Performance analysis on hybrid parallel programming on SMP cluster system

点击翻译按钮获取中文摘要

In this research, we constructed a PC cluster connecting multiple SMP-based PC nodes with various network interfaces. Such an SMP cluster system has both shared memory and distributed memory architectures together, and there are several possibility for programming like message passing, shared memory and mixture of them. Our experimental cluster contains 4-way and 2-way SMP of Pentium-III processors and two types of interconnection network are available, Myrinet800 and Fast Ethernet.We have evaluated and analyzed the performance of hybrid programming to mixture both MPI and OpenMP, and message passing programming with MPI only targeting NAS Parallel Benchmarks as basic benchmarking and SPAM (Smoothed Particle Applied Mechanics) particle code for actual scientific program. Against to the preliminary estimation, MPI-only programming achieved better performance in most of these programs. To analyze these results, we applied the cache hit ratio measurement for the research on cache behavior according to the programming style. As a result, we have cleared the hybrid program with MPI for inter-node communication and OpenMP for intra-node multithreading often breaks well-tuned cache utilization on MPI-only program.This research concludes that the performance of hybrid program is strongly affected by data access pattern, and it is not always the best scheme to apply OpenMP multithreading after we finish to write the MPI-only program. In some cases, the advantage in communication time of direct access to shared memory on SMP is overcome by the disadvantage of such cache inefficiency. However, when the program naturally has load imbalancing with a certain size of granularity, there is a possibility of the performance of hybrid program overcomes the MPI-only one with dynamic load balancing feature. SPAM particle code is one of such applications.