Yansen Zhang(张岩森)

Love Life. Enjoy Research.

Biography

    I am currently a Ph.D candidate (the third year) at the School of Computing, City University of Hong Kong. My supervisor is Dr. Chen Ma and I am doing the research about Explainable AI, Data Valuation, LLMs for OR.
    I received the master's degree from the School of Computer Science and Engineering, Sun Yat-sen University, where I was enrolled in the Outstanding Postgraduate Candidates Exempt from Admission Exam program. My supervisor was Prof. Yubao Liu and I did the research of graph-based sequential recommendation.
    I received the bachelor's degree from the School of Software College, Northeastern University, where my academic enlightenment advisor was Prof. Guibing Guo and I followed him to research the topic of explainable recommendation.

Ph.D in Computer Science
City University of Hong Kong
Hong Kong SAR, China
Sep 2022 - Present

M.S. in Software Engineering
Sun Yat-sen University
Guangzhou, China
Sep 2019 - Jun 2022

B.S. in Software Engineering
Northeastern University
Shenyang, China
Sep 2015 - Jun 2019


News

  • 2025-05: One paper about explainable diversity in recommendation has been accepted in ECMLPKDD 2025!
  • 2025-05: One paper about data pruning by Shapley values in recommendation has been accepted in KDD 2025!
  • 2025-01: One paper about explainable operation research within large language models has been accepted in ICLR 2025!
  • 2025-01: One paper about cross-domain sequential recommendation has been accepted in TOIS 2025!
  • 2024-03: One paper about diversity in search and recommendation has been accepted in TKDE 2024!

  • Publications

    Counterfactual Multi-player Bandits for Explainable Recommendation Diversification

    ECMLPKDD 2025

    we propose a \textbf{C}ounterfactual \textbf{M}ulti-player \textbf{B}andits (CMB) method to deliver explainable recommendation diversification across a wide range of diversity metrics. Leveraging a counterfactual framework, our method identifies the factors influencing diversity outcomes. Meanwhile, we adopt the multi-player bandits to optimize the counterfactual optimization objective, making it adaptable to both differentiable and non-differentiable diversity metrics.

    Yansen Zhang, Bowei He, Xiaokun Zhang, Haolun Wu, Zexu Sun, Chen Ma.

    Paper Code

    Shapley Value-driven Data Pruning for Recommender Systems

    KDD 2025

    We propose Shapley Value-driven Valuation (SVV), a framework that evaluates interactions based on their objective impact on model training rather than subjective intent assumptions. In SVV, a real-time Shapley value estimation method is devised to quantify each interaction's value based on its contribution to reducing training loss. Afterward, SVV highlights the interactions with high values while downplaying low ones to achieve effective data pruning for recommender systems. In addition, we develop a simulated noise protocol to examine the performance of various denoising approaches systematically. This work shifts denoising from heuristic filtering to principled, model-driven interaction valuation.

    Yansen Zhang, Xiaokun Zhang, Ziqiang Cui, Chen Ma.

    Paper Code

    Decision Information Meets Large Language Models: The Future of Explainable Operations Research

    ICLR 2025

    We propose a comprehensive framework, Explainable Operations Research (EOR), emphasizing actionable and understandable explanations accompanying optimization. The core of EOR is the concept of Decision Information, which emerges from what-if analysis and focuses on evaluating the impact of complex constraints (or parameters) changes on decision-making. Specifically, we utilize bipartite graphs to quantify the changes in the OR model and adopt LLMs to improve the explanation capabilities.

    Yansen Zhang, Qingcan Kang, Wing Yin Yu, Hailei Gong, Xiaojin Fu, Xiongwei Han, Tao Zhong, Chen Ma.

    Paper Code

    Hierarchical Gating Network for Cross-Domain Sequential Recommendation

    TOIS 2025

    We propose a Hierarchical Gating Network for Cross-Domain Sequential Recommendation (HGNCDSR). Specifically, we simultaneously train single-domain and cross-domain interaction sequences, utilizing a hierarchical gating network to capture user interest representations in single-domain and cross-domain, respectively. A feature gating and an instance gating are applied respectively to extract user interests at item feature level and instance level.

