The fusion machine

Philippa Gardner, Cosimo Laneve, Lucian Wischik. Extended abstract at CONCUR 2002


We present a new model for the distributed implementation of pi-like calculi, which permits strong correctness results that are simple to prove. We describe the distributed channel machine - a distributed version of a machine proposed by Cardelli. The distributed channel machine groups pi processes at their channels (or locations), in contrast with the more common approach of incorporating additional location information within pi processes. We go on to describe the fusion machine. It uses a form of concurrent constraints called fusions - equations on channel names - to distribute fragments of these processes between remote channels. This fragmentation avoids the movement of large continuations between locations, and leads to a more efficient implementation model.

  author = "Philippa Gardner and Cosimo Laneve and Lucian Wischik",
  title  = "The Fusion Machine (extended abstract)",
  booktitle = "CONCUR 2002",
  year   = 2002,
  editor = "L. Brim and P. Jancar and M. Kretinsky",
  volume = "2421",
  series = "Lecture Notes in Computer Science",
  pages  = "418--433",
  publisher = "Springer-Verlag",
  url    = "",


  • Extended abstract in PDF format, 160k, 16 pages.
  • Slides from a talk in Pisa July 2002, 270k, 6 pages. (Also full size)
  • Latex example code (ZIP, 25k) to draw fusion machines.
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    See also

  • Fusion machine online prototype - A Java implementation of the abstract machine described in this paper
  • Explicit fusions: theory & implementation - Wischik's PhD dissertation, contains full versions of proofs in this paper.
  • Overview of fusions - outline of all related work on fusions.