Multi-label Cluster Discrimination for Visual Representation Learning
This work addresses the problem of improving visual representation learning for AI systems by incorporating multi-label signals, offering incremental but practical gains over existing cluster discrimination methods.
The paper tackles the limitation of CLIP's instance discrimination in encoding semantic structure by proposing Multi-Label Cluster Discrimination (MLCD), which uses multiple cluster centers as pseudo-labels and a novel loss function, achieving state-of-the-art performance on tasks like linear probe, zero-shot classification, and image-text retrieval.
Contrastive Language Image Pre-training (CLIP) has recently demonstrated success across various tasks due to superior feature representation empowered by image-text contrastive learning. However, the instance discrimination method used by CLIP can hardly encode the semantic structure of training data. To handle this limitation, cluster discrimination has been proposed through iterative cluster assignment and classification. Nevertheless, most cluster discrimination approaches only define a single pseudo-label for each image, neglecting multi-label signals in the image. In this paper, we propose a novel Multi-Label Cluster Discrimination method named MLCD to enhance representation learning. In the clustering step, we first cluster the large-scale LAION-400M dataset into one million centers based on off-the-shelf embedding features. Considering that natural images frequently contain multiple visual objects or attributes, we select the multiple closest centers as auxiliary class labels. In the discrimination step, we design a novel multi-label classification loss, which elegantly separates losses from positive classes and negative classes, and alleviates ambiguity on decision boundary. We validate the proposed multi-label cluster discrimination method with experiments on different scales of models and pre-training datasets. Experimental results show that our method achieves state-of-the-art performance on multiple downstream tasks including linear probe, zero-shot classification, and image-text retrieval. Code and models have been released at https://github.com/deepglint/unicom .