CAD系统的Broker-Agent结构

本文在研究以往的以数据为中心，以执行为中心和面向对象的几类ＣＡＤ系统模型的基础上，着眼于ＣＡＤ系统的开放性和有效性，逐步提出了ＣＡＤ系统的Ｂｒｏｋｅｒ－Ａｇｅｎｔ结构，并详细研究了结构中Ｂｒｏｋｅｒ和Ａｇｅｎｔ的功能实现，之后进一步分析了Ｂｒｏｋｅｒ－Ａｇｅｎｔ结构对ＣＡＤ系统构成的影响，最后给出了该结构的应用实例。ＣＡＤ系统Ｂｒｏｋｅｒ－Ａｇｅｎｔ结构的提出为更开放和更有效的ＣＡＤ系统建模打下了     

推出新的TXSeries组件IBM进一步简化企业应用开发IBM TXSeries可以与基于Windows的开发工具协同工作

不久前在美国旧金山召开的ＧＩＧＡ中间件会议期间,ＩＢＭ公司正式宣布,它的主要交易管理平台ＴＸＳｅｒｉｅｓ的应用开发工具包又有新组件,这个名为ＩＢＭＣｏｍｐｏｎｅｎｔＢｒｏｋｅｒ的新ＴＸＳｅｒｉｅｓ组件可以支持微软ＣｏｍｐｏｎｅｎｔＯｂｊｅｃｔＭｏｄｅｌ（ＣＯＭ）编程模型,能够与ＥｎｔｅｒｐｒｉｓｅＪａｖａＢｅａｕｓ、ＣＣＲＢＡ和ＣＯＭ协同操作。通过这个新组件,ＩＢＭＴＸＳｅｒｉｅｓ的用户完全可以方便地应用基于Ｗｉｎｄｏｗｓ的开发工具,高效率地开发电子商务商易处理应用。借助ＴＸＳｅｒｉｅｓ应用开发…     

用VisiBroker开发CORBA程序

本文简要介绍了ＣＯＲＢＡ并以一个实例叙述了如何在Ｃ＋＋Ｂｕｉｌｄｅｒ４企业版环境下ＶｉｓｉＢｒｏｋｅｒ（ｆｏｒ Ｃ＋＋Ｂｕｉｌｄｅｒ）开发ＣＯＲＢＡ应用程序。     

CPDM基于CORBA/WEB的PDM

对ＰＤＭ系统产生巨大影响的两种技术──ＣＯＲＢＡ（ＣｏｍｍｏｎＯｂｊｅｃｔＲｅｑｕｉｒｅＢｒｏｋｅｒＡｒｃｈｉｔｅｃｔｕｒｅ）和ＷＥＢ,促使ＰＤＭ迈向新的台阶,ＰＤＭ作为支持并行工程的使能技术,要能够集成不同环境下的应用系统,ＣＯＲＢＡ技术的成熟为实现这一要求提供了一个较好的解决方案。南京新模式软件集成有限公司ＣＰＤＭ就是采用Ｃ＋＋和ＪａｖＳａ语言开发,系统底层基于ＣＯＲＢＡ平台,对于企业外部用户,ＣＰＤＭ将以浏览器作为统一的客户端界面。ＣＰＤＭ作为支持并行工程（ＣＥ）的使能技术,支持异构的计算…     

YH-ITM中数据缓冲部件的设计与实现

智能工具机ＹＨ－ＩＴＭ是一个基于ＲＩＳＣ、支持多种人工智能语言和传统Ｃ语言的通用智能计算机系统。数据缓冲部件ＤＢＵ是该系统中的一个重要组成部分。本文论述了ＤＢＵ的功能、结构、工作状态、对多处理机环境及对Ｐｒｏｌｏｇ的支持，以及对各类访问的处理。     

基于CORBA的网络作业管理系统的开发与研究

描述了一个基于Ｃｏｍｍｏｎ Ｏｂｉｅｃｔ ＲｅｑｕｅｓｔＢｒｏｋｅｒ Ａｒｃｉｔｅｃｔｕｒｅ（ＣＯＲＢＡ）的网络管理系统模型及其实现,对系统所使用的模块间通信协议体制ＣＯＲＢＡ作了比较详尽的介绍,并给出了作业管理系统的结构和功能。     

