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Nic

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3 papers

1 author row

IJCAI Conference 2005 Conference Paper

Decision Diagrams for the Computation of Semiring Valuations

This paper describes a new approach to computation in a semiring-based system, which includes semiring-based CSPs (in particular weighted CSPs, fuzzy CSPs and standard CSPs) as well as Bayesian networks. The approach to computation is based on what we call semiring-labelled decision diagrams (SLDDs). These can be generated in a similar way to a standard search tree (decision tree) for solving a CSP, but some nodes are merged, creating a more compact representation; for certain classes of CSPs, the number of nodes in the resulting network will be a tiny fraction of the number of nodes in the corresponding search tree. A method is given for generating an SLDD that represents e. g. , a particular instance of a semiring-based CSP; it is shown how this can be used to perform various computations of interest, such as solving a semiring-based CSP, finding optimal solutions, determining the possible values of each variable and counting solutions of a CSP.

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IJCAI Conference 2005 Conference Paper

Proactive Algorithms for Scheduling with Probabilistic Durations

J. Christopher Beck
Nic

Proactive scheduling seeks to generate high quality solutions despite execution time uncertainty. Building on work in [Beck and Wilson, 2004], we conduct an empirical study of a number of algorithms for the job shop scheduling problem with probabilistic durations. The main contributions of this paper are: the introduction and empirical analysis of a novel constraint-based search technique that can be applied beyond probabilistic scheduling problems, the introduction and empirical analysis of a number of deterministic filtering algorithms for probabilistic job shop scheduling, and the identification of a number of problem characteristics that contribute to algorithm performance.

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IJCAI Conference 2005 Conference Paper

The computational complexity of dominance and consistency in CP-nets

Judy Goldsmith
Jérôme Lang
Miroslaw Truszczynski
Nic

We investigate the computational complexity of testing dominance and consistency in CP-nets. Up until now, the complexity of dominance has been determined only for restricted classes in which the dependency graph of the CP-net is acyclic. However, there are preferences of interest that define cyclic dependency graphs; these are modeled with general CP-nets. We show here that both dominance and consistency testing for general CP-nets are PSPACE-complete. The reductions used in the proofs are from STRIPS planning, and thus establish strong connections between both areas.

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