Abstract

Bayesian networks (BN) are a popular representation for reasoning under uncertainty. The analysis of many real-world use cases, that in principle can be modeled by BNs, suffers however from the computational complexity of inference. Inference methods based on Weighted Model Counting (WMC) reduce the cost of inference by exploiting patterns exhibited by the probabilities associated with BN nodes. However, these methods require a computationally intensive compilation step in search of these patterns, which effectively prohibits the handling of larger BNs. In this paper, we propose a solution to this problem by extending WMC methods with a framework called Compositional Weighted Model Counting (CWMC). CWMC reduces compilation cost by partitioning a BN into a set of subproblems, thereby scaling the application of state-of-the-art innovations in WMC to scenarios where inference cost could previously not be amortized over compilation cost. The framework supports various target representations that are less or equally succinct as decision-DNNF. At the same time, its inference time complexity O(nexp⁡(w)), where n is the number of variables and w is the tree-width, is comparable to mainstream algorithms based on variable elimination, clustering and conditioning.

Highlights

  • The field of probabilistic inference has made considerable progress in the past three decades with the development of novel probabilistic graphical models, such as Bayesian networks (BNs) and chain graphs [10]

  • The current article proposes Compositional Weighted Model Counting (CWMC), a framework for probabilistic inference that partitions the compilation into subproblems, which are recomposed in the inference query

  • We introduce Compositional Weighted Model Counting (CWMC), which combines Compositional Framework (CF) and WMC

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Summary

Introduction

The field of probabilistic inference has made considerable progress in the past three decades with the development of novel probabilistic graphical models, such as Bayesian networks (BNs) and chain graphs [10]. Various symbolic formalisms have been proposed for KC, e.g., [34],[29] and [44], which all have different characteristics in terms of compilation effort and query times Because this symbolic approach represents local structure concisely, like the decision tree in Fig. 1c and the diagrams [45, Th.3], KC is generally seen as a method that renders many practical reasoning problems tractable [33]. The current article proposes Compositional Weighted Model Counting (CWMC), a framework for probabilistic inference that partitions the compilation into subproblems, which are recomposed in the inference query. It builds upon, and extends [15]. Empirical evaluation shows that both compilation and inference cost are reduced while employing CWMC, sometimes by multiple orders of magnitude (Section 8)

Preliminaries and background
Set and graph theory
Bayesian networks
Inference by weighted model counting
Decision diagrams
Removing unintended models
The compositional framework
Partitioning
Composition
Inference
Compositional weighted model counting
Partitioning and compilation
Traversing monolithic representations
The cost of compositional inference
Optimizing the framework
Finding a partitioning
Finding a composition-tree
Finding a compilation ordering
Related work
Compilation
Conclusion
Full Text
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