Archive for the ‘Operations Research’ Category

Distributed Dual Decomposition (DDD) in GraphLab

Thursday, April 18th, 2013

Distributed Dual Decomposition (DDD) in GraphLab by Danny Bickson.

From the post:

Our collaborator Dhruv Batra, from Virginia Tech has kindly contributed DDD code for GraphLab. Here are some explanation about the method and how to deploy it.

The full documentation is found here.

Distributed Dual Decomposition

Dual Decomposition (DD), also called Lagrangian Relaxation, is a powerful technique with a rich history in Operations Research. DD solves a relaxation of difficult optimization problems by decomposing them into simpler subproblems, solving these simpler subproblems independently and then combining these solutions into an approximate global solution.

More details about DD for solving Maximum A Posteriori (MAP) inference problems in Markov Random Fields (MRFs) can be found in the following:

D. Sontag, A. Globerson, T. Jaakkola. Introduction to Dual Decomposition for Inference. Optimization for Machine Learning, editors S. Sra, S. Nowozin, and S. J. Wright: MIT Press, 2011.

Always bear in mind that string matching is only one form of subject identification.

pumpkin patches and queuing theory

Wednesday, October 12th, 2011

pumpkin patches and queuing theory

From the post:

This weekend, my family and I went to a pumpkin patch. Everyone else had the same idea. The line stretched out of the pumpkin patch gates and through the parking lot. We waited in line for ten minutes and then balked. When we left, about 90% of those that were leaving did not have pumpkins. We arrived in the morning on Sunday. It was only going to get busier. I cannot imagine the amount of revenue that was lost. We found out later that it took nearly two hours to get through the line.

During our short wait and on our drive to another orchard, we discussed queuing and pumpkin patches.

With a lead-in like that, how could I resist pointing to it? (Besides, I am a Charlie Brown fan.)

A little operations research discussion won’t hurt you and might be useful in terms of dealing with organizations that like that sort of thing. The US DoD, etc. Might even provide some insight into how they assign/create subject identity.