Publications
Here are some selected publications. You can find a fuller list on my Google Scholar profile page.
Published in Rigorous State-Based Methods: 12th International Conference (ABZ 2026), 2026
We used constraint programming to complement existing verification methods, being able to tackle much larger instances of some problems.
Recommended citation: Victoria Johnson, Pedro Ribeiro, Simon Foster, Peter Nightingale, Felix Ulrich-Oltean, "Verifying Properties of State-Based Models Using Constraint Programming", Rigorous State-Based Methods: 12th International Conference (ABZ 2026), https://doi.org/10.1007/978-3-032-26752-8_6 https://eprints.whiterose.ac.uk/id/eprint/239752/
Published in 31st International Conference on Principles and Practice of Constraint Programming (CP 2025), 2025
Fun with patience games; trying to solve thousands of Klondike Solitaire instances using a variety of constraint models which relax some of the rules, as well as using schedules of algorithms to maximise the number of solutions found.
Recommended citation: Nguyen Dang, Ian P. Gent, Peter Nightingale, Felix Ulrich-Oltean, Jack Waller, "Constraint Models for Klondike", 31st International Conference on Principles and Practice of Constraint Programming (CP 2025) https://doi.org/10.4230/LIPIcs.CP.2025.9
Published in 31st International Conference on Principles and Practice of Constraint Programming (CP 2025), 2025
Fascinating application of constraint programming to scheduling scientific observation on an array of telescopes which could be rearranged according to complex constraints.
Recommended citation: Michael Prümm, Peter Nightingale, Felix Ulrich-Oltean, "Scheduling Telescope Observations for the European Southern Observatory", 31st International Conference on Principles and Practice of Constraint Programming (CP 2025) https://doi.org/10.4230/LIPIcs.CP.2025.43
Published in Journal of Artificial Intelligence Research, 2025
One of the first papers I was able to contribute to during my PhD, conducting extensive experiments, and presenting complex results concisely.
Recommended citation: Akgün, Özgür, Ian Gent, Christopher Jefferson, Zeynep Kiziltan, Ian Miguel, Peter Nightingale, András Salamon, and Felix Ulrich-Oltean. "TabID: automatic identification and tabulation of subproblems in constraint models." Journal of Artificial Intelligence Research 82 (2025): 1999-2056. https://doi.org/10.1613/jair.1.17032
Published in Proceedings of the 36th International Conference on Tools with Artificial Intelligence (ICTAI 2024) , 2024
Learning to select SAT encodings for individual constraints in a CSP instance.
Recommended citation: Felix Ulrich-Oltean, Peter Nightingale, James A. Walker, "IndiCon: Selecting SAT Encodings for Individual Pseudo-Boolean and Linear Integer Constraints", Proceedings of the 36th International Conference on Tools with Artificial Intelligence (ICTAI 2024) https://pure.york.ac.uk/portal/en/publications/indicon-selecting-sat-encodings-for-individual-pseudo-boolean-and
Published in White Rose E-theses Repository, 2024
My PhD thesis on using ML to select SAT encodings for constraints
Recommended citation: Felix Ulrich-Oltean, "Learning SAT Encodings for Constraint Satisfaction Problems", PhD Thesis, University of York, March 2024. https://etheses.whiterose.ac.uk/34581/
Published in Proceedings of the Thirty-Second International Joint Conference on Artificial Intelligence , 2023
Using ML strategies to decide whether to reformulate parts of constraint models as table constraints.
Recommended citation: Carlo Cena, Özgür Akgün, Zeynep Kiziltan, Ian Miguel, Peter Nightingale, Felix Ulrich-Oltean, "Learning When to Use Automatic Tabulation in Constraint Model Reformulation", Proceedings of the Thirty-Second International Joint Conference on Artificial Intelligence Main Track. Pages 1902-1910. https://doi.org/10.24963/ijcai.2023/211
Published in Constraints, 2021
Extended journal version of the work in the first two technical chapters of my PhD thesis
Recommended citation: Felix Ulrich-Oltean, Peter Nightingale & James A. Walker, "Learning to select SAT encodings for pseudo-Boolean and linear integer constraints". Constraints 28, 397–426 (2023). https://doi.org/10.1007/s10601-023-09364-1
Published in Artificial Intelligence, 2021
A thorough presentation of SAT encodings for pseudo-boolean constraints optimised for the existence of at-most-one constraints on the variables in their scope. The first paper I was able to contribute to during my PhD.
Recommended citation: Miquel Bofill, Jordi Coll, Peter Nightingale, Josep Suy, Felix Ulrich-Oltean, Mateu Villaret, "SAT encodings for Pseudo-Boolean constraints together with at-most-one constraints", Artificial Intelligence, Volume 302, 2022, 103604, ISSN 0004-3702. https://doi.org/10.1016/j.artint.2021.103604
