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2 | pj | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> |
2 | <html> |
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3 | <head><title> |
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4 | FFTW FAQ - Section 1 |
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5 | </title> |
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6 | <link rev="made" href="mailto:fftw@theory.lcs.mit.edu"> |
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7 | <link rel="Contents" href="index.html"> |
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8 | <link rel="Start" href="index.html"> |
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9 | <link rel="Next" href="section2.html"><link rel="Bookmark" title="FFTW FAQ" href="index.html"> |
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10 | </head><body text="#000000" bgcolor="#FFFFFF"><h1> |
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11 | FFTW FAQ - Section 1 <br> |
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12 | Introduction and General Information |
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13 | </h1> |
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14 | |||
15 | <ul> |
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16 | <li><a href="#whatisfftw" rel=subdocument>Q1.1. What is FFTW?</a> |
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17 | <li><a href="#whereisfftw" rel=subdocument>Q1.2. How do I obtain FFTW?</a> |
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18 | <li><a href="#isfftwfree" rel=subdocument>Q1.3. Is FFTW free software?</a> |
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19 | <li><a href="#nonfree" rel=subdocument>Q1.4. What is this about non-free licenses?</a> |
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20 | </ul><hr> |
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21 | |||
22 | <h2><A name="whatisfftw"> |
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23 | Question 1.1. What is FFTW? |
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24 | </A></h2> |
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25 | |||
26 | FFTW is a free collection of fast C routines for computing the |
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27 | Discrete Fourier Transform in one or more dimensions. It includes |
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28 | complex, real, and parallel transforms, and can handle arbitrary array |
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29 | sizes efficiently. FFTW is typically faster than other |
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30 | publically-available FFT implementations, and is even competitive with |
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31 | vendor-tuned libraries. (See our web page for extensive benchmarks.) |
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32 | To achieve this performance, FFTW uses novel code-generation and |
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33 | runtime self-optimization techniques (along with many other tricks). |
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34 | |||
35 | <h2><A name="whereisfftw"> |
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36 | Question 1.2. How do I obtain FFTW? |
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37 | </A></h2> |
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38 | |||
39 | FFTW can be found at <A href="http://theory.lcs.mit.edu/~fftw/">the FFTW web page</A>. You can also retrieve it from <code>theory.lcs.mit.edu</code> in <A href="ftp://theory.lcs.mit.edu/pub/fftw"><code>/pub/fftw</code></A>. |
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40 | <h2><A name="isfftwfree"> |
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41 | Question 1.3. Is FFTW free software? |
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42 | </A></h2> |
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43 | |||
44 | Starting with version 1.3, FFTW is Free Software in the technical |
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45 | sense defined by the Free Software Foundation (see |
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46 | <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 |
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47 | distributed without fee for noncommercial use, but were not |
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48 | technically ``free.'' |
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49 | <p> |
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50 | Non-free licenses for FFTW are also available that permit different |
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51 | terms of use than the GPL. |
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52 | <h2><A name="nonfree"> |
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53 | Question 1.4. What is this about non-free |
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54 | licenses? |
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55 | </A></h2> |
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56 | |||
57 | The non-free licenses are for companies that wish to use FFTW in their |
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58 | products but are unwilling to release their software under the GPL |
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59 | (which would require them to release source code and allow free |
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60 | redistribution). Such users can purchase an unlimited-use license |
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61 | from MIT. Contact us for more details. |
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62 | |||
63 | <p> |
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64 | We could instead have released FFTW under the LGPL, or even disallowed |
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65 | non-Free usage. Suffice it to say, however, that MIT owns the |
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66 | copyright to FFTW and they only let us GPL it because we convinced |
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67 | them that it would neither affect their licensing revenue nor irritate |
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68 | existing licensees. <hr> |
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69 | Next: <a href="section2.html" rel=precedes>Installing FFTW</a>.<br> |
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70 | <a href="index.html" rev=subdocument>Return to contents</a>.<p> |
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71 | <address> |
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72 | <A href="http://theory.lcs.mit.edu/~fftw/">Matteo Frigo and Steven G. Johnson</A> / <A href="mailto:fftw@theory.lcs.mit.edu">fftw@theory.lcs.mit.edu</A> |
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73 | - 18 May 1999 |
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74 | </address><br> |
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75 | Extracted from FFTW Frequently Asked Questions with Answers, |
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76 | Copyright © 1999 Massachusetts Institute of Technology. |
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77 | </body></html> |