17,089 research outputs found
Integer linear programming for the Bayesian network structure learning problem.
Bayesian networks are a commonly used method of representing conditional probability relationships between a set of variables in the form of a directed acyclic graph (DAG). Determination of the DAG which best explains observed data is an NP-hard problem. This problem can be stated as a constrained optimisation problem using Integer Linear Programming (ILP). This paper explores how the performance of ILP-based Bayesian network learning can be improved through ILP techniques and in particular through the addition of non-essential, implied constraints. There are exponentially many such constraints that can be added to the problem. This paper explores how these constraints may best be generated and added as needed. The results show that using these constraints in the best discovered configuration can lead to a significant improvement in performance and show significant improvement in speed using a state-of-the-art Bayesian network structure learner
Empirical Hardness of Finding Optimal Bayesian Network Structures: Algorithm Selection and Runtime Prediction
Various algorithms have been proposed for finding a Bayesian network structure that is guaranteed to maximize a given scoring function. Implementations of state-of-the-art algorithms, solvers, for this Bayesian network structure learning problem rely on adaptive search strategies, such as branch-and-bound and integer linear programming techniques. Thus, the time requirements of the solvers are not well characterized by simple functions of the instance size. Furthermore, no single solver dominates the others in speed. Given a problem instance, it is thus a priori unclear which solver will perform best and how fast it will solve the instance. We show that for a given solver the hardness of a problem instance can be efficiently predicted based on a collection of non-trivial features which go beyond the basic parameters of instance size. Specifically, we train and test statistical models on empirical data, based on the largest evaluation of state-of-the-art exact solvers to date. We demonstrate that we can predict the runtimes to a reasonable degree of accuracy. These predictions enable effective selection of solvers that perform well in terms of runtimes on a particular instance. Thus, this work contributes a highly efficient portfolio solver that makes use of several individual solvers.Peer reviewe
Advances in Learning Bayesian Networks of Bounded Treewidth
This work presents novel algorithms for learning Bayesian network structures
with bounded treewidth. Both exact and approximate methods are developed. The
exact method combines mixed-integer linear programming formulations for
structure learning and treewidth computation. The approximate method consists
in uniformly sampling -trees (maximal graphs of treewidth ), and
subsequently selecting, exactly or approximately, the best structure whose
moral graph is a subgraph of that -tree. Some properties of these methods
are discussed and proven. The approaches are empirically compared to each other
and to a state-of-the-art method for learning bounded treewidth structures on a
collection of public data sets with up to 100 variables. The experiments show
that our exact algorithm outperforms the state of the art, and that the
approximate approach is fairly accurate.Comment: 23 pages, 2 figures, 3 table
Consistent Second-Order Conic Integer Programming for Learning Bayesian Networks
Bayesian Networks (BNs) represent conditional probability relations among a
set of random variables (nodes) in the form of a directed acyclic graph (DAG),
and have found diverse applications in knowledge discovery. We study the
problem of learning the sparse DAG structure of a BN from continuous
observational data. The central problem can be modeled as a mixed-integer
program with an objective function composed of a convex quadratic loss function
and a regularization penalty subject to linear constraints. The optimal
solution to this mathematical program is known to have desirable statistical
properties under certain conditions. However, the state-of-the-art optimization
solvers are not able to obtain provably optimal solutions to the existing
mathematical formulations for medium-size problems within reasonable
computational times. To address this difficulty, we tackle the problem from
both computational and statistical perspectives. On the one hand, we propose a
concrete early stopping criterion to terminate the branch-and-bound process in
order to obtain a near-optimal solution to the mixed-integer program, and
establish the consistency of this approximate solution. On the other hand, we
improve the existing formulations by replacing the linear "big-" constraints
that represent the relationship between the continuous and binary indicator
variables with second-order conic constraints. Our numerical results
demonstrate the effectiveness of the proposed approaches
Bayesian network learning with cutting planes
The problem of learning the structure of Bayesian networks from complete
discrete data with a limit on parent set size is considered. Learning is cast
explicitly as an optimisation problem where the goal is to find a BN structure
which maximises log marginal likelihood (BDe score). Integer programming,
specifically the SCIP framework, is used to solve this optimisation problem.
Acyclicity constraints are added to the integer program (IP) during solving in
the form of cutting planes. Finding good cutting planes is the key to the
success of the approach -the search for such cutting planes is effected using a
sub-IP. Results show that this is a particularly fast method for exact BN
learning
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