FFTW

FFTW is a widely used subroutine library for performing the discrete Fourier transform (DFT) calculations in one or more dimensions, on arbitrary input data sizes. It comes packed with the capability to perform DFT calculations on both real and complex data, and also supports even/odd data for computing the discrete cosine/sine transforms, known as DCT/DST.

One of the most interesting features of FFTW is its flexibility in handling input data of differing sizes and data types, effectively making it a versatile tool for any application that requires DFT computation. From signal processing applications to image processing tasks, this software can be employed in a variety of scenarios making life easier for developers.

Overall, FFTW is an efficient and robust software library that has played a crucial role in the development of many high-performance computing applications. It is certainly a software worth exploring if you are planning on performing complex calculations involving Fourier transforms.