Contrastive Conditional Transport for Representation Learning

Contrastive learning (CL) has achieved remarkable success in learning data representations without label supervision. However, the conventional CL loss is sensitive to how many negative samples are included and how they are selected. This paper proposes contrastive conditional transport (CCT) that defines its CL loss over dependent sample-query pairs, which in practice is realized by drawing a random query, randomly selecting positive and negative samples, and contrastively reweighting these samples according to their distances to the query, exerting a greater force to both pull more distant positive samples towards the query and push closer negative samples away from the query. Theoretical analysis shows that this unique contrastive reweighting scheme helps in the representation space to both align the positive samples with the query and reduce the mutual information between the negative sample and query. Extensive large-scale experiments on standard vision tasks show that CCT not only consistently outperforms existing methods on benchmark datasets in contrastive representation learning but also provides interpretable contrastive weights and latent representations. PyTorch code will be provided.