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Try a double-precision kissfft
author Chris Cannam
date Wed, 07 Sep 2016 10:40:32 +0100
parents 26056e866c29
children
rev   line source
Chris@19 1 <html lang="en">
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Chris@19 3 <title>Extended and quadruple precision in Fortran - FFTW 3.3.4</title>
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Chris@19 48 <a name="Extended-and-quadruple-precision-in-Fortran"></a>
Chris@19 49 <p>
Chris@19 50 Previous:&nbsp;<a rel="previous" accesskey="p" href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface">Overview of Fortran interface</a>,
Chris@19 51 Up:&nbsp;<a rel="up" accesskey="u" href="Overview-of-Fortran-interface.html#Overview-of-Fortran-interface">Overview of Fortran interface</a>
Chris@19 52 <hr>
Chris@19 53 </div>
Chris@19 54
Chris@19 55 <h4 class="subsection">7.1.1 Extended and quadruple precision in Fortran</h4>
Chris@19 56
Chris@19 57 <p><a name="index-precision-518"></a>
Chris@19 58 If FFTW is compiled in <code>long double</code> (extended) precision
Chris@19 59 (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>), you may be able to call the
Chris@19 60 resulting <code>fftwl_</code> routines (see <a href="Precision.html#Precision">Precision</a>) from Fortran if
Chris@19 61 your compiler supports the <code>C_LONG_DOUBLE_COMPLEX</code> type code.
Chris@19 62
Chris@19 63 <p>Because some Fortran compilers do not support
Chris@19 64 <code>C_LONG_DOUBLE_COMPLEX</code>, the <code>fftwl_</code> declarations are
Chris@19 65 segregated into a separate interface file <code>fftw3l.f03</code>, which you
Chris@19 66 should include <em>in addition</em> to <code>fftw3.f03</code> (which declares
Chris@19 67 precision-independent &lsquo;<samp><span class="samp">FFTW_</span></samp>&rsquo; constants):
Chris@19 68
Chris@19 69 <p><a name="index-iso_005fc_005fbinding-519"></a>
Chris@19 70 <pre class="example"> use, intrinsic :: iso_c_binding
Chris@19 71 include 'fftw3.f03'
Chris@19 72 include 'fftw3l.f03'
Chris@19 73 </pre>
Chris@19 74 <p>We also support using the nonstandard <code>__float128</code>
Chris@19 75 quadruple-precision type provided by recent versions of <code>gcc</code> on
Chris@19 76 32- and 64-bit x86 hardware (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>),
Chris@19 77 using the corresponding <code>real(16)</code> and <code>complex(16)</code> types
Chris@19 78 supported by <code>gfortran</code>. The quadruple-precision &lsquo;<samp><span class="samp">fftwq_</span></samp>&rsquo;
Chris@19 79 functions (see <a href="Precision.html#Precision">Precision</a>) are declared in a <code>fftw3q.f03</code>
Chris@19 80 interface file, which should be included in addition to
Chris@19 81 <code>fftw3l.f03</code>, as above. You should also link with
Chris@19 82 <code>-lfftw3q -lquadmath -lm</code> as in C.
Chris@19 83
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Chris@19 86