Alban Grastien

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The diagnosis of a discrete-event system is the problem of computing possible behaviors of the system given observations of the actual behavior, and testing whether the behaviors are normal or faulty. We show how the diagnosis problems can be translated into the propositional satisfiability problem (SAT) and solved by algorithms for SAT. Our experiments(More)
This report provides a comprehensive complexity study of line switching in the Linear DC model for the feasibility problem and the optimization problems of maximizing the load that can served (maximum switching flow, MSF) and minimizing generation cost (optimal transmission switching, OTS). Our results show that these problems are NP-complete and that there(More)
Diagnosis of discrete event systems amounts to finding good explanations, in the form of system trajectories consistent with a given set of partially ordered observations. This problem is closely related to planning, and in fact can be recast as a classical planning problem. We formulate a PDDL encoding of this diagnosis problem, and use it to evaluate(More)
In the satisfiability domain, it is well-known that a SAT algorithm may solve a problem instance easily and another instance hardly, whilst these two instances are equivalent CNF encodings of the original problem. Moreover, different algorithms may disagree on which encoding makes the problem easier to solve. In this paper, we focus on the CNF encoding of(More)
Diagnosability ensures that the occurrence of a failure on the system can always be diagnosed by a diagnosis engine. In this paper, we explore symbolic techniques to test diagnosability of DES. We present several algorithms that can be implemented with symbolic tools, and show how to combine decentralised approach with symbolic approach. Finally, we discuss(More)
The goal of Web service effort is to achieve universal interoperability between applications by using Web standards: this emergent technology is a promising way to integrate business applications. A business process can then be seen as a set of Web services that could belong to different companies and interact with each other by sending messages. In that(More)
Any-angle pathfinding is a fundamental problem in robotics and computer games. The goal is to find a shortest path between a pair of points on a grid map such that the path is not artificially constrained to the points of the grid. Prior research has focused on approximate online solutions. A number of exact methods exist but they all require supra-linear(More)
We give online and offline optimisation techniques to improve the performance of Jump Point Search (JPS): a recent and very effective symmetry-breaking algorithm that speeds up pathfinding in computer games. First, we give a new and more efficient procedure for online symmetry breaking by manipulating “blocks” of nodes at a single time rather than(More)