ABSTRACT We introduce Grid-based SensorDCSP, a geometri cally structured benchmark problem for the study of distributed CSP algorithms. This domain pro vides realistic structure of the communication and tracking constraints. We formally define this prob lem, and perform its worst-case complexity analy sis. Likewise, we provide an average case empirical analysis of the AWC algorithm, studying its behav ior on tractable and intractable sub-classes of our problem.
Full-textDOI: · Available from: Ramón Béjar, Jul 07, 2015
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ABSTRACT: Constraint satisfaction is a well-known technique in artificial intelligence which can be applied to a large variety of problems. Many algorithms have been developed, and many implementations of these algorithms are available and have been studied. Hence, it is not surprising that the recent developments of dcstributed systems are also successfully extended to this area. Chapter 1 defines constraint satisfaction problems in general and presents the most important algorithms (e.g. backtracking, weak-commitment search, hill-climbing et al.). This introduction is used as the background for distributed constraint satisfaction problems. The given problem is assigned to agents, one agent is responsible for one variable of the problem, constraints are to be considered between different agents. One agent knows all constraints relevant to its variable.Based on these assumptions, the next chapters discuss different methods and algorithms to solve this problem: – asynchronous backtracking (chapter 3), – asynchronous weak-commitment search (chapter 4), – distributed breakout (chapter 5), – distributed consistency (chapter 6). In chapter 7, the assumption that one agent deals with one variable is deleted, multiple local variables are considered. Chapter 8 shows some over-constrained problems – the constraints do not allow any solution – the problem consists now in finding values for the variables so that only a “small” number of constraints remains unsatisfied. The presentation in this book is excellent. Each algorithm is presented by a sequence “basic ideas – details of the algorithm – example of algorithm execution – evaluation”. This allows a very economic representation. The examples are rather small, they allow, however, the understanding of the ideas, and the reader is not overloaded with too many (unimportant) details. By means of this book, an understanding of the problems, solutions and further research fields and topics can be achieved in a rather short time. It is pleasure to read this book.
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ABSTRACT: this paper looks at optimization versions of random k+p-Sat
Conference Paper: Communication and Computation in Distributed CSP Algorithms.[Show abstract] [Hide abstract]
ABSTRACT: We introduce SensorDCSP, a naturally distributed benchmark based on a real-world application that arises in the context of networked distributed systems. In order to study the performance of Distributed CSP (DisCSP) algorithms in a truly distributed setting, we use a discrete-event network simulator, which allows us to model the impact of different network traffic conditions on the performance of the algorithms. We consider two complete DisCSP algorithms: asynchronous backtracking (ABT) and asynchronous weak-commitment search (AWC). In our study of different network traffic distributions, we found that random delays, in some cases combined with a dynamic decentralized restart strategy, can improve the performance of DisCSP algorithms. More interestingly, we also found that the active introduction of message delays by agents can improve performance and robustness while reducing the overall network load. Finally, our work confirms that AWC performs better than ABT on satisfiable instances. On unsatis-fiable instances, however, the performance of AWC is considerably worse than ABT.Principles and Practice of Constraint Programming - CP 2002, 8th International Conference, CP 2002, Ithaca, NY, USA, September 9-13, 2002, Proceedings; 01/2002