library for computing Fast Fourier Transforms The FFTW library computes Fast Fourier Transforms (FFT) in one or more dimensions. It is extremely fast. This package contains the shared library versions of the fftw libraries in single, double and long double precisions. Note that on some architectures double is the same as long double in which case there is no long double library. To get the static library and the header files, you need to install libfftw3-dev. For documentation, see libfftw3-doc.