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1 <html lang="en">
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2 <head>
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3 <title>Extended and quadruple precision in Fortran - FFTW 3.3.3</title>
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4 <meta http-equiv="Content-Type" content="text/html">
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5 <meta name="description" content="FFTW 3.3.3">
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6 <meta name="generator" content="makeinfo 4.13">
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7 <link title="Top" rel="start" href="index.html#Top">
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8 <link rel="up" href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface" title="Overview of Fortran interface">
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9 <link rel="prev" href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface" title="Overview of Fortran interface">
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10 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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11 <!--
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12 This manual is for FFTW
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13 (version 3.3.3, 25 November 2012).
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14
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15 Copyright (C) 2003 Matteo Frigo.
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16
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17 Copyright (C) 2003 Massachusetts Institute of Technology.
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18
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19 Permission is granted to make and distribute verbatim copies of
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20 this manual provided the copyright notice and this permission
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21 notice are preserved on all copies.
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22
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23 Permission is granted to copy and distribute modified versions of
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24 this manual under the conditions for verbatim copying, provided
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25 that the entire resulting derived work is distributed under the
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26 terms of a permission notice identical to this one.
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27
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28 Permission is granted to copy and distribute translations of this
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29 manual into another language, under the above conditions for
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30 modified versions, except that this permission notice may be
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31 stated in a translation approved by the Free Software Foundation.
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32 -->
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34 <style type="text/css"><!--
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44 --></style>
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45 </head>
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46 <body>
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47 <div class="node">
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48 <a name="Extended-and-quadruple-precision-in-Fortran"></a>
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49 <p>
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50 Previous: <a rel="previous" accesskey="p" href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface">Overview of Fortran interface</a>,
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51 Up: <a rel="up" accesskey="u" href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface">Overview of Fortran interface</a>
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52 <hr>
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53 </div>
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54
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55 <h4 class="subsection">7.1.1 Extended and quadruple precision in Fortran</h4>
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56
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57 <p><a name="index-precision-515"></a>
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58 If FFTW is compiled in <code>long double</code> (extended) precision
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59 (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>), you may be able to call the
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60 resulting <code>fftwl_</code> routines (see <a href="Precision.html#Precision">Precision</a>) from Fortran if
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61 your compiler supports the <code>C_LONG_DOUBLE_COMPLEX</code> type code.
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62
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63 <p>Because some Fortran compilers do not support
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64 <code>C_LONG_DOUBLE_COMPLEX</code>, the <code>fftwl_</code> declarations are
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65 segregated into a separate interface file <code>fftw3l.f03</code>, which you
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66 should include <em>in addition</em> to <code>fftw3.f03</code> (which declares
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67 precision-independent ‘<samp><span class="samp">FFTW_</span></samp>’ constants):
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68
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69 <p><a name="index-iso_005fc_005fbinding-516"></a>
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70 <pre class="example"> use, intrinsic :: iso_c_binding
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71 include 'fftw3.f03'
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72 include 'fftw3l.f03'
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73 </pre>
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74 <p>We also support using the nonstandard <code>__float128</code>
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75 quadruple-precision type provided by recent versions of <code>gcc</code> on
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76 32- and 64-bit x86 hardware (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>),
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77 using the corresponding <code>real(16)</code> and <code>complex(16)</code> types
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78 supported by <code>gfortran</code>. The quadruple-precision ‘<samp><span class="samp">fftwq_</span></samp>’
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79 functions (see <a href="Precision.html#Precision">Precision</a>) are declared in a <code>fftw3q.f03</code>
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80 interface file, which should be included in addition to
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81 <code>fftw3l.f03</code>, as above. You should also link with
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82 <code>-lfftw3q -lquadmath -lm</code> as in C.
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83
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84 <!-- -->
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85 </body></html>
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86
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