VxWorks中主备数据一致性功能组件的设计与实现

数据一致性是主备用系统必须解决的问题.目前主备系统的一致性都采用手工编程来实现,导致代码结构繁杂,且效率不高.利用VxWorks的异常处理机制,结合RISC CPU的特性,设计实现了一个数据一致性功能组件.这个组件可使数据的一致性处理自动化.     

面向企业应用集成的主数据管理系统

针对企业数据集成中存在的数据质量问题,为解决集成数据的不一致性问题,提出基于CFD、CIND进行数据一致性检测和基于订阅规则进行数据发布的主数据管理系统。系统搭建于SOA架构之上,通过主数据抽取、主数据质量控制、主数据发布等组件功能为各应用系统提供透明的单一主数据视图,并实现了主数据变更流程的自动管理。应用结果表明,使用主数据管理有效地解决了在各应用系统中流转数据的一致性问题,从而提高了集成数据的质量。     

集群数据库系统的日志复制和故障恢复

互联网、社交、购物、金融等各类应用直接面临海量用户的高并发访问,传统的单点数据库逐渐成为这些应用系统的瓶颈,而众多互联网应用能够良好运行的主要原因是使用了基于集群环境的数据管理系统作支撑。与传统数据库系统相比,基于集群环境的数据库系统具有更好的扩展性和可用性,而日志复制是保证这些特性的核心组件。传统的主备架构的日志复制在异常情况下对未决事务日志处理不佳,导致数据副本之间存在不一致的风险,另外,分布式系统领域的一致性算法缺乏对事务一致性的处理,而且在选主时存在活锁、多主和频繁选主的问题,无法直接适用于事务日志复制。本文提出了一种集群环境下的事务日志复制策略和恢复机制,能够有效处理未提交日志,提供了强弱两种读一致性,并且提出了一种轻量级的选主算法,可以避免以上的选主问题。本文在开源OceanBase分布式数据库系统中实现了上述机制,并使用基准测试工具对系统进行测试,通过一系列实验验证了系统的扩展性和可用性。     

数据复制系统的主端IO策略研究

在数据复制系统中,主端IO策略必须在保证主端数据视图一致性和从端数据一致性的同时,提高主端请求响应速度。针对已有的主端IO策略中存在的各种缺陷,设计并实现了并行IO策略。在该策略中制定了五条规则,通过按照请求提交的顺序来返回请求成功及更新日志控制信息,保证了主端数据视图一致性和从端数据一致性的要求,同时它对请求进行了并行处理,大大提高了主端IO效率。     

用EJB技术实现Web信息系统的代码表组件

对于由多个子应用系统组成的Web信息系统，使用组件技术解决其代码数据的一致性问题，文中介绍了相关的EJB组件技术，采用实体Bean组件实现代码表组件，并给出了具体实现和使用方法。     

组件事务特征一致性测试

组件事务服务器是三层Ｃｌｉｅｎｔ／Ｓｅｒｖｅｒ体系结构中的核心部件,虽然它提供了组件事务管理机制,但由于应用系统中组件之间的相互关系复杂,所以设计人员很难在设计阶段恰当地处理组件事务的一致性。文中首先对组件事务一致性进行讨论,提出了组件事务特征一致性测试的方法,该方法可以在应用系统设计阶段测试组件事务特征的一致性,最后通过实验验证该方法的有效性。     

远程复制系统数据一致性研究与实现

针对远程数据复制容灾系统中的数据一致性问题,提出了保证数据一致性和视图一致性并优化系统性能的实现思想,即使用日志卷记录用户请求顺序,通过保持主、从两端数据卷上数据块的更新顺序来保证数据一致性,对于不同的数据类型采用不同的传输方法。论述了它的组织结构、实现流程以及关键技术。     

Jaguar—CTS组件事务一致性测试

虽然Jaguar-CTS提供了组件事务管理机制。但由于应用系统中组件之间的相互关系复杂,所以设计开发人员很难在设计阶段恰当地处理组件事务的一致性。文中提出用软件结构描述语言来测试组件事务一致性的方法,并通过一个具体实例说明该方法的应用。     

海量数据分布式处理的研究与实现

介绍了涉及海量数据的大型软件的分布式解决方案。将繁重任务分解到Internet／Intranet上的多台机器提高性能是分布式系统的出发点,借此思想处理海量数据、实现数据的分开配置。对DCOM组件的实现原理、组件的划分、远程组件服务器的配置以及采用MMF处理超大型文件进行了详细阐述,而且该方案极易应用到实际开发中,对同类问题极具参考性。     

物理集成的多数据库系统中数据一致性维护方法

局部数据库中的数据与集成数据库中的数据一致性问题一直是采用物理集成策略的多数据库系统的关键问题。本文针对ＣＩＭ环境特点,一种基于松散一致性模型的主副本异步更新机制一公告机制,来解决这一问题,本文详细这了公告机制、公告系统的设计与实现,并给出了公告处理算法,该公告机制已在甸开发的ＣＩＭＳ信息集成平台的原形系统ＳｕｐｅｒＢａｓｅ中得以实现。     

