Molecule: using monadic and streaming I/O to compose process networks on the JVM

This is a paper we presented at OOPSLA 2012:

Molecule is a domain specific language library embedded in Scala for easing the creation of scalable and modular concurrent applications on the JVM. Concurrent applications are modeled as parallel process networks that exchange information over mobile and type-safe messaging interfaces.

In this paper, we present a concurrent programming environment that combines functional and imperative programming. Using a monad, we structure the sequential or parallel coordination of user-level threads, without JVM modifications or compiler support. Our mobile channel interfaces expose reusable and parallelizable higher-order functions, as if they were streams in a lazily evaluated functional programming language. The support for graceful termination of entire process networks is simplified by integrating channel poisoning with monadic exceptions and resource control. Our runtime and system-level interfaces leverage message batching and a novel flow parallel scheduler to limit expensive context switches in multicore environments. We illustrate the expressiveness and performance benefits on a 24-core AMD Opteron machine with three classical examples: a thread ring, a genuine prime sieve and a chameneos-redux.

We have been asked several times if the code was open source during the reviews but unfortunately we did not have the permission to share the code at the time. Now that we have it, I'm pleased to announce that the sources of the library and the benchmarks are available on GitHub. There is also a mailing-list for project specific questions.