ORCHESTRA: an asyncrhonous non-blocking distributed GVT algorithm

Taking advantage of high computing capabilities of modern distributed architectures is fundamental to run large-scale simulation models based on the Parallel Discrete Event Simulation (PDES) paradigm. In particular, by exploiting clusters of modern multi-core architectures it is possible to efficiently overcome both the power and the memory wall. This is more the case when relying on the speculative Time Warp simulation protocol. Nevertheless, to ensure the correctness of the simulation, a form of coordination such as the GVT is fundamental. To increase the scalability of this mandatory synchronization, we present in this paper a coordination algorithm for clusters of share-everything multi-core simulation platoforms which is both wait-free and asynchronous. The nature of this protocol allows any computing node to carry on simulation activities while the global agreement is reached

A Scalable GVT Estimation Algorithm for PDES: Using Lower Bound of Event-Bulk-Time

Global Virtual Time computation of Parallel Discrete Event Simulation is crucial for conducting fossil collection and detecting the termination of simulation. The triggering condition of GVT computation in typical approaches is generally based on the wall-clock time or logical time intervals. However, the GVT value depends on the timestamps of events rather than the wall-clock time or logical time intervals. Therefore, it is difficult for the existing approaches to select appropriate time intervals to compute the GVT value. In this study, we propose a scalable GVT estimation algorithm based on Lower Bound of Event-Bulk-Time, which triggers the computation of the GVT value according to the number of processed events. In order to calculate the number of transient messages, our algorithm employs Event-Bulk to record the messages sent and received by Logical Processes. To eliminate the performance bottleneck, we adopt an overlapping computation approach to distribute the workload of GVT computation to all worker-threads. We compare our algorithm with the fast asynchronous GVT algorithm using PHOLD benchmark on the shared memory machine. Experimental results indicate that our algorithm has a light overhead and shows higher speedup and accuracy of GVT computation than the fast asynchronous GVT algorithm