小型DGCNET的远程通信

小型分布式通用计算机网络(简称小型DGCNET)是一种开放式的、可按任意拓扑结构互连的、具有两级结构的网络。它的主要特点之一就是它不仅可以进行短距离局部的信息交换,也支持长距离的远程通信。这部分远程通信工作主要是在远程通信结点机和远程主机上完成的。如图1所示,远程通信结点机作为远程主机的前端机,负责远程通信部分的工作,实现信息的存贮、转发。从通信协议上讲,远程通信结点机作为主机HC与结点计算机NC直接相连,它们之间进行全双工同步通信。通信协议遵守CCITT X.25协议。另一方     

一种嵌入式结构传感器网络中数据传输方法实现

本文针对具有嵌入式结构的无线传感器网络的典型应用结构及现有协议进行分析,给出了一种较为简单的适用于小型无线传感器网络的通信协议,对通信数据格式及数据传输流程进行了较为详细的定义。为进一步验证协议性能,设计了一个小型的无线传感器网络实验系统,并在此系统上完成了对所设计通信协议的验证,实验结果表明了本文所给出协议的有效性。     

远程数据采集系统通信协议设计与实现

数据传输是远程数据采集系统重要功能．要求精简高效的通信协议支持。本文根据《水情数据采集系统》通信结构与流程分析。使用Petri Net模型进行协议定义的形式化描述和可达树验证。设计一种适应PSTN远程数据传输的专用数据链路层通信协议，并给出协议编码规范、帧结构和基于组件的实现框架。     

智能抄表系统上层通信接口通信协议

文章提出了一种基于点对点协议(PPP)的智能抄表系统上层接口通信协议。首先,给出了抄表系统的上层通信接口及其硬件配置。然后,介绍了一种抄表系统的三层通信协议结构。其中,基于需求驱动适用原则论述了抄表系统通信中不采用IP层的理由;并着重介绍了数据链路层的类PPP协议。最后,按功能分类介绍了一种水表抄表应用层协议的通信命令。     

嵌入式智能家居终端通信模块的设计与实现

针对嵌入式系统的存储和处理器等硬件资源受限,设计出一个简单高效的串口通信协议和网络通信协议是开发的难点.讨论了基于ARM嵌入式Linux平台实现智能家居终端通信子系统的技术难点和关键实现技术,给出了其中串口通信协议以及网络通信协议的设计与实现,很好地解决了不同带宽和速率的通信匹配问题.该通信子系统已在Linux下调试通过,可与相应串口设备以及网络中心进行正常通信,目前已投入实际使用.     

基于分布式并行处理的远程监控通信系统设计

论文针对小区泵站远程监控系统中的被控设备来源不同地区和不同的厂家,所使用的通信协议各异、通信效率较低的特点,通过对计算机监控中的协议的剖析,提取了该类型通信协议的主要特征,采用了分布式并行处理技术,在每个小区引入一个具有路由功能的通信单元,缩短了各个小区的通信时间,取得了很好的效果。文中给出了系统的设计思路,并进行加速比等效率的分析。     

一种分层式2PC协议通信算法研究

针对分布式数据库系统的分层式2PC协议提出了一种实用的通信算法——通信树算法。该算法关于结点数N所用时间为O(In(N))阶。其基本思想是给除通信源节点外的其它参与节点分配适量的通信工作，减少发送源结点的工作量，以达到缩短系统响应时间的目的文章给出了通信树的构造算法和通信时间函数，最后列出了不同结点数的几个主要通信时间参数比较数据。     

基于GPRS的车辆监控系统及数据通信可靠性研究

基于嵌入式系统、GPS、GPRS、软件架构设计等技术,对工程车辆监控系统进行设计研究,阐述系统的整体结构和模块功能。由于系统采用UDP通信协议进行数据传输和恶劣的施工环境等因素,通信过程中容易出现数据包丢失、车我终端断线等问题。为此,本文在制定数据通信协议交互机制中给出解决方案,提高了系统的可靠性和性能。     

LED实时焊接系统软件构件通信方法与设计

LED焊接系统的硬件构成复杂,采用了功能构件的思想对系统进行设计,为了保证系统的实时性要求,不同的构件之间采用了不同的通信方式,对于消息通信方式,给出了消息的分层设计结构,针对硬件通信方式,给出了硬件通信协议的设计方案;系统的最后运行能够达到性能需求.     

