Sequence Adaptation via Reinforcement Learning in Recommender Systems

TL;DR

This paper introduces SAR, a reinforcement learning-based model that personalizes sequence length in recommender systems to improve accuracy by capturing individual user behavior patterns.

Contribution

The study proposes a novel actor-critic RL framework that dynamically adjusts sequence length for each user, enhancing recommendation performance over fixed-length models.

Findings

SAR outperforms baseline methods on four real-world datasets.

Personalized sequence length improves recommendation accuracy.

The model effectively captures diverse user sequential behaviors.

Abstract

Accounting for the fact that users have different sequential patterns, the main drawback of state-of-the-art recommendation strategies is that a fixed sequence length of user-item interactions is required as input to train the models. This might limit the recommendation accuracy, as in practice users follow different trends on the sequential recommendations. Hence, baseline strategies might ignore important sequential interactions or add noise to the models with redundant interactions, depending on the variety of users' sequential behaviours. To overcome this problem, in this study we propose the SAR model, which not only learns the sequential patterns but also adjusts the sequence length of user-item interactions in a personalized manner. We first design an actor-critic framework, where the RL agent tries to compute the optimal sequence length as an action, given the user's state representation at a certain time step. In addition, we optimize a joint loss function to align the accuracy of the sequential recommendations with the expected cumulative rewards of the critic network, while at the same time we adapt the sequence length with the actor network in a personalized manner. Our experimental evaluation on four real-world datasets demonstrates the superiority of our proposed model over several baseline approaches. Finally, we make our implementation publicly available at https://github.com/stefanosantaris/sar.