开销敏感的多处理器最优节能实时调度算法

嵌入式多处理器系统的能耗问题变得日益重要,如何减少能耗同时满足实时约束成为多处理器系统节能实时调度中的一个重要问题.目前绝大多数研究基于关键速度降低处理器的频率以减少动态能耗,采用关闭处理器的方法减少静态能耗.虽然这种方法可以实现节能,但是不能保证最小化能耗.而现有最优的节能实时调度未考虑处理器状态切换的时间和能量开销,因此在切换开销不可忽视的实际平台中不再是最优的.文中针对具有独立动态电压频率调节和动态功耗管理功能的多处理器系统,考虑处理器切换开销,提出一种基于帧任务模型的最优节能实时调度算法.该算法根据关键速度来判断系统负载情况,确定具有最低能耗值的活跃处理器个数,然后根据状态切换开销来确定最优调度序列.该算法允许实时任务在处理器之间任意迁移,计算复杂度小,易于实现.数学分析证明了该算法的最优性.     

基于ARM小波复合判据的小电流接地系统故障选线的研究与设计

针对小电流接地系统单相接地故障选线准确度低的难题,分析故障时电压、电流的信号特征,提出采用复合判据的故障选线方案,从而提高故障选线的准确度.本文设计了一种基于ARM的嵌入式高速数据采集及复合判据选线算法的故障选线系统,该系统以LPC2138微处理器为核心,利用硬件同步与软件纠错相结合的方法实现电网故障模拟量信号的采集与处理;该系统可通过RS-422总线与主CPU通信完成数据的存储、传输与处理;也可通过本地人机交互接口对系统进行维护和升级.     

面向容错计算机的仲裁系统的设计与实现*

为了解决传统仲裁机制故障覆盖率和故障诊断成功率低的问题,针对容错计算机,提出了一种基于仲裁处理器的仲裁机制,并设计了仲裁系统和仲裁算法.其中仲裁处理器使用三模冗余系统和芯片级的容错设计技术,仲裁算法采用分级方式,同时采用自检测和心跳监测相结合的故障监测机制,有效地解决了单点故障和检测成功率低的问题.最后通过故障注入方式验证了仲裁系统的可用性.     

同构DVS集群中基于自适应阈值的并行任务节能调度算法

目前,高能效的并行任务调度算法设计已经成为集群系统的研究热点.现有基于复制的节能调度算法主要利用阈值平衡系统的性能和能耗,但随机设置的阈值无法根据性能需求和环境参数等特征自动调节,导致调度算法存在一定的局限性.文中提出一种面向同构集群系统的两阶段节能调度算法ATES(Adaptive Threshold-based Energy-efficient Scheduling).首先,设计一种基于自适应阈值的任务复制策略,该策略能够自动计算最佳阈值,利用该阈值获取近似最优的任务分组.然后,将各分组任务调度到支持DVS的处理器上,并充分利用任务之间的空闲时间降低处理器电压.该算法将任务复制策略与电压调节技术有机结合,在调度过程中能够自动调整阈值,有效提高调度算法的能效.为了验证ATES算法的合理性,通过典型应用进行仿真实验,并与常见任务调度算法进行比较,结果表明ATES算法能够更好地实现性能和能耗之间的平衡.     

面向高可靠片上网络通信的可重构路由算法

为了满足系统芯片对通信带宽的要求,片上网络正逐渐取代总线成为当前多核及众核系统的主流互连方案,然而由于芯片特征尺寸的不断减小,芯片内发生故障的概率显著增加.为了提供可靠的片上通信,提出一种低成本的可重构路由算法.该算法基于无共享边界的矩形故障模型,按照故障区与网络边界的相对位置对故障区进行分类;针对不同类型的故障区定义了具体的路由器状态更新策略;重构后的片上网络可以容忍任意数目、任意分布的路由器以及链路故障.与当前容错设计方案不同,文中算法不需要增加虚拟通道来保证网络的无死锁特性,因此具有低成本、高可靠的特性.仿真实验结果表明,文中算法适用于处理器与缓存,或缓存与缓存之间的片上通信.     

