Summary

GUM (Graph reduction for a Unified Machine model) is a portable Haskell parallel implementation [22], The basic design concepts are more fully described in [13], [14].

• It is a runtime system for GHC. [16]
• It is portable.
• It is message based and uses PVM.[18]
• It requires networked processor-memory units (PE).
• It provides tools for monitoring and visualising PE activities as well as thread activities over time.
• Two-level addressing scheme: one for local heap and another for the global heap is used. Global virtual heap is formed from all the local heaps.
• It supports independent garbage collection on each PE's local heap. Garbage Collections for the individual PE local heaps within a single global virtual heap without any need for their synchronisation. Each PE implements part of the global heap in its local heap.
• Threads distribution is performed lazily: no thread movement between PEs for load balancing; thread moved to another PE only if the latter is idle.
• Data distribution is performed eagerly: data copied between PEs as and when requested.
• All messages are asynchronous: this has the effect of favouring long-latency machines in the network.
• GUM bases: Sun Sparcs, DEC Alphas, Sun's symmetric multiprocessors SPARC server.
• Significant speedups (for problems with large-grained parallelism) is claimed.