DOMjudge is a system for running programming contests, like the ICPC regional and world finals programming contests.
This usually means that teams are on-site and have a fixed time period (mostly 5 hours) and one computer to solve a number of problems (mostly 8-12). Problems are solved by writing a program in one of the allowed languages, that reads input according to the problem input specification and writes the correct, corresponding output.
The judging is done by submitting the source code of the solution to the jury. There the jury system automatically compiles and runs the program and compares the program output with the expected output.
This software can be used to handle the submission and judging during such contests. It also handles feedback to the teams and communication on problems (clarification requests). It has web interfaces for the jury, the teams (their submissions and clarification requests) and the public (scoreboard).
A global overview of the features that DOMjudge provides:
- Automatic judging with distributed (scalable) judge hosts
- Web interface for portability and simplicity
- Modular system for plugging in languages/compilers and validators
- Detailed jury information (submissions, judgings, diffs) and options (rejudge, clarifications, resubmit)
- Designed with security in mind
DOMjudge has been used in many live contests (see https://www.domjudge.org/about for an overview) and is Open Source, Free Software.
Requirements and contest planning¶
- At least one machine to act as the DOMjudge server (or domserver for brevity). The machine needs to be running Linux (or possibly a Unix variant) and a webserver with PHP 7.2.5 or newer. A MySQL or MariaDB database is also needed.
- A number of machines to act as judgehosts (at least one). They need to run Linux with (sudo) root access. Required software is the PHP commandline client and compilers for the languages you want to support.
- Team workstations, one for each team. They require only a modern web browser to interface with DOMjudge, but of course need a local development environment for teams to develop and test solutions. Optionally these have the DOMjudge submit client installed.
- Jury / admin workstations. The jury members (persons) that want to configure and monitor the contest need just any workstation with a web browser to access the web interface. No DOMjudge software runs on these machines.
One (virtual) machine is required to run the DOMserver. The minimum amount of judgehosts is also one, but preferably more: depending on configured timelimits, and the amount of testcases per problem, judging one solution can tie up a judgehost for several minutes, and if there’s a problem with one judgehost it can be resolved while judging continues on the others.
As a rule of thumb, we recommend one judgehost per 20 teams.
However, overprovisioning does not hurt: DOMjudge scales easily in the number of judgehosts, so if hardware is available, by all means use it. But running a contest with fewer machines will equally work well, only the waiting time for teams to receive an answer may increase.
Each judgehost should be a dedicated (virtual) machine that performs no other tasks. For example, although running a judgehost on the same machine as the domserver is possible, it’s not recommended except for testing purposes. Judgehosts should also not double as local workstations for jury members. Having all judgehosts be of uniform hardware configuration helps in creating a fair, reproducible setup; in the ideal case they are run on the same type of machines that the teams use.
DOMjudge supports running multiple judgedaemons in parallel on a single judgehost machine. This might be useful on multi-core machines.
The judgehost requires Linux cgroup support for memory and swap accounting. Platforms that do not provide this support (some virtualization environments, for example WSL 1 / 2) will not work with the judgehost.
Copyright and licencing¶
DOMjudge is developed by Jaap Eldering, Nicky Gerritsen, Keith Johnson, Thijs Kinkhorst and Tobias Werth; Peter van de Werken has retired as developer. Many other people have contributed: Michael Baer, Jeroen Bransen, Matt Claycomb, Stijn van Drongelen, Rob Franken, Marc Furon, Ragnar Groot Koerkamp, Matt Hermes, Michał Kaczanowicz, Jacob Kleerekoper, Jason Klein, Andreas Kohn, Ruud Koot, Ilya Kornakov, Jan Kuipers, Robin Lee, Tom Levy, Richard Lobb, Alex Muntada, Dominik Paulus, Bert Peters, Mart Pluijmaekers, Ludo Pulles, Tobias Polzer, Jeroen Schot, Matt Steele, Shuhei Takahashi, Michael Vasseur, Sergei Vorobev, Hoai-Thu Vuong, Jeroen van Wolffelaar, and Github users mpsijm, sylxjtu. Some code has been ported from the ETH Zurich fork by Christoph Krautz, Thomas Rast et al.
DOMjudge is Copyright (c) 2004 - 2021 by the DOMjudge developers and contributors.
DOMjudge, including its documentation, is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. See the file COPYING for details.
This software is partly based on code by other people. Please refer to individual files for acknowledgements.
About the name and logo¶
The name of this judging system is inspired by a very important and well known landmark in the city of Utrecht: the Dom tower. The logo of the 2004 Dutch Programming Championships (for which this system was originally developed) depicts a representation of the Dom in zeros and ones. We based the name and logo of DOMjudge on that.
We would like to thank Erik van Sebille, the original creator of the logo. The logo is under a GPL licence, although Erik first suggested a “free as in beer” licence first: you’re allowed to use it, but you owe Erik a free beer in case might you encounter him.
The DOMjudge homepage can be found at: https://www.domjudge.org/
We have a low volume mailing list for announcements of new releases. The authors can be reached through the development mailing list. You need to be subscribed before you can post. See the development list information page for subscription and more details.
There is a wiki which collects other pieces of information about specific configurations or integrations: https://github.com/DOMjudge/domjudge/wiki
DOMjudge has a Slack workspace where a number of developers and users of DOMjudge linger. Feel free to drop by with your questions and comments, but note that it may sometimes take a bit longer than a few minutes to get a response, partly because people might be in different timezones.