Non-Adversarial Novelty Detection with Generative Latent Nearest Neighbors

Novelty detection is the task of identifying whether a new data point is considered to be an inlier or an outlier. Generative Adversarial Networks (GAN)-based methods suffer from mode dropping and unstable training issue, which poses the greatest threat to learn the target class distribution. To solve mode dropping issues, the nearest neighbor generator is designed to ensure that for every training image there exists a candidate generated image that is near to it at optimality. The generator considers the entire distribution of training data without mode dropping. To avoid the instability training issue, we consider capturing the distribution of the target class by non-adversarial strategy. In addition, to provide great image priors and fully diversity candidate samples for the generator, we also design a two-step mapping process. Finally, Experiments show that our model has clear superiority over cutting-edge novelty detectors and achieves state-of-the-art results on the datasets.