Generative Adversarial Networks and Actor-Critic methods

Abstract

Both generative adversarial networks (GAN) in unsupervised learning and actor-critic methods in reinforcement learning (RL) have gained a reputation for being difficult to optimize. Practitioners in both fields have amassed a large number of strategies to mitigate these instabilities and improve training. Here we show that GANs can be viewed as actor-critic methods in an environment where the actor cannot affect the reward. We review the strategies for stabilizing training for each class of models, both those that generalize between the two and those that are particular to that model. We also review a number of extensions to GANs and RL algorithms with even more complicated information flow. We hope that by highlighting this formal connection we will encourage both GAN and RL communities to develop general, scalable, and stable algorithms for multilevel optimization with deep networks, and to draw inspiration across communities.

Notes

The paper discusses how similar Generative Adversial Networks are to Actor-Critic methods, and how both methods are difficult to optimize.

GANs are models with two neural networks, one that generates images and one that tries to classify images. The generator tries to best the classifier.

Actor-Critic methods are models from reinforcement learning in which a model learns an action-value function $Q^\pi(s, a)$ that predicts the expected discounted reward (the Critic), and a policy that is optimal for that value (the Actor).

The paper shows how GANs can be constructed as an Actor-Critic model, and discusses the strategies that can be used to optimize each type of model, with the idea being that these strategies can be used to optimize the other type of model.