Generative Ratio Matching Networks
Authors: Akash Srivastava, Kai Xu, Michael U. Gutmann, Charles Sutton
Keywords: deep generative model, deep learning, maximum mean discrepancy, density ratio estimation
TL;DR: MMD-based, saddle-point optimisation free, stable-to-train generative model that beats GAN on generative quality without playing any  zero-sum games.
Abstract: Deep generative models can learn to generate realistic-looking images, but many of the most effective methods are adversarial and involve a saddlepoint optimization, which requires a careful balancing of training between a generator network and a critic network. Maximum mean discrepancy networks (MMD-nets) avoid this issue by using kernel as a fixed adversary, but unfortunately, they have not on their own been able to match the generative quality of adversarial training. In this work, we take their insight of using kernels as fixed adversaries further and present a novel method for training deep generative models that does not involve saddlepoint optimization. We call our method generative ratio matching or GRAM for short. In GRAM, the generator and the critic networks do not play a zero-sum game against each other, instead, they do so against a fixed kernel. Thus GRAM networks are not only stable to train like MMD-nets but they also match and beat the generative quality of adversarially trained generative networks.