|   | CMU-CS-97-107 Computer Science Department
 School of Computer Science, Carnegie Mellon University
 
    
     
 CMU-CS-97-107
 
Using Optimal Dependency-Trees for Combinatorial
Optimization: Learning the Structure of the Search Space 
Shumeet Baluja*, Scott Davies 
January 1997  
CMU-CS-97-107.ps Keywords: Combinatorial optimization, dependency trees, probability
models, bayesian networks
 Many combinatorial optimization algorithms have no mechanism to
capture inter-parameter dependencies. However, modeling such
dependencies may allow an algorithm to concentrate its sampling more
effectively on regions of the search space which have appeared
promising in the past. We present an algorithm which incrementally
learns second-order probability distributions from good solutions seen
so far, uses these statistics to generate optimal (in terms of maximum
likelihood) dependency trees to model these distributions, and then
stochastically generates new candidate solutions from these trees. We
test this algorithm on a variety of optimization problems. Our results
indicate superior performance over other tested algorithms that either
(1) do not explicitly use these dependencies, or (2) use these
dependencies to generate a more restricted class of dependency graphs.
 
20 pages 
*Justsystem Pittsburgh Research Center, 4616 Henry Street, Pittsburgh, 
PA  15213
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