Ian Ross

Radian was a declarative HTML plotting library I wrote a few years ago for a literate Bayesian statistics programming environment, which unfortunately never saw the light of day. (A real shame, because there was some clever stuff in there.) Radian uses d3.js and Angular to allow you to embed interactive plots directly into HTML. I don’t think anyone other than me ever used it much, but it has some interesting ideas in it (I think!).

This (long) series of blog posts describes the development of a pure Haskell arbitrary length fast Fourier transform library. This goes well beyond the usual textbook treatment of the FFT, dealing with efficient decomposition of transforms of arbitrary lengths (i.e. not just powers of two), specialised transforms for small sizes and treatment of prime-length transforms using Rader’s algorithm. As well as implementation of the main algorithms, there’s quite a bit of material covering empirical optimisation of this type of numerical code, using profiling and benchmarking to guide the optimisation process, and using gradual refinement with localised mutability, unboxing and other optimisations to eventually get within a factor of five or so of the vector-fftw package (“the fastest Fourier transform in the West”). Repository link: https://github.com/ian-ross/arb-fft