https://www.youtube.com/watch?v=u3vVyFVU_lI

GANs and VAEs have demonstrated impressive performance results on challenging tasks such as learning distributions of natural images. However, several issues limit their application in practice. Neither allows for ex-act evaluation of the probability density of new points.

Normalizing Flow is a transformation of a simple probability distribution (e.g., a standard normal) into a more complex distribution by a sequence of invertible and differentiable mappings.

Flow-based generative models, first described in NICE (Dinh et al., 2014) and extended in RealNVP (Dinh et al., 2016). We explain the key ideas behind this class of model in the following sections.