An Aligning and Training Framework for Multimodal Recommendations

With the development of multimedia applications, multimodal recommendations are playing an essential role, as they can leverage rich contexts beyond user interactions. Existing methods mainly regard multimodal information as an auxiliary, using them to help learn ID features; however, there exist semantic gaps among multimodal content features and ID features, for which directly using multimodal information as an auxiliary would lead to misalignment in representations of users and items. In this paper, we first systematically investigate the misalignment issue in multimodal recommendations, and propose a solution named AlignRec. In AlignRec, the recommendation objective is decomposed into three alignments, namely alignment within contents, alignment between content and categorical ID, and alignment between users and items. Each alignment is characterized by a specific objective function and is integrated into our multimodal recommendation framework. To effectively train our AlignRec, we propose starting from pre-training the first alignment to obtain unified multimodal features and subsequently training the following two alignments together with these features as input. As it is essential to analyze whether each multimodal feature helps in training, we design three new classes of metrics to evaluate intermediate performance. Our extensive experiments on three real-world datasets consistently verify the superiority of AlignRec compared to nine baselines. We also find that the multimodal features generated by AlignRec are better than currently used ones, which are to be open-sourced.

Sliding Spectrum Decomposition for Diversified Recommendation

Content feed, a type of product that recommends a sequence of items for users to browse and engage with, has gained tremendous popularity among social media platforms. In this paper, we propose to study the diversity problem in such a scenario from an item sequence perspective using time series analysis techniques. We derive a method called sliding spectrum decomposition (SSD) that captures users' perception of diversity in browsing a long item sequence. We also share our experiences in designing and implementing a suitable item embedding method for accurate similarity measurement under long tail effect. Combined together, they are now fully implemented and deployed in Xiaohongshu App's production recommender system that serves the main Explore Feed product for tens of millions of users every day. We demonstrate the effectiveness and efficiency of the method through theoretical analysis, offline experiments and online A/B tests.

RLzoo: A Comprehensive and Adaptive Reinforcement Learning Library

Recently, we have seen a rapidly growing adoption of Deep Reinforcement Learning (DRL) technologies. Fully achieving the promise of these technologies in practice is, however, extremely difficult. Users have to invest tremendous efforts in building DRL agents, incorporating the agents into various external training environments, and tuning agent implementation/hyper-parameters so that they can reproduce state-of-the-art (SOTA) performance. In this paper, we propose RLzoo, a new DRL library that aims to make it easy to develop and reproduce DRL algorithms. RLzoo has both high-level APIs and low-level APIs, useful for constructing and customising DRL agents, respectively. It has an adaptive agent construction algorithm that can automatically integrate custom RLzoo agents into various external training environments. To help reproduce the results of SOTA algorithms, RLzoo provides rich reference DRL algorithm implementations and effective hyper-parameter settings. Extensive evaluation results show that RLzoo not only outperforms existing DRL libraries in its simplicity of API design; but also provides the largest number of reference DRL algorithm implementations.