一种新的分级扭Torus结构RTTM

针对互连网络中长方形Torus链路利用率低和负载不匀衡问题,提出了一种新的分级互连网络结构RTTM.该拓扑结构分为N级,第1级由2m×2m个节点的 Mesh拓扑结构构成,第2级到第N级由a×2a个节点的长方形扭Torus拓扑结构以递归方式连接而成.RTTM结构具有网络直径短、平均距离小以及良好的扩展性等特点.通过OPNET建模与仿真,结果表明RTTM拓扑结构链路利用率高,端到端延迟小,吞吐量大.     

The hierarchical Petersen network: a new interconnection network with fixed degree

Network cost and fixed-degree characteristic for the graph are important factors to evaluate interconnection networks. In this paper, we propose hierarchical Petersen network (HPN) that is constructed in recursive and hierarchical structure based on a Petersen graph as a basic module. The degree of HPN(n) is 5, and HPN(n) has \(10^n\) nodes and \(2.5 \times 10^n\) edges. And we analyze its basic topological properties, routing algorithm, diameter, spanning tree, broadcasting algorithm and embedding. From the analysis, we prove that the diameter and network cost of HPN(n) are \(3\log _{10}N-1\) and \(15 \log _{10}N-1\), respectively, and it contains a spanning tree with the degree of 4. In addition, we propose link-disjoint one-to-all broadcasting algorithm and show that HPN(n) can be embedded into FP\(_k\) with expansion 1, dilation 2k and congestion 4. For most of the fixed-degree networks proposed, network cost and diameter require \(O(\sqrt{N})\) and the degree of the graph requires O(N). However, HPN(n) requires O(1) for the degree and \(O(\log _{10}N)\) for both diameter and network cost. As a result, the suggested interconnection network in this paper is superior to current fixed-degree and hierarchical networks in terms of network cost, diameter and the degree of the graph.     

Limits on interconnection network performance

The latency of direct networks is modeled, taking into account both switch and wire delays. A simple closed-form expression for contention in buffered, direct networks is derived and found to agree closely with simulations. The model includes the effects of packet size and communication locality. Network analysis under various constraints and under different workload parameters reveals that performance is highly sensitive to these constraints and workloads. A two-dimensional network is shown to have the lowest latency only when switch delays and network contention are ignored; three- or four-dimensional networks are favored otherwise. If communication locality exists, two-dimensional networks regain their advantage. Communication locality decreases both the base network latency and the network bandwidth requirements of applications. It is shown that a much larger fraction of the resulting performance improvement arises from the reduction in bandwidth requirements than from the decrease in latency     

Multistage ring network: An interconnection network for large scale shared memory multiprocessors

Unidirectional ring-based networks are currently popular choices for high performance large scale shared memory multiprocessors. This class of networks is attractive for their simple hardware interfaces, high speed communication, wider data path, and easy addition of extra nodes. However, a single ring does not scale well due to the fixed bandwidth, and the hierarchical ring networks as a natural extension of a single ring show limited scalability due to their limited bandwidth near the root. In this paper we present a new interconnection network called the Multistage Ring Network (MRN). The MRN has a 2-level hierarchy of rings, and its interconnection of global rings forms a type of the multistage network. The architecture of the MRN is effective at diffusing the global traffic on the network to all global rings, and the bandwidth of the network increases proportionally with increases in the system size. Our results show that in a peak throughput, the MRN performs seven times better than the hierarchical ring network for system size of 1024.     

基三分层互连网络及其路由算法设计

从降低节点度、减少网络链路数和缩短网络直径的角度出发,提出一种新型的互连网络结构--基三分层互连网络,深入地研究了该网络的静态度量并和2-D Mesh做了相应的比较.针对基三分层互连网络提出了一种使消息沿两节点间确定路径传递的分布式确定路由算法DDRA.该算法充分利用基三分层互连网络的层次特性,不需要构建路由表,且算法实现简单,路由效率高,且易于硬件实现.     

一种用于并行计算系统的分级光环互连网络

介绍了大规模并行计算的一个新互连网络——分级光环互连,适用于多处理器与多计算机的可升级网络。分级光环互连由一个衡量无阻塞、容错的单跳可升级互连拓扑组成,并通过波分多址技术充分地利用了光纤的TeraHz带宽。此光网络融合了分级环的互连节点接口简单、节点度恒定、容错等各种吸引人的特征以及光通信的各种优点。提出了分级光环互连拓扑,分析了其结构特征并描述了光设计的方法,导出了一个简短可行的分级光环互连研究。     

Uniform load sharing on a hierarchical content delivery network interconnection model

Content management system (CMS) is an infrastructure for efficient distribution, organization, and delivery of digital content. It is desirable that the content must be successfully delivered regardless of the end users location or attachment network. For the end to end delivery of content, a virtual open content delivery infrastructure is formed by interconnecting several CDNs. In this paper, we focus on content delivery network interconnection. An efficient and suitable to implement hierarchical CDNI architecture, named as HCDNI, is proposed to reduce the limitations of CDNIs. Next, a content distribution and redistribution scheme is proposed so that the searching time and the round trip time for the content delivery can be minimized. Next, we find a reliable and fault tolerant scheme for web server replica placement and content caching. Finally, analysis and simulation studies show that proposed algorithm results in a significant improvement in terms of data routing, path selection, content distribution and redistribution, load balancing and network scalability.     

