一种基于微片分组的片上网络微节点交叉开关调度机制

在基于微片(flit)分组的动态缓存分配基础上,提出一种基于微片分组的片上网络交叉开关调度机制.该机制与静态独立分割缓存的思想不同,首先对输入端缓存进行统一管理,对微片根据其流向进行分组,并为所分各“组”动态分配缓存,然后引入一种基于“组”规模的概率仲裁算法,通过“组”分配和开关分配实现调度过程.为进一步降低开销,还在该机制基础上提出一种各“组”共享仲裁的策略.理论分析与实验结果均表明:所提出的机制相对于传统和动态虚通道机制,可节约25％以上的硬件开销并可获得更优的网络延迟与吞吐性能;共享仲裁策略可在所提机制基础上进一步降低硬件开销,但其代价是网络性能有所下降.     

基于片上网络的低偏转率微缓存路由器

片上网络通常使用输入输出缓存或交叉开关缓存存储微片以提高路由器性能,导致大量消耗片上资源并显著增加功耗。无缓存路由器被提出用于解决该问题,但存在低效率的偏转,不适用于中、高负载的网络。为此,设计一种基于方向向量路由策略的低偏转率微缓存路由器。采用一个旁路寄存器和一个回环寄存器的设计,通过二分图最大匹配调度算法优化微片路由。在Xilinx Vivado上的仿真结果表明,该路由器的性能与RIDER路由器相当,但寄存器使用减少55%,并且在高负载网络中性能优于CHIPPER,Min BD和RIDER路由器。     

一种异构片上网络路由算法的研究

随着集成电路工艺的迅速发展,传统的片上网络由于缓存引起芯片面积开销和能耗增加,从而使得无缓存路由技术得到了广泛关注。通过消除缓存, 整体的流水线进程大大得到简化,性能得到提高。但当网络负载量较大时,数据包被多次偏转或误传,导致网络的延迟增加,系统健壮性较差。针对片上网络运行应用的多样性,异构网络作为一种相对灵活的网络结构,能有效地降低网络的传输时延,提高系统性能。文中设计了无缓存NoC和带缓存NoC两种路由方式相结合的异构片上网络,并匹配静态路由算法和动态的自适应路由算法(AFC)进行数据包的传输。同时,还提出了一种针对AFC的优化算法(AFC-LP),其通过对无缓存路由计算的二次仲裁,进一步降低了通信的平均时延,提高了网络性能。实验表明,AFC-LP算法相比于传统带缓存的维序X-Y路由算法,片上网络的平均延迟降低了28.4%,CPU每一时钟周期内所执行的指令数IPC(Instruction Per Cycle)提升了10.4%。     

片上网络路由节点优化设计

针对虚输出队列结构的路由节点所构成的片上网络(NoC),提出了一种定制化路由节点中各个虚拟通道缓存大小的方法,以提高片上网络的整体通信性能。在有限的片上缓存资源约束下,分析各个虚输入队列中缓存大小对数据通过片上网络的平均延迟的影响,并在此基础上提出一种缓存资源配置方法,以便将缓存资源分配到片上网络通信瓶颈处,从而在不增加缓存资源开销的情况下提高片上网络的通信性能。最后通过仿真验证了路由节点优化设计对提高片上网络性能的可行性,并同未优化的路由节点构成的片上网络性能进行了比较。     

输入缓存Clos网络中分布式正交分路路由算法

提出了一种采用输入缓存MSM结构的Clos网络,该结构适用于高速交换网络。提出了这一结构中的路由算法,该算法采用正交分路的方法来减小网络内部的冲突,引入路由优先级来提高网络内部的链路利用率,使用优先级轮转来均衡网络内部负载。针对这一路由算法,还给出了与之对应的信元调度算法。仿真表明,尽管采用共享缓存的MSM结构内部使用了很高的加速比,但是采用了正交分路的路由算法后,输入缓存MSM结构,可以获得比共享缓存MSM结构更好的时延及吞吐性能,更适合在高速大容量多端口的路由器或交换机中采用。     

基于故障链路缓存再利用的NoC容错路由算法

建立故障模型是进行片上网络容错研究的基础,传统的细粒度故障模型未能有效地区分链路故障和通道故障.为了进一步提高片上资源的利用率,构建了一种粒度更细的微粒度故障模型,并在该模型的基础上提出了基于故障链路缓存再利用的容错路由算法.该算法为每个通信节点增加4条自收发通道,并采用基于缓存再利用的透传机制,通过复用故障链路两端的正常缓存和通道来透传故障通道上的数据包,提高了数据包采用最优输出端口的概率.实验结果表明,文中算法在高故障比例的片上网络中优势明显,且能以相对较小的硬件开销换取平均吞吐量、平均延迟和数据包平均跳数等性能的大幅度提升.     

动态非探测式路由选择策略的设计与分析

本文研究了动态的、非探测式的路由选择策略提高了自适应路由算法的传输效率,由于避免使用网络状态探测包,减少了缓存面积开销和额外能耗,是一种适合于片上网络自适应路由算法的选择策略设计方法。     

面向片上网络缓冲资源争用的路由器设计

针对片上网络典型路由器的缓冲资源利用率不高、大容量缓存设计受限等问题,在不增加缓存和虚通道的情况下,提出一种新的面向片上网络缓冲资源争用的路由器设计方案。在该路由器中,当某个输入端繁忙发生资源争用情况时,将阻塞数据包分配到其他拥有空闲缓存资源的输入端口,解决缓冲资源的争用问题,从而提高网络整体性能。SystemC仿真结果表明,相对于基本路由器,该路由器在热点模式和均衡模式下均具有较高的网络饱和率和吞吐量,尤其在热点模式下提高了约11.4%的饱和率。FPGA实现结果表明,该路由器的面积开销较小,能较好满足片上网络的应用需求。     

基于自相似排队模型的片上网络缓存分配算法

为提升片上网络在自相似通信特征下的网络性能,依据片上网络数据流的自相似特性,通过建立虚通道自相似排队模型,提出一种基于自相似排队模型的片上网络缓存分配算法.算法首先利用已建立的排队模型计算虚通道缓存溢出概率,然后依次为溢出概率最大的虚通道缓存队列递增缓存深度,每次增加一个微片,直至达到总缓存配额阈值.实验结果表明,与现有的基于排队模型的算法相比,文中算法在相同缓存开销下可获得更小的平均包延迟,在同等平均包延迟下可节约25％的缓存开销.     

移动Ad Hoc网络DSR路由协议性能分析

无线移动Ad Hoc自组网是由不依赖任何已有的网络设施的移动节点组成,该网络可以通过节点路由发现机制转发分组,并进行路由维护.Ad Hoc网络路由协议中DSR路由协议在不同发包率和节点移动速率的情况下各项网络性能都优于其他路由协议,尤其当网络业务量不大时性能更优.基于路由缓存大小和路由更新时间对协议性能的影响,利用OPNET建立DSR路由协议的Ad Hoc网络,并对路由出错、路由开销和时延等关键参数的仿真统计.仿真结果与理论分析一致,一般地,随着路由缓存变大和路由更新时间变短,网络中路由出错、路由开销和时延性能都有所提高.     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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