I’m fascinated by tools and programs you can actually prove things about—no hand-wavy “it works on my machine” stuff. My research focus is somewhere between algorithm design, combinatorial optimization, and functional programming.

During my PhD, I explored how formal methods from programming-language theory — especially the Bird–Meertens formalism (also known as transformational programming) — can be used to tackle intractable combinatorial optimization problems. Much of my earlier work focused on classical machine-learning tasks, including clustering, classification, and decision-tree learning.

I am currently a Postdoctoral researcher in Zhenjiang Hu’s research group at Peking University. Our team is developing a new programming language, referred to as C*, that aims to unify programming and formal verification for C, enabling developers to write high-assurance systems without separating the acts of coding and proving correctness.

Experience

Working Experience

• Oct. 2025 – present: Postdoctoral researcher, Programming language Lab, Peking University.

Education

• Dec. 2021- Apr. 2025: Doc of Philosophy at University of Birmingham (School of Computer Science). I am supervised by Prof. Max. Little, and my thesis examiners are Prof. Jeremy Gibbons, University of Oxford (Department of Computer Science), Prof. Shuo Wang, University of Birmingham (School of Computer Science)

• Sept. 2017- June 2021: Bachelor of Science at Zhejiang Normal University, where I majored in Mechanical Design Manufacturing and Automation.

Research

• Recursive optimization: exact and efficient combinatorial optimization algorithm design principles with applications to machine learning Xi He, PhD thesis.

• Proper decision trees: An axiomatic framework for solving optimal decision tree problems with arbitrary splitting rules Xi He, Max A. Little (Under review)

• Foundational theory for optimal decision tree problems. I. Algorithmic and geometric foundations Xi He (Under review)

• Foundational theory for optimal decision tree problems. II. Optimal hypersurface decision tree algorithm Xi He (Under review)

• Combination generators with optimal cache utilization and communication free parallel execution Xi He, Max A. Little (Under review)

• Deep-ICE: The first globally optimal algorithm for empirical risk minimization of two-layer maxout and ReLU networks Xi He, Yi Miao， Max A. Little (Under review)

• Dynamic programming by polymorphic algebraic shortcut fusion Max A. Little, Xi He, Ugur Kayas, Formal Aspects of Computing.
• An efficient, provably exact, practical algorithm for the 0-1 loss linear classification problem Xi He, Waheed Ul Rahman, Max A. Little (Under review)

All the papers that are in preparation can be found in the discussion of my (draft) thesis Recursive optimization framework.

Software

You can find the Python implementations of my algorithms from my Git repositories.

Activities

• 2-6 April, 2023 Attending Midlands Graduate School 2023 (bham.ac.uk), Birmingham, UK
• 13 June, 2023 Attending Advances in Data Science and AI Conference 2023 (manchester.ac.uk), Manchester

Profile

My name is Xi He, which is the Chinese transcription of “何希”, “Xi” pronounce as “She”, it means “hope” in Chinese.

I enjoy lifting weights, basketball and hiking in my free time. I also write some blogs sometimes.