Xiaocheng Tang
Senior Staff Research Scientist, Engineering Manager
Machine Learning @ DiDi Labs, Mountain View, CA
xiaochengtang at didiglobal dot com

Xiaocheng works at the intersection of machine learning, reinforcement learning, optimization, and operation research. He currently leads a team of researchers and engineers to improve the ride-hailing marketplace efficiency at DiDi AI Labs. He has published 20+ top-conference, patents and journal papers in the field. Additionally, his work on joint optimization of order dispatching and reposition via reinforcement learning won Best Demo Awards at NeurIPS 2018. He and his team received Daniel H. Wagner prize for Excellence in Operations Research practice at INFORMS 2019. His work on AutoML in collaboration with UCLA won Outstanding Paper Awards at ICLR 2021 (code).

Xiaocheng received his PhD degrees in Optimization and Machine Learning advised by Prof. Katya Scheinberg (wiki). During his graduate study, he has been actively engaged in analyzing and designing novel optimization theories and algorithms for large-scale problems arising from various applications and in particular those in Artificial Intelligence. His work in fast and scalable training algorithms and convergence theory was presented at NIPS 2013 and was published in the journal of Mathematical Programming which is ranked the No.1 journal in the field of Mathematical Optimization by Google Scholar. Xiaocheng is also an Apache Committer contributing to Apache MADlib — a distributed in-database machine learning library started by Chris Ré from Stanford and Joe Hellerstein from Berkeley among others.

He used to work in Numerical Methods group in IBM T.J. Watson Research, Yorktown Heights, NY, and was funded by Yahoo FREP award working on online AD targeting and user personalization in Machine Learning group in Yahoo Labs, Sunnyvale, CA in 2014. He earned his undergrad degree with High Honors from Chu KoChen Honors College and College of Control Science and Engineering in Zhejiang University, Hangzhou, China .

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I'm interested in reinforcement learning, machine learning, optimization and operation research. Representative papers are highlighted.

RANK-NOSH: Efficient Predictor-Based Architecture Search via Non-Uniform Successive Halving

Ruochen Wang, Xiangning Chen, Minhao Cheng, Xiaocheng Tang, Cho-Jui Hsieh
ICCV, 2021
arxiv /

We propose NOn-uniform Successive Halving (NOSH), a hierarchical scheduling algorithm, combined within a GNN-based learning to rank with pairwise comparisons formulation for predictor-based architecture search. The resulting method - RANK-NOSH, reduces the search budget by ~5x while achieving competitive or even better performance than previous state-of-the-art predictor-based methods on various spaces and datasets.

Measuring Sample Efficiency and Generalization in Reinforcement Learning Benchmarks: NeurIPS 2020 Procgen Benchmark

Sharada Mohanty, Jyotish Poonganam, Adrien Gaidon, Andrey Kolobov, Blake Wulfe, Dipam Chakraborty, Gražvydas Šemetulskis, João Schapke, Jonas Kubilius, Jurgis Pašukonis, Linas Klimas, Matthew Hausknecht, Patrick MacAlpine, Quang Nhat Tran, Thomas Tumiel, Xiaocheng Tang, Xinwei Chen, Christopher Hesse, Jacob Hilton, William Hebgen Guss, Sahika Genc, John Schulman, Karl Cobbe
Proceedings of the NeurIPS 2020 Competition and Demonstration Track, PMLR 133:361-395, 2021
arxiv / video /

The NeurIPS 2020 Procgen Competition by OpenAI was designed as a centralized benchmark with clearly defined tasks for measuring Sample Efficiency and Generalization in Reinforcement Learning. This paper presents the competition setup and the details and analysis of the top solutions identified through this setup in context of 2020 iteration of the competition at NeurIPS.

Value Function is All You Need: A Unified Learning Framework for Ride Hailing Platforms

Xiaocheng Tang, Fan Zhang, Zhiwei Tony Qin, Yansheng Wang, Dingyuan Shi, Bingchen Song, Yongxin Tong, Hongtu Zhu, Jieping Ye
Oral presentation, ACM/SIGKDD, 2021
arxiv / video / slides /

We propose a unified value-based dynamic learning framework (V1D3) for tackling both order dispatching and vehicle repositioning. At the center of the framework is a globally shared value function that is updated continuously using online experiences generated from real-time platform transactions. V1D3 outperforms the first prize winners of both dispatching and repositioning tracks in the KDD Cup 2020 RL competition, achieving state-of-the-art results on improving both total driver income and user experience related metrics.

