2026 Quarterly Report 3

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

ACP.1: CP 2026 in Lisbon

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 32nd 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-379.

This year, CP has been co-located with the Federated Logic Conference (FLoC) 2026.

There were two invited talks (https://cp2026.a4cp.org/invited-talks.html):

  • Decision Diagrams for Constraint Reasoning and Optimization, by Willem-Jan Van Hoeve.
  • Bridging the Gap: Foundedness, Defaults, and Expressivity in Constraint Answer Set Programming, by Torsten Schaub.

There were also four tutorials (https://cp2026.a4cp.org/tutorials.html):

  • From CP Fundamentals with MiniCP to Solving Routing and Scheduling Applications with MaxiCP, by Augustin Delecluse and Pierre Schaus.
  • Despicable Cores: Thousands of GPU Minions for Constraint Propagation, by Laurent Michel and Fabio Tardivo.
  • Exploiting Combinatorial Structure in Constraint Programming: Going Beyond Domain Filtering to Model Counting and Marginal Distributions over Domains, by Gilles Pesant.
  • Hexaly, a Global Hybrid Optimization Solver, by Thierry Benoist.

There were 3 best papers awarded and 3 runners-up:

  • Best Paper: Fabio Tardivo, Laurent Michel, and Willem-Jan van Hoeve for their paper GPU-Accelerated Relaxed Decision Diagrams for Branch-and-Bound Optimization.
  • Best Paper Runner-up: Martin C. Cooper and Imane Bousdira for their paper Fairness of Classifiers in the Presence of Constraints between Features.
  • Best Student Paper: Théo Cantaloube, Xiao Peng, Christine Solnon, and Anastasia Volkova for their paper Solving the Multiple Constant Multiplication Problem with Constraint Programming.
  • Best Student Paper Runner-Up: Tanguy Terrien and Cyrille Briand for their paper An Iterative Constraint Programming Approach to Integrate Maximum Workload Constraints in Preemptive Jobshop Scheduling.
  • Best Application Paper: Matthias Klapperstueck, Frits de Nijs, Ilankaikone Senthooran, Matteo Miceli, and Michael Wybrow for their paper CrewAId: Interactive Optimisation for Human-In-The-Loop Crew Rostering and Rerostering.
  • Best Application Paper Runner-up: Luca Di Gaspero, Alessia Grosso, and Giovanni Longo for their paper A Scheduling-Based Approach to Railway Capacity Estimation for Industrial Freight Junctions.

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

Alongside the conference, there has been a joint CP/SAT doctoral program (https://satcpdp26.github.io/), and a four day workshop programme taking place on 18/07–19/07 and 24/07–25/07 (https://cp2026.a4cp.org/workshops.html), featuring:

  • Workshop on Models and Solvers for Dynamic Programming (DPSOLVE)
  • Workshop on Machine Learning on Solvers and Provers (ML4SP)
  • International Workshop on Highlights in Organizing and Optimizing Proof-logging Systems (WHOOPS)
  • Constraint Modelling and Reformulation (ModRef)
  • LLMs meet Constraint Solving (LLM-Solve)
  • Soft Constraints, Discrete Optimization, and Machine Learning (SOFT)
  • Explainable Logic-Based Knowledge Representation (XLoKR)
  • Explanations with Constraints and Satisfiability (ExCoS)
  • Automated Reasoning for Future Space Logistics (AR4Space)

Some competitions and challenges have been held as part of the FLoC Olympic Games https://www.floc26.org/olympics.

ACP.2: Constraints Journal Awards

At the 30th Anniversary of the Constraints Journal panel at CP 2026 in Lisbon the winners of the annual Constraints Journal awards were announced.

  • Constraints Journal Classic Paper Award to Stefano Bistarelli, Ugo Montanari, Francesca Rossi, Thomas Schiex, Gérard Verfaillie, and Hélène Fargier for their paper Semiring-Based CSPs and Valued CSPs: Frameworks, Properties, and Comparison published at Constraints 4, 199-240 (1999). https://doi.org/10.1023/A:1026441215081

The award recognises outstanding papers published at least 15 calendar years ago in the Constraints journal that are exceptional in their significance and impact. The citation for the award states "For outstanding contributions to foundational and integrative frameworks for one of the primary aspects of constraint programming, the handling of soft constraints."

  • Constraints Journal Prominent Paper Award to Chaitanya K. Joshi, Quentin Cappart, Louis-Martin Rousseau, and Thomas Laurent for their paper Learning the travelling salesperson problem requires rethinking generalization published at Constraints 27, 70–98 (2022). https://doi.org/10.1007/s10601-022-09327-y

The award recognizes outstanding papers published not more than 7 years ago in the Constraints journal that are exceptional in their significance and impact. The citation for the award states "For outstanding contributions to neural combinatorial optimization, establishing search and generalization as its essential ingredients, and connecting the CP and ML communities."

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, and including a 30th Anniversary Special Issue with “Commentaries” on some of the most highly-cited papers published in the journal. 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:

  • Distinguished Service Award to J. Christopher Beck, from the University of Toronto, Canada.
  • Early Career Researcher Award to Jeremias Berg, from the University of Helsinki, Finland.
  • Doctoral Research Award to Tamio-Vesa Nakajima, from the University of Marburg, Germany.
  • Honourable mention for the doctoral research award to Ryo Kuroiwa, from the National Institute of Informatics, Japan.

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 vote about changing our publishing model were presented:

143 members voted (37%)

  • Question 1: I agree to transition to a new publishing model for our community, as outlined above, i.e., papers are submitted to a journal and accepted papers are offered a presentation spot at the CP conference.

Yes 74 (52%), No 60 (42%), Abstain 9

  • Question 2: I agree to create a new diamond open access journal for our community.

Yes 92 (64%), No 31 (22%), Abstain 20

Based on the result for Question 2, the EC will initiate the creation of an open access journal for the community.

For Question 1, a majority voted in favour but the community appears to be more divided. Therefore a special committee composed of the EC and of a few additional members of our community will work on putting in place a smooth transition, possibly starting with a hybrid model with the presentation of papers at the CP conference both from the new journal and from proceedings.

Given that these initiatives will take time, the 2027 edition of the CP conference will proceed as usual for the submission and publication of papers in its proceedings.

The EC understands that such changes can be unsettling for some. Therefore, it will do its best to take into consideration each member's research ecosystem when implementing these changes.

ACP.5: Summer School 2026 in Changchun, China

The ACP Summer School 2026 has been hosted by Jilin University and successfully held in Changchun, China. It has been organized by CP community members Peter Stuckey and Jimmy Lee.

The program, themed "CP: Explanation, Verification and Applications", included seminars and hands-on lab sessions from key researchers in the field. A hackathon was also organised, allowing learners to further practise their skills. More information at https://school.a4cp.org/summer2026/.

ACP.6: CP 2027 in Changchun, China

The 33rd CP conference will take place in Changchun, China, from 16th to 20th of August 2027.

The Conference Chairs will be Yonggang Zhang and Jimmy Lee, with Program Chair Claude-Guy Quimper.

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Executive Committee Decisions