基于Modbus协议的加气站多机通信系统

结合加气站条件,提出采用RS-485标准总线和Modbus协议来构建加气站总线系统的方法.给出了基于RS-485的加气站现场总线系统通信结构和基于Modbus协议的通信机制、差错检测机制等.加气站Modbus协议,缩减了指令数量并扩充了指令信息量,同时建立了通信应答、信息多重验证、动态信息读取等机制.实际应用表明,基于Medbus协议的加气站现场总线系统能够很好地适应加气站现场环境,提高了加气站管理水平.     

Distributed Shared Arrays: An Integration of Message Passing and Multithreading on SMP Clusters

This paper presents a Distributed Shared Array runtime system to support Java-compliant multithreaded programming on clusters of symmetric multiprocessors (SMPs). As a hybrid of message passing and shared address space programming models, the DSA programming model allows programmers to explicitly control data distribution so as to take advantage of the deep memory hierarchy, while relieving them from error-prone orchestration of communication and synchronization at run-time. The DSA system is developed as an integral component of mobility support middleware for grid computing so that DSA-based virtual machines can be reconfigured to adapt to the varying resource supplies or demand over the course of a computation. The DSA runtime system also features a directory-based cache coherence protocol in support of replication of user-defined sharing granularity and a communication proxy mechanism for reducing network contention. We demonstrate the programmability of the model in a number of parallel applications and evaluate its performance on a cluster of SMP servers, in particular, the impact of the coherence granularity.     

OpenMP for Networks of SMPs

In this paper, we present the first system that implements OpenMP on a network of shared-memory multiprocessors. This system enables the programmer to rely on a single, standard, shared-memory API for parallelization within a multiprocessor and between multiprocessors. It is implemented via a translator that converts OpenMP directives to appropriate calls to a modified version of the TreadMarks software distributed shared-memory (SDSM) system. In contrast to previous SDSM systems for SMPs, the modified TreadMarks system uses POSIX threads for parallelism within an SMP node. This approach greatly simplifies the changes required to the SDSM in order to exploit the intranode hardware shared memory. We present performance results for seven applications (Barnes-Hut, CLU, and Water from SPLASH-2, 3D-FFT from NAS, Red-Black SOR, TSP, and MGS) running on an SP2 with four four-processor SMP nodes. A comparison between the thread implementation and the original implementation of TreadMarks shows that using the hardware shared memory within an SMP node significantly reduces the amount of data and the number of messages transmitted between nodes and consequently achieves speedups that are up to 30% better than the original versions. We also compare SDSM against message passing. Overall, the speedups of multithreaded TreadMarks programs are within 7–30% of the MPI versions.     

网络并行超级计算系统THNPSC—1

网络并行计算（也称集群式计算）是实现高性能计算的重要方式,该文介绍了一个清华大学研制的网络并行超级计算系统THNPSC－1,它是由Pentium Ⅲ SMP计算结点组成;网络互联采用两种高速网：一种是自制的具有动态仲裁与路由寻经的交叉开关网络THNet,另一种是100Mpbs的Ethernet.THNet中的交叉开关THSwitch是用15万门的ALTERA FPGA芯片构成,THNet还包括具有DMA引擎的网络适配器THNIA.THNet每一端口可以提供数据传输率为1．056Gbps,其聚合频宽可达8．4Gbps;采用固定用户缓冲和扩展的主动消息传递等法,THNet执行用户层的消息传递,旁路操作系统的系统调用,做到零拷贝的消息传递,乒乓测试结果表明：单向消息传递延迟可减少到8μs。THNetl软件包括THNIA驱动程序和支持用户层通信的函数库。此文对相关工作进行了简要对比,并说明了该系统的应用情况。     

基于最小生成树的非均匀分簇路由协议

针对无线传感器网络中利用分簇技术,簇首到Sink节点通信采用多跳路由方式容易引起"能量空洞"的问题,提出了基于最小生成树的非均匀分簇路由协议.该协议在簇首选举阶段,以节点剩余能量、节点度、节点能量消耗速度为权重计算簇首竞争等待时间,选用簇首竞争等待时间小的节点为簇首,以均衡能量;簇形成后,以剩余能量、簇间的距离和能量消耗为参数构建基于最小生成树的最优传输路径通过多跳方式将数据发送到Sink节点.仿真结果表明,该路由协议能有效均衡能耗,延长网络生命周期,延缓"能量空洞"的形成.     

