cannam@127: cannam@127: cannam@127: cannam@127: FFTW FAQ - Section 1 cannam@127: cannam@127: cannam@127: cannam@127: cannam@127: cannam@127:

cannam@127: FFTW FAQ - Section 1
cannam@127: Introduction and General Information cannam@127:

cannam@127: cannam@127:
cannam@127: cannam@127:

cannam@127: Question 1.1. What is FFTW? cannam@127:

cannam@127: cannam@127: FFTW is a free collection of fast C routines for computing the cannam@127: Discrete Fourier Transform in one or more dimensions. It includes cannam@127: complex, real, symmetric, and parallel transforms, and can handle cannam@127: arbitrary array sizes efficiently. FFTW is typically faster than cannam@127: other publically-available FFT implementations, and is even cannam@127: competitive with vendor-tuned libraries. (See our web page for cannam@127: extensive benchmarks.) To achieve this performance, FFTW uses novel cannam@127: code-generation and runtime self-optimization techniques (along with cannam@127: many other tricks). cannam@127:

cannam@127: Question 1.2. How do I obtain FFTW? cannam@127:

cannam@127: cannam@127: FFTW can be found at the FFTW web page. You can also retrieve it from ftp.fftw.org in /pub/fftw. cannam@127:

cannam@127: Question 1.3. Is FFTW free software? cannam@127:

cannam@127: cannam@127: Starting with version 1.3, FFTW is Free Software in the technical cannam@127: sense defined by the Free Software Foundation (see cannam@127: Categories of Free and Non-Free Software), and is distributed under the terms of the GNU General Public License. Previous versions of FFTW were cannam@127: distributed without fee for noncommercial use, but were not cannam@127: technically ``free.'' cannam@127:

cannam@127: Non-free licenses for FFTW are also available that permit different cannam@127: terms of use than the GPL. cannam@127:

cannam@127: Question 1.4. What is this about non-free cannam@127: licenses? cannam@127:

cannam@127: cannam@127: The non-free licenses are for companies that wish to use FFTW in their cannam@127: products but are unwilling to release their software under the GPL cannam@127: (which would require them to release source code and allow free cannam@127: redistribution). Such users can purchase an unlimited-use license cannam@127: from MIT. Contact us for more details. cannam@127: cannam@127:

cannam@127: We could instead have released FFTW under the LGPL, or even disallowed cannam@127: non-Free usage. Suffice it to say, however, that MIT owns the cannam@127: copyright to FFTW and they only let us GPL it because we convinced cannam@127: them that it would neither affect their licensing revenue nor irritate cannam@127: existing licensees. cannam@127:

cannam@127: Question 1.5. In the West? I thought MIT was in the cannam@127: East? cannam@127:

cannam@127: cannam@127: Not to an Italian. You could say that we're a Spaghetti Western cannam@127: (with apologies to Sergio Leone).
cannam@127: Next: Installing FFTW.
cannam@127: Return to contents.

cannam@127:

cannam@127: Matteo Frigo and Steven G. Johnson / fftw@fftw.org cannam@127: - 30 July 2016 cannam@127:

cannam@127: Extracted from FFTW Frequently Asked Questions with Answers, cannam@127: Copyright © 2016 Matteo Frigo and Massachusetts Institute of Technology. cannam@127: