Analyzing performance of sequencing mechanisms for simple layered task systems

Considers the problem of sequencing a set of parallel activities in the presence of nonzero overheads. Mechanisms for sequence control may range from explicit inter-task synchronization to more restrictive mechanisms such as blocking barriers. It is highly desirable to be able to base the choice of a sequence control mechanism for a parallel algorithm upon specific characteristics of the algorithm´s structure and the underlying architecture. The paper presents approximate models for simple layered task systems that can predict overall performance and provide a useful understanding of key performance parameters and tradeoffs. The analytic results are compared with simulation to demonstrate their accuracy. Some simple applications of the model are presented that demonstrate non-intuitive behavior of layered graphs with inter-task versus barrier-based sequencing