Méthodes pour améliorer la qualité des implantations matérielles de systèmes informatiques

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Novel approaches to cyclic job-shop problems with transportation

Scheduling problems can be found in almost any field of application in the real world. These problems may not only have different characteristics but they also imply more or less complex requirements. One specific class within this domain is the cyclic job-shop problem. It occurs in various areas reaching from industrial production planning down to the systems architecture of computers. With manufacturers in particular, one can find increasing demand for effective solution methods in order to tackle these scheduling problems efficiently. This thesis will deal with the Cyclic Job-Shop Problem with Blocking and Transportation. It arises in modern manufacturing companies, where the products move automatically between the different workstations, for instance. The problem itself is not new to the research community, but hardly any work has been done in solving it. Within this thesis we will try to close this gap and present some first approaches, discussing the structure of the problem and how it can be solved. As a result, we will provide three different solution methods, including an integer programming formulation, which is solved with a commercial solver, a branch and bound algorithm and a tabu search heuristic. All algorithms are tested on a range of data sets and compared with each other. Additionally, we have worked on a polynomial solvable subproblem, which has gained more interest in the literature. As a result, a new polynomial algorithm, that outperforms the existing ones in theory as well as in empirical tests (except for some special cases) is presented. This thesis concludes with a discussion about ideas of how to improve the presented methods and some other extensions to the investigated problem

Retiming with wire delay and post-retiming register placement.

Tong Ka Yau Dennis.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 77-81).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Motivations --- p.1Chapter 1.2 --- Progress on the Problem --- p.2Chapter 1.3 --- Our Contributions --- p.3Chapter 1.4 --- Thesis Organization --- p.4Chapter 2 --- Background on Retiming --- p.5Chapter 2.1 --- Introduction --- p.5Chapter 2.2 --- Preliminaries --- p.7Chapter 2.3 --- Retiming Problem --- p.9Chapter 3 --- Literature Review on Retiming --- p.10Chapter 3.1 --- Introduction --- p.10Chapter 3.2 --- The First Retiming Paper --- p.11Chapter 3.2.1 --- """Retiming Synchronous Circuitry""" --- p.11Chapter 3.3 --- Important Extensions of the Basic Retiming Algorithm --- p.14Chapter 3.3.1 --- """A Fresh Look at Retiming via Clock Skew Optimization""" --- p.14Chapter 3.3.2 --- """An Improved Algorithm for Minimum-Area Retiming""" --- p.16Chapter 3.3.3 --- """Efficient Implementation of Retiming""" --- p.17Chapter 3.4 --- Retiming in Physical Design Stages --- p.19Chapter 3.4.1 --- """Physical Planning with Retiming""" --- p.19Chapter 3.4.2 --- """Simultaneous Circuit Partitioning/Clustering with Re- timing for Performance Optimization" --- p.20Chapter 3.4.3 --- """Performance Driven Multi-level and Multiway Parti- tioning with Retiming" --- p.22Chapter 3.5 --- Retiming with More Sophisticated Timing Models --- p.23Chapter 3.5.1 --- """Retiming with Non-zero Clock Skew, Variable Register, and Interconnect Delay""" --- p.23Chapter 3.5.2 --- """Placement Driven Retiming with a Coupled Edge Tim- ing Model""" --- p.24Chapter 3.6 --- Post-Retiming Register Placement --- p.26Chapter 3.6.1 --- """Layout Driven Retiming Using the Coupled Edge Tim- ing Model""" --- p.26Chapter 3.6.2 --- """Integrating Logic Retiming and Register Placement""" --- p.27Chapter 4 --- Retiming with Gate and Wire Delay [2] --- p.29Chapter 4.1 --- Introduction --- p.29Chapter 4.2 --- Problem Formulation --- p.30Chapter 4.3 --- Optimal Approach [2] --- p.31Chapter 4.3.1 --- Original Mathematical Framework for Retiming --- p.31Chapter 4.3.2 --- A Modified Optimal Approach --- p.33Chapter 4.4 --- Near-Optimal Fast Approach [2] --- p.37Chapter 4.4.1 --- Considering Wire Delay Only --- p.38Chapter 4.4.2 --- Considering Both Gate and Wire Delay --- p.42Chapter 4.4.3 --- Computational Complexity --- p.43Chapter 4.4.4 --- Experimental Results --- p.44Chapter 4.5 --- Lin's Optimal Approach [23] --- p.47Chapter 4.5.1 --- Theoretical Results --- p.47Chapter 4.5.2 --- Algorithm Description --- p.51Chapter 4.5.3 --- Computational Complexity --- p.52Chapter 4.5.4 --- Experimental Results --- p.52Chapter 4.6 --- Summary --- p.54Chapter 5 --- Register Insertion in Placement [36] --- p.55Chapter 5.1 --- Introduction --- p.55Chapter 5.2 --- Problem Formulation --- p.57Chapter 5.3 --- Placement of Registers After Retiming --- p.60Chapter 5.3.1 --- Topology Finding --- p.60Chapter 5.3.2 --- Register Placement --- p.69Chapter 5.4 --- Experimental Results --- p.71Chapter 5.5 --- Summary --- p.74Chapter 6 --- Conclusion --- p.75Bibliography --- p.7

