Archive for the ‘Graphical Models’ Category

Accelerating Inference: towards a full Language, Compiler and Hardware stack

Friday, December 14th, 2012

Accelerating Inference: towards a full Language, Compiler and Hardware stack by Shawn Hershey, Jeff Bernstein, Bill Bradley, Andrew Schweitzer, Noah Stein, Theo Weber, Ben Vigoda.

Abstract:

We introduce Dimple, a fully open-source API for probabilistic modeling. Dimple allows the user to specify probabilistic models in the form of graphical models, Bayesian networks, or factor graphs, and performs inference (by automatically deriving an inference engine from a variety of algorithms) on the model. Dimple also serves as a compiler for GP5, a hardware accelerator for inference.

From the introduction:

Graphical models alleviate the complexity inherent to large dimensional statistical models (the so-called curse of dimensionality) by dividing the problem into a series of logically (and statistically) independent components. By factoring the problem into subproblems with known and simple interdependencies, and by adopting a common language to describe each subproblem, one can considerably simplify the task of creating complex Bayesian models. Modularity can be taken advantage of further by leveraging this modeling hierarchy over several levels (e.g. a submodel can also be decomposed into a family of sub-submodels). Finally, by providing a framework which abstracts the key concepts underlying classes of models, graphical models allow the design of general algorithms which can be efficiently applied across completely different fields, and systematically derived from a model description.

Suggestive of sub-models of merging?

I first saw this in a tweet from Stefano Bertolo.

Stan: A (Bayesian) Directed Graphical Model Compiler

Sunday, January 22nd, 2012

Stan: A (Bayesian) Directed Graphical Model Compiler

Post with link to presentation to NYC machine learning meetup.

Stan: a C++ library for probability and sampling has not (yet) been released (BSD license) but has the following components:

From the Google Code page:

  • Directed Graphical Model Compiler
  • (Adaptive) Hamiltonian Monte Carlo Sampling
  • Hamiltonian Monte Carlo Sampling
  • Gibbs Sampling for Discrete Parameters
  • Reverse Mode Algorithmic Differentiation
  • Probability Distributions
  • Special Functions
  • Matrices and Linear Algebra

Slides for the NIPS 2011 tutorial

Monday, December 12th, 2011

Slides for the NIPS 2011 tutorial by Alex Smola.

From the post:

The slides for the 2011 NIPS tutorial on Graphical Models for the Internet are online. Lots of stuff on parallelization, applications to user modeling, content recommendation, and content analysis here.

Very cool! Wish I could have seen the tutorial!

Read slowly and carefully!

Your Help Needed: the Effect of Aesthetics on Visualization – Post

Friday, March 4th, 2011

Your Help Needed: the Effect of Aesthetics on Visualization

Your opportunity to make a contribution to the study of visualization!

From the website:

We have just launched an online study on measuring the effect of aesthetics in data visualization. If you have about 10-20 minutes of uninterrupted time, please head over to Aesthetic Impact [aesthetic-impact.com] and take part in our online study. The main task that will be expected from you, is to interact with a visualization, and describe what you have learned from it.

The study is not only meant for visualization fanatics, so please pass around the URL to any person who might be interested in participating. The only thing you need to know is that the study is less about usability, utility or usefulness, and more about measuring what non-trivial and unexpected insights you actually ‘get’ from interacting with a specific data representation.

As communicating insight is the main reason for any interactive visualization, we think that measuring this aspect has become really important. Yet, we require the help of many ‘users’ to be able to say something meaningful…

Chris Harrison’s Graphics – Post

Wednesday, January 12th, 2011

Chris Harrison’s Graphics reported by Bob Carpenter at LingPipe Blog.

Visualizations are like slide presentations.

They can be painful but you do encounter those that simply work.

These are ones that just work.

It is possible to visualize a topic map as a graph, yawn, but when was the last time you saw a graph outside of math class?

True, all maps are graphs but I would be willing to bet most people would not name a map as an example of a graph.

Why?

Because a map, at least a well done one, assists its reader in accomplishing some task of interest to them. Using the map is a goal, not an end unto itself.

Hmmm, maps with nodes and edges connecting those nodes,…, I know, how about Disney World Maps!

Those are maps of physical locations.

Questions:

  1. What are some of the characteristics of any one or more of the Disney maps? (3-5 pages, no citations)
  2. Find five examples of maps that are not maps of physical locations.
  3. What is different/same about the maps in #1 versus #2? (3-5 pages, no citations)

*****
PS: Depending on the status of diplomatic cables (hopefully from a number of countries), consider that a graph between the cables could be interesting.

More interesting would be photos of the folks mentioned, arranged by events or contacts they share in the US. Has characteristics of a graph but perhaps more immediately compelling.

Say showing photos of all the School of the Americas graduates clustered together, like in a high school yearbook or police mug photo book.

Or showing those same photos with US officials.

To facilitate human recognition of additional subjects to pursue.

Graphical Models

Tuesday, December 21st, 2010

Graphical Models Author: Zoubin Ghahramani

Abstract:

An introduction to directed and undirected probabilistic graphical models, including inference (belief propagation and the junction tree algorithm), parameter learning and structure learning, variational approximations, and approximate inference.

  • Introduction to graphical models: (directed, undirected and factor graphs; conditional independence; d-separation; plate notation)
  • Inference and propagation algorithms: (belief propagation; factor graph propagation; forward-backward and Kalman smoothing; the junction tree algorithm)
  • Learning parameters and structure: maximum likelihood and Bayesian parameter learning for complete and incomplete data; EM; Dirichlet distributions; score-based structure learning; Bayesian structural EM; brief comments on causality and on learning undirected models)
  • Approximate Inference: (Laplace approximation; BIC; variational Bayesian EM; variational message passing; VB for model selection)
  • Bayesian information retrieval using sets of items: (Bayesian Sets; Applications)
  • Foundations of Bayesian inference: (Cox Theorem; Dutch Book Theorem; Asymptotic consensus and certainty; choosing priors; limitations)

Start with this lecture before Dirichlet Processes: Tutorial and Practical Course