SMP簇上的混合MPI-OpenMP范例：MPEG-2编码器和N体仿真
Hybrid MPI-OpenMP Paradigm on SMP Clusters: MPEG-2 Encoder and N-Body Simulation
摘要：
SMP节点的集群为各种并行编程范例提供支持。在同一个应用程序中结合共享内存和消息传递并行化，混合MPI-OpenMP范式是并行编程的一个新兴趋势，以充分利用分布式共享内存体系结构。在本文中，我们提高了性能的MPEG-2编码器和n体模拟采用混合MPI-OpenMP编程范例SMP集群。MPEG比特流的分层图像数据结构非常适合于混合模型以实现多级并行性：MPI用于跨SMP节点的图片组级的并行性，而OpenMP用于每个SMP节点内的切片级的图片内的并行性。类似地，力计算的工作负载在MPI进程之间的ORB域分解之后在OpenMP线程之间共享，该工作负载在n体仿真中的典型计算中占循环的90%以上。此外，采用了OpenMP线程的循环调度，适当的块大小，以提供更好的负载平衡的工作，从而提高性能。通过n-body仿真，实验结果表明，混合MPI-OpenMP程序在4路簇上的平均性能因子为1.52，在2路簇上的平均性能因子为1.21，优于相应的纯MPI程序。同样，混合模型提供了18%的性能改善相比，MPI模型的MPEG-2编码器。
英文摘要：
Clusters of SMP nodes provide support for a wide diversity of parallel programming paradigms. Combining both shared memory and message passing parallelizations within the same application, the hybrid MPI-OpenMP paradigm is an emerging trend for parallel programming to fully exploit distributed shared-memory architecture. In this paper, we improve the performance of MPEG-2 encoder and n-body simulation by employing the hybrid MPI-OpenMP programming paradigm on SMP clusters. The hierarchical image data structure of the MPEG bit-stream is eminently suitable for the hybrid model to achieve multiple levels of parallelism: MPI for parallelism at the group of pictures level across SMP nodes and OpenMP for parallelism within pictures at the slice level within each SMP node. Similarly, the work load of the force calculation which accounts for upwards of 90% of the cycles in typical computations in the n-body simulation is shared among OpenMP threads after ORB domain decomposition among MPI processes. Besides, loop scheduling of OpenMP threads is adopted with appropriate chunk size to provide better load balance of work, leading to enhanced performance. With the n-body simulation, experimental results demonstrate that the hybrid MPI-OpenMP program outperforms the corresponding pure MPI program by average factors of 1.52 on a 4-way cluster and 1.21 on a 2-way cluster. Likewise, the hybrid model offers a performance improvement of 18% compared to the MPI model for the MPEG-2 encoder.
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