Conditional Denoising Diffusion for Sequential Recommendation

TL;DR

This paper introduces a conditional denoising diffusion model for sequential recommendation that addresses limitations of GANs and VAEs, achieving superior performance on benchmark datasets.

Contribution

The paper proposes a novel diffusion-based model with a sequence encoder and cross-attentive decoder, improving stability and quality in sequential recommendation tasks.

Findings

Outperforms existing models on four benchmark datasets.

Effectively mitigates issues like posterior collapse and over-smoothing.

Demonstrates stable and high-quality sequence generation.

Abstract

Generative models have attracted significant interest due to their ability to handle uncertainty by learning the inherent data distributions. However, two prominent generative models, namely Generative Adversarial Networks (GANs) and Variational AutoEncoders (VAEs), exhibit challenges that impede achieving optimal performance in sequential recommendation tasks. Specifically, GANs suffer from unstable optimization, while VAEs are prone to posterior collapse and over-smoothed generations. The sparse and noisy nature of sequential recommendation further exacerbates these issues. In response to these limitations, we present a conditional denoising diffusion model, which includes a sequence encoder, a cross-attentive denoising decoder, and a step-wise diffuser. This approach streamlines the optimization and generation process by dividing it into easier and tractable steps in a conditional autoregressive manner. Furthermore, we introduce a novel optimization schema that incorporates both cross-divergence loss and contrastive loss. This novel training schema enables the model to generate high-quality sequence/item representations and meanwhile precluding collapse. We conducted comprehensive experiments on four benchmark datasets, and the superior performance achieved by our model attests to its efficacy.