Tracking of multidimensional TDOA for multiple sources with distributed microphone pairs

This paper presents a general framework for tracking the time differences of arrivals of multiple acoustic sources recorded by distributed microphone pairs. Tracking is based on a three-stage analysis. Complex-valued propagation models are extracted at different time instants and frequencies using either the independent component analysis or the phase of the cross-power spectrum evaluated at each microphone pair. In both cases, approximated densities of the propagation time delays are derived through the generalized state coherence transform. A sequential Bayesian tracking scheme with an integrated activity detection is finally implemented through disjoint particle filters based on a track-before-detect strategy. Experiments on both synthetic and real data recorded by two distributed microphone pairs show that the proposed framework can detect and track up to five sources simultaneously active in a reverberant environment.     

基于虚拟集中方法的异构分布式数据集成模型

网络和信息技术的发展导致新的数据格式不断涌现,数据整合的要求日益迫切,为此提出一个基于虚拟集中方法实现的异构数据集成模型,可以实现分布、异构数据的一致性访问,并能保证数据的一致性、实时性和数据源的“即插即用”,较好地解决了异构数据源的联合使用问题。最后给出了基于Java和XML技术的基本实现方法。     

Shared State for Distributed Interactive Data Mining Applications

Distributed data mining applications involving user interaction are now feasible due to advances in processor speed and network bandwidth. These applications are traditionally implemented using ad-hoc communication protocols, which are often either cumbersome or inefficient. This paper presents and evaluates a system for sharing state among such interactive distributed data mining applications, developed with the goal of providing both ease of programming and efficiency. Our system, called InterAct, supports data sharing efficiently by allowing caching, by communicating only the modified data, and by allowing relaxed coherence requirement specification for reduced communication overhead, as well as placement of data for improved locality, on a per client and per data structure basis. Additionally, our system supports the ability to supply clients with consistent copies of shared data even while the data is being modified.We evaluate the performance of the system on a set of data mining applications that perform queries on data structures that summarize information from the databases of interest. We demonstrate that providing a runtime system such as InterAct results in a 10–30 fold improvement in execution time due to shared data caching, the applications' ability to tolerate stale data (client-controlled coherence), and the ability to off-load some of the computation from the server to the client. Performance is improved without requiring complex communication protocols to be built into the application, since the runtime system uses knowledge about application behavior (encoded by specifying coherence requirements) in order to automatically optimize the resources utilized for communication. We also demonstrate that for our benchmark tests, the quality of the results generated is not significantly deteriorated due to the use of more relaxed coherence protocols.     

基于XMLC的EOS页面构件设计与实现

基于构件的软件开发是软件工程的基本目标之一,Primeton EOS中间件系统基于J2EE架构成功的实现了WEB应用开发的构件化,并创造性的以XML总线显著降低了各构件耦合度,使运算构件,逻辑构件,展现构件,数据构件,流程构件无缝的融合。但是对于页面构件,仍然使用传统的JSP页面,无论在构件设计理念还是运行效率方面都不尽人意。该文将探讨如何使用XMLC技术重新设计EOS表示购件,使其充分利用XML总线的设计优势,实现构件理念与运行效率的最优化。     

Cache-Based Synchronization in Shared Memory Multiprocessors

In shared memory multiprocessors, efficient synchronization is imperative to assure good performance. There are two aspects to the “cost” of a synchronization operation: the first is the waiting time at synchronization points, and the second is the intrinsic overhead in performing the operation. The overhead has two components. The first component deals with contention resolution for synchronization operation among competing processors. The second component deals with the shared data accesses that the processor has to perform once it enters a synchronization region. We present a mechanism to reduce the overhead of performing synchronization operations in a cache-based shared memory multiprocessor. The mechanism is based on the intuitive notion that parallel programs invariably use synchronization operations to govern the access to shared data. Traditional multiprocessor cache protocols treat synchronization accesses the same way as normal read/write memory accesses, leading to inefficiencies in performing synchronization operations which ultimately limit the scalability of such systems. The key idea in our approach is to combine synchronization with the coherence maintenance for the cached data. Each cache line maintains states for synchronization as well as for cache coherence, and the cache protocol ensures the correctness of the synchronization operations and the coherence of the data at these synchronization points. To assess the performance gain due to the proposed mechanism, simulation studies are performed using a workload model that represents a dynamic scheduling paradigm which forms the core of several parallel programs. Results from simulation studies show that the proposed cache-based synchronization performs significantly better than traditional cache coherence approaches.     

