16256467
Implementations of dispatch rules in parallel manufacturing simulation
Most features in commercial simulation packages are often omitted in parallel simulation benchmarks, because they neither affect the overall correctness of the simulation protocol nor the benchmark's performance. In our work on parallel simulation of a wafer fabrication plant, we however find several features which complicate the implementation of the simulation protocol and affect the program performance. One such feature is the dispatch rules which a machine set uses to decide the priority of the waiting wafer lots. In a sequential simulation, the dispatch rule can be implemented in a straightforward fashion, because the whole system state is at the same simulation time, and the rule simply reads the state variables (of any machine, resources, etc.) In a parallel simulation, the dispatch rule computation may be complicated by the fact that different portions of the simulated system can be at different simulation times. This paper describes our study of the implementation of dispatch rules in parallel simulation. This is actually an instance of the little-studied problem of providing shared-state information in parallel simulation. We briefly survey previous related work. We then outline two different approaches for a dispatch rule to access the shared-state information and compare them in terms of their ease of implementation.
201885623
Manufacturing supply chain applications: modeling computer assembly operations for supply chain integration
Factory operations have been modeled for years to understand the relationship between the different design and policy factors and the performance measures of interest. The increasing awareness of the need to manage factories as a link in the supply chain places a corresponding requirement for an enhanced approach for factory modeling. This paper describes the modeling of a computer assembly factory for supply chain integration by including aspects of inbound and outbound logistics and relevant business processes. Lessons are drawn based on the experience.
18971661
Development of a high-level supply chain simulation model
This paper describes an effort that involved development of a simulation model for evaluating the business processes and inventory control parameters of a logistics and distribution supply chain. A generic simulation tool, rather than a supply chain simulator, was developed for meeting customized needs of the effort. The paper describes, the approaches used to model at the selected level of abstraction, the development of interfaces for data and experimentation and the development and delivery of animation for communicating the approach and results to the client.
6477912
Stress testing a supply chain using simulation
Simulation provides the capability to evaluate performance of a system operating under current or proposed configurations, policies and procedures. It is very applicable to evaluation of strategic and operational level plans for supply chains. It is especially useful for exploring the viability of a supply chain before beginning production. This paper describes the use of simulation for determining the readiness of a supply chain designed by a small company for providing sub-systems to a defense contractor. The supply chain had to be stress tested at surge and mobilization volume levels to meet the requirements. Simulation provided the ideal methodology to identify and demonstrate the behavior of the supply chain under stress and evaluate strategies to meet the defined volumes. It was used to prove the readiness of the supply chain reducing perceived risks in using the virtual operation.
18211780
Supply chain opportunities: panel session: opportunities for simulation in supply chain management
It has become a matter of survival that many companies improve their supply chain efficiency. This presents an opportunity for simulation. However, there are many challenges that must be overcome for simulation to be a contributor to play an effective role. Four contributors discuss the opportunities that they see for simulation to play a meaningful role in the area of supply chain management.
32884753
Expert Simulation For On-line Scheduling
In recent years, the automotive industry has realized the importance of speed of new products to market and has mounted efforts for improving it. The Expert System Scheduler (ESS) facilitates these efforts by enabling manufacturing plants to generate viable schedules under increasing constraints and demands for flexibility. The scheduler takes advantage of the Computer Integrated Manufacturing (CIM) environment by utilizing the real-time information from the factory for responsive scheduling. The Expert System Scheduler uses heuristics developed by an experiences factory scheduler. It uses simulation concepts and these heuristics to generate schedules. Forward and "backward" simulation are used at different stages of the schedule generation process. The system is used to control parts flow on the factory floor at one automated facility. This highly automated facility is a testbed for implementation of CIM concepts. The scheduler runs on a Texas Instruments (TI) Explorer II computer using software developed inhouse utilizing IntelliCorp's Knowledge Engineering Environment (KEE) shell and the LISP language. The scheduling computer is networked to the factory control computer, which actually controls the plant floor. The TI Explorer II acquires current plant floor information from the factory control system, generates a new schedule and sends it back within a short time. The configuration allows fast response to changes in requirements and plant floor conditions.
30237295
Crowd Control: Coordinating Processes in Parallel
Tutorials • Bridget Rosewell and Paul Ormerod " Agent Based Models and Social Simulation in the Policy Process " [Room: Aula Magna] This tutorial will focus on practical examples of agent based models which are actually being used as part of the decision making process of policy makers. The tutorial will also address key issues in integrating ABMs and social simulation into the policy making process. The tutorial will introduce the Multi-Agent Simulation Suite (MASS), a novel, integrated simulation environment for agent-based social simulation. MASS was designed with scientific modelers and not professional programmers in mind. Therefore, ease of use and prudent scientific practices were at the focus of the suite's design. The tutorial consists in a brief introductory part providing a generalized definition of the basic elements composing a simulation model. Then, it will be shown how LSD allows users to transparently adopt the theoretical definition, automatically generating all the technical code necessary for developing, running and analysing a simulation model. A series of examples will show the advantages of the definition proposed and the most relevant features of LSD. The tutorial will introduce the Multi-Agent Simulation Suite (MASS), a novel, integrated simulation environment for agent-based social simulation. MASS was designed with scientific modelers and not professional programmers in mind. Therefore, ease of use and prudent scientific practices were at the focus of the suite's design.
2575335
The Intrinsic Complexity of Learning: A Survey
The theory of learning in the limit has been a focus of study by several researchers over the last three decades. There have been several suggestions on how to measure the complexity or hardness of learning. In this paper we survey the work done in one specific such measure, called intrinsic complexity of learning. We will be mostly concentrating on learning languages, with only a brief look at function learning.
31352625
Learning and extending sublanguages
A number of natural models for learning in the limit are introduced to deal with the situation when a learner is required to provide a grammar covering the input even if only a part of the target language is available. Examples of language families are exhibited that are learnable in one model and not learnable in another one. Some characterizations for learnability of algorithmically enumerable families of languages for the models in question are obtained. Since learnability of any part of the target language does not imply monotonicity of the learning process, we consider our models also under the additional monotonicity constraint.
1576847
On Aggregating Teams of Learning Machines
The present paper studies the problem of when a team of learning machines can be aggregated into a single learning machine without any loss in learning power. The main results concern aggregation ratios for vacillatory identification of languages from texts. For a positive integer n, a machine is said to TxtFexn-identify a language L just in case the machine converges to upto n grammars for L on any text for L. For such identification criteria, the aggregation ratio is derived for the n=2 case. It is shown that the collection of languages that can be TxtFex2 identified by teams with success ratio greater than 5/6 are the same as those collections of languages that can be TxtFex2-identified by a single machine. It is also established that 5/6 is indeed the cut-off point by showing that there are collections of languages that can be TxtFex2-identified by a team employing 6 machines, at least 5 of which are required to be successful, but cannnot be TxtFex2-identified by any single machine. Additionally, aggregation ratios are also derived for finite identification of languages from positive data and for numerous criteria involving language learning from both positive and negative data.
1567174
Approximate Inference and Scientific Method
Abstract A new identification criterion, motivated by notions of successively improving approximations in the philosophy of science, is defined. It shown that the class of recursive functions is identifiable under this criterion. This result is extended to apply to somewhat more realistic types of data than usual. This criterion is then modified to consider restrictions on the quality of approximations, and the new criteria are compared to existing criteria.