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author Chris Cannam
date Wed, 07 Sep 2016 10:40:32 +0100
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Chris@19 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
Chris@19 2 <html>
Chris@19 3 <head><title>
Chris@19 4 FFTW FAQ - Section 1
Chris@19 5 </title>
Chris@19 6 <link rev="made" href="mailto:fftw@fftw.org">
Chris@19 7 <link rel="Contents" href="index.html">
Chris@19 8 <link rel="Start" href="index.html">
Chris@19 9 <link rel="Next" href="section2.html"><link rel="Bookmark" title="FFTW FAQ" href="index.html">
Chris@19 10 </head><body text="#000000" bgcolor="#FFFFFF"><h1>
Chris@19 11 FFTW FAQ - Section 1 <br>
Chris@19 12 Introduction and General Information
Chris@19 13 </h1>
Chris@19 14
Chris@19 15 <ul>
Chris@19 16 <li><a href="#whatisfftw" rel=subdocument>Q1.1. What is FFTW?</a>
Chris@19 17 <li><a href="#whereisfftw" rel=subdocument>Q1.2. How do I obtain FFTW?</a>
Chris@19 18 <li><a href="#isfftwfree" rel=subdocument>Q1.3. Is FFTW free software?</a>
Chris@19 19 <li><a href="#nonfree" rel=subdocument>Q1.4. What is this about non-free licenses?</a>
Chris@19 20 <li><a href="#west" rel=subdocument>Q1.5. In the West? I thought MIT was in the East?</a>
Chris@19 21 </ul><hr>
Chris@19 22
Chris@19 23 <h2><A name="whatisfftw">
Chris@19 24 Question 1.1. What is FFTW?
Chris@19 25 </A></h2>
Chris@19 26
Chris@19 27 FFTW is a free collection of fast C routines for computing the
Chris@19 28 Discrete Fourier Transform in one or more dimensions. It includes
Chris@19 29 complex, real, symmetric, and parallel transforms, and can handle
Chris@19 30 arbitrary array sizes efficiently. FFTW is typically faster than
Chris@19 31 other publically-available FFT implementations, and is even
Chris@19 32 competitive with vendor-tuned libraries. (See our web page for
Chris@19 33 extensive benchmarks.) To achieve this performance, FFTW uses novel
Chris@19 34 code-generation and runtime self-optimization techniques (along with
Chris@19 35 many other tricks).
Chris@19 36 <h2><A name="whereisfftw">
Chris@19 37 Question 1.2. How do I obtain FFTW?
Chris@19 38 </A></h2>
Chris@19 39
Chris@19 40 FFTW can be found at <A href="http://www.fftw.org">the FFTW web page</A>. You can also retrieve it from <code>ftp.fftw.org</code> in <A href="ftp://ftp.fftw.org/pub/fftw"><code>/pub/fftw</code></A>.
Chris@19 41 <h2><A name="isfftwfree">
Chris@19 42 Question 1.3. Is FFTW free software?
Chris@19 43 </A></h2>
Chris@19 44
Chris@19 45 Starting with version 1.3, FFTW is Free Software in the technical
Chris@19 46 sense defined by the Free Software Foundation (see
Chris@19 47 <A href="http://www.gnu.org/philosophy/categories.html">Categories of Free and Non-Free Software</A>), and is distributed under the terms of the GNU General Public License. Previous versions of FFTW were
Chris@19 48 distributed without fee for noncommercial use, but were not
Chris@19 49 technically ``free.''
Chris@19 50 <p>
Chris@19 51 Non-free licenses for FFTW are also available that permit different
Chris@19 52 terms of use than the GPL.
Chris@19 53 <h2><A name="nonfree">
Chris@19 54 Question 1.4. What is this about non-free
Chris@19 55 licenses?
Chris@19 56 </A></h2>
Chris@19 57
Chris@19 58 The non-free licenses are for companies that wish to use FFTW in their
Chris@19 59 products but are unwilling to release their software under the GPL
Chris@19 60 (which would require them to release source code and allow free
Chris@19 61 redistribution). Such users can purchase an unlimited-use license
Chris@19 62 from MIT. Contact us for more details.
Chris@19 63
Chris@19 64 <p>
Chris@19 65 We could instead have released FFTW under the LGPL, or even disallowed
Chris@19 66 non-Free usage. Suffice it to say, however, that MIT owns the
Chris@19 67 copyright to FFTW and they only let us GPL it because we convinced
Chris@19 68 them that it would neither affect their licensing revenue nor irritate
Chris@19 69 existing licensees.
Chris@19 70 <h2><A name="west">
Chris@19 71 Question 1.5. In the West? I thought MIT was in the
Chris@19 72 East?
Chris@19 73 </A></h2>
Chris@19 74
Chris@19 75 Not to an Italian. You could say that we're a Spaghetti Western
Chris@19 76 (with apologies to Sergio Leone). <hr>
Chris@19 77 Next: <a href="section2.html" rel=precedes>Installing FFTW</a>.<br>
Chris@19 78 <a href="index.html" rev=subdocument>Return to contents</a>.<p>
Chris@19 79 <address>
Chris@19 80 <A href="http://www.fftw.org">Matteo Frigo and Steven G. Johnson</A> / <A href="mailto:fftw@fftw.org">fftw@fftw.org</A>
Chris@19 81 - 04 March 2014
Chris@19 82 </address><br>
Chris@19 83 Extracted from FFTW Frequently Asked Questions with Answers,
Chris@19 84 Copyright &copy; 2014 Matteo Frigo and Massachusetts Institute of Technology.
Chris@19 85 </body></html>