chris@42 92 </p>
Chris@42 93 <a name="index-iso_005fc_005fbinding-2"></a>
Chris@42 94 <div class="example">
Chris@42 95 <pre class="example"> use, intrinsic :: iso_c_binding
Chris@42 96 include 'fftw3.f03'
Chris@42 97 include 'fftw3l.f03'
Chris@42 98 </pre></div>
Chris@42 99
Chris@42 100 <p>We also support using the nonstandard <code>__float128</code>
Chris@42 101 quadruple-precision type provided by recent versions of <code>gcc</code> on
Chris@42 102 32- and 64-bit x86 hardware (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>),
Chris@42 103 using the corresponding <code>real(16)</code> and <code>complex(16)</code> types
Chris@42 104 supported by <code>gfortran</code>. The quadruple-precision &lsquo;<samp>fftwq_</samp>&rsquo;
Chris@42 105 functions (see <a href="Precision.html#Precision">Precision</a>) are declared in a <code>fftw3q.f03</code>
Chris@42 106 interface file, which should be included in addition to
Chris@42 107 <code>fftw3l.f03</code>, as above. You should also link with
Chris@42 108 <code>-lfftw3q -lquadmath -lm</code> as in C.
Chris@42 109 </p>
Chris@42 110
Chris@42 111
Chris@42 112
Chris@42 113 </body>
Chris@42 114 </html>