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real-time Systems Symposium (RTSS)

作者： C.-J. Hou K.G. Shin Real-Time Computing Laboratory Department of Elec. Engineering and Computer Science University of Michigan Ann Arbor MI USA

The authors propose a new loading sharing (LS) algorithm for real-time applications that accounts for the effect of future task arrivals on locating the best receiver for each unguaranteed task. The LS algorithm minimizes not only the probability of transferring an unguaranteed task T to an incapable node with Bayesian analysis, but also the probability that a remote node fails to guarantee T because of future arrivals of higher-laxity tasks with queuing analysis. All parameters needed for a node's LS decision are collected/estimated online using time-stamped region-change broadcasts and Bayesian estimation. Simulation results show that the proposed LS algorithm outperforms other existing algorithms in minimizing the probability of dynamic failure, task collisions, and excessive task transfers. The performance improvement becomes more pronounced as the degree of system heterogeneity increases.< >

关键词： real time systems Bayesian methods Failure analysis Algorithm design and analysis Broadcasting Chaos Distributed computing Laboratories computer science Application software

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real-time communication in multi-hop networks

Real-time communication in multi-hop networks

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International Conference on Distributed computing Systems

作者： D.D. Kandlur K.G. Shin D. Ferrari Real-Time Computing Laboratory Department of EE & CS University of Michigan Ann Arbor MI USA Computer Science Division EE & CS Department University of California Berkeley CA USA

A scheme is developed for providing predictable interprocess communication in real-time systems with (partially connected) point-to-point interconnection networks, which provides guarantees on the maximum delivery time for messages. This scheme is based on the concept of a real-time channel, a unidirectional connection between source and destination. A real-time channel has parameters which describe the performance requirements of the source-destination communication, e.g., from a sensor station to a control site. Methods to compute guarantees for the delivery time of messages belonging to real-time channels are examined. Problems associated with allocating buffers for these messages are addressed, and a scheme which preserves delivery time guarantees is developed.< >

关键词： Intelligent networks Spread spectrum communication real time systems Delay Multiprocessor interconnection networks time factors computer networks Laboratories Sensor phenomena and characterization Communication system control

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Modeling wormhole routing in a hypercube

Modeling wormhole routing in a hypercube

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International Conference on Distributed computing Systems

作者： J. Kim C.R. Das Real-Time Computing Laboratory Department of Elec. Engineering and Computer Science University of Michigan Ann Arbor MI USA Department of Elec. and Computer Engineering Pennsylvania State University University Park PA USA

An analytical model for the performance evaluation of asynchronous hypercubes is presented. This analysis is aimed at modeling a deadlock-free wormhole routing scheme prevalent on second-generation hypercube systems. Probability of blocking and average message delay are discussed. The communication traffic to find the probability of blocking is the starting point. The traffic analysis can capture any message destination distribution. The average message delay that consists of two parts is found. The analysis is extended to virtual cut-through routing and random wormhole routing techniques. The validity of the model is demonstrated.< >

关键词： Routing Hypercubes Delay Analytical models Traffic control Performance analysis Protocols Laboratories System recovery Power engineering and energy

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Fault-Tolerance in real-time Systems

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IFAC Proceedings Volumes 1991年第2期24卷 119-121页

作者： K.G. Shin G. Koob F. Jahanian Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor MI 48109-2122 USA Office of Naval Research Code 1133 800 N. Quincy Street Arlington VA 22217-5000 USA IBM T.J. Watson Research Center P.O. Box 704 Yorktown Heights NY 10598 USA

With ever-increasing reliance on digital computers in embedded systems such as in space, avionics, manufacturing, and life-support monitoring/control applications, the need for dependable systems that deliver services in a timely manner has become crucial. Embedded systems often interact with the external environment and operate under strict timeliness and reliability requirements. Fault tolerance and real-time requirements on a system often influence one another in subtle ways, for example, the requirements on a highly—available system, such as an air traffic control system, may derive the timing constraints imposed on certain critical tasks. In cases where a set of interacting tasks operate under strict timing constraints, missing a deadline may result in a catastrophic system failure, which was termed a dynamic failure in (Shin, Krishna, and Lee, 1985). This paper argues that fault- tolerance and real-time requirements are not orthogonal and it addresses some of the challenges that confront the designers of fault-tolerant real-time systems. These challenges include formal specification of reliability and timing requirements, appropriate language and operating system support for providing fault-tolerance in a time-critical system, new scheduling theories which consider multiple resources and fault-tolerance, tradeoff between time and space redundancy, and predictable redundancy management in the presence of faults.

关键词： Fault-tolerance real-time systems reliability time and space redundancy run-time monitoring specification

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DESIGN FOR TEST USING PARTIAL PARALLEL SCAN

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IEEE TRANSACTIONS ON computer-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS 1990年第2期9卷 203-211页

作者： LEE, SG SHIN, KG Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Traditional scan design techniques such as level-sensitive scan design, scan path, and random-access scan suffer from the drawback that the extra test application effort (which includes both time and memory) required is directly proportional to the number of latches and can become quite significant. A scan design technique termed partial parallel scan which reduces test application effort by one to two orders of magnitude is presented. Theoretical and practical aspects of the design method are discussed. The practical use of the partial parallel scan technique has been demonstrated with an LSI circuit and a VLSI circuit designed using silicon compiler tools.< >

关键词： Circuit testing Latches Design for testability Hardware Circuit faults Design automation Switches Design methodology Large scale integration Very large scale integration

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Load sharing in hypercube multicomputer in the presence of node failures 5

Load sharing in hypercube multicomputer in the presence of n...

