基于虫孔交换的树型多播无死锁充要条件分析

多播作为其他聚合通信的基础操作,对并行系统的性能有着重要的影响。在无死锁、无拥塞的情况下,基于虫孔交换的树型多播能够取得较高的性能和信道利用率。本文在对树型多播过程中消息依赖关系分析的基础上,给出了基于虫孔交换的树型多播无死锁的充要条件。     

多计算机互连网通信中关于死锁问题的一种理论

如何获得死锁而且通信性能良好的选路算法始终是人们十分关心的问题。本文提出了纯分流点的概念并证明了选路算法无死锁的充要条件，从理论上解决了死锁关系问题，为死锁的判定，消除和设计无死锁的算法提供了有力的依据。     

离散事件系统的无死锁模块化状态反馈控制

本文讨论离散事件系统的无死锁模块化状态反馈问题。首先我们定义自动机的交与并运算，然后通过引入自动机对的Ｄ－不变关系，我们证明当控制目标是两个谓词的交时，模块化状态反馈控制器是无死锁的充要条件是各子控制器是无死锁的且相应的控制器满足Ｄ－不变关系。我们证明了一个给定的自动机对于另一自动机的Ｄ－不变子自动机类有最大元存大，并由此给出一个综合算法。     

ASCI Option Red Supercomputer中MRC的选路问题

对Optional Red的Solit2-D网孔拓扑结构的虫孔路由问题进行了简单探讨,尤其对死锁问题和执行过程以及容错等几个突出问题进行了分析,最后给出了单一信包一到一的无死锁虫孔路由选择算法.     

不规则网络中基于拐弯模型的路由算法的设计

由虫孔路由交换器连接而成的不规则拓扑网络，越来越多地用于构建工作站机群系统（NOWs），以实现高性能价格比的并行处理．采用虫孔路由技术，网络中容易发生死锁．交换器之间连接的不规则性，使路由避免死锁问题变得更加复杂．本文给出了在不规则网络中，设计基于拐弯模型的无死锁路由算法的一般方法，并采用扩展链路方向的方法得到多种路由策略，确定了up-first与down-last两种性能较优的路由算法．最后通过模拟实验，评价了算法的性能．     

柔性制造系统中多路径条件下的死锁避免第二部分:控制策略

在第一部分推导出的面向资源的着色Ｐｅｔｒｉ的基础上讨论ＦＭＳ中多路径条件下的死锁避免控制策略问题，给出了无死锁运行的充要条件及其相应的控制策略。     

死锁的PETRI NETS模型

本文给出了操作系统(OS)的一种基于Petri网的形式化模型,由此把死锁问题转化为线性代数问题。我们得到了OS中死锁存在的充要条件,以及一种消除系统中所有的死锁、保证系统正常工作的最优化方法。特别是对于分布式OS,我们大大改进了以往的一些处理死锁的方法,最后还通过举例进行了说明。     

N-立方体消息通信时延的分析

本文利用生灭过程理论,对Ｎ－立方体的消息通信延时建立了一个计算模型,在存在消息堵塞的情况下对Ｎ－立方体采用虫孔寻径机制和ｅ－ｃｕｂｅ算法时的沙息通信延迟进行了分析求解,最后,通过模拟实验,证明了结果的正确性。     

一类并行互斥制造系统的死锁避免控制

本文用一种扩展Ｐｅｔｒｉ网，并行过程Ｐｅｔｒｉ网，对竞争使用有限资源的一类并行互斥制造系统进行建模。以此模型为基础，分析了这类制造系统中出现死锁的充要条件，并给出了避免死锁，对共享资源所采取的最大允许允馈控制策略。     

蜂窝网格的单播路由算法

六角形蜂窝网格是一种具有良好网络拓扑性质的并行多处理机互连网络.蜂窝网格在某些特性上优于二维网格.不过,这种网络不存在单信道最短路径无死锁路由算法.文中针对该网络设计了两个部分自适应无死锁虫孔路由算法.一个是基于转弯模型单信道非最短路径路由算法,另一个则是采用了虚拟双信道的最短路径路由算法.对第二个算法,还进一步使用转弯模型对其改进.通过仿真实验,结果显示这两个路由算法都具有较好的性能.     

Characterization of deadlocks in k-ary n-cube networks

A spate of deadlock avoidance-based and deadlock recovery-based routing algorithms have been proposed in recent years without full understanding of the likelihood and characteristics of actual deadlocks in interconnection networks. This work models the interrelationships between routing freedom, message blocking, correlated resource dependencies, and deadlock formation. It is empirically shown that increasing routing freedom, as achieved by allowing unrestricted routing over multiple physical and virtual channels, reduces the probability of deadlocks and the likelihood of other types of correlated message blocking that can degrade performance. Moreover, when true fully adaptive routing is used in k-ary n-cube networks with two or more virtual channels (wormhole OF virtual cut-through switched), it is empirically shown that deadlocks are virtually eliminated in networks with n⩾2. These results indicate that deadlocks are very infrequent when the network and routing algorithm inherently provide sufficient routing freedom, thus increasing the viability of deadlock recovery routing strategies     

A formal model of message blocking and deadlock resolution ininterconnection networks

This paper presents a theoretical model of resource allocations and dependencies in wormhole and virtual cut-through interconnection networks. This model allows various types of message blocking to be described precisely, including deadlock. The model distinguishes between messages involved in deadlock and those simply dependent upon deadlock, thus establishing a framework for evaluating the accuracy and correctness of deadlock detection mechanisms. The paper also identifies the necessary and sufficient conditions for the occurrence and resolution of deadlock in interconnection networks, thus providing efficiency and correctness criteria for deadlock resolution mechanisms. Theorems derived from the model are related to various routing algorithms which are based on deadlock recovery     

