Rajesh Ranganath: February 25th

Title: "Black Box Variational Inference"

Abstract: Variational inference has become a widely used method to approximate posteriors in complex latent variables models. However, deriving a variational inference algorithm generally requires significant model-specific analysis, and these efforts can hinder and deter us from quickly developing and exploring a variety of models for a problem at hand. We present a "black box" variational inference algorithm, one that can be quickly applied to many models with little additional derivation. Our method is based on a stochastic optimization of the variational objective where the noisy gradient is computed from Monte Carlo samples from the variational distribution. We develop a number of methods to reduce the variance of the gradient, always maintaining the criterion that we want to avoid difficult model-based derivations. We evaluate our method against the corresponding black box sampling based methods. We find that our method reaches better predictive likelihoods much faster than sampling methods. Finally, we demonstrate that Black Box Variational Inference lets us easily explore a wide space of models by quickly constructing and evaluating several models of longitudinal healthcare data.

Josh Merel: Feb 18th

ADADELTA and LSTMs

We will discuss the adadelta paper
http://arxiv.org/pdf/1212.5701v1.pdf

and talk about LSTM layers. The original paper is (for reference): http://deeplearning.cs.cmu.edu/pdfs/Hochreiter97_lstm.pdf
But we will probably discuss a more recent result using LSTM layers that uses a slightly different notation.