"FFTW" stands for "Fastest Fourier Transform in the West." FFTW is a C subroutine library for computing the discrete Fourier transform (DFT) in one or more dimensions, of arbitrary input size, and of both real and complex data, as well as of even/odd data, i.e. the discrete cosine/sine transforms, or DCT/DST.
FFTW’s speed is superior when compared to other publicly-available DFT programs and its performance is highly competitive with that of vendor-driven solutions. FFTW is also portable, so it will work well on most architectures without modification – something vendor-driven custom applications cannot match.
The FFTW package was developed at MIT by Matteo Frigo and Steven G. Johnson. It is available for commercial licensing from the MIT Technology Licensing Office through this website.
What type of license is right for me?
FFTW is available under two distinct licensing options:
1 - Free Open Source License
The GNU GPL version of FFTW is made available via Open Source licensing. You are free to redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation.
2 - Commercial License
Non-exclusive commercial licensing rights are granted to commercial entities, non profit organizations, government contractors, and government agencies by the MIT Technology Licensing Office. Instructions on how to obtain a commercial license can be found below.
Once you are clear as to which option is right for you, you may either download the GNU GPL Open Source version here, or complete the steps for commercial license instructions below.
Commercial License Options
There are nine types of commercial licenses available. They are:
1. Commercial License for FFTW version 2.1.5*
2. Commercial License for FFTW version 3.1.2
3. License to Non Profit Organizations for FFTW version 3.1.2
4. License to Government Contractor for FFTW version 3.1.2
5. License to Government Agency for FFTW version 3.1.2
6. Commercial License for FFTW version 3.2.2
7. License to Non Profit Organizations for FFTW version 3.2.2
8. License to Government Contractor for FFTW version 3.2.2
9. License to Government Agency for FFTW version 3.2.
* Download a Commercial License for version 2.1.5 on the right under Attachments.
Steps for Completing Commercial License
The free GNU GPL version of FFTW can be directly downloaded here simply by agreeing to its terms; no further action is necessary.
To obtain a license to FFTW, please access the link below:
Commercial License for Version 2.1.5
Version 2.1.5 PDF License Agreement | Other FFTW License Agreements
Non exclusive commercial licensing rights to an early version of the FFTW program are granted to signers of this license for a one time license fee of $2,500. Rights to use, copy, modify, and make derivatives are permitted. Sublicensing rights are also included. See license agreement for further details.
Please Note: We will consider minor revisions to the language in this contract if necessary but an additional (minimum) charge of $2,500 will be added to cover administrative time and cost. Larger fees may be incurred for requests deemed extensive. However, the following clauses no matter what the fee are non-negotiable in all agreements:
Indemnification and Insurance (See Section 5, page 5 of the agreement)
NO REPRESENTATION OR WARRANTIES (See Section 6, page 5 of the agreement)
Export Control (See Section 8.2, page 6 of the agreement)