FFTW is a C subroutine library for computing the Discrete Fourier Transform (DFT) in one or more dimensions, of both real and complex data, and of arbitrary input size. We believe that FFTW, which is free software, should become the FFT library of choice for most applications. Our benchmarks, performed on a variety of platforms, show that FFTW's performance is typically superior to that of other publicly available FFT software. Moreover, FFTW's performance is portable: the program will perform well on most architectures without modification. The FFTW package was developed at MIT by Matteo Frigo and Steven G. Johnson. Please send email to fftw@theory.lcs.mit.edu so that we can keep track of users and send you information about new releases. The latest version of FFTW, benchmarks, links, and other information can be found at the FFTW home page.