基于流处理器的图像灰度变换并行处理研究

提出了一种基于流处理器的图像灰度变换并行处理系统.该系统采用Strom-1 系列SP16HP-G220流数字信号处理器构建硬件平台,根据流处理器体系结构特点建立了适应图像灰度变换并行处理的流程序模型,并对图像灰度变换进行算法并行性分析与算法流化.对利用流化过的算法与传统灰度变换算法进行了对比实验.实验结果表明,灰度变换...     

容错处理器阵列的并行重构及VHDL实现

网格连接的处理器阵列是一种应用广泛的高性能体系结构,而容错处理器阵列的重构技术是近年来的研究热点之一.现有的研究多数集中在串行重构算法上,忽视了该结构重构时内在的可并行性.本文根据阵列结构的特点设计了一种基于VHDL语言的重构算法,该算法从第一行的各个无故障处理器单元同时向下选路,具有潜在的并行性,.实验结果表明,与现有的串行算法相比,本文提出的并行算法同样能够生成最大规模的目标阵列并且当物理阵列大小为48×48,本文提出的并行算法加速重构将近20倍.     

一种面向非对称多核处理器的虚拟机集成调度算法

在计算机体系结构领域,非对称多核处理器将成为未来的主流.对于非对称多核处理器上的虚拟处理器调度问题,现有研究缺乏理论分析,且没有考虑虚拟处理器的同步特性.针对该问题,文中首先建立非线性规划模型,分析得出全面考虑虚拟处理器同步特性、核心非对称性以及核心负载的调度原则.然后,基于调度原则提出一个集成调度算法,该算法定义了效用因子、比例系数、比例资源的概念,结合虚拟处理器的同步特性和核心的非对称性对资源和负载进行全面度量;同时通过运行队列分解降低调度开销.提出的算法是第一个在非对称多核处理器上利用虚拟处理器同步特性的调度算法.实际平台上的实验表明:该算法实现了公平调度,并且性能比其他同类算法提高19%~48%.     

一种实时异构嵌入式系统的任务调度算法

异构分布式系统已被广泛应用在实时嵌入式系统中,而调度算法是在进行嵌入式系统综合时,确保系统实现性能目标的一个关键问题,这是一个NP-完全问题.现有的算法主要是启发式算法,性能还有待提高.提出了一个异构分布式系统的动态BLevel优先(dynamic BLevel first,简称DBLF)算法,算法选择就绪任务中动态BLevel值最大的任务进行调度,用插入法为任务分配处理器,遵循以下3个插入原则:满足任务先后顺序关系;任务的最早完成时间(earliest-finish-time,简称EFT)最小;在EFT相等时,优先分配到利用率较低的处理器上.与现有算法比较可以看出,DBLF算法可以有效降低调度长度.     

异构分布式系统中实时周期任务的容错调度算法

提出一个基于抢占性实时周期任务的可靠性调度模型,该模型与现有可靠性模型相比充分考虑了单处理机故障容错情况下的系统可靠性,因而更加接近现实和精确.在此基础上,提出一个基于异构分布式系统的实时容错调度算法IRDFTAHS,IRDFTAHS算法以提高系统的可靠性为目标来进行任务的分配,从而在不增加硬件代价的前提条件下通过调度增加了系统的可靠性.该算法同时支持主动和被动两种方式的副版本,使得容错调度算法具有更大的灵活性.最后,通过仿真实验对IRDFTAHS和现有的调度算法在几个方面进行比较.实验结果表明,IRDFTAHS算法的综合性能优于现有算法.     