    Shuliang Wang, Jiabao Zhu, Yi Wang, Chen Ma, Xin Zhao, Yansen Zhang, Ziqiang Yuan, Sijie Ruan.

    Paper

    Result Diversification in Search and Recommendation: A Survey

    TKDE 2024

    In this survey, we are the first to propose a unified taxonomy for classifying the metrics and approaches of diversification in both search and recommendation, which are two of the most extensively researched fields of retrieval systems.

    Haolun Wu*, Yansen Zhang*, Chen Ma, Fuyuan Lyu, Bowei He, Bhaskar Mitra, Xue Liu.

    Paper Code

    Learning to Infer User Implicit Preference in Conversational Recommendation

    SIGIR 2022

    We propose a new CRS framework called Conversational Recommender with Implicit Feedback (CRIF). CRIF formulates the conversational recommendation scheme as a four-phase process consisting of offline representation learning, tracking, decision, and inference. In the inference module, by fully utilizing the relation between users' attribute-level and item-level feedback, our method can explicitly deduce users' implicit preferences.

    Chenhao Hu, Shuhua Huang, Yansen Zhang, Yubao Liu.

    Paper

    Self-Adaptive Graph Neural Networks for Personalized Sequential Recommendation

    ICONIP 2021

    We proposed a self-adaptive graph neural network with future contexts for sequential recommendation. SA-GNN applied a GNN model within both past and future contexts to model user dynamic interests, and utilized a self-adaptive module and attention module to weaken the negative effect of unsuitable connections in item graph.

    Yansen Zhang, Chenhao Hu, Genan Dai, Weiyang Kong, Yubao Liu.

    Paper Code

    Internship

  • Huawei Noah’s Ark Lab: Jun 2024 - Present, Hong Kong SAR, China
    • Developed a framework for explainable operations research, which utilizes LLMs to provide actionable and understandable explanations for optimization problems, which has been accepted in ICLR 2025.
    • Focus on the intersection of operations research and large language models, aiming to enhance the interpretability and usability of optimization solutions. Another work has been subbmitted to NeurIPS 2025.

  • Skills

  • Programming: Python, C/C++, LaTex, Markdown, Matlab, R, JavaScript, SQL.
  • Frameworks/Platforms: PyTorch, Linux, TensorFlow, Keras.
  • Software Tools: Git, Visio, PhotoShop, MS Office.
  • Languages: Chinese (native), English (IELTS 6.5).

  • Additional

    Teaching Experience

  • Teaching Assistant (Head): Semester B 2024/25, GE2324: The Art and Science of Data, City University of Hong Kong.
  • Teaching Assistant (Head): Semester A 2024/25, CS2334: Data Structures for DS, City University of Hong Kong.
  • Teaching Assistant: Semester B 2022/23, 2023/24, GE2324: The Art and Science of Data, City University of Hong Kong.
  • Teaching Assistant: Semester A 2022/23, 2023/24, CS2334: Data Structures for DS, City University of Hong Kong.
  • Teaching Assistant: 2019-2020, Mathematical Analysis, Sun Yat-sen University.
  • Activities

    Volunteering

  • Was a member of Public Relations Department of Northeastern University Volunteers Association.
  • Organized and participated in a variety of volunteer activities, including a campus marathon, visits to elderly homes, and a potted plant exchange, among others.
  • Hobbies

  • Love sports. I love hiking, swimming, running, riding. I just want to be a healthy person.
  • Love reading. I enjoy reading detective fiction, and also like to read books about philosophy.
  • Love anime. I love chinese anime now.
  • Honours & Awards

  • Graduate Student Second-class Academic Scholarship: 2021, Sun Yat-sen University
  • Graduate Student First-class Academic Scholarship: 2020, Sun Yat-sen University
  • Interdisciplinary Contest in Modeling: 2018, international-level, Honorable Mention
  • Excellent League Member Model: 2017–2018, Northeastern University
  • The Second Prize Scholarship: 2015–2018, Northeastern University
  • National Encouragement Scholarship: 2015-2018, Northeastern University
  • Excellent Students Awards: 2015–2017, Northeastern University
  • 28th High School Olympic Chemical Competition: 2014, provincial level, Third Prize
  • Contact Information

  • Phone: (+852) 6589-4045
  • Email: yanszhang7-c@my.cityu.edu.hk