虚网叠加构造自适应路由算法的有效框架

大规模并行处理机系统中路由算法对互联网络通信性能和系统性起着重要作用。     

A framework for designing deadlock-free wormhole routing algorithms

This paper presents a framework to design fully-adaptive, deadlock-free wormhole algorithms for a variety of network topologies. The main theoretical contributions are: (a) design of new wormhole algorithms using store-and-forward algorithms, (b) a sufficient condition for deadlock free routing by the wormhole algorithms so designed, and (c) a sufficient condition for deadlock free routing by these wormhole algorithms with centralized flit buffers shared among multiple channels. To illustrate the theory, several wormhole algorithms based on store-and-forward hop schemes are designed. The hop-based wormhole algorithms can be applied to a variety of networks including torus, mesh, de Brujin, and a class of Cayley networks, with the best known bounds on virtual channels for minimal routing on the last two classes of networks. An analysis of the resource requirements and performances of a proposed algorithm, called negative-hop algorithm, with some of the previously proposed algorithms for torus and mesh networks is presented     

A survey of wormhole routing techniques in direct networks

Several research contributions and commercial ventures related to wormhole routing, a switching technique used in direct networks, are discussed. The properties of direct networks are reviewed, and the operation and characteristics of wormhole routing are discussed in detail. By its nature, wormhole routing is particularly susceptible to deadlock situations, in which two or more packets may block one another indefinitely. Several approaches to deadlock-free. routing, along with a technique that allows multiple virtual channels to share the same physical channel, are described. In addition, several open issues related to wormhole routing are discussed     

Compressionless routing: a framework for adaptive andfault-tolerant routing

Compressionless routing (CR) is an adaptive routing framework which provides a unified framework for efficient deadlock free adaptive routing and fault tolerance. CR exploits the tight coupling between wormhole routers for flow control to detect and recover from potential deadlock situations. Fault tolerant compressionless routing (FCR) extends CR to support end to end fault tolerant delivery. Detailed routing algorithms, implementation complexity, and performance simulation results for CR and FCR are presented. These results show that the hardware for CR and FCR networks is modest. Further, CR and FCR networks can achieve superior performance to alternatives such as dimension order routing. Compressionless routing has several key advantages: deadlock free adaptive routing in toroidal networks with no virtual channels, simple router designs, order preserving message transmission, applicability to a wide variety of network topologies, and elimination of the need for buffer allocation messages. Fault tolerant compressionless routing has several additional advantages: data integrity in the presence of transient faults (nonstop fault tolerance), permanent fault tolerance, and elimination of the need for software buffering and retry for reliability. The advantages of CR and FCR not only simplify hardware support for adaptive routing and fault tolerance, they also can simplify software communication layers     

A general theory for deadlock avoidance in wormhole-routed networks

Most machines of the last generation of distributed memory parallel computers possess specific routers which are used to exchange messages between nonneighboring nodes in the network. Among the several technologies, wormhole routing is usually preferred because it allows low channel-setup time and reduces the dependency between latency and internode distance. However, wormhole routing is very susceptible to deadlock because messages are allowed to hold many resources while requesting others. Therefore, designing deadlock-free routing algorithms using few hardware facilities is a major problem for wormhole-routed networks. In this paper, we describe a general theoretical framework for the study of deadlock-free routing functions. We give a general definition of what can be a routing function. This definition captures many specific definitions of the literature (e.g., vertex dependent, input-dependent, source-dependent, path-dependent etc.). Using our definition, we give a necessary and sufficient condition which characterizes deadlock-free routing functions. Our theory embraces, at a high level, most of the theories related to deadlock avoidance in wormhole-routed networks previously derived in the literature. In particular, it applies not only to one-to-one routing, but also to one-to-many routing. The latter paradigm is used to solve the multicast problem with the path-based or tree-based facility     

Mesh网络耐故障虫孔路由

耐故障是互连网络设计中的一个重要问题。本文提出了一种新的耐故障路由算法,并将其应用于使用虫孔交换技术的Mesh网络。由于使用了较低的路由限制,这一算法具有很强的自适应性,可以在各种不同故障域的Mesh网络中保持路由的连通性和无死锁性;由于使用了最小限度的虚拟通道,这一算法所需的缓冲器资源很少,非常适宜构建低成本的耐故障互连网络;由于根据本地故障信息进行绕行故障节点的决策,这一算法的路由决策速度较快并且易于在互连网络中实现。最后网络仿真试验显示,这一算法具有良好的平滑降级使用的性能。     

Adaptive wormhole routing in k-ary n-cubes

Distributed memory multiprocessor (DMMP) systems have gained much attention because their performance can be easily scaled up by increasing the number of processor-memory modules. The k-ary n-cube is the most popular interconnection network topology currently used in DMMPs. Wormhole routing is one of the most promising switching technology and has been used in many new generation multicomputers. Wormhole routing makes the communication latency insensitive to the network diameter and reduces the size of the channel buffer of each router. The concept of virtual channels and virtual networks are widely invented for deadlock-free design. A fully adaptive wormhole routing method for k-ary n-cubes has been proposed by Linder in 1991 [10]. Unfortunately, the need of 2^{n − 1} virtual networks makes it unreasonable. In this paper, we propose a virtual network system to support an adaptive, minimal and deadlock free routing in k-ary n-cubes. It uses only four virtual networks but can get a higher degree of adaptability and higher traffic capacity. Simulation results are presented to verify the performance.