MiniZinc Challenge 2021

The Challenge

The aim of the challenge is to compare various constraint solving technology on the same problems sets. The focus is on finite domain propagation solvers. An auxiliary aim is to build up a library of interesting problem models, which can be used to compare solvers and solving technologies.

Challenge participants provide a FlatZinc or MiniZinc solver and global constraint definitions specialized for their solver. Each solver is run on 100 MiniZinc model instances. For FlatZinc solvers, we run the minizinc compiler on the MiniZinc model and instance using the provided global constraint definitions to create a FlatZinc file. The resultant FlatZinc file is then given as input to the provided FlatZinc solver. For MiniZinc solvers, the MiniZinc model and data are input to the provided solver. Points are awarded for solving problems, speed of solution, and goodness of solutions (for optimization problems).


  • 2021-11-03 Amendments to the results have been made due to an error during scoring. Thanks to ‪Laurent Perron, Krzysztof Kuchcinski and Mats Carlsson for reporting.
  • 2021-10-29 Announcements of the results are here.
  • 2021-05-07 Official Call for Problems for the MiniZinc Challenge.


  • Registration opens: Now.
  • Problem submission deadline: Fri, 9 July 2021.
  • Initial submission round begins: Mon, 9 August 2021.
  • Initial submission round ends: Fri, 27 August 2021.
  • Final submissions: Fri, 24 September 2021.
  • Announcement of results at CP2021: 25-29 October (Montpellier, France).


Entrants must register their intention to enter the contest before the final submission date.
The initial submission round is an opportunity for us to provide feedback concerning your entry; it does not count towards the final result.
Feel free to register and later withdraw.

To register send an email with the following subject line

    [MZNC21] registration


    mzn-challenge 'at'

In the body of the email, please include an email address at which we can contact you and the name of your solver.


All entrants need to extend the MiniZinc docker image (available at, tag latest) with their solver. Detailed information how to prepare the docker image are available here. The entrant will upload the extended image to Docker Hub and fill out a web form (provided after registration) providing the location of the image to the MiniZinc organisers.

Please carefully read the rules before submission.

Problem Submission

We strongly encourage all entrants to submit one or two MiniZinc models satisfying the contest requirements, together with instances for these models. All models will be considered for the MiniZinc Challenge, however we may need to make some modifications to them in order to ensure they are suitable for the challenge.

The sooner they are submitted the better, the deadline is Fri, 9 July 2021. The call for problem submission is available here. Please feel free to distribute it.


The rules for the MiniZinc Challenge 2021 are available here.
If we need to make changes to the rules, all registered entrants will be informed by email.


The judges will be responsible for selecting the tested instances, vetting the results, and ruling on any questions that arise during the competition.

  • Jimmy H.M. Lee. Chinese University of Hong Kong.
  • Barry O’Sullivan, University College Cork, Ireland.
  • Roland Yap, National University of Singapore.


This is the 13th time this challenge is being run, and there are many possibilities for comparing CP solvers. The rules try to make a sensible set of choices for the comparison. We welcome any comments or suggestions regarding the running of this challenge.

We can be contacted with the subject starting with [MZNC21] at:

    mzn-challenge 'at'

MiniZinc forums

The MiniZinc forum is for beginners, users, and developers to discuss MiniZinc. If you would like to join then sign up for the MiniZinc forums.

The MiniZinc page includes a list of resources related to MiniZinc and FlatZinc.

The MiniZinc 2.5.5 Distribution includes a MiniZinc-to-FlatZinc converter and a large suite of MiniZinc examples and benchmarks.

The MiniZinc Challenges 2008-2020 webpage, includes the results from each MiniZinc Challenge.