Validation and Application of the LoPC model

The LogP model is useful for modeling and optimizing tightly synchronized parallel algorithms with regular, ordered communication patterns on active-message based systems. However, it does not account for the contention for message processing resources at a node. The LoPC model accounts for costs of contention for message processing. In this work, we validate the LoPC model’s predictions against measured values of runtime on the Wisconsin Cluster Of Workstation (COW). We study three message-passing parallel applications: Radix-sort, Em3d and Barnes-Hut. However, we could validate the model predictions only for Em3d. To model the specific characteristics of the COW, we extended the LoPC model to include different overheads for the request and response handlers. Also, to determine the applicability of the LoPC model for applications with different characteristics, we developed a set of microbenchmarks and compare their runtime on the COW with the LoPC model predictions.