UMass LIVING

(Sep 18 12-2pm) Pre-meeting Overview: Best-First AND/OR Search for MPE (Marinescue, Dechter)

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Here is the reading for this week:

http://www.ics.uci.edu/%7Ecsp/r144.pdf

The motivation for reading this paper is as follows. In our work on both OCR and on Scene Text Recognition, I have been somewhat less focused on parameter setting, and somewhat more focused on finding the MAP solution, or the Most Probable Explanation (MPE) solution.

There are many ways to do this, including:

1) Loopy Belief Propagation, or Max Product; (problems: convergence not guaranteed; if it converges, still don’t know if we have the right solution)

2) Linear programming on a relaxed version of the marginal polytope, using techniques of Wainwright, or the cutting plane inequalities we just read about in Jaakkola and Sontag, currently under investigation by Gary.

3) A* search as being investigated by David and Jackie at the moment.

4) Graph cut methods.  These work on binary labelings with submodular potentials, and can be extended to multi-class labelings using -expansion moves.  For instance, see http://www.cs.cornell.edu/~rdz/Papers/KZ-PAMI04.pdf

and probably others.

I’m trying to learn more about the A* version, and in particular, compare it to the Jaakkola Sontag approach. I’m hoping this paper illuminates graph-search type methods of solving the MAP assignment problem.

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