Study of OpenMP applications on the InfiniBand-based software distributed shared-memory system

For the past decades computer engineers have focused on building high-performance and large-scale computer systems with low-cost. One of the examples is a distributed-memory computer system like a cluster, where fast processing nodes to use commodity processors are connected through a high speed network. But it is not easy to develop applications on this system, because a programmer must consider all data and control dependences between processes and program them explicitly. For alleviating this problem the distributed virtual shared-memory (DVSM) system has been proposed. It is well known that the performance of the DVSM system highly depends on the network’s performance and programming semantics, and currently its performance is very limited on a conventional network. Recently many advanced hardware-based interconnection technologies have been introduced, and one of them is the InfiniBand Architecture (IBA) which supports shared-memory programming semantics by means of remote direct-memory access (RDMA) and atomic operations. In this paper, we present the implementation of our InfiniBand-based DVSM system and analyze the performance of SPEC OMP benchmarks in detail by comparing with the DVSM based on the traditional network architecture and the hardware shared-memory multiprocessor (SMP) system. As experiment result, we show that our DVSM system to use full features of the IBA can improve the performance significantly over the IPoIB-based traditional system on the IBA, and furthermore the performance of one application on the IBA-based DVSM system is better than on the hardware SMP.     

Techniques for Improving Performance of Hybrid Snooping Cache Protocols

Bus-based multiprocessors constitute a cost-effective class of shared-memory multiprocessors. Private caches are the key to an efficient utilization of the shared bus, and most such systems use a write-invalidate cache-coherence protocol to keep the caches coherent. Two important factors that limit the performance of the system are cache misses that lead to long-latency reads and bus congestion because of read misses and coherence traffic. While hybrid write-invalidate/write-update snooping protocols lead to fewer read misses than write-invalidate protocols, previous studies have shown them to be incapable of providing consistent performance improvements because of heavily increased coherence traffic. In this paper, we analyze how the deficiencies of hybrid snooping protocols can be dramatically reduced by using write caches and read snarfing (also called read-broadcast) under release consistency. Our performance evaluation is based on program-driven simulation and a set of five scientific applications with different sharing behaviors including migratory sharing as well as producer–consumer sharing. We show that one of the evaluated hybrid protocols, extended with write caches as well as read snarfing, manages to reduce the number of coherence misses by between 83 and 93% as compared to a write-invalidate protocol for all five applications in this study. In addition, the number of bus transactions is reduced substantially. However, we also show that read snarfing and hybrid snooping protocols might lead to higher cache occupancy because of increased sharing. Because of the small implementation cost of the hybrid protocol and the two extensions, we believe the combination to be an effective approach to boosting the performance of bus-based multiprocessors.     

High-dimensional homotopy curve tracking on a shared-memory multiprocessor

Results are reported for a series of experiments involving numerical curve tracking on a shared-memory parallel computer. Several algorithms exist for finding zeros or fixed points of nonlinear systems of equations that are globally convergent for almost all starting points, that is, with probability one. The essence of all such algorithms is the construction of an appropriate homotopy map and then the tracking of some smooth curve in the zero set of this homotopy map. HOMPACK is a mathematical software package implementing globally convergent homotopy algorithms with three different techniques for tracking a homotopy zero curve, and has separate routines for dense and sparse Jacobian matrices. The HOMPACK algorithms for sparse Jacobian matrices use a preconditioned conjugate gradient algorithm for the computation of the kernel of the homotopy Jacobian matrix, a required linear algebra step for homotopy curve tracking. A parallel version of HOMPACK is implemented on a shared-memory parallel computer with various levels and degrees of parallelism (e.g., linear algebra, function, and Jacobian matrix evaluation), and a detailed study is presented for each of these levels with respect to the speedup in execution time obtained with the parallelism, the time spent implementing the parallel code, and the extra memory allocated by the parallel algorithm.     

S2MP服务器的结构与实现

叙述Ｓ２ＭＰ服务器的模块化结构，共享内存的分布处理，系统可扩展的新技术，缓冲一致规则和非一致性存储访问ＮＵＭＡ结构体系。显示出这种服务器具有巨大的处理能力、系统扩展的能力。     

基于广播共享存贮器的并行计算机EP—860的研究与实现

本文介绍了一种新型的并行计算机系统ＥＰ—８６０。由于它采用了独特的广播共享存贮器技术，使得整个系统兼顾有着松散耦合和紧密耦合两种系统的优点。系统扩展性好，便于用户编程。用户编程时只需将共享变量放到广播共享存贮器中，用访存指令即可实现通信，无需专门的通信命令。此外，本系统还具有结构简单，便于实现，经济实用等优点。