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| author | Chris Cannam |
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| date | Wed, 20 Mar 2013 15:35:50 +0000 |
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| 9:c0fb53affa76 | 10:37bf6b4a2645 |
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| 1 <html lang="en"> | |
| 2 <head> | |
| 3 <title>Precision - FFTW 3.3.3</title> | |
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| 5 <meta name="description" content="FFTW 3.3.3"> | |
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| 8 <link rel="up" href="Data-Types-and-Files.html#Data-Types-and-Files" title="Data Types and Files"> | |
| 9 <link rel="prev" href="Complex-numbers.html#Complex-numbers" title="Complex numbers"> | |
| 10 <link rel="next" href="Memory-Allocation.html#Memory-Allocation" title="Memory Allocation"> | |
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| 12 <!-- | |
| 13 This manual is for FFTW | |
| 14 (version 3.3.3, 25 November 2012). | |
| 15 | |
| 16 Copyright (C) 2003 Matteo Frigo. | |
| 17 | |
| 18 Copyright (C) 2003 Massachusetts Institute of Technology. | |
| 19 | |
| 20 Permission is granted to make and distribute verbatim copies of | |
| 21 this manual provided the copyright notice and this permission | |
| 22 notice are preserved on all copies. | |
| 23 | |
| 24 Permission is granted to copy and distribute modified versions of | |
| 25 this manual under the conditions for verbatim copying, provided | |
| 26 that the entire resulting derived work is distributed under the | |
| 27 terms of a permission notice identical to this one. | |
| 28 | |
| 29 Permission is granted to copy and distribute translations of this | |
| 30 manual into another language, under the above conditions for | |
| 31 modified versions, except that this permission notice may be | |
| 32 stated in a translation approved by the Free Software Foundation. | |
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| 46 </head> | |
| 47 <body> | |
| 48 <div class="node"> | |
| 49 <a name="Precision"></a> | |
| 50 <p> | |
| 51 Next: <a rel="next" accesskey="n" href="Memory-Allocation.html#Memory-Allocation">Memory Allocation</a>, | |
| 52 Previous: <a rel="previous" accesskey="p" href="Complex-numbers.html#Complex-numbers">Complex numbers</a>, | |
| 53 Up: <a rel="up" accesskey="u" href="Data-Types-and-Files.html#Data-Types-and-Files">Data Types and Files</a> | |
| 54 <hr> | |
| 55 </div> | |
| 56 | |
| 57 <h4 class="subsection">4.1.2 Precision</h4> | |
| 58 | |
| 59 <p><a name="index-precision-143"></a> | |
| 60 You can install single and long-double precision versions of FFTW, | |
| 61 which replace <code>double</code> with <code>float</code> and <code>long double</code>, | |
| 62 respectively (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>). To use these | |
| 63 interfaces, you: | |
| 64 | |
| 65 <ul> | |
| 66 <li>Link to the single/long-double libraries; on Unix, <code>-lfftw3f</code> or | |
| 67 <code>-lfftw3l</code> instead of (or in addition to) <code>-lfftw3</code>. (You | |
| 68 can link to the different-precision libraries simultaneously.) | |
| 69 | |
| 70 <li>Include the <em>same</em> <code><fftw3.h></code> header file. | |
| 71 | |
| 72 <li>Replace all lowercase instances of ‘<samp><span class="samp">fftw_</span></samp>’ with ‘<samp><span class="samp">fftwf_</span></samp>’ or | |
| 73 ‘<samp><span class="samp">fftwl_</span></samp>’ for single or long-double precision, respectively. | |
| 74 (<code>fftw_complex</code> becomes <code>fftwf_complex</code>, <code>fftw_execute</code> | |
| 75 becomes <code>fftwf_execute</code>, etcetera.) | |
| 76 | |
| 77 <li>Uppercase names, i.e. names beginning with ‘<samp><span class="samp">FFTW_</span></samp>’, remain the | |
| 78 same. | |
| 79 | |
| 80 <li>Replace <code>double</code> with <code>float</code> or <code>long double</code> for | |
| 81 subroutine parameters. | |
| 82 | |
| 83 </ul> | |
| 84 | |
| 85 <p>Depending upon your compiler and/or hardware, <code>long double</code> may not | |
| 86 be any more precise than <code>double</code> (or may not be supported at all, | |
| 87 although it is standard in C99). | |
| 88 <a name="index-C99-144"></a> | |
| 89 | |
| 90 <p>We also support using the nonstandard <code>__float128</code> | |
| 91 quadruple-precision type provided by recent versions of <code>gcc</code> on | |
| 92 32- and 64-bit x86 hardware (see <a href="Installation-and-Customization.html#Installation-and-Customization">Installation and Customization</a>). | |
| 93 To use this type, link with <code>-lfftw3q -lquadmath -lm</code> (the | |
| 94 <code>libquadmath</code> library provided by <code>gcc</code> is needed for | |
| 95 quadruple-precision trigonometric functions) and use ‘<samp><span class="samp">fftwq_</span></samp>’ | |
| 96 identifiers. | |
| 97 | |
| 98 <!-- =========> --> | |
| 99 </body></html> | |
| 100 |