CIMS中MRPⅡ与DCS的信息集成方法

本文以国８６３／ＣＩＭＳ示范应用工程ＹＨ－ＣＩＭＳ为背景,通过ＣＩＭＳ环境下ＭＲＰⅡ与ＤＣＳ有关的信息流分析,给出了ＭＲＰⅡ与ＤＣＳ的信息集成方法及具体实例。     

分叉计算问题在YH-2机上的向量算法

本文提出了在ＹＨ－２机上计算分叉问题的ＳＯＲＴＬＩＢ库分类向量算法，并和其他向量算法进行了比较，效能测试表明，这种算法是ＹＨ－２机上计算分叉问题的最优算法。     

分叉计算问题在YH－2机上的向量算法

本文提出了在ＹＨ－２机上计算分又问题的ＳＯＲＴＬＩＢ库分类向量算法，并和其他向量算法进行了比较，效能测试表明，这种算法是ＹＨ－２机上计算分又问题的最优算法。     

对象技术在分布式系统中的作用

对象管理集团公司（ＯｂｊｅｃｔＭａｎａｇｍｅｎｔＧｒｏｕｐ－ＯＭＧ）是一个致力于解决分布式环境中互操作问题的非盈利性协作组织，它遵循一个新的技术途径，即对象技术，产生了公认的基于可商用对象技术的事实标准。它的一套面向对象的标准化语言、接口和协议的基础是一种称作通用对象请求代理结构（ＣｏｍｍｏｎＯｂｊｅｃｔＲｅｑｕｅｓｔＢｒｏｋｅｒＡｒｃｈｉ－ｔｅｃｔｕｒｅ—ＣＯＲＢＡ）的通信约定。ＣＯＲＢＡ在具有不同的操作系统、语言、网络协议和硬件结构的系统间提供了应用层的互操作性。ＯＭＧ未来的计划是运用这些有力的服务和功能支持应用程序员的设计开发。     

Multi-mode operator for SHA-2 hash functions

We propose an improved implementation of the SHA-2 hash family, with minimal operator latency and reduced hardware requirements. We also propose a high frequency version at the cost of only two cycles of latency per message. Finally we present a multi-mode architecture able to perform either a SHA-384 or SHA-512 hash or to behave as two independent SHA-224 or SHA-256 operators. Such capability adds increased flexibility for applications ranging from a server running multiple streams to independent pseudorandom number generation. We also demonstrate that our architecture achieves a performance comparable to separate implementations while requiring much less hardware.     

Approximate sorting of packet-scheduling in high-speed networks

Fairness,latency and computational complexity are three important factors in evaluating the performance of a scheduling algorithm.Fairness must be satisfied so that service can be distributed according to the reserved rate.Only when latency is irrelevant to the number of connections,is it possible to minimize the end-to-end delay through controlling the reserved rate.Among existing scheduling algorithms,Round Robin is the least complex.However,conventional Round Robin is unable to ensure fairness,and the improved round robin algorithms like Deficit Round Robin,Weighted Round Robin and VIrtual Round Robin are unable to ensure that their latencies are irrelevant to the number of connections although they guarantee fairness,Potential Round Robin developed for analysis of fairness and latency reduction is thus propsed.It is based on the introduction of a new concept,Round Potential Function.The function splits service time into a number of service round periods to guarantee fairness regardless of the serving process used in the period.In the analysis of latency,service round periods are re-split into multiple scanning cycles for further service distribution with approximate sorting between scanning cycles,As a result,latency is no longer relevant to the number of connections while the low complexity of round robin is kept.     

Extension of practical channel transition broadcasting for near video-on-demand applications

Periodic broadcasting is a cost-effective solution for the large-scale distribution of popular videos. This strategy guarantees constant worst service latency to all clients, regardless of the number of video requests. The practical channel transition broadcasting (PCTB) scheme is an essential periodic broadcasting method that can dynamically add or release broadcasting channels (i.e., channel transition) according to video popularity. However, PCTB experiences bandwidth waste when performing channel transition. This study further finds that PCTB yields transition playback latency during channel addition. Therefore, an enhanced version referred to as PCTB+ is proposed to cause less bandwidth waste and lower transition playback latency. The applicability of this new scheme is verified, and an analytical evaluation is provided to demonstrate its performance advantage. The new scheme reduces bandwidth waste by 50 % to 100 % compared to the original PCTB scheme. Moreover, PCTB+ yields 50 % smaller transition playback latency than PCTB. The proposed scheme outperforms the seamless fast broadcasting (SFB) scheme for bandwidth waste under most conditions. No extra startup latency and client buffer demand are required when using PCTB+.     

P2PSIP系统子网间会话建立延迟的研究

为了解决由于网络节点的大量增加引起的分层P2PSIP系统中子网间用户会话建立的高延迟问题,提出了利用上层覆盖网采用单跳HDT算法的解决方案。对现有的P2PSIP网络进行了研究,把会话建立时用户定位的延迟分为在子网内部和上层覆盖网中两个部分。利用单跳DHT算法来减少子网间用户定位时消息在上层覆盖网中路由的跳数,从而可以降低平均延迟时间。通过对该方案的可行性分析和延迟的比较,表明了该方案是可行的。     

Single-Threaded vs. Multithreaded: Where Should We Focus?

