一种基于总线的多处理器共享内存机制

基于总线的分布式多处理器体系结构是目前常见的高性能路由器硬件体系结构,清华大学计算机系统在研制“863”重大项目“高性能安全路由器”的过程中,在基于CompactPCI总线的PowerPC多处理器平台上实现了一种多处理器共享内存机制,该共享内存机制（SM机制）实现了一系列核心对象,包括SM内存,SM信号量,SM消息队列和SM任务控制块等,本文详细介绍了SM机制的设计与实现并给出了性能测试结果。     

PC机群上JIAJIA与MPI的比较

对JIAJIA和MPI (message passing interface)是进行了比较.JIAJIA和MPI分别代表共享存储和消息传递的编程模式.MPI显式进行数据传输,编程复杂;JIAJIA由底层维护数据一致性,并附加提供简单的消息传递函数,编程容易、灵活.JIAJIA分配共享内存时开销较大,初始化时间比MPI长.提出了一个关于并行加速比与进程数目之间关系的近似经验公式,推出JIAJIA和MPI性能差距随着进程数目的增多而增大的结论.测试结果表明,大部分应用程序的JIAJIA和MPI版本的并行性能差距不超过10%.对于通信量很小的应用程序,其JIAJIA和MPI的性能差距较小,而通信量本身较大的应用程序,其JIAJIA和MPI的性能差距主要取决于运行时产生的实际通信量.     

Shared‐memory communication approaches for an MPI message‐passing library

This paper discusses several approaches to designing and implementing shared‐memory communication protocol modules for the message‐passing interface (MPI) libraries, colloquially called ‘shared‐memory devices’. The authors present a new taxonomy for classifying designs for shared‐memory MPI communication devices and formulate design evaluation criteria. Using these criteria, the authors compare three existing shared‐memory devices for MPICH and choose the best one. The authors also present experimental results that support their choice. The contributions of this paper are three‐fold. First, the authors present the taxonomy for shared‐memory communication devices. Second, they show advantages and potential problems of the devices that belong to different classes of their taxonomy using the formulated design criteria. Third, they analyze communication performance of existing MPICH shared‐memory devices, discuss optimizations of their performance, and show the performance gains that these optimizations yield. MPICH is used for comparison, since it is a widely used MPI implementation. Copyright © 2000 John Wiley & Sons, Ltd.     

A Comparison of MPI,SHMEM and Cache-Coherent Shared Address Space Programming Models on a Tightly-Coupled Multiprocessors

We compare the performance of three major programming models on a modern, 64-processor hardware cache-coherent machine, one of the two major types of platforms upon which high-performance computing is converging. We focus on applications that are either regular, predictable or at least do not require fine-grained dynamic replication of irregularly accessed data. Within this class, we use programs with a range of important communication patterns. We examine whether the basic parallel algorithm and communication structuring approaches needed for best performance are similar or different among the models, whether some models have substantial performance advantages over others as problem size and number of processors change, what the sources of these performance differences are, where the programs spend their time, and whether substantial improvements can be obtained by modifying either the application programming interfaces or the implementations of the programming models on this type of tightly-coupled multiprocessor platform.     

曙光1000A上消息传递与共享存储的比较

分布式共享存储虽然有易于编程的优点,但往往被认为效率不高、完全由软件实现的分布式共享存储系统（又称为虚拟共享存储系统）更是如此,文中以典型的消息传递系统ＰＶＭ与分布式共享存储系统ＪＩＡＪＩＡ粉列,报这两种并行程序设计环境的特点,并用７个应用程序在曙光１０００Ａ上分别比较了这两个系统的性能,实验３结果表明,ＪＩＡＪＩＡ的与ＰＶ玎当,但基于ＪＩＡＪＩＡ的并行程序设计却比ＰＶＮ简单得多。     

显式并行计算机系统的性能特征化方法

本文从应用程序的角度将并行计算机系统分为显式并行和隐式并行两类,给出了显式并行系统的一般性视图,并在此基础上研究了显式并行系统的性能特征化方法,包括选取必要的系统性能特征参数以及对各参数值的测量。我们的研究地显式并行系统的设计者和用户都有一定的参考价值。     

