我线互连网中的归约通讯

归约通讯作为聚合通讯中一类，是实现数值计算、进程控制的重要手段，以并行处理中的应用很广泛。由于归约通讯中的多个源结点主动地发送消息因此它具有与ｍｕｌｔｉｃａｓｔ通讯迥然不同的特为特点。此文即在对韶约通讯的行为特点和通讯过程的分析基础上，结合作者于［６］中提出的ＳＢＭＴ广播算法，提出了针对归约通讯的ＲＳＢＴ路由算法，并进一步作出了性能分析。     

BFGS算法在多Transputer系统上的并行实现

本文讨论了ＢＦＧＳ算法在多Ｔｒａｎｓｐｕｔｅｒ系统上的并行实现问题，利用向量和矩阵分解并充分考虑到多Ｔｒａｎｓｐｕｔｅｒ系统的硬件特点，构造了一个负载平衡度高，通讯量小的并行ＢＦＧＳ算法。     

巧用VB的Byte型变量实现与单片机通讯

本文分析ＶｉｓｕａｌＢＡＳＩＣ串行通讯控件的特点，提出利用ＡｓｃＢ（）函数的Ｂｙｔｅ型变量处理通讯数据，消除了Ｓｔｒｉｎｇ型变量只能处理ＡＳＣⅡ码为００Ｈ－７ＦＨ的变本字符的缺陷，真正实现Ｗｉｎｄｏｗｓ环境下ＰＣ机与单片机的通讯。     

TMS320C25与IBM—PC机的串行通讯

本文介绍了高数字信号处理（ＤＳＰ）芯片ＴＭ３２０Ｃ２５与ＩＢＭ－ＰＣ机进行串行通讯的实现方法，文中对ＴＭＳ３２０Ｃ２５的串行通讯接口电路和通讯程序作了论述。     

抽象算法C—T—ABS和ABSTRACT的理论推导与等价性证明

ＡＢＳＴＲＡＣＴ，Ｃ－Ｔ－ＡＢＳ是把λ表达式转换成ＳＫＩ表达式的抽象算法，是函数式语言实现的理论基础。本文从λ演算，ＳＫＩ演算的基本理论出发，对这两个算法进行了理论推导及功能的等价证明。展示了对一输入，Ｃ－Ｔ－ＡＢＳ能生成较优化的代码，并对它们生成代码的长度及归约效率进行了比较。     

一种Nehalem平台上的MPI多级分段归约算法

基于线程MPI环境提出一种适用于Nehalem平台长消息归约的多级分段归约算法(HSRA).HSRA考虑了Nehalem系统的体系结构特点,分处理器内归约和处理器外归约两个步骤实施节点内归约通信,在均匀分布计算负载的前提下仅需要较少的远端内存访问.首先在MPIActor的归约算法框架中设计、实现了HSRA算法,从访存角度分析了HSRA算法的开销,然后与单级分段和已有的另外三种节点内基于共享内存的归约算法进行比较;最后在真实系统上通过IMB(Intel MPI Benchmark)验证算法,实验结果表明,该算法是一种适用于在Nehalem系统中处理长消息节点内归约的高效算法.     

多媒体技术与通信系统──AT＆T国际商业通讯系统部及其产品介绍

多媒体技术与通信系统──ＡＴ＆Ｔ国际商业通讯系统部及其产品介绍ＧＢＣＳ（ＧｌｏｂａｌＢｕｓｉｎｅｓｓＣｏｍｍｕｎｉｃａｔｉｏｎｓＳｙｓ－ｔｅｍｓ），即ＡＴ＆Ｔ国际商业通讯系统部，它负责开发、生产和销售世界最先进的商业通讯系统，产品以商业电话系统、语音...     

