janhuenermann / svgd

Implementation of Stein Variational Gradient Descent to learn neural samplers.

Implementation of Stein Variational Gradient Descent

The paper titled Stein Variational Gradient Descent: A General Purpose Bayesian Inference Algorithm (link) describes how one can get samples from arbitrary distributions using a special kind of gradient descent.

In this implementation I created a neural sampler that – using SVGD – learns to sample from a given (unnormalized) log probability function, which could also be an energy function. This is also described by follow-up paper Learning to Draw Samples with Amortized Stein Variational Gradient Descent (link).

Figure 1: Convergence of a neural network learning to sample from a gaussian mixture model. Background is the likelihood of the mixture model.

Applications

SVGD is useful in the context of energy-based models; where one can learn the energy function (like a GAN) to distinguish between generated samples and dataset samples. But the sample space is often very high-dimensional (images) and sampling in this space is often hard. Markov-Chain Monte Carlo can be used, but is often very slow. SVGD on the other hand can learn a neural sampler, that is a neural network that learns to sample from the distribution given by the energy function.

Frameworks

This implementation is written using TensorFlow 2.0 and matplotlib.