PC机群上共享存储与消息传递的比较

共享存储和消息传递是目前两种主流的并行编程模型.一般认为,消息传递的可编程性不及共享存储友好.OpenMP是目前共享存储编程的实际工业标准.机群OpenMP系统在机群上提供了OpenMP编程环境,具有易编程和可扩展的特点,但是其性能如何一直是关注的热点.以机群OpenMP系统OpenMP/JIAJIA和典型的消息传递系     

A study into the feasibility of using two parallel sparse direct solvers for the Helmholtz equation on Linux clusters

Two state‐of‐the‐art parallel software packages for the direct solution of sparse linear systems based on LU‐decomposition, MUMPS and SuperLU_DIST have been tested as black‐box solvers on problems derived from finite difference discretizations of the Helmholtz equation. The target architecture has been Linux clusters, for which no consistent set of tests of the algorithms implemented in these packages has been published. The investigation consists of series of memory and time scalability checks and has focused on examining the applicability of the algorithms when processing very large sparse matrices on Linux cluster platforms. Special emphasis has been put on monitoring the behaviour of the packages when the equation systems need to be solved for multiple right‐hand sides, which is the case, for instance, when modelling a seismic survey. The outcome of the tests points at poor efficiency of the tested algorithms during application of the LU‐factors in the solution phase on this type of architecture, where the communication acts as an impasse. Copyright © 2005 John Wiley & Sons, Ltd.     

一种基于共享存储的叠前深度偏移并行算法

为了解决叠前深度偏移计算量巨大这个问题,人们投入了很大精力来开发高效的并行算法.就此,在对一些相关并行算法进行分析之后,根据三维叠前Kirchhoff深度偏移的特点,提出了一种基于共享存储的简化并行算法.其中Slave进程直接存储和读取射线旅行时,消息传递总量显著减少;同时合理地结合"任务池"技术与粗粒度级并行,前者确保动态负载平衡,后者使得Slave与Master之间的通信开销尽可能小.实际数据的测试结果表明,此并行算法高效且可扩展性较好.     

基于工作站机群的有限元结构分析并行计算

并行计算正成为科学和工程计算中的一个新趋势。将采用区域分裂技术的并行有限元方法应用于工作站机群的分布式并行环境。提出了基于单元区域分裂的共轭梯度并行算法。在工作站机群上对坝体结构进行求解,对其并行性能进行分析。     

Recommendations for tool-handle material choice based on finite element analysis

Huge areas of work are still done manually and require the usages of different powered and non-powered hand tools. In order to increase the user performance, satisfaction, and lower the risk of acute and cumulative trauma disorders, several researchers have investigated the sizes and shapes of tool-handles. However, only a few authors have investigated tool-handles' materials for further optimising them. Therefore, as presented in this paper, we have utilised a finite-element method for simulating human fingertip whilst grasping tool-handles. We modelled and simulated steel and ethylene propylene diene monomer (EPDM) rubber as homogeneous tool-handle materials and two composites consisting of EPDM rubber and EPDM foam, and also EPDM rubber and PU foam. The simulated finger force was set to obtain characteristic contact pressures of 20 kPa, 40 kPa, 80 kPa, and 100 kPa. Numerical tests have shown that EPDM rubber lowers the contact pressure just slightly. On the other hand, both composites showed significant reduction in contact pressure that could lower the risks of acute and cumulative trauma disorders which are pressure-dependent. Based on the results, it is also evident that a composite containing PU foam with a more evident and flat plateau deformed less at lower strain rates and deformed more when the plateau was reached, in comparison to the composite with EPDM foam. It was shown that hyper-elastic foam materials, which take into account the non-linear behaviour of fingertip soft tissue, can lower the contact pressure whilst maintaining low deformation rate of the tool-handle material for maintaining sufficient rate of stability of the hand tool in the hands. Lower contact pressure also lowers the risk of acute and cumulative trauma disorders, and increases comfort whilst maintaining performance.     