Real-world Ride-hailing Vehicle Repositioning using Deep Reinforcement Learning

Yan Jiao, Xiaocheng Tang, Zhiwei Tony Qin, Shuaiji Li, Fan Zhang, Hongtu Zhu, Jieping Ye
Transportation Research Part C: Emerging Technologies, 2021
arxiv /

We present a new practical framework based on deep reinforcement learning and decision-time planning for real-world vehicle repositioning on ride-hailing (a type of mobility-on-demand, MoD) platforms. We have also designed and run a real-world experiment program with regular drivers on a major ride-hailing platform. We have observed significantly positive results on key metrics comparing our method with experienced drivers who performed idle-time repositioning based on their own expertise.

Rethinking Architecture Selection in Differentiable NAS

Ruochen Wang, Minhao Cheng, Xiangning Chen, Xiaocheng Tang, Cho-Jui Hsieh
Outstanding Paper Awards, 8 out of 860 accepted papers, ICLR, 2021
arxiv / code /

We provide empirical and theoretical analysis on the magnitude of architecture parameters and find that several failure modes of Darts can be greatly alleviated with the proposed perturbation-based method, indicating that much of the poor generalization observed in Darts can be attributed to the failure of magnitude-based architecture selection rather than entirely the optimization of its supernet.

DrNAS: Dirichlet Neural Architecture Search

Xiangning Chen, Ruochen Wang, Minhao Cheng, Xiaocheng Tang, Cho-Jui Hsieh
ICLR, 2021
arxiv / code /

This paper proposes a novel differentiable architecture search method by formulating it into a distribution learning problem. We treat the continuously relaxed architecture mixing weight as random variables, modeled by Dirichlet distribution. We obtain a test error of 2.46% for CIFAR-10, 23.7% for ImageNet under the mobile setting.

KDDCUP 2020: Learning to Dispatch and Reposition on a Mobility-on-Demand Platform

Zhiwei Qin, Xiaocheng Tang, Lulu Zhang, Yanhui Ma, Jianhua Zhang, Fan Zhang, Cheng Zhang
video / code /

The challenge that the participants are to solve involves a combination of order dispatching (order matching) and vehicle repositioning (fleet management) on an MoD platform. The teams are to develop algorithms for either or both of these tasks. The algorithms are evaluated in a simulation environment that simulates the dynamics of an MoD platform.

Wagner Prize Winner: Ride-hailing Order Dispatching on DiDi via Reinforcement Learning

Zhiwei Qin, Xiaocheng Tang, Yan Jiao, Fan Zhang, Zhe Xu, Hongtu Zhu, Jieping Ye
INFORMS/Daniel H. Wagner prize for Excellence in Operations Research, 2019
arxiv / video / slides /

The evolution of our approach to the optimization problem of order dispatching from a myopic combinatorial optimization approach to one that encompasses a semi-MDP model and deep reinforcement learning for long-term optimization.

A Deep Value-network Based Approach for Multi-Driver Order Dispatching

Xiaocheng Tang, Zhiwei Tony Qin, Fan Zhang, Zhaodong Wang, Zhe Xu, Yintai Ma, Hongtu Zhu, Jieping Ye
Oral presentation, acceptance rate 6%, ACM/SIGKDD, 2019
arxiv / video / slides /

We propose a deep reinforcement learning based solution for order dispatching and we conduct large scale online A/B tests on DiDi’s ride-dispatching platform to show that the proposed method achieves significant improvement on both total driver income and user experience related metrics.

InBEDE: Integrating Contextual Bandit with TD Learning for Joint Pricing and Dispatch of Ride-Hailing Platforms

Haipeng Chen, Yan Jiao, Zhiwei Tony Qin,Xiaocheng Tang, Hao Li, Bo An, Hongtu Zhu, Jieping Ye
IEEE/International Conference on Data Mining (ICDM), 2019
arxiv /

Classic approaches to improve marketplace efficiency usually optimize pricing or dispatch separately. We show that these two processes are in fact intrinsically interrelated, and motivated by this observation, we make an attempt to simultaneously optimize pricing and dispatch strategies.

