Parallel Programming and Performance Evaluation with the URSA Tool Family

This paper contributes to the solution of several open problems with parallel programming tools and their integration with performance evaluation environments. First, we propose interactive compilation scenarios instead of the usual black-box-oriented use of compiler tools. In such scenarios, information gathered by the compiler and the compiler's reasoning are presented to the user in meaningful ways and on-demand. Second, a tight integration of compilation and performance analysis tools is advocated. M any of the existing, advanced instruments for gathering performance results are being used in the presented environment and their results are combined in integrated views with compiler information and data from other tools. Initial instruments that assist users in data mining this information are presented and the need for much stronger facilities is explained. The URSA Family provides two tools addressing these issues. URSA MINOR supports a group of users at a specific site, such as a research or development project. URSA MAJOR complements this tool by making available the gathered results to the user community at large via the World-wide Web. This paper presents objectives, functionality, experience, and next development steps of the URSA tool family. Two case studies are presented that illustrate the use of the tools for developing and studying parallel applications and for evaluating parallelizing compilers.     

Evaluating the Effect of Coherence Protocols on the Performance of Parallel Programming Constructs

The different implementations of parallel programming constructs interact heavily with a multiprocessor's coherence protocol and thus may have a significant impact on performance. The form and extent of this interaction have not been established so far however, particularly in the case of update-based coherence protocols. In this paper we study the running time and communication behavior of ticket and MCS spin locks; centralized, dissemination, and tree-based barriers; parallel and sequential reductions; linear broadcasting and producer and consumer-driven logarithmic broadcasting; and centralized and distributed task queues, under pure and competitive update coherence protocols on a scalable multiprocessor; results for a write invalidate protocol are presented mostly for comparison purposes. Our experiments indicate that parallel programming techniques that are well-established for write invalidate protocols, such as MCS locks and task queues, are often inappropriate for update-based protocols. In contrast, techniques such as dissemination and tree barriers achieve superior performance under update-based protocols. Our results also show that update-based protocols sometimes lead to different design decisions than write invalidate protocols. Our main conclusion is that indeed the interaction of the parallel programming constructs with the multiprocessor's coherence protocol has a significant impact on performance. The implementation of these constructs must be carefully matched to the coherence protocol if ideal performance is to be achieved.     

An Efficient Parallel Algorithm for the Layered Planar Monotone Circuit Value Problem

A planar monotone circuit (PMC) is a Boolean circuit that can be embedded in the plane and that contains only AND and OR gates. A layered PMC is a PMC in which all input nodes are in the external face, and the gates can be assigned to layers in such a way that every wire goes between gates in successive layers. Goldschlager, Cook and Dymond, and others have developed NC ² algorithms to evaluate a layered PMC when the output node is in the same face as the input nodes. These algorithms require a large number of processors (Ω(n ⁶ ), where n is the size of the input circuit). In this paper we give an efficient parallel algorithm that evaluates a layered PMC of size n in time using only a linear number of processors on an EREW PRAM. Our parallel algorithm is the best possible to within a polylog factor, and is a substantial improvement over the earlier algorithms for the problem. Received April 18, 1994; revised April 7, 1995.     

An efficient parallel strategy for the perfect domination problem on distance-hereditary graphs

A graph is distance-hereditary if the distance stays the same between any of two vertices in every connected induced subgraph containing both. Two well-known classes of graphs, trees and cographs, both belong to distance-hereditary graphs. In this paper, we first show that the perfect domination problem can be solved in sequential linear-time on distance-hereditary graphs. By sketching some regular property of the problem, we also show that it can be easily parallelized on distance-hereditary graphs.     

