An overview of Mermera: a system and formalism for non-coherent distributed parallel memory

The authors give an overview of Mermera, a system that gives the programmer the choice of coherent and noncoherent behavior in the same program. They sketch a formal model that describes Mermera's noncoherent behavior. This model helps identify a new noncoherent behavior called local consistency. Measurements from a pilot implementation on a BBN Butterfly are reported which show the response time of pipelined-RAM operations to be an order of magnitude faster than that of coherent operations. Thus, a new tradeoff is discovered in which the programmer can significantly improve shared memory performance at the cost of tolerating varying degrees of noncoherence.<
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