MoEP-AE: Autoencoding Mixtures of Exponential Power Distributions for Open-Set Recognition

Abstract

Open-set recognition aims to identify unknown classes while maintaining classification performance on known classes and has attracted increasing attention in the pattern recognition field. However, how to learn effective feature representations whose distributions are usually complex for classifying both known-class and unknown-class samples when only the known-class samples are available for training is an ongoing issue in open-set recognition. In contrast to methods implementing a single Gaussian, a mixture of Gaussians (MoG), or multiple MoGs, we propose a novel autoencoder that learns feature representations by modeling them as mixtures of exponential power distributions (MoEPs) in latent spaces called MoEP-AE. The proposed autoencoder considers that many real-world distributions are sub-Gaussian or super-Gaussian and can thus be represented by MoEPs rather than a single Gaussian or an MoG or multiple MoGs. We design a differentiable sampler that can sample from an MoEP to guarantee that the proposed autoencoder is trained effectively. Furthermore, we propose an MoEP-AE-based method for open-set recognition by introducing a discrimination strategy, where the MoEP-AE is used to model the distributions of the features extracted from the input known-class samples by minimizing a designed loss function at the training stage, called MoEP-AE-OSR. Extensive experimental results in both standard-dataset and cross-dataset settings demonstrate that the MoEP-AE-OSR method outperforms 14 existing open-set recognition methods in most cases in both open-set recognition and closed-set recognition tasks.