Evaluating the Performance and Accuracy Impact of Trace Generation to the BigSim Emulator

This paper quantitatively studies the trace effects to the performance and accuracy of the BigSim Emulator, a scalable parallel emulator for large-scale computers. To assess the accuracy effect we modify the emulator code to collect the predicted computation time. Four MPI programs with different computation to communication ratios are used as benchmarks. The emulation time and the predicted computation time, both when trace generation are enabled and disabled, are collected on two parallel host machines. The results show that although the BigSim Emulator only traces communication events and dependencies, trace generation still evidently degrades the emulation performance for programs with high communication to computation ratios. Trace generation also significantly affects the accuracy of the predicted computation time for communication intensive programs, which is an issue that can not be overlooked.