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4. Setting up a contest

After installation is successful, you want to run your contest! Configuring DOMjudge to run a contest (or a number of them, in sequence) involves the following steps:

4.1 Configure the contest data

DOMjudge stores and retrieves most of its data from the MySQL database. Some information must be filled in beforehand, other tables will be populated by DOMjudge.

You can use the jury web interface to add, edit and delete most types of data described below. It's advised to keep a version of phpMyAdmin handy in case of emergencies, or for general database operations like import and export.

This section describes the meaning of each table and what you need to put into it. Tables marked with an `x' are the ones you have to configure with contest data before running a contest (via the jury web interface or e.g. with phpMyAdmin), the other tables are used automatically by the software:
auditlog Log of every state-changing event.
balloon Balloons to be handed out.
clarification Clarification requests/replies are stored here.
xconfiguration Runtime configuration settings.
xcontest Contest definitions with start/end time.
event Log of events during contests.
judgehost Computers (hostnames) that function as judgehosts.
judging Judgings of submissions.
judging_run Result of one testcase within a judging.
xlanguage Definition of allowed submission languages.
xproblem Definition of problems (name, corresponding contest, etc.).
scoreboard_jury Cache of the scoreboards for public/teams and for the jury
scoreboard_publicseparately, because of possibility of score freezing.
submission Submission metadata of solutions to problems.
submission file Submitted code files.
xteam Definition of teams.
xteam_affiliation Definition of institutions a team can be affiliated with.
xteam_category Different category groups teams can be put in.
team_unread Records which clarifications are read by which team.
xtestcase Definition of testdata for each problem.

Now follows a longer description (including fields) per table that has to be filled manually. As a general remark: almost all tables have an identifier field. Most of these are numeric and automatically increasing; these do not need to be specified. The tables language, problem, team, and team_affiliation have text strings as identifier fields. These need to be manually specified and only alpha-numeric, dash and underscore characters are valid, i.e. a-z, A-Z, 0-9, -, _.

configuration

This table contains configuration settings and is work in progress. These entries are simply stored as name, value pairs.

contest

The contests that the software will run. E.g. a test session and the live contest.

cid is the reference ID and contestname is a descriptive name used in the interface.

activatetime, starttime and endtime are required fields and specify when this contest is active and open for submissions. Optional freezetime and unfreezetime control scoreboard freezing. For a detailed treating of these, see section Contest milestones.

The enabled field can be unset to allow for easier editing of contest times, as disabled contests are not checked to overlap with other contests. A disabled contest will also not become active.

language

Programming languages in which to accept and judge submissions. langid is a string of maximum length 8, which references the language; it is used internally as extension for source files and must match the first extension listed for the language in the LANG_EXTS setting in the configuration files. This reference is also used to call the correct compile script (lib/judge/compile_c.sh, etc.), so when adding a new language, check that these match.

name is the displayed name of the language; allow_submit determines whether teams can submit using this language; allow_judge determines whether judgehosts will judge submissions for this problem. This can for example be set to no to temporarily hold judging when a problem occurs with the judging of a specific language; after resolution of the problem this can be set to yes again.

time_factor is the relative factor by which the timelimit is multiplied for solutions in this language. For example Java is/was known to be structurally slower than C/C++.

problem

This table contains the problem definitions. probid is the reference ID, cid is the contest ID this problem is (only) defined for: a problem cannot be used in multiple contests. name is the full name (description) of the problem.

allow_submit determines whether teams can submit solutions for this problem. Non-submittable problems are also not displayed on the scoreboard. This can be used to define spare problems, which can then be added to the contest quickly; allow_judge determines whether judgehosts will judge submissions for this problem. See also the explanation for language.

timelimit is the timelimit in seconds within which solutions for this problem have to run (taking into account time_factor per language).

special_run if not empty defines a custom run program run_<special_run> to run compiled submissions for this problem and special_compare if not empty defines a custom compare program compare_<special_compare> to compare output for this problem.

The color tag can be filled with a CSS colour specification to associate with this problem; see also section Scoreboard: colours.

In problemtext a PDF, HTML or plain text document can be placed which allows team, public and jury to download the problem statement. Note that no additional filtering takes place, so HTML (and PDF to some extent) should be from a trusted source to prevent cross site scripting or other attacks. The file type is stored in problemtext_type.

team

Table of teams: login is the account/login-name of the team (which is referenced to in other tables as teamid) and name the displayed name of the team. categoryid is the ID of the category the team is in; affilid is the affiliation ID of the team.

authtoken is a generic field used by several of the supported authentication mechanisms to store a piece of information it needs to identify the team. The content of the field for each of the mechanisms is:

When enabled is set to 0, the team immediately disappears from the scoreboards and cannot use the team web interface anymore, even when already logged in. One use case could be to disqualify a team on the spot.

members are the names of the team members, separated by newlines and room is the location or room of the team, both for display only; comments can be filled with arbitrary useful information and is only visible to the jury. The timestamp teampage_first_visited and the hostname field indicate when/whether/from where a team visited its team web interface.

team_affiliation

affilid is the reference ID and name the name of the institution. country should be the 3 character ISO 3166-1 alpha-3 abbreviation of the country and comments is a free form field that is displayed in the jury interface.

