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comparison src/fftw-3.3.5/doc/FAQ/fftw-faq.html/section1.html @ 42:2cd0e3b3e1fd
Current fftw source
| author | Chris Cannam |
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| date | Tue, 18 Oct 2016 13:40:26 +0100 |
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| 41:481f5f8c5634 | 42:2cd0e3b3e1fd |
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| 1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> | |
| 2 <html> | |
| 3 <head><title> | |
| 4 FFTW FAQ - Section 1 | |
| 5 </title> | |
| 6 <link rev="made" href="mailto:fftw@fftw.org"> | |
| 7 <link rel="Contents" href="index.html"> | |
| 8 <link rel="Start" href="index.html"> | |
| 9 <link rel="Next" href="section2.html"><link rel="Bookmark" title="FFTW FAQ" href="index.html"> | |
| 10 </head><body text="#000000" bgcolor="#FFFFFF"><h1> | |
| 11 FFTW FAQ - Section 1 <br> | |
| 12 Introduction and General Information | |
| 13 </h1> | |
| 14 | |
| 15 <ul> | |
| 16 <li><a href="#whatisfftw" rel=subdocument>Q1.1. What is FFTW?</a> | |
| 17 <li><a href="#whereisfftw" rel=subdocument>Q1.2. How do I obtain FFTW?</a> | |
| 18 <li><a href="#isfftwfree" rel=subdocument>Q1.3. Is FFTW free software?</a> | |
| 19 <li><a href="#nonfree" rel=subdocument>Q1.4. What is this about non-free licenses?</a> | |
| 20 <li><a href="#west" rel=subdocument>Q1.5. In the West? I thought MIT was in the East?</a> | |
| 21 </ul><hr> | |
| 22 | |
| 23 <h2><A name="whatisfftw"> | |
| 24 Question 1.1. What is FFTW? | |
| 25 </A></h2> | |
| 26 | |
| 27 FFTW is a free collection of fast C routines for computing the | |
| 28 Discrete Fourier Transform in one or more dimensions. It includes | |
| 29 complex, real, symmetric, and parallel transforms, and can handle | |
| 30 arbitrary array sizes efficiently. FFTW is typically faster than | |
| 31 other publically-available FFT implementations, and is even | |
| 32 competitive with vendor-tuned libraries. (See our web page for | |
| 33 extensive benchmarks.) To achieve this performance, FFTW uses novel | |
| 34 code-generation and runtime self-optimization techniques (along with | |
| 35 many other tricks). | |
| 36 <h2><A name="whereisfftw"> | |
| 37 Question 1.2. How do I obtain FFTW? | |
| 38 </A></h2> | |
| 39 | |
| 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>. | |
| 41 <h2><A name="isfftwfree"> | |
| 42 Question 1.3. Is FFTW free software? | |
| 43 </A></h2> | |
| 44 | |
| 45 Starting with version 1.3, FFTW is Free Software in the technical | |
| 46 sense defined by the Free Software Foundation (see | |
| 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 | |
| 48 distributed without fee for noncommercial use, but were not | |
| 49 technically ``free.'' | |
| 50 <p> | |
| 51 Non-free licenses for FFTW are also available that permit different | |
| 52 terms of use than the GPL. | |
| 53 <h2><A name="nonfree"> | |
| 54 Question 1.4. What is this about non-free | |
| 55 licenses? | |
| 56 </A></h2> | |
| 57 | |
| 58 The non-free licenses are for companies that wish to use FFTW in their | |
| 59 products but are unwilling to release their software under the GPL | |
| 60 (which would require them to release source code and allow free | |
| 61 redistribution). Such users can purchase an unlimited-use license | |
| 62 from MIT. Contact us for more details. | |
| 63 | |
| 64 <p> | |
| 65 We could instead have released FFTW under the LGPL, or even disallowed | |
| 66 non-Free usage. Suffice it to say, however, that MIT owns the | |
| 67 copyright to FFTW and they only let us GPL it because we convinced | |
| 68 them that it would neither affect their licensing revenue nor irritate | |
| 69 existing licensees. | |
| 70 <h2><A name="west"> | |
| 71 Question 1.5. In the West? I thought MIT was in the | |
| 72 East? | |
| 73 </A></h2> | |
| 74 | |
| 75 Not to an Italian. You could say that we're a Spaghetti Western | |
| 76 (with apologies to Sergio Leone). <hr> | |
| 77 Next: <a href="section2.html" rel=precedes>Installing FFTW</a>.<br> | |
| 78 <a href="index.html" rev=subdocument>Return to contents</a>.<p> | |
| 79 <address> | |
| 80 <A href="http://www.fftw.org">Matteo Frigo and Steven G. Johnson</A> / <A href="mailto:fftw@fftw.org">fftw@fftw.org</A> | |
| 81 - 30 July 2016 | |
| 82 </address><br> | |
| 83 Extracted from FFTW Frequently Asked Questions with Answers, | |
| 84 Copyright © 2016 Matteo Frigo and Massachusetts Institute of Technology. | |
| 85 </body></html> |