The 36th International Conference on Logic Programming

LP/CP Programming Contest (21-22 September 2020)

The traditional LP/CP Programming Contest will be run in virtual mode during ICLP 2020. The contest will start on Monday 21 at 12:00 (midday, CEST, UTC+2) and will last 24 hours.

The contest combines some features of Prolog programming contest, Answer Set Programming (ASP) Model and Solve contest, and Constraint Programming (CP) Model and Solve contest. A variety of systems can be used in the competition, but in contrast to previous editions participants are not constrained to use a single system and can also combine declarative and imperative programming languages. Submitted solutions are expected to have a declarative predominant core, and imperative programming is expected to be used for input and output processing. Deviations from this recommendation will be evaluated case by case (and very likely not accepted).

Differently from previous editions, input and output format of problems will not be system-based. Instances will be provided according to some easy-to-parse representation, and similarly output must be provided according to some easy-to-write format. Sample instances will come with additional data to self-test solutions (essentially, SHA-1 and number of characters in the expected output). An example is provided here.

Each team consists of up to three participants. Submitted solutions will be tested on additional instances, and are expected to terminate in 10 minutes on an Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz. Memory usage will be limited to 6 GiB. Limits on the input will be given for each problem.


The following systems can be used

A Docker image where all systems are installed in is available from the previous edition of the contest. Details on the installation and usage of the Docker image can be found here. It is suggested to try your systems of choice within the Docker image, and write us an email in case some wanted feature or system is missing.


Participants will be ranked by number of solved problems. Ties are broken by cumulative submission time. For example, if team A solved one problem after 30 minutes (hence, at 12:30) and one problem after 90 minutes (hence, at 13:30), the cumulative submission time of team A is 30+90 = 120 minutes. Note that a team submitting two solutions after 70 minutes (hence, at 13:10) has a cumulative submission time of 140 minutes, which is worst than team A. As a general suggestion, submit solutions as soon as you have them. Further ties are broken by partial solutions, that is, number of solved instances for problems with some timeouts (but no mistakes; I test 12 instances for each problem), and finally by execution time.


Send an email to with subject LP/CP Programming Contest 2020 - Registration and the following content:

  • Team name;

  • Comma-separated list of participants;

  • Comma-separated list of affiliations;

  • Whether you prefer to be contacted by email or to be added to a Slack workspace for a faster communication experience;

  • Comma-separated list of emails (to be contacted or to be added to the Slack workspace).

A confirmation email will be sent to you as soon as possible (usually within 24 hours).


Via EasyChair at the following URL:

For each problem you solved, submit a ZIP archive with all files needed to run your solution (use .zip.txt as extension, otherwise EasyChair will complain). The title must obey the following format:


A good entry-point is a script like reading input instances from STDIN and producing output on STDOUT. If you opt for a different entry-point or different usage, provide instructions on how to execute your solution in the abstract.

Keywords are not important, but you have to provide at least three of them. Use the following:





On GitHub:

Chair: Mario Alviano, University of Calabria, Italy