循环载荷作用下两类楼板抗震性能的非线性有限元分析

为比较组合楼板和普通混凝土楼板的抗震性能,采用非线性有限元分析方法研究它们在循环载荷作用下的受力行为,并由此得到两类楼板的滞回曲线、骨架曲线及应力应变分布规律．计算结果表明,采用可靠构造措施的压型钢板与混凝土组合作用明显,在不失较高承载力的同时,组合楼板仍具有良好的抗震性能．将计算结果与试验数据相比较,验证该数值分析方法的有效性。     

基于有效并行求解策略的显式有限元分析并行算法

针对大规模结构非线性动力问题的有限元分析非常耗时,基于消息传递接口（MPI）机群环境,提出多种基于并行求解策略的显式有限元并行算法。基于显式消息传递的区域分解技术,采取重叠、非重叠区域分解技术及动态任务分配方法,通过将计算与通信重叠,优化处理器间的通信,对非重叠通信区域分解并行算法、重叠通信区域分解并行算法、群动态任务分配算法、动态任务分配算法及动态负载平衡算法进行研究。为在机群环境下实现非线性动力有限元分析,开发了基于有效并行求解策略的显式有限元并行算法。编写了基于消息传递编程模式的并行有限元程序,在工作站机群上实现了数值算例,分析了算法的性能,并与传统的Newmark算法进行了比较。算例表明：群动态任务分配算法的性能优于动态任务分配算法,低于区域分解算法的性能,动态负载平衡算法最优。对相同规模的问题提出的算法比Newmark算法快,优于Newmark算法。对结构非线性动力问题的有限元分析,所提出的并行算法是可行有效的。     

An object-oriented framework for finite element analysis based on a compact topological data structure

This paper describes an ongoing work in the development of a finite element analysis system, called TopFEM, based on the compact topological data structure, TopS [1], [2]. This new framework was written to take advantage of the topological data structure together with object-oriented programming concepts to handle a variety of finite element problems, spanning from fracture mechanics to topology optimization, in an efficient, but generic fashion. The class organization of the TopFEM system is described and discussed within the context of other frameworks in the literature that share similar ideas, such as GetFEM++, deal.II, FEMOOP and OpenSees. Numerical examples are given to illustrate the capabilities of TopS attached to a finite element framework in the context of fracture mechanics and to establish a benchmark with other implementations that do not make use of a topological data structure.     

基于PANDA框架的并行有限元模态分析程序开发和应用

为提高大型结构振动分析的规模、精度和效率,基于面向对象有限元并行计算框架PANDA和高性能矩阵特征问题并行求解算法,开发出适用于大规模结构振动问题计算的并行有限元模态分析程序;在超级计算机银河YH和曙光5000A上,通过不同算例验证该程序的正确性和可靠性.以某靶室结构为研究对象演示该程序的应用,指出实际应用时需注意加速...     

Superconvergence analysis of nonconforming finite element method for time-fractional nonlinear parabolic equations on anisotropic meshes

In this paper, we prove a novel result of the consistency error estimate with order $O\left(h^2\right)$ for $E{Q}_1^{rot}$ element (see Lemma 2) on anisotropic meshes. Then, a linearized fully discrete Galerkin finite element method (FEM) is studied for the time-fractional nonlinear parabolic problems, and the superclose and superconvergent estimates of order $O(\tau +h^2)$ in broken $H^1$-norm on anisotropic meshes are derived by using the proved character of $E{Q}_1^{rot}$ element, which improve the results in the existing literature. Numerical results are provided to confirm the theoretical analysis.     

基于有限元分析的ICF靶半自动装配系统的微夹钳设计

根据惯性约束聚变(ICF)靶零件的特点,确定用于ICF靶半自动装配系统微夹钳的技术指标,并完成其结构设计.该微夹钳采用柔性铰链机构和压电陶瓷驱动,可根据需要更换不同形状和开口距离的夹口,以适应夹持不同靶零件.以压电陶瓷的2种极限参数为载荷,分析了微夹钳的张合量、应力分布、应变量,并采用非线性接触分析对夹持力和夹持效果进...