The rapid changing business environment of high-tech asset intensive enterprises such as semiconductor manufacturing constantly drives production managers to look for better solutions to improve the manufacturing process. Simulation, though identified to be the most appropriate technique to generate and test out possible execution plans, suffers from long cycle-time in the process of model update, analysis and verification. It is thus very difficult to carry out prompt "what-if" analysis to respond to abrupt changes in these systems. Symbiotic simulation systems have been proposed as a way of solving this problem by having the simulation and the physical system interact in a mutually beneficial manner. In this paper, we describe our work in developing a prototype proof-of-concept symbiotic simulation system that employs software agents in the monitoring, optimization and control of a semiconductor assembly and test operation.
Increasingly, software agents are evolving from the roles of facilitators into decision-makers in managing complex, real-time systems such as logistics enterprise. Emergent behavior is that which is not attributed to any individual (agent), but is a global outcome of individual (agent) coordination. While agent's degree of autonomy and responsibility will continue to increase with time, the impact of emergent behavior in agent system on the performance and stability of these systems become an important issue. We found that emergent behavior is a major concern of potential users while we try to apply agent technology to such industry areas as transportation planning and logistics coordination. To really make agent technology work in industry convincingly, it is valuable to do a study of emergent behaviour and its impacts to the application of agent technology. This paper reviews the research on emergent behaviour, discuss its research challenge and application impact, and suggest research directions on agent emergent behaviour.
Abstract. The High Level Architecture promotes simulation interoperability and reusability, making it an ideal candidate to model large-scale systems. However, a large-scale simulation running in a distributed environment is often affected by the imbalance of load level at different computing hosts. Migrating processes from heavily-loaded hosts to less-loaded hosts can overcome this shortcoming. We have previously developed a SimKernel framework to execute HLA-based simulations in the Grid environment with migration support as a prominent design feature. In this paper, we will introduce a transparent migration protocol for SimKernel-based federates that minimizes migration overhead.
With the wide use of Commercial Off-The-Shelf (COTS) simulation packages and the advent of the HighLevel Architecture (HLA) standard which supports interoperability and reusability, it is desirable to build distributed simulations by linking various types of simulation models developed using best-fit COTS packages. While almost all current work on integrating COTS packages and the HLA is based on conservative synchronization, it is worthwhile to investigate the optimistic synchronization approach. The optimistic approach can exploit parallelism and achieve promising performance in situations where causality errors may occur but in fact seldom occur. In our paper, we introduce a rollback controller using a middleware approach to handle the complex rollback procedure on behalf of the simulation model. To fully utilize the benefits of optimistic synchronization, we also introduce a novel time advance algorithm using the services provided by the HLA. A comparison of performance between the conservative and optimistic synchronization approaches based on a typical reference model is also provided.
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