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I am a Physics PhD candidate at the University of Southern California, advised by Dr. Satish Kumar Thittamaranahalli (T. K. Satish Kumar) and Dr. Sven Koenig.

Email: hongx@usc.edu

I am currently on the academic job market.

Research Interests

In general, I am interested in constraint programming, machine learning, and other areas related to artificial intelligence. During my PhD life in the past few years, I have dived in multiple directions related to these fields. In particular, I am interested in (but not limited to) the following directions in the future:

  • Facilitating search using machine learning. I currently have published and ongoing works that target at integrating deep learning with constraint satisfaction solving and integrating branch and bound search with decision tree learning. I am interested in continuing this direction, including investigating SAT and mixed integer linear programming.
  • Developing distributed and parallel algorithms for combinatorial optimization and satisfaction problems. I currently have published and ongoing works that apply message passing algorithms, variants of belief propagation that have been widely used in distributed settings, for solving combinatorial problems such as the (weighted) constraint satisfaction problem and minimum vertex cover problem. I also have works that use message passing algorithms as a theoretical tool to understand combinatorial optimization problems. I am interested in continuing this direction with, for example, other algorithms and GPU integration.
  • Solving practical problems using constraint programming and machine learning. I currently have published and ongoing works that try to solve practical problems using constraint programming and machine learning, including execution monitoring, intelligent user interface, civil war analysis, and path planning. I am interested in continuing solving more practical problems in various application domains.

In addition to these, on the technical side, I am also interested in (and have experiences in) other directions such as kernelization algorithms, hybrid quantum-classical algorithms, and phase transition in combinatorial problems; on the practical side, I am also motivated in improving privacy protection, promoting free and open intellectual properties (especially computer programs), and optimizing workflow for productivity. But once again, my interests are not limited to these. Feel free to contact me and there is a good chance to get me interested!

Publications

Stars (*) next to names in the author lists indicate equal contribution.

2018

  • Hong Xu, Kexuan Sun, Sven Koenig, and T. K. Satish Kumar. A warning propagation-based linear-time-and-space algorithm for the minimum vertex cover problem on giant graphs. In Proceedings of the 15th International Conference on the Integration of Constraint Programming, Artificial Intelligence, and Operations Research (CPAIOR). 2018.
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  • Masaru Nakajima*, Hong Xu*, Sven Koenig, and T. K. Satish Kumar. Towards understanding the min-sum message passing algorithm for the minimum weighted vertex cover problem: An analytical approach. In Proceedings of the 15th International Symposium on Artificial Intelligence and Mathematics (ISAIM). 2018. URL: http://isaim2018.cs.virginia.edu/papers/ISAIM2018_Nakajima_etal.pdf.
    [abstract▼] [details] [full text] [slides] [BibTeX▼]
  • Ferdinando Fioretto, Hong Xu, Sven Koenig, and T. K. Satish Kumar. Constraint composite graph-based lifted message passing for distributed constraint optimization problems. In Proceedings of the 15th International Symposium on Artificial Intelligence and Mathematics (ISAIM). 2018. URL: http://isaim2018.cs.virginia.edu/papers/ISAIM2018_Fioretto_etal.pdf.
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  • Hong Xu, Xin-Zeng Wu, Cheng Cheng, Sven Koenig, and T. K. Satish Kumar. The Buss reduction for the \(k\)-weighted vertex cover problem. In Proceedings of the 15th International Symposium on Artificial Intelligence and Mathematics (ISAIM). 2018. URL: http://isaim2018.cs.virginia.edu/papers/ISAIM2018_Xu_etal.pdf.
    [abstract▼] [details] [full text] [slides] [BibTeX▼]
  • T. K. Satish Kumar, Hong Xu, Zheng Tang, Anoop Kumar, Craig Milo Rogers, and Craig A. Knoblock. Alert generation in execution monitoring using resource envelopes. In Proceedings of the 31st International Florida Artificial Intelligence Research Society Conference (FLAIRS), 38–43. 2018. URL: https://aaai.org/ocs/index.php/FLAIRS/FLAIRS18/paper/view/17615/16853.
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2017

