2019

On the Expressiveness of Approximate Inference in Bayesian Neural Networks

Foong, Andrew Y. K., Burt, David R., Li, Yingzhen et al.

Understand

While Bayesian neural networks (BNNs) hold the promise of being flexible, well-calibrated statistical models, inference often requires approximations whose consequences are poorly understood.

  • We study the quality of common variational methods in approximating the Bayesian predictive distribution.
  • For single-hidden layer ReLU BNNs, we prove a fundamental limitation in function-space of two of the most commonly used distributions defined in weight-space: mean-field Gaussian and Monte Carlo dropout.
  • We find there are simple cases where neither method can have substantially increased uncertainty in between well-separated regions of low uncertainty.

Reading the bibliography…