一种改善BP神经网络性能的方法研究

BP神经网络目前被广泛应用,但是其收敛速度慢、预测精度不高的缺点却一直被人所诟病,因此,在传统BP神经网络中使用附加动量项法以及动态学习速率法,并以两者的融合为基础提出了陡峭因子可调激活函数法来改进BP神经网络。以非线性函数拟合为实例,从收敛速度和预测精度两方面对比分析两种方法,实验证明所提出的改进方法明显提高BP神经网络的收敛速度以及精度。     

CGIN: a fault tolerant modified Gamma interconnection network

To improve the terminal reliability of the Gamma interconnection network (GIN), we consider altering its connecting patterns between stages to attain multiple disjoint paths between any source and destination pair. The new modified GIN, referred to as a CGIN with connecting patterns between stages exhibiting a cyclic feature, is able to tolerate any arbitrary single fault and to lift up terminal reliability accordingly. If several rows of switching elements are fabricated in one chip using the VLSI technology, a CGIN could lead to reduced cost because the pin count per chip decreases and the layout area taken by connections shrinks. To make routing and rerouting in the CGIN more efficient and simpler to implement, destination tag routing and rerouting is also provided     

Gemini: an optical interconnection network for parallel processing

The Gemini interconnect is a dual technology (optical and electrical) interconnection network designed for use in tightly-coupled multicomputer systems. It consists of a circuit-switched optical data path in parallel with a packet-switched electrical control/data path. The optical path is used for transmission of long data messages and the electrical path is used for switch control and transmission of short data messages. The paper describes the architecture of the interconnection network and related communications protocols. Fairness issues associated with network operation are addressed and a discrete-event simulation model of the entire system is described. Network performance characteristics derived from the simulation model are presented. The results show significant performance benefits when using virtual output queuing and quantify the tradeoffs between throughput and fairness in the system     

随机网络的连通率研究

随机图是一种简单并且可用于抽象现实社会多种实际系统的网络。与其他网络模型不同,随机图的构造方式决定其节点具有对等性,且网络中可能存在孤立节点和子图。对随机图尤其是其连通性的研究有助于更深入地了解具有随机连接特性及节点对等特性的真实网络。文章采用理论与仿真相结合的方法,重点研究随机图的连通性和随机图连通率的计算方法,揭示了随机图在演化过程中的形态变化,表明随机图中树结构的广泛存在。研究还发现,在巨大连通子图形成前,随机图的子图大小呈幂律分布。本研究结果为复杂网络相关的实证研究和性质复杂的网络相变态研究提供了理论依据。     

机会网络中一种提高TCP性能的跨层改进算法

针对机会网络中TCP与传染路由结合时,传染路由的"洪泛"特性和机会网络的间断特性会使得TCP性能变差的问题,提出了一种基于传染路由协议和TCP/Reno协议的跨层改进算法——ACK-EPI.该算法对连接开始阶段的慢开始门限值进行修改,以避免因网络错误进入拥塞避免阶段而导致拥塞窗口增长速度过于缓慢.同时,为了避免网络中已经成功交付但仍存储在网络中其他节点的数据包的复本继续在网络中存在并扩散,造成网络资源浪费,算法还利用ACK作为到达通告来删除这些冗余数据包.通过深入的仿真分析和比较,结果表明ACK-EPI算法能明显改善TCP性能.     

Algebraic specification of interconnection network relationships by permutation voltage graph mappings

Symmetries of large networks are used to simplify the specification of a guest-host network relationship. The relevant kinds of symmetries occur not only in Cayley graphs and in group-action graphs, but elsewhere as well. In brief, the critical topological symmetry property of a guest or host is that it is algebraically specifiable as a covering space of a smaller graph. A first objective is to understand the circumstances under which a mapping (a.k.a. “embedding”) between two base graphs can be lifted topologically to a mapping between their respective coverings. A suitable assignment of algebraic elements called “permutation voltages” to a base graph for the intended host network facilitates the construction not only of the intended host, but also of the intended guest and of the intended mapping of the guest into the host. Explicit formulas are derived for measurement of the load, of the congestion, and of the dilation of the lifted mapping. A concluding example suggests how these new formulas open the opportunity to develop optimization methods for algebraically specified guest-host mappings. The first author was partially supported by ONR Contract N00014-85-0768, and the second author was partially supported by NSF Grant CCR-9110824.     