基于4MAT系统的程序设计基础教学模式探讨

本文针对普遍存在的程序设计基础课程难学难教的问题,分析了存在一些影响因素,然后结合现代的认知学原理和信息加工理论,提出了一种基于4MAT系统的程序设计基础教学模式,并在教学中取得了很多积极的效果。     

基于IPv6组播的P2P文件的分发

本文首先分析了P2P技术优势与缺陷,介绍了IPv6组播技术与应用现状.最后对在JXTA平台上以IPv6组播为主、P2P为辅的数据发送方式的解决方案,进行了初步的设计分析与研究,并给出实例的框架.     

A P4P-integrated data-driven P2P system for the live multimedia streaming service

The Proactive network Provider Participation for the P2P (P4P) architecture deploys central servers, which perceives network status and provides peering suggestions to P2P systems in order to achieve better network resource utilization while supporting best possible application performance. However, P4P alone may not be able to make appropriate peering suggestions for live multimedia streaming since it does not include mechanisms to reflect some of the parameters that are important to the QoS of live multimedia streaming such as upload bandwidth and stability of a peer as a stream deliverer. Furthermore, peer synchronization and parent replacement in the middle of a session, which are critical issues to the QoS of live multimedia streaming, are also left as the matters to be dealt with by the P2P systems alone. Most of the existing data-driven P2P systems leverage periodic information exchanges among neighboring peers in order to cope with these problems, which may incur long delay and high control overhead. In this paper, we proposed P4P-integrated data-driven P2P system for live multimedia streaming service. The proposed system includes not only the peering suggestion mechanism appropriate for live multimedia streaming but also the peer synchronization and parent replacement mechanisms, which exploit the centralized P4P framework and do not require periodic control information exchanges. We implemented the system in NS-2 simulator and compared its performance to the P4P and existing data-driven P2P systems. The results from experiments show that the proposed system enhances QoS compared to the existing data-driven P2P systems while maintaining the same level of network efficiency of the original P4P.     

宏程序加工圆弧螺纹的编程研究

以变半径圆弧形螺纹数控车削加工为例，介绍了用户宏程序在圆弧形螺纹加工中的应用。文中较为详细地阐述了圆弧形螺纹在实际加工时数学表达式的建立方法以及宏程序在其中的应用技巧与注意事项等，并给出了相应的加工程序。希望对从事数控编程与操作的人员有一定的帮助和借鉴作用。     

多核平台上程序在线评测辅助教学系统

选用LAMP作为开发环境,进行了程序设计在线评测辅助教学系统的设计与开发。着重论述了基于多核平台上的多线程或多进程在线评测系统的设计与实现,与单核系统相比,解决了单线程或单进程评测效率低的问题。经过与单核串行评测系统比较得出,多核系统评测速度显著提高,评测结果和串行评测所得一致,准确率高。     

MPI程序容错系统的分析和设计

MPI是大规模集群和网格平台中最通用的编程环境,但其运行环境经常会因为节点或网络的故障而出现错误,所以有必要为MPI编程提供容错机制。本文分析了实现MPI程序容错的关键技术,并针对运行MPICH-P4的LINUX集群,利用检查点和消息日志技术,通过改造和扩充MPI底层的P4通信库,提出了一套MPI程序容错系统的具体实施方案。     

P2P流媒体点播的缓存机制研究

基于P2P的流媒体点播系统,由于实时点播和拖动等VCR操作没有得到有效支持,以及用户不能随意发布节点等原因,没有得到广泛应用。本文提出了一种基于混合P2P的流媒体点播模型TTVOD,讨论了模型的缓存机制,提高了数据冗余度和分发性能,最后通过实验验证了模型的有效性。     

适用于程序规范说明的Institution范畴的完备性研究

Institution作为一般框架下的逻辑系统,在数据库理论、程序设计语言、模块化技术和人工智能等方面有着重要的应用。论文主要研究了Institution范畴的完备性,它直观上表明如果基调类可分解,那么它们对应的Institution也可分解。这为大规模程序设计中模块化程序的安全分解和调用提供了一定的逻辑支持。首先,根据基调类范畴中的极限r:SignD',构造了一个Institution&,讨论了&中的一些性质,特别是闭包引理和表示定理;然后又建立了Institution范畴Ins中相应的极限r:&D,得到了遗忘函子U:Ins→Sig反射极限的重要结论,从而推广了Sign:Th→Sign反射余极限的关键性结果;最后给出了Ins的完备性定理。     

