Browsing by Author "Yong Meng TEO"
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- ItemA Cost-Effective State Saving Scheme for Optimistic Parallel Simulation(1999-10-01T00:00:00Z) Seng Chuan TAY; Yong Meng TEO; Chin Hock NGUnlike the conservative approach, Time Warp (TW) executes simulation events greedily and uses a rollback mechanism to recover from causality errors. The TW protocol has the potential to exploit a higher degree of parallelism in the simulated system but it is realized with an overhead. For the simulator to carry out a rollback, the system state must be checkpointed. While increasing the checkpointing frequency increases the state saving cost, an infrequent scheme also escalates the coast forward effort when a large number of executed events are redone. Such a paradox indicates the need for a cost model to decide if a system state should be saved. This paper uses a probabilistic approach to weigh the performance gain and loss of each checkpointing. Logical processes of the TW simulation and their processing elements are assumed to be homogeneous. By the use of exponential distribution on inter-arrival time and service time, we can derive the rollback probability, thereby calculate the expected coast forward effort if a state is not saved. Based on the derived expectation, a state vector is saved only if the expected coast forward effort is larger than the state saving cost and vice versa. Our experiments show that the cost model reduces the simulation elapsed time by close to 30% as compared to saving the system state after each event execution, and saving the system state at a predefined interval. Keywords: performance optimization, optimistic simulation, state saving, rollback, cost model
- ItemMapping Parallel Simulation onto Distributed-Memory Systems: Model and Performance(1995-03-01T00:00:00Z) Seng Chuan TAY; Yong Meng TEOThis paper presents an analytical model to evaluate the performance of conservative parallel simulation using a finite-buffered multistage interconnection network as an example. The model is formalized based on two important time components in parallel and distributed processing: computation time and communication time. Performance metrics such as elapsed time, speedup and simulation bandwidth associated with different schemes for partitioning/mapping parallel simulation onto physical processors are evaluated. Our mathematical analysis identifies the major constituents of simulation overheads in these mapping strategies necessary for improving parallel simulation efficiency. We also show that a perfectly balanced workload distribution may not necessarily translates into better performance. On the contrary, we have shown that a balanced mapping of workload may increase communication overheads resulting in a longer simulation elapsed time. The analytical performance model has been validated against implementation results from a parallel simulation model. The analytical framework can be easily extended to analyze other conservative parallel simulation schemes.
- ItemPerformance Prediction of Optimistic Simulation with Rollback Thrashing(1997-11-01T00:00:00Z) Seng Chuan TAY; Yong Meng TEO; Rassul AYANIAbstract not available.