适用于IDS中数据分类的数值归约算法*

以提高IDS中数据分类效率为目标,分析了IDS中被检测数据的特点,设计了一种适用于IDS中数据分类的数值归约算法（NRAADCI）。该算法一方面用值域来减少特征值数目,另一方面将孤立的点放大为一个区域以预测类似行为。最后以决策树分类算法为例,通过实验验证了该数值归约算法的有效性。实验结果表明,该算法在降低已有分类算法的时间复杂度的同时使分类准确率有所提升。     

实现PC机与多台单片机实时通讯的新方法

本文根据实际应用系统，介绍了一种ＩＢＭ－ＰＣ微机与ＭＣＳ－５１单片机多机系统实时通讯的新方法，并用ＴＵ ＲＢＯＣ语言编程实现，详细讨论了通讯的实现原理及软件设计思想。     

VB通讯数据局限性的分析与对策

分析了ＶＢ串行通讯控件的特点,提出利用ＡｓｃＢ（）函数和Ｂｙｔｅ型变量处理通讯数据,消除了使用Ｓｔｒｉｎｇ型变量只能处理ＡＳＣＩＩ码为ＯＯＨ－７ＦＨ的文本字符的缺陷,真正实现Ｗｉｎｄｏｗｓ环境下ＰＣ机与单片机的通讯。     

Optimal software multicast in wormhole-routed multistage networks

Multistage interconnection networks are a popular class of interconnection architecture for constructing scalable parallel computers (SPCs). The focus of this paper is on the multistage network system which supports wormhole routed turnaround routing. Existing machines characterized by such a system model include the IBM SP-1 and SP-2, TMC CM-5, and Meiko CS-2. Efficient collective communication among processor nodes is critical to the performance of SPCs. A system-level multicast service, in which the same message is delivered from a source node to an arbitrary number of destination nodes, is fundamental in supporting collective communication primitives including the application-level broadcast, reduction, and barrier synchronization. This paper addresses how to efficiently implement multicast services in wormhole-routed multistage networks, in the absence of hardware multicast support, by exploiting the properties of the turnaround switching technology. An optimal multicast algorithm is proposed. The results of implementations on a 64-node SP-1 show that the proposed algorithm significantly outperforms the application-level broadcast primitives provided by currently existing collective communication libraries including the public domain MPI     

TTPM – An efficient deadlock-free algorithm for multicast communication in 2D torus networks

A torus network has become increasingly important to multicomputer design because of its many features including scalability, low bandwidth and fixed degree of nodes. A multicast communication is a significant operation in multicomputer systems and can be used to support several other collective communication operations. This paper presents an efficient algorithm, TTPM, to find a deadlock-free multicast wormhole routing in two-dimensional torus parallel machines. The introduced algorithm is designed such that messages can be sent to any number of destinations within two start-up communication phases; hence the name Torus Two Phase Multicast (TTPM) algorithm. An efficient routing function is developed and used as a basis for the introduced algorithm. Also, TTPM allows some intermediate nodes that are not in the destination set to perform multicast functions. This feature allows flexibility in multicast path selection and therefore improves the performance. Performance results of a simulation study on torus networks are discussed to compare TTPM algorithm with a previous algorithm.     

Turn Grouping for Multicast in Wormhole-Routed Mesh Networks Supporting the Turn Model

Multicast is an important collective communication in scalable parallel computers. One efficient scheme to perform multicast is multidestination messaging[8]. In multidestination messaging, destination nodes of a multicast are partitioned into disjoint groups. Nodes in each group are reached with a multidestination message that conforms to the base routing algorithm of the system. A systematic way of partitioning the nodes is critical to the efficiency of multidestination messaging. In this paper we propose a node grouping method, called turn grouping, for partitioning the destination nodes in a multicast. Turn grouping is general in the sense that it supports any base routing algorithm derivable from the turn model [5]. Given such a base routing algorithm and the corresponding prohibited turns, turn grouping can systematically produce a proper schedule for multicasting the message. We evaluated the performance of turn grouping using three typical turn model-based routing algorithms. The simulation results show that our approach performs better than the Umesh [12] and the Hamiltonian-path [8] algorithms.     

Efficient and Scalable Hardware-Based Multicast in Fat-Tree Networks

This article presents an efficient and scalable mechanism to overcome the limitations of collective communication in switched interconnection networks in the presence of faults. Considering that current trends in supercomputing are moving toward massively parallel computers, with many thousands of components, reliability becomes a challenge. In such scenario, fat-tree networks that provide hardware support for collective communication suffer from serious performance degradation due to the presence of, even, a single faulty node. This paper describes a new mechanism to provide high-performance collective communication in such situations. The feasibility of the proposed technique is formally demonstrated. We present the design of a new hardware-based routing algorithm for multicast, that is at the base of our proposal. The proposed mechanism is implemented and experimentally evaluated. Our experimental results show that hardware-based multicast trees provide an efficient and scalable solution for collective communication in fat-tree networks, significantly outperforming traditional solutions.     

