ZHAO Xi (赵希)

Research Postgraduate (Started in Sep. 2022, funded by HKPFS)

Computer Science and Engineering

Hong Kong University of Science and Technology

I am a research postgraduate (PhD. Candidate) of DSF Group, Computer Science and Engineering at Hong Kong University of Science and Technology (HKUST), under the supervision of Prof. Xiaofang Zhou. Prior to studying at HKUST, I received my M.Eng from the school of Computer Science and Technology, Huazhong University of Science and Technology (HUST), under the supervision of Prof. Bolong Zheng.

My research lies in the area of high-dimensional search in vector database and I focus on the algorithm and theory in high-dimensional vector search, aiming at designing high-performance indexes to manage large-scale high-dimensional datasets. Specifically, I work on studying locality-sensitive hashing (LSH), Vector Quantization (VQ) and proximity graph for approximate nearest neighbor search (ANNS) and maximum inner product search (MIPS) in high-dimensional vector spaces.

Welcome to contact me if you are interested in my works.

PhD in Engineering, Computer Science and Engineering (Funded by HKPFS)

Hong Kong University of Science and Technology, Hong Kong SAR, China (Sept. 2022-)

Visiting Scholar, School of Computing (Supervised by Prof. Xiaokui Xiao)

National University of Singapore, Singapore (Apr. 2025- Aug. 2025)

Research Assistant, Computer Science and Engineering

Hong Kong University of Science and Technology, Hong Kong SAR, China (Sept. 2021- Sept. 2022)

Master of Engineering, Computer Software and Theory

Huazhong University of Science and Technology, Wuhan, China (Sept. 2018 - Jun. 2021)

Overall GPA: 89.8/100 (3.94/4.00, ranking 1/37)

Bachelor of Engineering, Optoelectronic Information Science and Engineering (Honors Class)

Huazhong University of Science and Technology, Wuhan, China (Sept. 2014 - Jun. 2018)

Overall GPA: 88.4/100 (3.84/4.00)

