Diffusion Priors In Variational Autoencoders

Antoine Wehenkel, Gilles Louppe

Keywords: Diffusion models, VAE, autoencoder, variational inference, likelihood based models, prior modelling.

TL;DR: The paper introduce diffusion models as prior distributions of variational autoencoders.

Abstract: Among likelihood-based approaches for deep generative modelling, variational autoencoders (VAEs) offer scalable amortized posterior inference and fast sampling. However, VAEs are also more and more outperformed by competing models such as normalizing flows (NFs), deep-energy models, or the new denoising diffusion probabilistic models (DDPMs). In this preliminary work, we improve VAEs by demonstrating how DDPMs can be used for modelling the prior distribution of the latent variables. The diffusion prior model improves upon Gaussian priors of classical VAEs and is competitive with NF-based priors. Finally, we hypothesize that hierarchical VAEs could similarly benefit from the enhanced capacity of diffusion priors.