Controlled Asynchronous GVT: Accelerating Parallel Discrete Event Simulation on Many-Core Clusters

In this paper, we investigate the performance of Parallel Discrete Event Simulation (PDES) on a cluster of many-core Intel KNL processors. Specifically, we analyze the impact of different Global Virtual Time (GVT) algorithms in this environment and contribute three significant results. First, we show that it is essential to isolate the thread performing MPI communications from the task of processing simulation events, otherwise the simulation is significantly imbalanced and performs poorly. This applies to both synchronous and asynchronous GVT algorithms. Second, we demonstrate that synchronous GVT algorithm based on barrier synchronization is a better choice for communication-dominated models, while asynchronous GVT based on Mattern's algorithm performs better for computation-dominated scenarios. Third, we propose Controlled Asynchronous GVT (CA-GVT) algorithm that selectively adds synchronization to Mattern-style GVT based on simulation conditions. We demonstrate that CA-GVT outperforms both barrier and Mattern's GVT and achieves about 8% performance improvement on mixed computation-communication models. This is a reasonable improvement for a simple modification to a GVT algorithm.