On the performance of multicomputer interconnection networks

Several researchers have analysed the performance of k-ary n-cubes taking into account channel bandwidth constraints imposed by implementation technology, namely the constant wiring density and pin-out constraints for VLSI and multiple-chip technology respectively. For instance, Dally [IEEE Trans. Comput. 39(6) (1990) 775], Abraham [Issues in the architecture of direct interconnection networks schemes for multiprocessors, Ph.D. thesis, University of Illinois at Urbana-Champaign, 1992], and Agrawal [IEEE Trans. Parallel Distributed Syst. 2(4) (1991) 398] have shown that low-dimensional k-ary n-cubes (known as tori) outperform their high-dimensional counterparts (known as hypercubes) under the constant wiring density constraint. However, Abraham and Agrawal have arrived at an opposite conclusion when they considered the constant pin-out constraint. Most of these analyses have assumed deterministic routing, where a message always uses the same network path between a given pair of nodes. More recent multicomputers have incorporated adaptive routing to improve performance. This paper re-examines the relative performance merits of the torus and hypercube in the context of adaptive routing. Our analysis reveals that the torus manages to exploit its wider channels under light traffic. As traffic increases, however, the hypercube can provide better performance than the torus. Our conclusion under the constant wiring density constraint is different from that of the works mentioned above because adaptive routing enables the hypercube to exploit its richer connectivity to reduce message blocking.     

Topological properties of the Extended OTIS-n-Cube interconnection network

We have recently introduced the Extended OTIS-n-Cube to overcome the weakness of some limitations found in the well-known OTIS-n-Cube such as the degree and the diameter. This paper investigates the topological properties of the new interconnection network by proposing an extensive study on some attractive topological properties of the extended OTIS-n-Cube interconnection network. Inspired by the attractive features of the new network, such as regular degree, small diameter, and semantic structure, we present a theoretical study on some topological properties of the Extended OTIS-n-Cube including routing paths and embedded cycles. Furthermore, the paper presents a performance evaluation on the topology by comparing it with the OTIS-n-Cube. Results prove the superiority of the new topology especially in minimizing routing distances.     

Communication aspects of the star graph interconnection network

Basic communication algorithms for star graph interconnection networks are developed by using the hierarchical properties of the star graph, with the assumption that one input channel can drive only one output communication channel at a time. With this constraint, communication algorithms for each node can be expressed only as sequences of generators corresponding to the communication channels. Sequences that are identical exploit the symmetry and hierarchical properties of the star graph and can be easily integrated in communication hardware. Their time complexities are evaluated and compared with the corresponding results for the hypercube     

Design of 4-disjoint gamma interconnection network layouts and reliability analysis of gamma interconnection Networks

Multistage interconnection networks (MINs) are widely used for reliable data communication in a tightly coupled large-scale multiprocessor system. High reliability of MINs can be achieved using fault tolerance techniques. The fault tolerance is generally achieved by disjoint paths available through multiple connectivity options. The gamma interconnection network (GIN) is a class of fault tolerant MINs providing alternate paths for source–destination node pairs. Various 2-disjoint and 3-disjoint GIN architectures have been presented in the literature. In this paper, two new designs of 4-disjoint paths multistage interconnection networks, called 4-disjoint gamma interconnection networks (4DGIN-1 and 4DGIN-2) are proposed. The proposed 4DGINs provide four disjoint paths for each source–destination pair and can tolerate three switches/link failures in intermediate interconnection layers. Proposed designs are highly reliable GIN with higher fault-tolerant capability than other gamma networks at low cost. Terminal pair reliabilities of proposed designs and various other 2-disjoint and 3-disjoint GINs are evaluated, analyzed and compared. Reliability values of proposed designs are found higher.     

微机网络环境下提高PVM并行程序性能的策略

网络并行计算是并行计算与分布式计算技术非常重要的发展方向之一,结合具体的数值试验,探讨了Windows操作系统下基于PVM的网络并行数值计算中影响PVM并行程序性能的几个重要因素,包括负载平衡、通信开销、网络性能、任务粒度、处理机个数、精度要求及处理机内存容量问题等,并提出了提高PVM并行程序性能的相应策略,以高效快速地实现问题的求解.     

VoiceMarks: restructuring hierarchical voice menus for improving navigation

Interactive Voice Response (IVR) systems, or touch-tone telephony interfaces, are nowadays a common medium of interaction between organizations or companies and their customers, allowing users to access or enter specific company-based information. These telephony interfaces typically involve the use of hierarchically structured voice menus, through which a user has to navigate in order to locate a specific desired menu item. This navigation process is often inefficient and time-consuming, leaving users at times frustrated and annoyed. In this paper, we describe the foundation of VoiceMarks, a system designed to improve the ease and efficiency of navigation in menu-based voice interfaces. The system features personalized menus through the use of voicemarks, in a process similar to bookmarking, but adapted to voice interfaces. VoiceMarks are essentially bookmarked nodes in the voice menu hierarchy, which are stored for the respective user in a directly accessible, personal menu. We developed and tested VoiceMarks interfaces for two applications: a bus schedule information system and a cinema ticket purchase system. A comparative study of VoiceMarks and traditional interfaces of these applications showed that VoiceMarks can significantly improve the interaction between users and systems, in terms of time and number of keystrokes needed to locate a menu item, as well as regarding user satisfaction. In general, users responded very positively to the VoiceMarks interface. In addition, the study pointed to some useful modifications of VoiceMarks, which should be considered before employing the system in a commercial setting.