Today, with the increasing popularity of multicore processors, one approach to optimizing the processor's performance is to reduce the execution times of individual applications running on each core by designing and implementing more powerful cores. Another approach, which is the polar opposite of the first, optimizes the processor's performance by running a larger number of applications on a correspondingly larger number of cores, albeit simpler ones. The difference between these two approaches is that the former focuses on reducing the latency of individual applications or threads (it optimizes the processor's single-threaded performance), whereas the latter focuses on reducing the latency of the applications' threads taken as a group (it optimizes the processor's multithreaded performance). The panel, from the 2007 Workshop on Computer Architecture Research Directions, discusses the relevant issues.     

Flattened Butterfly Topology for On-Chip Networks

With the trend towards increasing number of cores in a multicore processors, the on-chip network that connects the cores needs to scale efficiently. In this work, we propose the use of high-radix networks in on-chip networks and describe how the flattened butterfly topology can be mapped to on-chip networks. By using high-radix routers to reduce the diameter of the network, the flattened butterfly offers lower latency and energy consumption than conventional on-chip topologies. In addition, by properly using bypass channels in the flattened butterfly network, non-minimal routing can be employed without increasing latency or the energy consumption.     

SFFS：低延迟的面向小文件的分布式文件系统

社交网站和电子商务等网络服务发展迅速,这类服务需要存储大量图片、音乐、微博文本等小文件。传统的分布式存储系统,如HDFS（Hadoop distributed file system）,是面向大文件而设计的,在存储小文件时会产生元数据开销过大,访问延迟较高等问题,不能适应存储海量小文件的应用环境。分析了TFS（Taobao file system）的系统架构和读写流程,发现TFS在每次读/写过程中至少要建立3次网络连接,增大了读写延迟。针对海量小文件存储带来的挑战和TFS存在的问题,提出了一种新的低延迟、高可用的面向海量小文件的分布式存储方案,并实现了分布式文件系统SFFS（small-file file system）。性能测试表明,SFFS和TFS相比,写延迟降低了76.6%,读延迟降低了约10%。通过对系统结构的分析,相比于TFS,SFFS在中心节点的负载更轻,失效恢复更快,在可用性方面更有优势。     

A Latency-Aware Partitioning Method for Distributed Virtual Environment Systems

Distributed virtual environment (DVE) systems allow multiple users working on different client computer's interconnected through different networks to interact in a shared virtual world. In these systems, latency is crucial for providing an acceptable quality of service (QoS), since it determines how fast client computers are reported about changes in the shared virtual scene produced by other client computers. This paper presents in a unified manner a partitioning approach for providing a latency below a threshold to the maximum number of users as possible in DVE systems. This partitioning approach searches the assignment of avatars, which represents the best trade-off among system latency, system throughput, and partitioning efficiency when solving the partitioning problem. Evaluation results show that the proposed approach not only maximizes system throughput, but also allows the system to satisfy, if possible, any specific latency requirement needed for providing QoS. This improvement is achieved without decreasing either image resolution or quality of animation, and it can be used together with other techniques already proposed. Therefore, it can contribute to provide QoS in DVEs.     

Multidestination message passing in wormhole k-ary n-cube networkswith base routing conformed paths

This paper proposes multidestination message passing on wormhole k-ary n-cube networks using a new base-routing-conformed-path (BRCP) model. This model allows both unicast (single-destination) and multidestination messages to co-exist in a given network without leading to deadlock. The model is illustrated with several common routing schemes (deterministic, as well as adaptive), and the associated deadlock-freedom properties are analyzed. Using this model, a set of new algorithms for popular collective communication operations, broadcast and multicast, are proposed and evaluated. It is shown that the proposed algorithms can considerably reduce the latency of these operations compared to the Umesh (unicast-based multicast) and the Hamiltonian path-based schemes. A very interesting result that is presented shows that a multicast can be implemented with reduced or near-constant latency as the number of processors participating in the multicast increases beyond a certain number. It is also shown that the BRCP model can take advantage of adaptivity in routing schemes to further reduce the latency of these operations. The multidestination mechanism and the BRCP model establish a new foundation to provide fast and scalable collective communication support on wormhole-routed systems     

Designing content distribution networks for optimal cost and performance

One strategy for alleviating excess latency (delay) in the Internet is the caching of web content at multiple locations. This reduces the number of hops necessary to reach the desired content. This strategy is used for web content such as html pages, images, streaming video, and Internet radio. The network of servers which store this content, and the collections of objects stored on each server, is called a content distribution network (CDN). In order to optimally design a CDN, given a network topology with available server storage capacity at various points in the network, one must decide which object collections to place on each server in order to achieve performance or cost objectives. The placements must be within the storage limits of the servers and must reflect the request patterns for each collection of objects to be cached. Researchers have suggested formulations for the CDN problem which address performance by minimizing latency (the average number of hops is a commonly accepted measure of latency) from client to content, or formulations that focus on minimizing cost of storage and/or bandwidth. In this research, we develop a model which allows for the simultaneous treatment of performance and cost, present examples to illustrate the application of the model and perform a detailed designed experiment to gain insights into cost/hops tradeoff for a variety of network parameters.