基于SMP集群的混合并行编程模型研究

提出一种适用于SMP集群的混合MPI＋OpenMP并行编程模型。该模型贴近于SMP集群的体系结构且综合了消息传递和共享内存2种编程模型的优势,能获得较好的性能。讨论该混合模型的实现机制以及MPI消息传递模型的特点。实验结果表明,在一定条件下,该混合并行编程模型是SMP集群的最优选择。     

Efficient communication using message prediction for clusters of multiprocessors

With the increasing uniprocessor and symmetric multiprocessor computational power available today, interprocessor communication has become an important factor that limits the performance of clusters of workstations/multiprocessors. Many factors including communication hardware overhead, communication software overhead, and the user environment overhead (multithreading, multiuser) affect the performance of the communication subsystems in such systems. A significant portion of the software communication overhead belongs to a number of message copying operations. Ideally, it is desirable to have a true zero‐copy protocol where the message is moved directly from the send buffer in its user space to the receive buffer in the destination without any intermediate buffering. However, due to the fact that message‐passing applications at the send side do not know the final receive buffer addresses, early arrival messages have to be buffered at a temporary area. In this paper, we show that there is a message reception communication locality in message‐passing applications. We have utilized this communication locality and devised different message predictors at the receiver sides of communications. In essence, these message predictors can be efficiently used to drain the network and cache the incoming messages even if the corresponding receive calls have not yet been posted. The performance of these predictors, in terms of hit ratio, on some parallel applications are quite promising and suggest that prediction has the potential to eliminate most of the remaining message copies. We also show that the proposed predictors do not have sensitivity to the starting message reception call, and that they perform better than (or at least equal to) our previously proposed predictors. Copyright © 2002 John Wiley & Sons, Ltd.     

一种高效节能的无线传感网分簇路由协议

提出了一种高校节能的无线传感器网络分簇路由协议 ACEDG(Algorithm for Culster Establishment and Data Gathering).在该协议中,节能根据其剩余能量以及忠诚邻居节点数来竞争簇头,节点间通过信息反馈的方式经过三轮迭代形成交叠区域小的放以高效覆盖整个网络.为了进一步减小能量消耗和保证节点能量的均衡性,簇头使用数据融合将来自簇成员和其它簇头的一个或多个数据报融合成一个数据报,簇头之间以多跳方式将收集到的数据发送到指定的根簇头,然后通过根簇头将整个网络收集的数据发送到基站.仿真实验证明,ACEDG协议与其它两种早期的分放路由协议LEACH和DCHS相比,其网络寿命(第一个节点死亡)分别提高达270%和240%.     

一种优化MPI程序性能的改进方法

在分布式存储系统上,MPI已被证实是理想的并行程序设计模型。MPI是基于消息传递的并行编程模型,进程间的通信是通过调用库函数来实现的,因此MPI并行程序中,通信部分代码的效率对该并行程序的性能有直接的影响。通过用集群通信函数替代点对点通信函数以及通过派生数据类型和建立新通信域这两种方式,两次改进DNS的MPI并行程序实现,并通过实验给出一个优化MPI并行程序的一般思路与方法。     

基于预约和反馈的无线传感器网络MAC协议研究

针对无线传感器网络中对通信实时性要求较高的应用环境,引入信道预约机制和反馈机制到S-MAC协议,提出了一种低时延的RF-MAC协议。该协议在有数据需要发送时先预约信道,各节点根据预约时间表进行数据传输。采用在数据传输过程中向源节点发送反馈信息的方法,实现后续数据的提前发送。通过仿真实验表明:RF-MAC协议有效地降低了数据传输的时延,同时改善了丢包率和网络吞吐量。     

The Effect of Process Topology and Load Balancing on Parallel Programming Models for SMP Clusters and Iterative Algorithms

This article focuses on the effect of both process topology and load balancing on various programming models for SMP clusters and iterative algorithms. More specifically, we consider nested loop algorithms with constant flow dependencies, that can be parallelized on SMP clusters with the aid of the tiling transformation. We investigate three parallel programming models, namely a popular message passing monolithic parallel implementation, as well as two hybrid ones, that employ both message passing and multi-threading. We conclude that the selection of an appropriate mapping topology for the mesh of processes has a significant effect on the overall performance, and provide an algorithm for the specification of such an efficient topology according to the iteration space and data dependencies of the algorithm. We also propose static load balancing techniques for the computation distribution between threads, that diminish the disadvantage of the master thread assuming all inter-process communication due to limitations often imposed by the message passing library. Both improvements are implemented as compile-time optimizations and are further experimentally evaluated. An overall comparison of the above parallel programming styles on SMP clusters based on micro-kernel experimental evaluation is further provided, as well.