Overview

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).

Features

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

DOMjudge requires the following to be available to run. Please refer to the DOMserver and Judgehost chapters for detailed software requirements.

  • 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.

Warning

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.

Contact

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.