A faster FFT in the Mid-West

FFT implementations today generally fall into two categories: Library generators (such as FFTW and Spiral) and specialized FFTs (such as prime95). Specialized FFTs have the obvious limitation of being specialized. However they are hand-tuned and generally offer superior performance. Library generators are generic and easier to port. But their performance is generally suboptimal. We describe in this paper an FFT library that was built while paying special attention to locality. The library achieves significantly better performance than FFTW, for long vectors. Unlike FFTW or Spiral, the recursive decomposition of the FFT is not created by a library generator; it is created by macro expansion that has a few selectable parameters. This provides an interface that can be more easily modified by users