annotate src/fftw-3.3.5/doc/FAQ/fftw-faq.html/section1.html @ 83:ae30d91d2ffe

Replace these with versions built using an older toolset (so as to avoid ABI compatibilities when linking on Ubuntu 14.04 for packaging purposes)
author Chris Cannam
date Fri, 07 Feb 2020 11:51:13 +0000
parents 2cd0e3b3e1fd
children
rev   line source
Chris@42 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
Chris@42 2 <html>
Chris@42 3 <head><title>
Chris@42 4 FFTW FAQ - Section 1
Chris@42 5 </title>
Chris@42 6 <link rev="made" href="mailto:fftw@fftw.org">
Chris@42 7 <link rel="Contents" href="index.html">
Chris@42 8 <link rel="Start" href="index.html">
Chris@42 9 <link rel="Next" href="section2.html"><link rel="Bookmark" title="FFTW FAQ" href="index.html">
Chris@42 10 </head><body text="#000000" bgcolor="#FFFFFF"><h1>
Chris@42 11 FFTW FAQ - Section 1 <br>
Chris@42 12 Introduction and General Information
Chris@42 13 </h1>
Chris@42 14
Chris@42 15 <ul>
Chris@42 16 <li><a href="#whatisfftw" rel=subdocument>Q1.1. What is FFTW?</a>
Chris@42 17 <li><a href="#whereisfftw" rel=subdocument>Q1.2. How do I obtain FFTW?</a>
Chris@42 18 <li><a href="#isfftwfree" rel=subdocument>Q1.3. Is FFTW free software?</a>
Chris@42 19 <li><a href="#nonfree" rel=subdocument>Q1.4. What is this about non-free licenses?</a>
Chris@42 20 <li><a href="#west" rel=subdocument>Q1.5. In the West? I thought MIT was in the East?</a>
Chris@42 21 </ul><hr>
Chris@42 22
Chris@42 23 <h2><A name="whatisfftw">
Chris@42 24 Question 1.1. What is FFTW?
Chris@42 25 </A></h2>
Chris@42 26
Chris@42 27 FFTW is a free collection of fast C routines for computing the
Chris@42 28 Discrete Fourier Transform in one or more dimensions. It includes
Chris@42 29 complex, real, symmetric, and parallel transforms, and can handle
Chris@42 30 arbitrary array sizes efficiently. FFTW is typically faster than
Chris@42 31 other publically-available FFT implementations, and is even
Chris@42 32 competitive with vendor-tuned libraries. (See our web page for
Chris@42 33 extensive benchmarks.) To achieve this performance, FFTW uses novel
Chris@42 34 code-generation and runtime self-optimization techniques (along with
Chris@42 35 many other tricks).
Chris@42 36 <h2><A name="whereisfftw">
Chris@42 37 Question 1.2. How do I obtain FFTW?
Chris@42 38 </A></h2>
Chris@42 39
Chris@42 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@42 41 <h2><A name="isfftwfree">
Chris@42 42 Question 1.3. Is FFTW free software?
Chris@42 43 </A></h2>
Chris@42 44
Chris@42 45 Starting with version 1.3, FFTW is Free Software in the technical
Chris@42 46 sense defined by the Free Software Foundation (see
Chris@42 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@42 48 distributed without fee for noncommercial use, but were not
Chris@42 49 technically ``free.''
Chris@42 50 <p>
Chris@42 51 Non-free licenses for FFTW are also available that permit different
Chris@42 52 terms of use than the GPL.
Chris@42 53 <h2><A name="nonfree">
Chris@42 54 Question 1.4. What is this about non-free
Chris@42 55 licenses?
Chris@42 56 </A></h2>
Chris@42 57
Chris@42 58 The non-free licenses are for companies that wish to use FFTW in their
Chris@42 59 products but are unwilling to release their software under the GPL
Chris@42 60 (which would require them to release source code and allow free
Chris@42 61 redistribution). Such users can purchase an unlimited-use license
Chris@42 62 from MIT. Contact us for more details.
Chris@42 63
Chris@42 64 <p>
Chris@42 65 We could instead have released FFTW under the LGPL, or even disallowed
Chris@42 66 non-Free usage. Suffice it to say, however, that MIT owns the
Chris@42 67 copyright to FFTW and they only let us GPL it because we convinced
Chris@42 68 them that it would neither affect their licensing revenue nor irritate
Chris@42 69 existing licensees.
Chris@42 70 <h2><A name="west">
Chris@42 71 Question 1.5. In the West? I thought MIT was in the
Chris@42 72 East?
Chris@42 73 </A></h2>
Chris@42 74
Chris@42 75 Not to an Italian. You could say that we're a Spaghetti Western
Chris@42 76 (with apologies to Sergio Leone). <hr>
Chris@42 77 Next: <a href="section2.html" rel=precedes>Installing FFTW</a>.<br>
Chris@42 78 <a href="index.html" rev=subdocument>Return to contents</a>.<p>
Chris@42 79 <address>
Chris@42 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@42 81 - 30 July 2016
Chris@42 82 </address><br>
Chris@42 83 Extracted from FFTW Frequently Asked Questions with Answers,
Chris@42 84 Copyright &copy; 2016 Matteo Frigo and Massachusetts Institute of Technology.
Chris@42 85 </body></html>