Performance Evaluation of Hierarchy Annotation and Credit Distribution Quiescence Mechanisms

This paper evaluates the execution characteristics of two high-capability software-based approaches for detecting termination in distributed environments. The Tiered Algorithm relies on use of a global invariant that indicates equality between process production and consumption at each level of process nesting. The Credit Algorithm relies on the distribution of a unit value from the initial parent process that can only be reconstituted if the barrier is complete. While both strategies can detect termination correctly regardless of the execution ordering, avoid potential race conditions caused by unpredictable transit times, and support arbitrary run-time binding of logical processes to physical processors, they each exhibit different message count complexity, message bit complexity, controller overhead, and detection delay. These metrics were assessed under 100 randomly generated trials consisting of 101 to 703 tasks under a variety of task creation and termination ordering scenarios. The Tiered Algorithm exchanged an average 12.9% fewer synchronization messages and 24.1% fewer bits in total than the Credit Algorithm. Results indicate that while the Tiered Algorithm required 80% fewer controller operations, the Credit Algorithm contributed an average of 3.9 fewer operations affecting detection latency with less variability.