Publications

Xi Zhao, Zhoujin Tian, Kai Huang, Yao Tian, Xiaokui Xiao, Bolong Zheng, Xiaofang Zhou: Enhancing Graph-based Approximate Maximum Inner Product Search via Norm-Adaptive Partitioning. Submitted to SIGMOD 2026.
Xi Zhao, Yao Tian, Kai Huang, Zhonghan Chen, Bolong Zheng, Xiaofang Zhou. Norm-Aware Proximity Graph Structure and Locality-Sensitive Quantization for Large-Scale Inner Product Search. Submitted to SIGMOD 2026.
Yao Tian, Zhoujin Tian, Xi Zhao, Ruiyuan Zhang, Xiaofang Zhou: GEM: A Native Graph-based Index for Multi-Vector Retrieval. Submitted to SIGMOD 2026.
Jianheng Tang, Xi Zhao, Lemin Kong, Xiaofang Zhou, Jia Li: Fused Gromov-Wasserstein Alignment for Graph Edit Distance Computation and Beyond. VLDB 2025.
Haoyu Tang, Ye Liu, Xi Zhao, Xukai Liu, Yanghai Zhang, Kai Zhang, Xiaofang Zhou, Enhong Chen: Learn while Unlearn: An Iterative Unlearning Framework for Generative Language Models. ICDM 2025.
Zhonghan Chen, Ruiyuan Zhang, Xi Zhao, Xiaojun Cheng, Xiaofang Zhou: Exploring the Meaningfulness of Nearest Neighbor Search in High-Dimensional Space. ADC 2024
Xi Zhao, Zhonghan Chen, Kai Huang, Ruiyuan Zhang, Bolong Zheng, Xiaofang Zhou: Efficient Approximate Maximum Inner Product Search over Sparse Vectors. ICDE 2024 [PDF, Technical Report, Slide] [Code]
Kai Huang, Yunqi Li, Qingqing Ye, Yao Tian, Xi Zhao, Yue Cui, Haibo Hu, Xiaofang Zhou: FRESH: Towards Efficient Graph Queries in an Outsourced Graph. ICDE 2024
Jing Zhao, Lei Li, Mengxuan Zhang, Zihan Luo, Xi Zhao, Xiaofang Zhou: A Just-In-Time Framework for Continuous Routing. ICDE 2024
Yao Tian, Ziyang Yue, Ruiyuan Zhang, Xi Zhao, Bolong Zheng, Xiaofang Zhou: Approximate Nearest Neighbor Search in High Dimensional Vector Databases: Current Research and Future Directions. TCDE 2024 (The authors are listed in alphabetical order)[PDF]
Kai Huang, Yue Cui, Qingqing Ye, Yan Zhao, Xi Zhao, Yao Tian, Kai Zheng, Haibo Hu, Xiaofang Zhou: TED+: Towards Discovering Top-k Edge-Diversified Patterns in a Graph Database. TKDE 2023
Yao Tian, Xi Zhao, Xiaofang Zhou: DB-LSH 2.0: Locality-Sensitive Hashing With Query-Based Dynamic Bucketing. TKDE 2023
Xi Zhao, Yao Tian, Kai Huang, Bolong Zheng, Xiaofang Zhou: Towards Efficient Index Construction and Approximate Nearest Neighbor Search in High-Dimensional Spaces. PVLDB 2023 [ PDF ] [ Code ]
Xi Zhao, Bolong Zheng, Xiaomeng Yi, Xiaofan Luan, Charles Xie, Xiaofang Zhou, Christian S. Jensen: FARGO: Fast Maximum Inner Product Search via Global Multi-Probing. PVLDB 2023 [PDF] [Code]
Kai Huang, Qingqing Ye, Jing Zhao, Xi Zhao, Haibo Hu, Xiaofang Zhou: VINCENT: Towards Efficient Exploratory Subgraph Search in Graph Databases. PVLDB 2022 (Demo)
Yao Tian, Tingyun Yan, Xi Zhao, Kai Huang, Xiaofang Zhou: A Learned Index for Exact Similarity Search in Metric Spaces. TKDE 2022
Yao Tian, Xi Zhao, Xiaofang Zhou: DB-LSH: Locality-Sensitive Hashing with Query-based Dynamic Bucketing. ICDE 2022 [PDF] [Code]
Bolong Zheng, Xi Zhao, Lianggui Weng, Nguyen Quoc Viet Hung, Hang Liu, Christian S. Jensen: PM-LSH: a fast and accurate in-memory framework for high-dimensional approximate NN and closest pair search. The VLDB Journal 2021
Bolong Zheng, Lianggui Weng, Xi Zhao, Kai Zeng, Xiaofang Zhou, Christian S. Jensen: REPOSE: Distributed Top-k Trajectory Similarity Search with Local Reference Point Tries. ICDE 2021
Zhong Yang, Bolong Zheng, Guohui Li, Xi Zhao, Xiaofang Zhou, Christian S. Jensen: Adaptive Top-k Overlap Set Similarity Joins. ICDE 2020
Bolong Zheng, Xi Zhao, Lianggui Weng, Nguyen Quoc Viet Hung, Hang Liu, Christian S. Jensen: PM-LSH: A Fast and Accurate LSH Framework for High-Dimensional Approximate NN Search. PVLDB 2020 (one of the best PVLDB 2020 papers) [PDF] [Code]

Awards

Hong Kong PhD Fellowship, HKUST, 2022
HKUST RedBird PhD Scholarship, HKUST, 2022
Outstanding Graduates, HUST, 2021
One of the best PVLDB 2020 papers, HUST, 2020
National Scholarship for Graduates, HUST, 2020
Outstanding Undergraduates, HUST, 2018
National Encouragement Scholarship, HUST, 2017
The 1st Prize in Mathematics Competition of Chinese College Students, HUST, 2016

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