PerWiz: A what-if prediction tool for tuning message passing programs

This paper presents PerWiz, a performance prediction tool for improving the performance of message passing programs. PerWiz focuses on locating where a significant improvement can be achieved. To locate this, PerWiz performs a post-mortem analysis based on a realistic parallel computational model, LogGPS, so that predicts what performance will be achieved if the programs are modified according to typical tuning techniques, such as load balancing for a better workload distribution and message scheduling for a shorter waiting time. We also show two case studies where PerWiz played an important role in improving the performance of regular applications. Our results indicate that PerWiz is useful for application developers to assess the potential reduction in execution time that will be derived from program modification.