2025 Quarterly Report 3

This quarterly report brings you reports on the CP conference, including the awards handed out and the general assembly, the ACP Summer School, and more.

ACP.1: CP 2025 in Glasgow

The International Conference on Principles and Practice of Constraint Programming (CP) is the premier annual conference on all aspects of computing with constraints, including theory, algorithms, models, solvers, and a diverse range of applications in machine learning/artificial intelligence, planning, and scheduling, to name a few. This was the 31st version of the CP series organized by the Association for Constraint Programming.

The proceedings are available at https://drops.dagstuhl.de/entities/volume/LIPIcs-volume-340.

This year, CP has been co-located with the 28th International Conference on Theory and Applications of Satisfiability Testing (SAT 2025) and the 18th International Symposium on Combinatorial Search (SoCS 2025). Additionally, the SAT/SMT/AR Summer School was held in St Andrews during the week before the conference.

There were three invited talks (https://cp2025.a4cp.org/invited-talks.html):

• Privacy-preserving SAT Solving, by Ruzica Piskac.
• Anytime and exact search for planning problems: How to explore a DP-based state transition graph with A*, CP and LS?, by Christine Solnon.
• Graph Learning for Planning, by Sylvie Thiebaux.

There were also two tutorials (https://cp2025.a4cp.org/tutorials.html):

• Modeling and Solving Combinatorial Optimization Problems with Domain-Independent Dynamic Programming, by Chris Beck and Ryo Kuroiwa.
• Constraint Programming with JuMP, by Benoit Legat.

There were 3 best papers awarded:

• Best Technical Paper Award to J. Christopher Beck, Ryo Kuroiwa, Jimmy H. M. Lee, Peter J. Stuckey, and Allen Z. Zhong for their paper Transition Dominance in Domain-Independent Dynamic Programming.
• Best Application Paper Award to Ignace Bleukx, Ryma Boumazouza, Tias Guns, Nadine Laage, and Guillaume Poveda for their paper Modeling and Explaining an Industrial Workforce Allocation and Scheduling Problem.
• Best Student Paper Award to Hannes Ihalainen, Jeremias Berg, Matti Järvisalo, and Bart Bogaerts for their paper Symmetric Core Learning for Pseudo-Boolean Optimization by Implicit Hitting Sets.

The list of all previous CP paper awards can be found at https://www.a4cp.org/awards/paper-awards.

Alongside the three conferences, there has been a joint CP/SAT doctoral program (https://satcpdp25.github.io/), and a two day workshop programme on the 10th and 11th August (https://cp2025.a4cp.org/workshops.html), featuring:

• Satisfiability Modulo Theories (SMT)
• Explanations with Constraints and Satisfiability (ExCoS)
• Machine Learning for Solvers and Provers (ML4SP)
• LLMs meet Constraint Solving (LLM-solve)
• Constraint Modelling and Reformulation (ModRef)
• Pragmatics of SAT international workshop (PoS)
• Counting, Sampling, and Synthesis (MC)
• Quantified Boolean Formulas and Beyond (QBF)
• Progress Towards the Holy Grail (PTHG)

Some competitions and challenges have been held as part of the co-located conferences: The MiniZinc Challenge, The XCSP Competition, The SAT Competition, The Pseudo-Boolean Competition, and The Model Counting Competition. The results are available at https://cp2025.a4cp.org/competitions.html.

ACP.2: Constraint Journal Awards

The following Constraints journal awards were given during the CP conference:

• Prominent Paper Award to Hélène Verhaeghe, Siegfried Nijssen, Gilles Pesant, Claude-Guy Quimper and Pierre Schaus for their paper Learning optimal decision trees using constraint programming published at Constraints 25, 226-250 (2020).

This award honours papers that are exceptional in both their significance and impact on the field of Constraint Programming, and that were published in Constraints between 2018 and 2024 (inclusive).

• Classic Paper Award to Olya Ohrimenko, Peter Stuckey and Michael Codish for their paper Propagation via lazy clause generation published at Constraints 14, 357-391 (2009).

This award celebrates outstanding papers published at least 15 calendar years ago in the Constraints journal, and are exceptional in their significance and impact on the field of Constraint Programming.

Through the generosity of Springer’s SharedIt program, we are providing access to the journal issues at the ACP site https://www.a4cp.org/cj2, starting with Volume 29, Issues 3,4. In addition we are providing short introductory videos for the papers, provided by the authors.

Further information about the journal, earlier issues, a search facility, submission information, etc., is included in the Springer website for the journal, which can be found at https://link.springer.com/journal/10601.

ACP.3: ACP Awards

The Association for Constraint Programming (ACP) gives annual awards to exceptional individuals of different seniority levels. This year, the following awards were given:

• Research Excellence Award to Laurent Michel from the University of Connecticut, USA.
• Early Career Researcher Award to Emir Demirović from TU Delft, The Netherlands.
• Doctoral Research Award to Ruiwei Wang from National University of Singapore, Singapore.
• Honorable mention for the doctoral research award to Isaac Rudich from Polytechnique Montréal, Canada.

All awards can be found on the A4CP website: https://www.a4cp.org/

ACP.4: General Assembly

The Association for Constraint Programming aims at promoting constraint programming in every aspect of the scientific world, by encouraging its theoretical and practical developments, its teaching in the academic institutions, its adoption in the industrial world, and its use in the application fields.

Its yearly General Assembly is held during CP, and the report of the president of the Executive Committee, Gilles Pesant, can be found at: https://www.a4cp.org/about/general-assembly-archive.

In particular, the results of the survey on CP research publication outlets and the future of the Constraints journal were presented.

ACP.5: Summer School 2025 in Benin, Africa

The first ACP Summer School in Africa, organized by CP community members Ratheil Houndji and John Aoga, was successfully held in Benin, marking a milestone for the global CP community. The event focused on Constraint Programming for Sustainable Development (CP4SD), aligning theoretical foundations with practical applications critical to African challenges (e.g., resource allocation and healthcare logistics).

It had a total of 50 participants (86% African, 20% women), with 14 full scholarships (flights, accommodation and fees) and 30 partial scholarships (fees and meals).

The program included seminars and hands-on lab sessions from key researchers in the field.

Days 1–3 were devoted to core CP fundamentals (modeling, filtering, search) with hands-on labs (manual and computer-based) to ensure accessibility despite potential infrastructure limitations. Day 4 was devoted to applications (e.g., healthcare logistics, and transportation). Day 5 included a public-facing session on CP for sustainability, targeting a broader audience.

More information at https://school.a4cp.org/summer2025/.

ACP.6: CP 2026 in Lisbon, Portugal

The 32nd CP conference will take place in Lisbon, Portugal, from 20th to 23rd of July 2026, as part of FLoC 2026 (https://www.floc26.org/).

The Conference Chair is Inês Lynce, with Program Chair Nicolas Beldiceanu.

ACP.7: Summer School 2026 in Jilin, China

Next year's ACP Summer School will be in Jilin, China, organized by Peter Stuckey and Jimmy Lee. The dates are set at 3th–6th August 2026.

ACP.8: CP 2027 in Jilin, China

The 33rd CP conference will take place in Jilin, China, in August or early September, 2027. It will be organized by faculty members from the Jilin university, with support from Peter Stuckey, Jimmy Lee and Christian Bessiere.