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5th Distributed Memory computing Conference, DMCC 1990

作者： Chang, Yi-Chieh Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)0818621133

This paper discusses and analyzes two load sharing (LS) issues: adjusting preferred lists and implementing a fault-tolerant mechanism in the presence of node failures. In an early paper, we have proposed to order the nodes in each node's proximity into a preferred list for the purpose of load sharing in distributed real-time systems. The preferred list of each node is constructed in such a way that each node will be selected as the kth preferred node by one and only one other node. Such lists are proven to allow the tasks to be evenly distributed in a system. However, the presence of faulty nodes will destroy the original structure of a preferred list if the faulty nodes are simply skipped in the preferred list. An algorithm is therefore proposed to modify each preferred list to retain its original features regardless of the number of faulty nodes in the system. The communication overhead introduced by this algorithm is shown to be minimal. Based on the modified preferred lists, a simple fault-tolerant mechanism is implemented. Each node is equipped with a backup queue which stores and updates the arriving/completing tasks at its most preferred node. Whenever a node becomes faulty, its most preferred node will treat the tasks in the ba,ckup queue as externally arriving tasks. Our simulation results show that this approach, despite of the simplicity, can reduce the number of task losses dramatically, as compared to the approaches without any faulttolerant mechanism. © 1990 IEEE.

关键词： real time systems

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Traffic routing for multi-computer networks with virtual cut-through capability

Traffic routing for multi-computer networks with virtual cut...

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International Conference on Distributed computing Systems

作者： D.D. Kandlur K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor USA

The problem of selecting routes for interprocess communication in a network with virtual cut-through capability, while balancing the network load and minimizing the number of times that a message gets buffered, is addressed. The approach taken is to formulate the route selection problem as a minimization problem, with a link cost function that depends on the traffic through the link. The form of this cost function is derived on the basis of the probability of establishing a virtual cut-through route. It is shown that this route selection problem is NP-hard, and so an approximate algorithm that tries to reduce the cost incrementally by rerouting traffic is developed. The performance of this algorithm is evaluated for two popular network topologies: the hypercube and the C-wrapped hexagonal mesh.< >

关键词： Telecommunication traffic Routing Packet switching Delay Cost function Hypercubes Application software Multiprocessor interconnection networks Telecommunication network reliability Communication system control

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A distributed I/O architecture for HARTS

A distributed I/O architecture for HARTS

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Annual International Symposium on computer Architecture, ISCA

作者： K.G. Shin G. Dykema Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The issue of I/O device access in HARTS (Hexagonal Architecture for real-time Systems)-a distributed real-time computer system under construction at the University of Michigan-is explicitly addressed. Several candidate solutions are introduced, explored and evaluated according to cost, complexity, reliability, and performance: (1) 'node-direct' distribution with the intranode bus and a local I/O bus; (2) use of dedicated I/O nodes, which are placed in the hexagonal mesh as regular applications nodes, but which provide I/O services rather than computing services; and (3) use of a separate I/O network; which has led to the proposal of an 'interlaced' I/O network. The interlaced I/O network is intended to provide both high performance without burdening node processors with I/O overhead and a high degree of reliability. Both static and dynamic multiownership protocols are developed for managing I/O device access in this I/O network. The relative merits of the two protocols are explored, and the performance and accessibility which each provides are simulated.< >

关键词： real time systems Distributed computing Topology computer architecture Laboratories Costs Proposals Access protocols Hypercubes computer networks

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Design of a Knowledge-Based Controller for Intelligent Control Systems

Design of a Knowledge-Based Controller for Intelligent Contr...

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American Control Conference (ACC)

作者： Kang G. Shin Xianzhong Cui Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

A hierarchical knowledge-based controller is proposed to improve the performance of complex control systems, such as robots. Unlike parameter- and performance- adaptive controllers, this controller is designed only to modify the reference input of a low-level servo controller. Because the internal parameters and structure of the low-level controller are not affected, commercial servo controllers can be made to perform more sophisticated tasks than originally intended. The principle of the knowledge-based controller, modification of the reference input, knowledge representation, existence of the solution, and analyses of the controller's stability and tracking error are described in detail. A self-tuning multiple-step predictor is designed as a part of the controller to eliminate the undesirable effects of system time delay. Both linear and nonlinear example control systems are tested via extensive simulations and have all shown promising performances.

关键词： Control systems Intelligent control Servomechanisms Robots Programmable control Adaptive control Knowledge representation Stability analysis Error correction Delay effects

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Shortest path planning with dominance relation

Shortest path planning with dominance relation

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IEEE International Conference on Robotics and Automation (ICRA)

作者： S. Jun K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

A method of partitioning a workspace using rectilinear visibility in 3-D or higher space is presented. Unlike the case of 2-D space, where the space of a partition is a rectangle, the shape of a partition in 3-D or higher space is arbitrary. In spite of the arbitrary shape of partitioned regions, it is proved that there exist dominance relations between regions. This relation is then utilized to solve efficiently the shortest path planning problem in 3-D or higher space.< >

关键词： Path planning Shape Costs Application software Manipulators Laboratories Remotely operated vehicles Mobile robots Routing Very large scale integration

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