arXiv subjects

Tomoya Yanagi

Publications and source records attributed to Tomoya Yanagi.

3 recordsLinked to original sources

arXiv2026

Distributionally robust optimization for recommendation selection

Recommender systems play an essential role in online services by providing personalized item lists to support users' decision-making processes. While collaborative filtering methods can achieve high accuracy, it is crucial to consider not only accuracy but also the diversity of recommended items to improve user satisfaction. Although financial portfolio theory has been applied to balance these factors, existing models are often sensitive to estimation errors in rating statistics. To overcome these challenges, we establish a computational framework of distributionally robust optimization (DRO) for recommendation selection. We first formulate a cardinality-constrained DRO model based on moment-based ambiguity sets to select a specified number of items for each user. We then design a penalty alternating direction method (PADM) to efficiently compute high-quality solutions and prove its convergence properties. Computational experiments using three publicly available rating datasets demonstrate that our DRO model generates more diverse recommendations than existing models while maintaining the same level of accuracy. Additionally, our solution method computes these recommendations for each user in just a few seconds, proving its practical effectiveness. This study establishes a DRO framework that has the potential to enhance the recommendation quality of various collaborative filtering methods.

math.OC↗

arXiv2024

Robust portfolio optimization for recommender systems considering uncertainty of estimated statistics

This paper is concerned with portfolio optimization models for creating high-quality lists of recommended items to balance the accuracy and diversity of recommendations. However, the statistics (i.e., expectation and covariance of ratings) required for mean--variance portfolio optimization are subject to inevitable estimation errors. To remedy this situation, we focus on robust optimization techniques that derive reliable solutions to uncertain optimization problems. Specifically, we propose a robust portfolio optimization model that copes with the uncertainty of estimated statistics based on the cardinality-based uncertainty sets. This robust portfolio optimization model can be reduced to a mixed-integer linear optimization problem, which can be solved exactly using mathematical optimization solvers. Experimental results using two publicly available rating datasets demonstrate that our method can improve not only the recommendation accuracy but also the diversity of recommendations compared with conventional mean--variance portfolio optimization models. Notably, our method has the potential to improve the recommendation quality of various rating prediction algorithms.

cs.IR↗

arXiv2024

Privacy-preserving recommender system using the data collaboration analysis for distributed datasets

In order to provide high-quality recommendations for users, it is desirable to share and integrate multiple datasets held by different parties. However, when sharing such distributed datasets, we need to protect personal and confidential information contained in the datasets. To this end, we establish a framework for privacy-preserving recommender systems using the data collaboration analysis of distributed datasets. Numerical experiments with two public rating datasets demonstrate that our privacy-preserving method for rating prediction can improve the prediction accuracy for distributed datasets. This study opens up new possibilities for privacy-preserving techniques in recommender systems.

cs.IR↗