Felix Ulrich-Oltean

Felix Ulrich-Oltean

Researcher in Artificial Intelligence with extensive teaching experience

Posts by Collection

portfolio

publications

SAT encodings for Pseudo-Boolean constraints together with at-most-one constraints

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

Learning When to Use Automatic Tabulation in Constraint Model Reformulation

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

IndiCon: Selecting SAT Encodings for Individual Pseudo-Boolean and Linear Integer Constraints

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

TabID: Automatic Identification and Tabulation of Subproblems in Constraint Models

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

Scheduling Telescope Observations for the European Southern Observatory

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

Constraint Models for Klondike

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

Verifying Properties of State-Based Models Using Constraint Programming

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/

talks

Literature Review Seminar

Published:

This is my first presentation as a PhD research student, given in month 3 of the programme. The presentation introduced the field of constraint programming, the idea of encoding to Boolean SAT and how some of the choices involved in the process could be made using machine learning.

Research Topic Intro for EEML2020

Published:

I’m very pleased to be attending Eastern European Machine Learning summer school in July (shame it couldn’t be in the flesh in Warsaw). As part of the application / registration process I prepared a short video presentation to summarise my research interest. Watch it here.

Presenting IndiCon at ICTAI2024

Published:

Thumbnail from presentation slidesI am presenting our paper IndiCon: Selecting SAT Encodings for Individual Pseudo-Boolean and Linear Integer Constraints at ICTAI2024. This paper is a concise preview of the final chapter of my PhD thesis, attempting to select different encodings for each individual constraint in a combinatorial problem. It will be exciting to make my first ever trip to the USA too.

teaching

Graduate Teaching Assistant for various AI & Data Science courses

GTA on UG Programme, Department of Computer Science, University of York, 2020

During my PhD, I was a graduate teaching assistant (GTA) in a number of courses - my work ranged from providing support to students in person during a practical lab session, to leading zoom-based online lab sessions during the Covid19 pandemic, to marking exams and even carrying out one-to-one maths support sessions for students who had gaps in A-level topics due to schooling missed during the lockdowns.

Foundations of AI and ML (FOAM)

Masters Course, Department of Computer Science, University of York, 2023

I gave a guest 1 hour lecture on Logics in week 3 of this Master’s level course, and assisted in the 1 hour seminar and 2 hour lab. The week introduced ideas around:

AI Problem Solving with Search and Logic (AIPS)

Masters Course, Department of Computer Science, University of York, 2024

I co-taught this module which covered search algorithms, game theory and constraint programming. I was responsible for writing and delivering half of the material, ranging across lectures, labs, formative quizzes and final exams.

Foundations of AI and ML (FOAM)

Masters Course, Department of Computer Science, University of York, 2024

I presented the whole week on Logics for this Master’s level course, including the lecture, seminar and lab. As in last year’s version, this week focussed on:

AI Problem Solving with Search and Logic (AIPS)

Masters Course, Department of Computer Science, University of York, 2025

I co-taught this module once again, covering search algorithms, game theory and constraint programming. I was responsible for writing and delivering half of the material, ranging across lectures, labs, formative quizzes and final exams.