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Hierarchical VAEs Know What They Don’t Know
Jakob D. Havtorn · Jes Frellsen · Søren Hauberg · Lars Maaløe

Tue Jul 20 06:30 AM -- 06:35 AM (PDT) @

Deep generative models have been demonstrated as state-of-the-art density estimators. Yet, recent work has found that they often assign a higher likelihood to data from outside the training distribution. This seemingly paradoxical behavior has caused concerns over the quality of the attained density estimates. In the context of hierarchical variational autoencoders, we provide evidence to explain this behavior by out-of-distribution data having in-distribution low-level features. We argue that this is both expected and desirable behavior. With this insight in hand, we develop a fast, scalable and fully unsupervised likelihood-ratio score for OOD detection that requires data to be in-distribution across all feature-levels. We benchmark the method on a vast set of data and model combinations and achieve state-of-the-art results on out-of-distribution detection.

Author Information

Jakob D. Havtorn (Technical University of Denmark)
Jes Frellsen (Technical University of Denmark)
Søren Hauberg (Technical University of Denmark)

I was born, and now I exist.

Lars Maaløe (Corti)

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