基于云存储的P2P视频点播系统数据复制策略

交互性支持对P2P视频点播系统具有重要的意义,视频点播服务的大规模普及离不开用户交互性的支持。讨论了如何有效利用对等节点的带宽和存储资源来主动复制数据块,提出了一种基于云存储的数据复制策略CSPR。仿真实验结果表明,相比于现有的数据复制策略,CSPR可以显著提高用户进行随机搜索操作时的响应速度,并降低网络复制开销。     

基于支持向量机分类的回归方法

支持向量机(support vector machine,简称SVM)是一种基于结构风险最小化原理的分类技术,也是一种新的具有很好泛化性能的回归方法.提出了一种将回归问题转化为分类问题的新思想.这种方法具有一定的理论依据,与SVM回归算法相比,其优化问题几何意义清楚明确.     

电信运营商运营支撑流程化管理研究

全业务运营时代给运营商带来了运营模式的巨大变革,从原有的产品化营销理念,逐步走向了市场化营销理念,传统的运营支撑手段已不能满足市场运营的发展需求。基于对实际问题的研究,本文提出一种新型的运营支撑流程化管理模式。     

An algorithm for the asynchronous Write-All problem based on process collision

Summary. The problem of using P processes to write a given value to all positions of a shared array of size N is called the Write-All problem. We present and analyze an asynchronous algorithm with work complexity , where (assuming and ). Our algorithm is a generalization of the naive two-processor algorithm where the two processes each start at one side of the array and walk towards each other until they collide. Received: October 1999 / Accepted: September 2000     

VC6．0与MATLAB7．X混合编程方法研究

VC 与MATLAB混合编程,可以将VC优秀的可视化编程能力和MATLAB强大的计算能力结合起来.分析了C语言与MATLAB7.X在接口的特点,详细介绍了VC 6.0与MATLAB7.X混合编程的三种方法:MATLAB引擎、MATLAB编译器和MATLAB COM编译器.比较分析了各种方法的适用范围,介绍了发布混编程序的方法.     

导师制模式下大学生程序设计创新能力提高的研究

针对国家和学校对于专业教学计划和教学时数不断精简的问题,提出一种基于本科生导师制度模式的程序设计竞赛教学方法改革。以程序设计的在线评判技术与系统为核心,以计算机学生程序设计能力提高为出发点,研究构建面向计算机语言课程的学生自主实践平台,提出了一整套基于现代化的网络技术和通信技术提高学生编程能力的培养方案,探索了计算专业学生编程实践能力的培养模式。     

Designing Efficient and Robust Caching Algorithms for Streaming-on-Demand Services on the Internet

Content Delivery Networks (CDN) have been used on the Internet to cache media content so as to reduce the load on the original media server, network congestion, and latency. Due to the large size of media content compared to normal web objects, current caching algorithms used in the Internet are no longer suitable. This paper presents a high-performance prefetch system that accommodates user time-varying behavior. A hybrid caching technique, which combines prefetch and replacement algorithms, is also introduced. The robustness of the cache system against imperfect user request information is evaluated using three request noise models. Two prefetch performance indices are also presented to help content administrators in deciding when to update the user request profile for caching algorithms.     

基于动态规划的红外弱小运动目标的实时检测方法研究

文章针对低信噪比下红外弱小运动目标的特点,提出了一种正向动态规划算法。分析了算法的检测性能,并对算法实现中的一些关键问题进行了讨论。实验表明,该算法适应性强,能有效地完成对低信噪比下弱小运动目标的实时检测、识别与跟踪。