{H}askell on a Shared-Memory Multiprocessor

(Tim Harris, Simon Marlow, Simon Peyton Jones) Haskell ’05: Proceedings of the 2005 ACM SIGPLAN workshop on Haskell, pages 49–61, Tallinn, Estonia, ACM Press, September 2005

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Multi-core processors are coming, and we need ways to program them. The combination of purely-functional programming and explicit, monadic threads, communicating using transactional memory, looks like a particularly promising way to do so. This paper describes a full-scale implementation of shared-memory parallel Haskell, based on the Glasgow Haskell Compiler. Our main technical contribution is a lock-free mechanism for evaluating shared thunks that eliminates the major performance bottleneck in parallel evaluation of a lazy language. Our results are preliminary but promising: we can demonstrate wall-clock speedups of a serious application (GHC itself), even with only two processors, compared to the same application compiled for a uni-processor.