Statically Unrolling Recursion to Improve Opportunities for Parallelism

We present an algorithm for unrolling recursion in the Haskell functional language. Adapted from a similar algorithm proposed by Rugina and Rinard for imperative languages, it essentially inlines a function in itself as many times as requested. This algorithm aims to increase the available parallelism in recursive functions, with an eye toward its eventual application in a Haskell-to-hardware compiler. We first illustrate the technique on a series of examples, then describe the algorithm, and finally show its Haskell source, which operates as a plug-in for the Glasgow Haskell Compiler