基于非完备性测试的一种分布式计算机系统诊断算法的设计

利用现有的商用并行、分布式计算机系统本身所固有的冗余可以实现低成本的容错。为了提高整个分布式计算机系统的可靠性,将系统中的故障结点与正确结点隔离至关重要。文章提出了一个有效的分布式系统级故障诊断算法：在利用系统中各结点机有限的故障检测能力的基础上,将所有的故障结点从系统中隔离,并测试了该算法对系统性能的影响。     

基于PMC故障模型的NASD诊断算法

在PMC故障模型下,现有的自适应顺序诊断算法（ASD算法）不能充分利用所有的测试结果。为了有效地减少测试次数,提高诊断效率,提出一种新的自适应顺序诊断算法（NASD算法）。引入相对故障单元的概念,给出并证明了故障单元和无故障单元的判别定理。据此给出系统诊断的策略：（1）边寻求无故障单元边确诊故障单元;（2）已确认的故障单元不再参与任何测试;（3）找到无故障单元或故障单元数接近一半时,系统诊断结束。实例表明,NASD算法优于其他ASD算法。     

An evolutionary algorithm for generalized comparison-based self-diagnosis of multiprocessor systems

In this article, we consider the problem of self-diagnosis of multiprocessor and multicomputer systems under the generalized comparison model. In this approach, a system consists of a collection n independent heterogeneous processors (or units) interconnected via point-to-point communication links, and it is assumed that at most t of these processors are permanently faulty. For the purpose of diagnosis, system tasks are assigned to pairs of processors and the results are compared. The agreements and disagreements among units are the basis for identifying faulty processors. Such a system is said to be t-diagnosable if, given any complete collection of comparison results, the set of faulty processors can be unambiguously identified. We present an efficient fault identification method based on genetic algorithms. Analysis and simulations are provided, first, to evaluate the genetic parameters of the diagnosis algorithm; second, to show the efficiency of the genetic approach. The new strategy is shown to correctly identify the set of faulty processors, making it an attractive and viable addition or alternative to present fault diagnosis techniques.     

The conditional diagnosability of crossed cubes under the comparison model

The growing size of the multiprocessor systems increases their vulnerability to component failures. It is crucial to locate and replace the faulty processors to maintain the system's high reliability. The fault diagnosis is the process of identifying faulty processors in a system through testing. The conditional diagnosis requires that for each processor v in a system, all the processors that are directly connected to v do not fail simultaneously. In this paper, we show that the conditional diagnosability of the crossed cubes CQ _n under the comparison diagnosis model is 3n?5 when n≥7. Hence, the conditional diagnosability of CQ _n is three times larger than its classical diagnosability.     

A (4n − 9)/3 diagnosis algorithm on n-dimensional cube network

As a generalization of the precise and pessimistic diagnosis strategies of system-level diagnosis of multicomputers, the t/k diagnosis strategy can significantly improve the self-diagnosing capability of a system at the expense of no more than k fault-free processors (nodes) being mistakenly diagnosed as faulty. In the case k ? 2, to our knowledge, there is no known t/k diagnosis algorithm for general diagnosable system or for any specific system. Hypercube is a popular topology for interconnecting processors of multicomputers. It is known that an n-dimensional cube is (4n − 9)/3-diagnosable. This paper addresses the (4n − 9)/3 diagnosis of n-dimensional cube. By exploring the relationship between a largest connected component of the 0-test subgraph of a faulty hypercube and the distribution of the faulty nodes over the network, the fault diagnosis of an n-dimensional cube can be reduced to those of two constituent (n − 1)-dimensional cubes. On this basis, a diagnosis algorithm is presented. Given that there are no more than 4n − 9 faulty nodes, this algorithm can isolate all faulty nodes to within a set in which at most three nodes are fault-free. The proposed algorithm can operate in O(N log₂ N) time, where N = 2ⁿ is the total number of nodes of the hypercube. The work of this paper provides insight into developing efficient t/k diagnosis algorithms for larger k value and for other types of interconnection networks.     

