Research and Development Engineer in Constraint Programming

WORK ENVIRONMENT

As a leading general engineering school within IMT-Institut Mines-Télécom, France's foremost group of engineering schools, IMT Atlantique aims to support transitions, train responsible engineers, and leverage scientific and technical excellence for teaching, research, and innovation.

Within the Automation, Production Engineering, and Computer Science Department, this position will be associated with the TASC team (Theory, Algorithms, and Constraint Systems). The team's research focuses on constraint programming, from theory to applications and hybridization. In this context, the position's objective is to support the development of the choco-solver constraint solver (http://choco-solver.org) maintained by the TASC team.

MISSIONS

Under the functional responsibility of the project manager and lead developer of the Choco-solver platform, and in collaboration with the members of the TASC team, the main missions of the position are:

1. Adapt the bimodal algorithm to constraints involving depth-first traversals, such as GlobalCardinality, StableKeysort, or Circuit;

2. Study the transposition of the benefits of the bimodal approach to the core of a constraint solver (e.g., the propagation engine);

3. Evaluate the impact of lazy explanations in Sum and AllDifferent constraints, among others;

4. Participate in the writing of scientific articles related to these topics.

 ACTIVITIES: Activity per mission

1.      Adapt the bimodal algorithm to constraints involving depth-first traversals

·       Analyze the filtering algorithms for GlobalCardinality, StableKeysort, and Circuit available in choco-solver and identify depth-first traversals (strongly connected components, alternating paths, etc.) that could benefit from the bimodal approach.

·       Design and implement bimodal variants of these algorithms in Java, ensuring the expected level of consistency.

·       Verify the correctness of the implementations through unit tests and random tests comparing results with existing propagators.

·       Measure the gains obtained (filtering time, scalability) on benchmark instance sets (XCSP3, MiniZinc Challenge).

·       Integrate validated developments into the public version of choco-solver (code review, documentation, continuous integration).

2.      Study the transposition of the benefits of the bimodal approach to the core of a constraint solver

·       Study the internal workings of choco-solver (propagation engine, propagator scheduling, event management) to identify mechanisms that can leverage a bimodal strategy.

·       Propose and prototype one or more adaptations, for example, dynamic switching between propagation modes.

·       Experimentally evaluate these prototypes and analyze trade-offs between cost and benefit.

3.      Evaluate the impact of lazy explanations (

·       Implement or extend lazy clause generation for Sum, AllDifferent, and other global constraints.

·       Compare lazy explanations with explanations computed during propagation (size of learned clauses, resolution time, number of explored nodes).

·       Design and conduct a reproducible experimental protocol, then analyze and synthesize the results.

4.      Participate in the writing of scientific articles related to these topics.

·       Write scientific articles in English presenting the contributions, for submission to international conferences (CP, IJCAI, AAAI, CPAIOR) or journals (Constraints).

·       Prepare associated experimental artifacts (code, scripts, data) to ensure the reproducibility of results.

·       Present the work in team seminars and, if applicable, at conferences.

EDUCATION AND SKILLS:

Minimum required education level and/or experience:

·       Master's degree (Bac + 5) or equivalent

·       Bachelor's degree (Bac + 4) or equivalent with ≥ 4 years of professional experience

·       Associate's degree (Bac + 3) or equivalent with ≥ 6 years of professional experience

·       Technical degree (Bac + 2) or equivalent with ≥ 10 years of professional experience 

Desired education level and/or experience:

·       PhD in computer science in the field of constraint programming, or a PhD in progress with a defense scheduled during the contract period.

Essential skills, knowledge, and experience:

·       Solid mastery of constraint programming, particularly global constraint filtering algorithms (generalized arc consistency).

·       Very good knowledge of graph algorithms: depth-first search, strongly connected components, matchings, and flows.

·       Advanced proficiency in Java and experience developing within choco-solver (internal architecture, propagators, propagation engine).

·       Experience in designing and conducting rigorous experimental evaluations of algorithms.

·       Experience in writing scientific articles in English.

Desirable skills, knowledge, and experience:

·       Publication(s) on global constraint filtering in leading international conferences in the field (CP, IJCAI, AAAI, CPAIOR…)

·       Knowledge of lazy clause generation (LCG) and CDCL-type SAT solving.

·       Experience with free and collaborative software development (Git/GitHub, continuous integration, testing, micro-benchmarks with JMH).

·       Familiarity with XCSP3 and MiniZinc modeling formats.

Abilities and aptitudes:

·       Autonomy and ability to conduct end-to-end research, from idea to publication.

·       Scientific and methodological rigor.

·       Aptitude for teamwork and proficiency in scientific communication, both written and oral.

·       Organizational skills to manage multiple research avenues within a tight schedule.

2-    ADDITIONAL INFORMATION

·       Occasional travel in France and abroad to present work at conferences.

·       Software developments will be released under a free license within choco-solver.

WHY JOIN US:

👉 Exceptional work environment

👉 Stimulating innovation ecosystem (startups, students, research, companies)

👉 Collaborations with renowned research organizations

PERKS:

🥗 On-site collective catering

🏃‍♀️ Leisure/sports offerings

🚌 Public transport reimbursement

🚴‍♂️ Sustainable mobility package (for carpooling or cycling)

👨‍👩‍👧‍👦 Family allowance

💶 Wide range of social benefits

🖥️ Partial remote work possible

🌴 Numerous holidays

REMUNERATION INDICATORS:

💰 Indicative remuneration: from €33,748 gross per year, depending on profile and experience (reduced employee contributions in the public sector).

FOR ANY INFORMATION:

• Regarding the content of the position: Charles PRUD’HOMME – Research Professor: Regarding administrative/HR aspects: Mélissandre MORVAN – Recruitment Assistant

Application deadline: 10/25/2026

Contract start date: 01/01/2027

Interviews: ongoing

Legal Mentions:

• Nature and duration of the contract: Fixed-term contract (CDD) of 3 months under public law or detachment on contract for civil servants, renewable.

• Job location: IMT Atlantique Nantes campus - 4 Rue Alfred Kastler, 44300 Nantes

• For internal use:

  • Category – job role: II R

  • Category and job role of eligible candidates:

    • II: D, E, F, G, H, I, R

    • III: J1, J2, K, L, M

• The positions offered for recruitment are open to all, with, upon request, accommodations for candidates with disabilities.

• Job open to public service titleholders and/or contract employees.

• All applications may be subject to an administrative investigation.

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