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Stochastic simulation in dynamic probabilistic networks using compact representation Cheuk, Adrian Y.W.
Abstract
In recent years, researchers in the A l domain have used Bayesian belief networks to build models of expert opinion. Though computationally expensive deterministic algorithms have been devised, it has been shown that exact probabilistic inference in belief networks, especially multiply connected ones, is intractable. In view of this, various approximation methods based on stochastic simulation appeared in an attempt to perform efficient approximate inference in large and richly interconnected models. However, due to convergence problems, approximation in dynamic probabilistic networks has seemed unpromising. Reversing arcs into evidence nodes can improve convergence performance in simulation, but the resulting exponential increase in network complexity and, in particular, the size of the conditional probability tables (CPTs) can often render this evidence reversal method computationally inefficient. In this thesis, we describe a structured simulation algorithm that uses the evidence reversal technique based on a tree-structured representation for CPTs. Most real systems exhibit a large amount of local structure. The tree can reduce network complexity by exploiting this structure to keep CPTs in a compact way even after arcs have been reversed. The tree also has a major impact on improving computational efficiency by capturing context-specific independence during simulation. Experimental results show that in general our structured evidence reversal algorithm improves convergence performance significantly while being both spatially and computationally much more efficient than its unstructured counterpart.
Item Metadata
Title |
Stochastic simulation in dynamic probabilistic networks using compact representation
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1996
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Description |
In recent years, researchers in the A l domain have used Bayesian belief networks to build
models of expert opinion. Though computationally expensive deterministic algorithms have been devised,
it has been shown that exact probabilistic inference in belief networks, especially multiply connected
ones, is intractable. In view of this, various approximation methods based on stochastic simulation
appeared in an attempt to perform efficient approximate inference in large and richly interconnected
models. However, due to convergence problems, approximation in dynamic probabilistic networks
has seemed unpromising. Reversing arcs into evidence nodes can improve convergence performance
in simulation, but the resulting exponential increase in network complexity and, in particular,
the size of the conditional probability tables (CPTs) can often render this evidence reversal
method computationally inefficient.
In this thesis, we describe a structured simulation algorithm that uses the evidence reversal
technique based on a tree-structured representation for CPTs. Most real systems exhibit a large
amount of local structure. The tree can reduce network complexity by exploiting this structure to keep
CPTs in a compact way even after arcs have been reversed. The tree also has a major impact on improving
computational efficiency by capturing context-specific independence during simulation. Experimental
results show that in general our structured evidence reversal algorithm improves convergence
performance significantly while being both spatially and computationally much more efficient
than its unstructured counterpart.
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Extent |
3954175 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-03-13
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0051525
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1996-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.