Optimal regulation of finite Markov Chains

Imperial Users onl

Systems Analysis of Hydrologic Problems

Introduction: Increasing national and international interest in water resources in recent years has stimulated much new activity and progress in hydrology. It is now generally recognized that the science of hydrology is basic to an understanding of water resources problems and to planning for water resources development. Accompanying this demand upon the science of hydrology is an urgent need for improved education at the university level. In resopnse to this need for improved education, the First International Seminar for Hydrology Professors was held at Urbana, Illinois, in July 1969. The Second International Seminar was held at Logan, Utah, during August 2-14, 1970, and was a continuation of the program to acquaint hydrology professors with modern concepts and technologies. The major overall objective of the second seminar was to emphasize the systems approach as applied to hydrology, in which the various fundamental hydrologic processes and their interrelationships were studied and examined. Because of the need to apply new concepts and technologies to the development and utilization of the limited supply of water resources throughout the world, hydrologic programs in our colleges and universities generally require much improvement, particularly with reference to the application of systems concepts and methods. Accordingly, the specific objectives of the Seminar were as follows: 1. To impress upon hydrology professors the improtance of the systems approach to the science of hydrology, and to acquaint them with the fundamental and basic concepts of the the hydrologic system. 2. To present concepts for defining or describing the hydrologic system in terms of particular management objectives. 3. To examine various techniques for monitoring the hydrologic system, including the design of monitoring networks in terms of particular objectives. 4. To acquaint the participants with several methods of modeling hydrologic systems, and to provide them with experiences which demonstrate the utility of modeling for (a) examining various system interrelationships and sensitivies; and (b) maximizing particular objective functions subject to given external contraints and production functions

Outsourcing warranty repairs: models for the allocation of failed items to multiple vendors

We consider a scenario in which several external service vendors are contracted to repair purchased items which fail under warranty. We develop and analyze various allocation models concerning how the repair work should be distributed among the vendors in a cost-effective manner. Furthermore, we depart from previous work by arguing the importance of approaches to the modelling of goodwill costs which penalize long waits experienced by individual customers.We firstly study a simple static allocation model with a fixed warranty population. Both theoretical considerations and numerical results show that a simple greedy approach to the distribution of items under static models works outstandingly well. However, such a static formulation ignores the stochastic nature of the warranty population. Hence, we develop a second allocation model in which new equipment purchases are made according to a compound Poisson process. As in the static allocation model, the current information regarding the repair queue at each vendor is not available to the decision maker. The resulting stochastic dynamic optimization problem is non-standard. We develop an effective allocation procedure to this non-standard problem using a dynamic programming policy improvement approach. We report representative results from a simulation investigation to evaluate the status of the allocation heuristic developed in comparison to two simpler heuristics suggested by static models. Thirdly, we propose a dynamic allocation model which utilizes data on the queue length at each vendor for decisions on the routing of real-time failures to the vendors. Due to the problem size and state space in practice, traditional stochastic dynamic programming is not a realistic and computationally viable option. Hence, Whittle's restless bandits approach is deployed to develop the index-based heuristic for this dynamic allocation problem. A crucial theoretical result in this part of the study is that the system considered is indeed indexable. All the numerical results reported show that the performance of the derived index policy from the restless bandit is superior to that of a range of alternatives

Perturbation theory and Markovian decision processes.

Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1965. Sc.D.Sc.D

Learning bounded optimal behavior using Markov decision processes

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.Includes bibliographical references (p. 171-175).Creating agents that behave rationally in the real-world is one goal of Artificial Intelligence. A rational agent is one that takes, at each point in time, the optimal action such that its expected utility is maximized. However, to determine the optimal action the agent may need to engage in lengthy deliberations or computations. The effect of computation is generally not explicitly considered when performing deliberations. In reality, spending too much time in deliberation may yield high quality plans that do not satisfy the natural timing constraints of a problem, making them effectively useless. Enforcing shortened deliberation times may yield timely plans, but these may be of diminished utility. These two cases suggest the possibility of optimizing an agent's deliberation process. This thesis proposes a framework for generating meta level controllers that select computational actions to perform by optimally trading off their benefit against their costs. The metalevel optimization problem is posed within a Markov Decision Process framework and is solved off-line to determine a policy for carrying out computations. Once the optimal policy is determined, it serves efficiently as an online metalevel controller that selects computational actions conditioned upon the current state of computation. Solving for the exact policy of the metalevel optimization problem becomes computationally intractable with problem size. A learning approach that takes advantage of the problem structure is proposed to generate approximate policies that are shown to perform relatively well in comparison to optimal policies. Metalevel policies are generated for two types of problem scenarios, distinguished by the representation of the cost of computation. In the first case, the cost of computation is explicitly defined as part of the problem description. In the second case, it is implicit in the timing constraints of problem. Results are presented to validate the beneficial effects of metalevel planning over traditional methods when the cost of computation has a significant effect on the utility of a plan.by Hon Fai Vuong.Ph.D

Corporate decision analysis : an engineering approach

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2006.Includes bibliographical references (p. 313-330).We explore corporate decisions and their solutions under uncertainty using engineering methods. Corporate decisions tend to be complex; they are interdisciplinary and defy programmable solutions. To address these challenges, we take an engineering approach. Our proposition is that as in an engineering system, corporate problems and their potential solutions deal with the behavior of systems. Since systems can be studied with experiments, we use Design of Experiments (DOE) to understand the behavior of systems within which decisions are made and to estimate the consequences of candidate decisions as scenarios. The experiments are a systematically constructed class of gedanken experiments comparable to "what if' studies, but organized to span the entire space of controllable and uncontrollable options. In any experiment, the quality of data is important. Grounded on the work of scholars, we develop a debiasing process for eliciting data. And consistent with our engineering approach, we consider the composite consisting of the organization, their knowledge, data bases, formal and informal procedures as a measurement system. We then use Gage theory from Measurement Systems Analysis (MSA) to analyze the quality of the measuring composite.(cont.) To test this engineering approach to decision analysis, we perform four experiments. The first two are a set of simulations using a company surrogate. Using a progression of experiments, we simulate two major corporate decisions. Simulation data show that there is support for the validity of our decision analysis method. We then perform two in situ experiments: with a manufacturing company and with a technology services company. Findings from these company experiments also support the validity and efficacy of our decision analysis method. The company executives were very satisfied with our findings. Finally, we evaluate our method using method-evaluation criteria. The evaluation suggests that our DOE-based decision analysis method is valid. Unexpectedly every experiment resulted in near-decomposable systems at the scale we formulated our problems. Scaling of corporate decision problems at the appropriate level of abstraction and the resultant properties of their dynamic behavior are identified as areas of future work. This research breaks new ground in corporate decision-analysis as engineering and it furthers DOE and MSA research to a new domain and a new class of problems.by Victor Tang.Ph.D