PGAS in the Message-Driven Execution Model

Asynchrony is increasingly important for high performance on modern parallel machines. A common approach to providing asynchrony in PGAS languages is to add additional language constructs to support asynchronous execution. In this paper we describe Multiphase Shared Arrays (MSA), a restricted PGAS programming model that takes the opposite approach, layering PGAS semantics over a fundamentally asynchronous runtime environment. We sidestep many of the difficulties of asynchronous programming through a discipline that offers desirable safety properties while exposing opportunities for optimization at multiple levels. We retain generality by offering composability with general purpose parallel programming models.