``"Best-of-Many-Samples" Distribution Matching

Apratim Bhattacharyya, Mario Fritz, Bernt Schiele

TL;DR: We propose a new objective for training hybrid VAE-GANs which lead to significant improvement in mode coverage and quality.

Abstract: Generative Adversarial Networks (GANs) can achieve state-of-the-art sample quality in generative modelling tasks but suffer from the mode collapse problem. Variational Autoencoders (VAE) on the other hand explicitly maximize a reconstruction-based data log-likelihood forcing it to cover all modes, but suffer from poorer sample quality. Recent works have proposed hybrid VAE-GAN frameworks which integrate a GAN-based synthetic likelihood to the VAE objective to address both the mode collapse and sample quality issues, with limited success. This is because the VAE objective forces a trade-off between the data log-likelihood and divergence to the latent prior. The synthetic likelihood ratio term also shows instability during training. We propose a novel objective with a ``"Best-of-Many-Samples" reconstruction cost and a stable direct estimate of the synthetic likelihood. This enables our hybrid VAE-GAN framework to achieve high data log-likelihood and low divergence to the latent prior at the same time and shows significant improvement over both hybrid VAE-GANS and plain GANs in mode coverage and quality.

Code: https://drive.google.com/drive/folders/10RCFaA8kOgkRHXIJpXIWAC-uUyLiEhlY?usp=sharing

Keywords: Distribution Matching, Generative Adversarial Networks, Variational Autoencoders