Multi-pair Contrastive Learning Based on Same-Timestamp Data Augmentation for Sequential Recommendation

The core of sequential recommendations is to model users’ dynamic preferences from their sequential historical behaviors. Bidirectional representation models can make better sequential recommendations because each item in user’s historical behaviors fuses information from both left and right sides. Despite their effectiveness, we argue that such bidirectional models are sub-optimal due to the limitations including: a) items with the same timestamp interactions have adverse effect on user modeling; b) the random masking process often produces noises. To address these limitations, we propose Multi-pair Contrastive Learning based on same-timestamp data augmentation for Sequential Recommendation (MCL4SR). Specifically, we firstly modify the masking strategies of BERT encoder. Then we propose a multi-pair contrastive learning framework by exploring data augmentation of the same timestamp interactions. During the training and testing process, we design three types of samples so as to imitate human learning. Extensive experiments on two benchmark datasets show that our model outperforms state-of-the-art sequential models.