Multicast communication in wormhole-routed 2D torus networks with hamiltonian cycle model

In this paper, we propose an efficient multipath multicast routing algorithm in wormhole-routed 2D torus networks. We first introduce a hamiltonian cycle model for exploiting the feature of torus networks. Based on this model, we find a hamiltonian cycle in torus networks. Then, an efficient multipath multicast routing algorithm with hamiltonian cycle model (mulitpath-HCM) is presented. The proposed multipath multicast routing algorithm utilizes communication channels more uniformly in order to reduce the path length of the routing messages, making the multicasting more efficient. Simulation results show that the multicast latency of the proposed multipath-HCM routing algorithm is superior to that of fixed and dual-path routing algorithms.     

二维环网中基于自适应维度气泡路由的组播算法

介绍了一种称为二维环网维度气泡组播路由(2DTDBMR)的新型算法.基于在一套网络中,采用相同的路由策略支持报文的单播操作和组播操作的思想,在二维环网中,基于TADBR自适应路由,设计实现了2DTDBMR组播算法.该组播算法在路由器中实现了多目标路由以及报文复制,而且算法是无死锁的.通过对二维环网中报文所有可能的路由情况进行分析发现当采用2DTDBMR组播算法时,报文最终都可以到达目标点.最后,在自行设计的模拟工具RingNetSim上实现了2DTDBMR组播算法.在RingNetSim上分析了2DTDBMR算法的性能,结果显示环网维度气泡组播算法的性能优异.     

一种改进负载均衡的网络编码多播路由算法

已有研究证明,在多播网络中使用网络编码可以显著提高多播通信的性能。总结了网络编码多播理论的研究进展,同时对网络编码多播路由问题进行了研究与分析。考虑到影响链路负载和资源消耗的因素,提出了一种改进链路负载均衡的网络编码多播路由算法,优化了路径间链路的共享。通过使用常见的Waxman网络拓扑模型,产生随机网络拓扑。在这些拓扑中,分别针对传统IP多播路由、低速率网络下的网络编码多播路由以及提出的路由算法进行性能仿真。仿真结果表明,与其他两种路由算法相比,该算法在可达吞吐量、资源消耗和负载均衡等性能上均有很好的表现。     

动态优化的分布式组播路由算法

为了在真实的网络环境中寻找一棵延迟受限、耗费最小的组播转发树,以便更好地支持组播通信,提出了一个可以动态优化的分布式组播路由算法,该算法利用蚁群思想解决上述组播路由问题.由于不同代的蚂蚁之间可以通过信息素来实现间接通信,而信息素又是一种可以反映环境变化的媒介质,因此,该算法能够根据网络环境的变化及时做出调整.结合实际的网络拓扑,进行仿真实验,实验结果表明,通过蚂蚁一代代的进化,算法可以找到一棵满足延迟约束并且耗费尽可能小的组播树.     

组播路由综合优化及其算法

路由优化是组播通信的一个关键问题,它的目标是将低路由费用。论文中首次提出了组播路由费用综合优化的思想,即组播路由的网络费用和目的地费用同时得到优化：优化网络费用以降低路由消耗的网络资源;优化目的地费用以减少源到目的地的平均时延。并提出了一种组播路由综合优化算法,该算法的时间复杂性低,实现简单,还可以分布式实现。     

并行量子遗传算法在QoS组播路由中的应用

随着网络通信技术的发展和Internet的普及,性能出色的组播路由越来越重要。著名的组播路由Steiner树问题是NP完全问题,应采用启发式方法求解。文中在常规量子遗传算法中引入并行进化模型,提出了一种解决多约束QoS组播路由优化问题的算法。在满足带宽、时延约束条件下寻找代价最小的组播树,并合理安排节点负荷,减少通信开销。仿真实验结果表明本算法搜索速度快、全局寻优能力强,性能和效率优于常规量子遗传算法。