Splitting Atoms with Rely/Guarantee Conditions Coupled with Data Reification
Cliff B. Jones, Ken G. Pierce · School of Computing Science Technical Report Series · 2010
This paper presents a novel formal development of a non-trivial parallel program: Simpson's implementation of asynchronous communication mechanisms (ACMs). Although the correctness of the algorithm has been shown elsewhere, earlier developments are by no means intuitive. The aims of this paper include both the presentation of an understandable (yet formal) design history and the establishment of another way of splitting (software) atoms. Using the fiction of as an aid to understanding the initial steps of development, the top-level specification is developed to code. The rely-guarantee approach is, here, combined with notions of read/write frames and phased specifications; the atomicity assumptions implied by rely/guarantee conditions are realised by clever choice of data representation. The development method herein is compared with other approaches ---in a spirit of cooperation--- as the authors believe that constructive comparison elucidates many of the finer points in the 4-slot specification/development and of parallel programs in general.