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annotate fft/fftw/fftw-3.3.4/doc/html/Precision.html @ 40:223f770b5341 kissfft-double tip

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Try a double-precision kissfft
author Chris Cannam
date Wed, 07 Sep 2016 10:40:32 +0100
parents 26056e866c29
children
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Chris@19 1 <html lang="en">
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Chris@19 3 <title>Precision - FFTW 3.3.4</title>
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Chris@19 12 <!--
Chris@19 13 This manual is for FFTW
Chris@19 14 (version 3.3.4, 20 September 2013).
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Chris@19 16 Copyright (C) 2003 Matteo Frigo.
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Chris@19 46 </head>
Chris@19 47 <body>
Chris@19 48 <div class="node">
Chris@19 49 <a name="Precision"></a>
Chris@19 50 <p>
Chris@19 51 Next:&nbsp;<a rel="next" accesskey="n" href="Memory-Allocation.html#Memory-Allocation">Memory Allocation</a>,
Chris@19 52 Previous:&nbsp;<a rel="previous" accesskey="p" href="Complex-numbers.html#Complex-numbers">Complex numbers</a>,
Chris@19 53 Up:&nbsp;<a rel="up" accesskey="u" href="Data-Types-and-Files.html#Data-Types-and-Files">Data Types and Files</a>
Chris@19 54 <hr>
Chris@19 55 </div>
Chris@19 56
Chris@19 57 <h4 class="subsection">4.1.2 Precision</h4>
Chris@19 58
Chris@19 59 <p><a name="index-precision-143"></a>
Chris@19 60 You can install single and long-double precision versions of FFTW,
Chris@19 61 which replace <code>double</code> with <code>float</code> and <code>long double</code>,
Chris@19 62 respectively (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>). To use these
Chris@19 63 interfaces, you:
Chris@19 64
Chris@19 65 <ul>
Chris@19 66 <li>Link to the single/long-double libraries; on Unix, <code>-lfftw3f</code> or
Chris@19 67 <code>-lfftw3l</code> instead of (or in addition to) <code>-lfftw3</code>. (You
Chris@19 68 can link to the different-precision libraries simultaneously.)
Chris@19 69
Chris@19 70 <li>Include the <em>same</em> <code>&lt;fftw3.h&gt;</code> header file.
Chris@19 71
Chris@19 72 <li>Replace all lowercase instances of &lsquo;<samp><span class="samp">fftw_</span></samp>&rsquo; with &lsquo;<samp><span class="samp">fftwf_</span></samp>&rsquo; or
Chris@19 73 &lsquo;<samp><span class="samp">fftwl_</span></samp>&rsquo; for single or long-double precision, respectively.
Chris@19 74 (<code>fftw_complex</code> becomes <code>fftwf_complex</code>, <code>fftw_execute</code>
Chris@19 75 becomes <code>fftwf_execute</code>, etcetera.)
Chris@19 76
Chris@19 77 <li>Uppercase names, i.e. names beginning with &lsquo;<samp><span class="samp">FFTW_</span></samp>&rsquo;, remain the
Chris@19 78 same.
Chris@19 79
Chris@19 80 <li>Replace <code>double</code> with <code>float</code> or <code>long double</code> for
Chris@19 81 subroutine parameters.
Chris@19 82
Chris@19 83 </ul>
Chris@19 84
Chris@19 85 <p>Depending upon your compiler and/or hardware, <code>long double</code> may not
Chris@19 86 be any more precise than <code>double</code> (or may not be supported at all,
Chris@19 87 although it is standard in C99).
Chris@19 88 <a name="index-C99-144"></a>
Chris@19 89
Chris@19 90 <p>We also support using the nonstandard <code>__float128</code>
Chris@19 91 quadruple-precision type provided by recent versions of <code>gcc</code> on
Chris@19 92 32- and 64-bit x86 hardware (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>).
Chris@19 93 To use this type, link with <code>-lfftw3q -lquadmath -lm</code> (the
Chris@19 94 <code>libquadmath</code> library provided by <code>gcc</code> is needed for
Chris@19 95 quadruple-precision trigonometric functions) and use &lsquo;<samp><span class="samp">fftwq_</span></samp>&rsquo;
Chris@19 96 identifiers.
Chris@19 97
Chris@19 98 <!-- =========> -->
Chris@19 99 </body></html>
Chris@19 100