Contrastive Principal Component Learning: Modeling Similarity by Augmentation Overlap

Traditional self-supervised contrastive learning methods learn embeddings by pulling views of the same sample together and pushing views of different samples away. Since views of a sample are usually generated via data augmentations, the semantic relationship between samples is ignored. Based on the observation that semantically similar samples are more likely to have similar augmentations, we propose to measure similarity via the distribution of augmentations, i.e., how much the augmentations of two samples overlap. To handle the dimensional and computational complexity, we propose a novel Contrastive Principal Component Learning (CPCL) method composed of a contrastive-like loss and an on-the-fly projection loss to efficiently perform PCA on the augmentation feature, which encodes the augmentation distribution. By CPCL, the learned low-dimensional embeddings theoretically preserve the similarity of augmentation distribution between samples. Empirical results show our method can achieve competitive results against various traditional contrastive learning methods on different benchmarks.