Publications & Technical Reports | |
R225 | |
From Exact to Anytime Solutions for Marginal MAP
Junkyu Lee, Radu Marinescu, Rina Dechter and Alexander Ihler
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Abstract
This paper explores the anytime performance of search-based
algorithms for solving the Marginal MAP task over graphical
models. The current state-of-the-art for solving this challenging
task is based on best-first search exploring the AND/OR
graph with the guidance of heuristics based on mini-bucket
and variational cost-shifting principles. Yet, those schemes
are uncompromising in that they solve the problem exactly,
or not at all, and often suffer from memory problems. In
this work, we explore the well known principle of weighted
search for converting best-first search solvers into anytime
schemes. The weighted best-first search schemes report a
solution early in the process by using inadmissible heuristics,
and subsequently improve the solution. While it was
demonstrated recently that weighted schemes can yield effective
anytime behavior for pure MAP tasks, Marginal MAP
is far more challenging (e.g., a conditional sum must be evaluated
for every solution). Yet, in an extensive empirical analysis
we show that weighted schemes are indeed highly effective
anytime solvers for Marginal MAP yielding the most
competitive schemes to date for this task.
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