DRD—基于诊断的高可靠分布式计算机系统的设计

提出了一种基于Fail-silent节点故障行为的高可靠分布式计算机系统,提出了减少上述系统节点故障检测延迟的两条有效途径,利用单机有限的故障检测能力和增加任务特征状态比较,利用节点故障的诊断技术,将系统中的故障节点与正确节点隔离,通过节点故障恢复和系统重构,以提高整个系统的可靠性。     

The incremental agreement

To achieve reliable distributed systems, the fault-tolerance must be studied. One of the most important problems of fault-tolerance issues lies in the Byzantine Agreement (BA) problem. The primary issue surrounding BA is that fault-free processors must obtain common agreement even in cases where faults persist. In this field, the fault diagnosis protocol has been proposed so that each fault-free processor detects/locates a common set of faulty processors. However, in this study, the incremental agreement is invoked to make each processor able to agreement upon executing the fault diagnosis protocol using minimal rounds of message exchange in the presence of dual failure characteristics of processors.     

Distributed computing on oriented anonymous hypercubes with faulty components

We give efficient algorithms for distributed computation on oriented, anonymous, asynchronous hypercubes with possible faulty components (i.e. processors and links) and deterministic processors. Initially, the processors know only the size of the network and that they are inter-connected in a hypercube topology. Faults may occur only before the start of the computation (and that despite this the hypercube remains a connected network). However, the processors do not know where these faults are located. As a measure of complexity we use the total number of bits transmitted during the execution of the algorithm and we concentrate on giving algorithms that will minimize this number of bits. The main result of this paper is an algorithm for computing Boolean functions on anonymous hypercubes with bit cost , where is the number of faulty components (i.e. links plus processors), is the number of links which are either faulty, or non-faulty but adjacent to faulty processors, and is the diameter of the hypercube with faulty components. Received: October 1992 / Accepted: April 2001     

Optimal asynchronous agreement and leader election algorithm for complete networks with Byzantine faulty links

Summary.  We consider agreement and leader election on asynchronous complete networks when the processors are reliable, but some of the channels are subject to failure. Fischer, Lynch, and Paterson have already shown that no deterministic algorithm can solve the agreement problem on asynchronous networks if any processor fails during the execution of the algorithm. Therefore, we consider only channel failures. The type of channel failure we consider in this paper is Byzantine failure, that is, channels fail by altering messages, sending false information, forging messages, losing messages at will, and so on. There are no restrictions on the behavior of a faulty channel. Therefore, a faulty channel may act as an adversary who forges messages on purpose to prevent the successful completion of the algorithm. Because we assume an asynchronous network, the channel delays are arbitrary. Thus, the faulty channels may not be detectable unless, for example, the faulty channels cause garbage to be sent. We present the first known agreement and leader election algorithm for asynchronous complete networks in which the processors are reliable but some channels may be Byzantine faulty. The algorithm can tolerate up to [n−22] faulty channels, where n is the number of processors in the network. We show that the bound on the number of faulty channels is optimal. When the processors terminate their corresponding algorithms, all the processors in the network will have the same correct vector, where the vector contains the private values of all the processors. Received: May 1994/Accepted: July 1995     

Minimum Assignment of Test Links for Hypercubes with Lower Fault Bounds

In ann-dimensional hypercube multiprocessor system, to correctly diagnose faulty processors among themselves, the maximum allowed number of faulty processors isnunder the well-known PMC diagnostic model. When thenfault bound is adopted, all links between processors will be used in the diagnosis. However, if the fault bound is lower thann, many links can be freed from the task of performing diagnosis. In this paper, we show that each drop of the fault bound by 1 will free 2^n-1links from diagnosis. We will present an algorithm that selects, in a symmetric manner, the to-be-freed links, so that only a minimum number of links will be used to perform diagnosis. A rigorous proof for the algorithm's correctness is given. The freed links will never be used for the purpose of diagnosis, so that the diagnosis and some conventional computations may be carried out simultaneously, improving the performance of the system as a whole.