Teapot: a domain-specific language for writing cache coherenceprotocols

In this paper, we describe Teapot, a domain-specific language for writing cache coherence protocols. Cache coherence is of concern when parallel and distributed systems make local replicas of shared data to improve scalability and performance. In both distributed shared memory systems and distributed file systems, a coherence protocol maintains agreement among the replicated copies as the underlying data are modified by programs running on the system. Cache coherence protocols are notoriously difficult to implement, debug, and maintain. Moreover, protocols are not off-the-shelf, reusable components, because their details depend on the requirements of the system under consideration. The complexity of engineering coherence protocols can discourage users from experimenting with new, potentially more efficient protocols. We have designed and implemented Teapot, a domain-specific language that attempts to address this complexity. Teapot's language constructs, such as a state-centric control structure and continuations, are better suited to expressing protocol code than those of a typical systems programming language. Teapot also facilitates automatic verification of protocols, so hard to find protocol bugs, such as deadlocks, can be detected and fixed before encountering them on an actual execution. We describe the design rationale of Teapot, present an empirical evaluation of the language using two case studies, and relate the lessons that we learned in building a domain-specific language for systems programming     

Screen-Area Coherence for Interactive Scanline Display Algorithms

This article proposes and demonstrates a technique enabling polygon-based scanline hidden-surface algorithms to be used in applications that require a moderate degree of user interaction. Interactive speeds have been achieved through the use of screen-area coherence,a derivative of frame-to-frame coherence and object coherence. This coherence takes advantage of the face that most of the area of the screen does not change from one frame to the next in applications that have constant viewing positions for a number of frames and in which a majority of the image remains the same. One such application, the user interface of constructive solid geometry (CSG) based modelers, allows a user to modify a model by adding, deleting, repositioning, and performing volumetric Boolean operations on solid geometric primitives. Other possible applications include robot simulation, NC verification, facility layout, surface modeling, and some types of animation. In this article, screen-area coherence is used as the rationale for recalculating only those portions of an image that correspond to a geometric change. More specifically, this article describes a scanline hidden-surface removal procedure that uses screen-area coherence to achieve interactive speeds. A display algorithm using screen-area coherence within a CSG-based scanline hidden-surface algorithm was implemented and tested. Screen-area coherence reduced the average frame update time to about one quarter of the original time for three test sequences of CSG modeling operations.     

支持数据库访问的进程检查点技术研究与实现

现有的检查点技术不支持socket连接的恢复,也没有将进程恢复和数据恢复结合起来,因此不能支持含有数据库访问的应用程序.本文提出一种支持含有数据库访问的进程检查点技术.对于含有数据库访问的应用程序,在设置进程检查点之前,先设置数据库检查点,获取当前数据库的系统改变号SCN,然后生成进程检查点.当程序从进程检查点处恢复运...     

Analysis of coherence strategies for stereo occlusion culling

This paper explores the benefits that can be achieved for stereoscopic visualization when using occlusion culling strategies. Graphics processing units (GPUs) are improving their computational power and functionalities. On the other hand, models are also increasing their size and users require more demanding image quality. Occlusion culling provides significant frame rate speed‐ups in densely occluded scenarios. This paper shows the limitations placed by compact and not densely occluded scenarios and the gains that can be achieved when rendering stereo images using occlusion culling. The experiments carried out test combinations of occlusion stereo coherence and occlusion frame coherence. The methods also take advantage of efficient depth sorting strategy and aggressive occlusion frame coherence, whose image artefacts have been found to be negligible. Results clearly point out that eye‐independent frame coherence offers more benefits than mixing frame and stereo coherence. As in monoscopic occlusion culling, using simplified geometric models, instead of bounding boxes, when posting occlusion queries, improves significantly the number of objects discriminated as occluded. The algorithm presented can be easily implemented and provides a significant boost in performances. Copyright © 2007 John Wiley & Sons, Ltd.     

An optical interconnection network and a modified snooping protocol for the design of large-scale symmetric multiprocessors (SMPs)

In symmetric multiprocessors (SMPs), the cache coherence overhead and the speed of the shared buses limit the address/snoop bandwidth needed to broadcast transactions to all processors. As a solution, a scalable address subnetwork called symmetric multiprocessor network (SYMNET) is proposed in which address requests and snoop responses of SMPs are implemented optically. SYMNET not only uses passive optical interconnects that increases the speed of the proposed network, but also pipelines address requests at a much faster rate than electronics. This increases the address bandwidth for snooping, but the preservation of cache coherence can no longer be maintained with the usual snooping protocols. A modified coherence protocol, coherence in SYMNET (COSYM), is introduced to solve the coherence problem. COSYM was evaluated with a subset of Splash-2 benchmarks and compared with the electrical bus-based MOESI protocol. The simulation studies have shown a 5-66 percent improvement in execution time for COSYM as compared to MOESI for various applications. Simulations have also shown that the average latency for a transaction to complete using COSYM protocol was 5-78 percent better than the MOESI protocol. It is also seen that SYMNET can scale up to hundreds of processors while still using fast snooping-based cache coherence protocols, and additional performance gains may be attained with further improvement in optical device technology.