Deep Reinforcement Learning for Dynamic Multi-Driver Dispatching and Repositioning Problem

John Holler, Risto Vuorio, Tiancheng Jin, Satinder Singh, Zhiwei Qin, Jieping Ye, Xiaocheng Tang, Yan Jiao, and Chenxi Wang
IEEE/International Conference on Data Mining (ICDM), 2019
arxiv /

We present a deep reinforcement learning approach for tackling the full fleet management and dispatching problems. In addition to treating the drivers as individual agents, we consider the problem from a system-centric perspective, where a central fleet management agent is responsible for decision-making for all drivers.

CoRide: Joint Order Dispatching and Fleet Management for Multi-Scale Ride-Hailing Platforms

Jiarui Jin, Ming Zhou, Weinan Zhang, Minne Li, Zilong Guo, Zhiwei Qin, Yan Jiao, Xiaocheng Tang, Chenxi Wang, Jun Wang, Guobin Wu, Jieping Ye
ACM/International Conference on Information and Knowledge Management (CIKM), 2019
arxiv /

We model ride-hailing as a large-scale parallel ranking problem and study the joint decision-making task of order dispatching and fleet management. We leverage the geographical hierarchy of the region grids to perform hierarchical reinforcement learning. And to deal with the heterogeneous and variant action space for joint order dispatching and fleet management, we design the action as the ranking weight vector to rank and select the specific order or the fleet management destination in a unified formulation.

NeurIPS Best Demo Awards: Deep RL for Online Order Dispatching and Driver Repositioning

Xiaocheng Tang, Zhiwei Qin, Yan Jiao, Jieping Ye, Chenxi Wang
NeurIPS, 2018
video /

An end-to-end attention-based learning system to demonstrate the joint training of dispatching and repositioning that is capable of adaptively optimizing the distribution alignment between orders and drivers in a manner that maximizes the total income for the drivers.

Deep Reinforcement Learning with Knowledge Transfer for Online Rides Order Dispatching

Zhaodong Wang*, Zhiwei Qin*, Xiaocheng Tang*, Jieping Ye, Hongtu Zhu
IEEE/International Conference on Data Mining (ICDM), 2018
arxiv /

Ride dispatching is a central operation task on a ride-sharing platform to continuously match drivers to trip-requesting passengers. We propose learning solutions based on deep Q-networks with action search to optimize the dispatching policy for drivers on ride-sharing platforms. We train and evaluate dispatching agents for this challenging decision task using real-world spatio-temporal trip data from the DiDi ride-sharing platform.

Practical inexact proximal quasi-Newton method with global complexity analysis

Katya Scheinberg, Xiaocheng Tang
Mathematical Programming A, 2016
arxiv / video / code / slides /

Recently several methods were proposed for sparse optimization which make careful use of second-order information to improve local convergence rates. We propose a general framework, which includes slightly modified versions of existing algorithms and also a new algorithm, which uses limited memory BFGS Hessian approximations, and provide a novel global convergence rate analysis, which covers methods that solve subproblems via coordinate descent.

A Fast Decomposition Approach for Traffic Control

Xiaocheng Tang,Sebastien Blandin, Laura Wynter
International Federation of Automatic Control, 2014
arxiv /

We present a fast decomposition method for network optimization problems, with application to real-time traffic control. Our approach is based on a nonlinear programming formulation of the network control problem and consists of an alternating directions method using forward numerical simulation inplace of one of the optimization subproblems. The method is scalable to realistic city-size road networks for real-time applications, and is shown to perform well on synthetic and real traffic networks.

HIPAD-A Hybrid Interior-Point Alternating Direction algorithm for knowledge-based SVM and feature selection

Zhiwei Qin, Xiaocheng Tang, Ioannis Akrotirianakis, Amit Chakraborty
International Conference on Learning and Intelligent Optimization, 2014
arxiv /

We propose a new hybrid optimization algorithm that solves the elastic-net support vector machine (SVM) through an alternating direction method of multipliers in the first phase, followed by an interior-point method for the classical SVM in the second phase. Both SVM formulations are adapted to knowledge incorporation. Our proposed algorithm addresses the challenges of automatic feature selection, high optimization accuracy, and algorithmic flexibility for taking advantage of prior knowledge.

This guy makes a nice webpage.