  • Hong Xu, T. K. Satish Kumar, and Sven Koenig. The Nemhauser-Trotter reduction and lifted message passing for the weighted CSP. In Proceedings of the 14th International Conference on Integration of Artificial Intelligence and Operations Research Techniques in Constraint Programming (CPAIOR), 387–402. 2017. doi:10.1007/978-3-319-59776-8_31.
    [abstract▼] [details] [full text] [slides] [BibTeX▼]
  • Hong Xu, Sven Koenig, and T. K. Satish Kumar. A constraint composite graph-based ILP encoding of the Boolean weighted CSP. In Proceedings of the 23rd International Conference on Principles and Practice of Constraint Programming (CP), 630–638. 2017. doi:10.1007/978-3-319-66158-2_40.
    [abstract▼] [details] [full text] [slides] [BibTeX▼]
  • T. K. Satish Kumar, Hong Xu, Zheng Tang, Anoop Kumar, Craig Milo Rogers, and Craig A. Knoblock. A distributed logical filter for connected row convex constraints. In Proceedings of the 29th IEEE International Conference on Tools with Artificial Intelligence (ICTAI), 96–101. 2017. doi:10.1109/ICTAI.2017.00026.
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  • Hong Xu, T. K. Satish Kumar, and Sven Koenig. Min-max message passing and local consistency in constraint networks. In Proceedings of the 30th Australasian Joint Conference on Artificial Intelligence (AI), 340–352. 2017. doi:10.1007/978-3-319-63004-5_27.
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  • Hang Ma, Wolfgang Hönig, Liron Cohen, Tansel Uras, Hong Xu, T. K. Satish Kumar, Nora Ayanian, and Sven Koenig. Overview: a hierarchical framework for plan generation and execution in multi-robot systems. IEEE Intelligent Systems, 32(6):6–12, 2017. doi:10.1109/MIS.2017.4531217.
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  • Wolfgang Hönig, T. K. Satish Kumar, Liron Cohen, Hang Ma, Hong Xu, Nora Ayanian, and Sven Koenig. Summary: Multi-agent path finding with kinematic constraints. In Proceedings of the 26th International Joint Conference on Artificial Intelligence (IJCAI), 4869–4873. 2017. Sister Conference Best Paper Track. doi:10.24963/ijcai.2017/684.
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  • Hong Xu, T. K. Satish Kumar, and Sven Koenig. A linear-time and linear-space algorithm for the minimum vertex cover problem on giant graphs. In Proceedings of the 10th International Symposium on Combinatorial Search (SoCS), 173–174. 2017. URL: https://aaai.org/ocs/index.php/SOCS/SOCS17/paper/viewFile/15789/15080.
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  • Therese Anders, Hong Xu, Cheng Cheng, and T. K. Satish Kumar. Measuring territorial control in civil wars using hidden Markov models: A data informatics-based approach. In Proceedings of the NIPS 2017 Workshop on Machine Learning for the Developing World. 2017. arXiv:1711.06786.
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2016

  • Hong Xu, T. K. Satish Kumar, and Sven Koenig. A new solver for the minimum weighted vertex cover problem. In Proceedings of the 13th International Conference on Integration of Artificial Intelligence and Operations Research Techniques in Constraint Programming (CPAIOR), 392–405. 2016. doi:10.1007/978-3-319-33954-2_28.
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  • Hong Xu, T. K. Satish Kumar, Dylan Johnke, Nora Ayanian, and Sven Koenig. SAGL: a new heuristic for multi-robot routing with complex tasks. In Proceedings of the 28th IEEE International Conference on Tools with Artificial Intelligence (ICTAI), 530–535. 2016. doi:10.1109/ICTAI.2016.0087.
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  • Liron Cohen, Tansel Uras, T. K. Satish Kumar, Hong Xu, Nora Ayanian, and Sven Koenig. Improved solvers for bounded-suboptimal multi-agent path finding. In Proceedings of the 25th International Joint Conference on Artificial Intelligence (IJCAI), 3067–3074. 2016. URL: http://www.ijcai.org/Abstract/16/435.
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  • Wolfgang Hönig, T. K. Satish Kumar, Liron Cohen, Hang Ma, Hong Xu, Nora Ayanian, and Sven Koenig. Multi-agent path finding with kinematic contraints. In Proceedings of the 26th International Conference on Automated Planning and Scheduling (ICAPS), 477–485. 2016. Outstanding paper award in the robotics track. URL: https://www.aaai.org/ocs/index.php/ICAPS/ICAPS16/paper/view/13183/12711.
    [abstract▼] [details] [full text] [video] [BibTeX▼]
  • Hang Ma, Sven Koenig, Nora Ayanian, Liron Cohen, Wolfgang Hoenig, T.K. Satish Kumar, Tansel Uras, Hong Xu, Craig Tovey, and Guni Sharon. Overview: generalizations of multi-agent path finding to real-world scenarios. In Proceedings of the 25th International Joint Conference on Artificial Intelligence (IJCAI) Workshop on Multi-Agent Path Finding. 2016. URL: https://www.andrew.cmu.edu/user/gswagner/workshop/IJCAI_2016_WOMPF_paper_6.pdf.
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