Lazy Event Prediction using Defining Trees and Schedule Bypass for Out-of-Order PDES

Out-of-order parallel discrete event simulation (PDES) has been shown to be very effective in speeding up system design by utilizing parallel processors on multi- and many-core hosts. As the number of threads in the design model grows larger, however, the original scheduling approach does not scale. In this work, we analyze the out-of-order scheduler and identify a bottleneck with quadratic complexity in event prediction. We propose a more efficient lazy strategy based on defining trees and a schedule bypass with O(m log2 m) complexity which shows sustained and improved performance gains in simulation of SystemC models with many processes. For models containing over 1000 processes, experimental results show simulation run time speedups of up to 90x using lazy event prediction against the original out-of-order PDES approach.