访存密集型应用在SMP机群系统中的性能分析

SMP机群系统因其良好的性价比、卓越的可扩展性与可用性，逐渐成为当前高性能计算机领域的主流结构．这种结点内共享存储、结点间消息传递的两级混合结构是目前并行计算研究的热点,在单个SMP结点中，总线和内存带宽是否满足CPU和I／O的需求对于访存密集型应用的性能影响很大。本文针对访存密集型应用的特点测试分析了在SMP机群中访存冲突对系统性能的影响，结果表明我们的SMP结点存在性能瓶颈，这种量化分析对于设计大规模的基于SMP的机群系统有很好的指导意义．     

SMP超结点机群系统的仿真分析

通过网络将独立的计算机结点连接起来协同工作 ,机群系统已经成为实现超级计算的一个重要手段 .随着计算机制造工艺的发展 ,处理器的运算能力得到迅速提高 ,使得网络性能成为机群系统的瓶颈问题 .因此 ,采用高频宽网络 ,减少通信开销是发展机群系统的首要任务 .采用交换式网络及用户层消息传递机制是提高网络性能的有效手段 .通过建立仿真模型 ,我们对机群系统进行模拟 ,定量分析了交换网络及用户层消息传递对其性能的影响 .本文介绍了交换式机群系统和用户层消息传递的原理及其仿真结构 .本文还描述了对机群系统的仿真测试 ,并对实验结果进行分析     

一种面向结点的加速比模型

ＳＭＰ机群系统是一种新型的系统结构。由于依赖于处理器的传统加速比模型不再适用于ＳＭＰ机群系统,文中提出了面向结点的加速比模型,它将传统的串行与并行的对比关系扩展为个体与整体之间的对比关系。通过对基于处理器的传统加速比概念的研究,推导出了基于ＳＭＰ机群系统的面向结点加速比的计算公式。面向结点加速比模型充分考虑了实际运行时间的可测性,反映出了系统在使用了多个结点之后性能的改变。事实上,传统的加速比模型     

机群系统中基于MPI的多维稀疏数组传递方法

机群系统是一种分布存储系统，它主要利用消息传递方式来实现各结点之间的通信。而MPI（Message Passing Interface）作为一种基于消息传递的并行程序设计环境，已广泛应用于多种并行系统，尤其是像机群系统那样的分布存储并行机。该文主要探讨了MPI中的消息传递调用接口，提出了几种有效的在结点间传递多维稀疏数组的方法，并通过实践加以比较。     

动态可扩展机群系统任务分配算法

结点机性能差异及动态运行环境是导致系统运行状态忙闲不均的主要原因。该文提出了结点机差异测量的指标和方法,结合机群系统主/从计算模型和SPMD应用类型提出了3种任务分配算法。实践证明了该算法的有效性。     

一种改进的机群SPMD编程模型静态任务分配算法

机群系统中，结点机差异及动态运行环境是导致系统运行状态不均衡的主要原因．提出了结点机差异及负载测量指标和方法．以SPMD编程模型中的单一并行任务为测试程序，在机群系统性能测试、分析的基础上，进行运行时间相同原则基础上的静态任务分配；在应用运行过程中，通过对并发线程运行状态测试，用已完成任务的高速设备重复执行低速机器未完成任务，选取最快运行结果．从而缩小不均衡因素的影响．以空间划分大规模Monte Carlo仿真问题为例进行算法实际测试，取得良好运行效果．     

基于WS-Management的分布式机群管理方案

为了解决目前机群管理中存在的缺乏统一管理标准、可扩展性差及可用性差等问题,首次把WS-Management标准引入到机群系统管理中,提出了分布式机群管理解决方案.对机群进行CIMOM建模,实现了机群的标准化管理;采用分层管理的方法,提高了机群系统的可扩展性、可用性、容错性和性价比.对该方案进行了实现和实验分析,实验结果表明了该方案性能良好.     

结构化P2P网络上基于类别树的索引机制

为解决结构化P2P系统的模糊检索问题,提出一种新的索引机制,构建并使用类别树对结点和实体进行标识.使用类别的静态描述产生查询请求;使用类别的动态描述优选下一跳结点,使查询始终围绕关键字列表逐步收敛到满足需求的P2P结点上.给出了分类树、静态描述和动态描述的存储、管理策略,避免了性能和可用性瓶颈.实验结果表明,该索引机制具有较好的检索效果,已成功应用于某服务计算平台.     

机群系统中一种新的自适应结点分配算法:受限负载平衡结点分配(LLBA)

在机群系统中结点分配策略根据一定的原则为作业确定运行结点是提高系统性能的关键。通过对机群结点分配策略的研究,作者发现当前基于负载平衡自适应的结点分配策略为并行作业选择负载最轻的结点,这不利于系统性能的充分发挥。作者提出了一种新的自适应负载平衡结点分配算法：受限负载平衡结点分配。     

用于描述网络拓扑的形式语言的研究

论述了应用随机线性文法及产生式描述计算机网络拓扑结构的方法.在该形式语言的描述中,设置了3个基元状态,通过对基元状态及各种状态规律的分析,准确地描述了网络中结点间通信及共享存储器的状态.同时,证明了用此方法在某种条件下从初始结点到终了结点间可以建立惟一的访问路径,并能避免冲突.此方法对计算机网络结点访问/冲突避免的研究具有一定的参考价值.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.