Both for the country and the affiliation, a logo can be displayed on the scoreboard. For this to work, the affilid must match a logo picture located in www/images/affiliations/<affilid>.png and country must match a (flag) picture in www/images/countries/<country>.png. All country flags are present there, named with their 3-character ISO codes. See also www/images/countries/README. If either file is not present the respective ID string will be printed instead.

team_category

categoryid is the reference ID and name is a string: the name of the category. sortorder is the order at which this group must be sorted in the scoreboard, where a higher number sorts lower and equal sort depending on score.

The color is again a CSS colour specification used to discern different categories easily. See also section Scoreboard: colours.

The visible flag determines whether teams in this category are displayed on the public/team scoreboard. This feature can be used to remove teams from the public scoreboard by assigning them to a separate, invisible category.

testcase

The testcase table contains testdata for each problem; testcaseid is a unique identifier, input and output contain the testcase input/output and md5sum_input, md5sum_output their respective md5 hashes to check for up-to-date-ness of cached versions by the judgehosts. probid is the corresponding problem and rank determines the order of the testcases for one problem. description is an optional description for this testcase. See also providing testdata.

4.2 Contest milestones

The contest table specifies timestamps for each contest that mark specific milestones in the course of the contest.

The triplet activatetime, starttime and endtime define when the contest runs and are required fields (activatetime and starttime may be equal).

activatetime is the moment when a contest first becomes visible to the public and teams (potentially replacing a previous contest that was displayed before). Nothing can be submitted yet and the problem set is not revealed. Clarifications can be viewed and sent.

At starttime, the scoreboard is displayed and submissions are accepted. At endtime the contest stops. New incoming submissions will be stored but not processed; unjudged submissions received before endtime will still be judged.

freezetime and unfreezetime control scoreboard freezing. freezetime is the time after which the public and team scoreboard are not updated anymore (frozen). This is meant to make the last stages of the contest more thrilling, because no-one knows who has won. Leaving them empty disables this feature. When using this feature, unfreezetime can be set to automatically `unfreeze' the scoreboard at that time. For a more elaborate description, see also section Scoreboard: freezing and defrosting.

The scoreboard, results and clarifications will remain to be displayed to team and public after a contest, until an activatetime of a later contest passes.

All events happen at the first moment of the defined time. That is: for a contest with starttime "12:00:00" and endtime "17:00:00", the first submission will be accepted at 12:00:00 and the last one at 16:59:59.

The following ordering must always hold: activatetime <= starttime < (freezetime <=) endtime (<= unfreezetime). No two contests may have overlap: there's always at most one active contest at any time.

4.3 Team authentication

The authentication system lets domserver know which team it is dealing with. This system is modular, allowing flexible addition of new methods, if required. The following methods are available by default for team authentication.

PHP session with passwords (default)

Each team receives a password and PHP's session management is used to keep track of which team is logged in. This method is easiest to setup. It does require the administrator to generate passwords for all teams (this can be done in the jury interface) and distribute those, though. Also, each team has to login each time they (re)start their browser. The password is stored in a salted MD5 hash in the authtoken field in database (team table).

IP-address based

The IP-address of a team's workstation is used as the primary means of authentication. The system assumes that someone coming from a specific IP is the team with that IP listed in the team table. When a team browses to the web interface, this is checked and the appropriate team page is presented.

This method has the advantage that teams do not have to login. A requirement for this method is that each team computer has a separate IP-address from the view of the domserver, though, so this is most suitable for onsite contests and might not work with online contests if multiple teams are located behind a router, for example. Furthermore, with this method the command line submitclient can be used next to the web interface submit.

There are three possible ways of configuring team IP-addresses.

Supply it beforehand

Before the contest starts, when entering teams into the database, add the IP that each team will have to that team's entry in the authtoken field. When the teams arrive, everything will work directly and without further configuration (except when teams switch workplaces). If possible, this is the recommended modus operandi, because it's the least hassle just before and during the contest.

Use one-time passwords

Supply the teams with a one time password with which to authenticate. Beforehand, generate passwords for each team in the jury interface. When the test session (or contest) starts and a team connects to the web interface and have an unknown IP, they will be prompted for username and password. Once supplied, the IP is stored and the password is removed and not needed anymore the next time.

This is also a secure option, but requires a bit more hassle from the teams, and maybe from the organisers who have to distribute pieces of paper.

Note: the web interface will only allow a team to authenticate themselves once. If an IP is set, a next authentication will be refused (to avoid trouble with lingering passwords). In order to fully re-authenticate a team, the IP address needs to be unset. You might also want to generate a new password for this specific team. Furthermore, a team must explicitly connect to the team interface, because with an unknown IP, the root DOMjudge website will redirect to the public interface.

Set IP upon first submission

This is only possible with the Dolstra protocol. The advantage is that no prior mapping needs to be configured, but the disadvantage is that the team interface cannot be viewed until at least one submission was made; there are also more constraints on the system. See the section on the Dolstra protocol for details.

The authtoken field in the database contains either the IP-address, or an MD5 hash of the one-time password if this was set and the team has not authenticated yet.

Using an external LDAP server

This method can be useful when you want to integrate DOMjudge into a larger system, or already have credentials on an LDAP server available. The authtoken field in the database must contain the LDAP username of the DOMjudge team. Furthermore, in etc/domserver-config.php the LDAP_* configuration settings must be adapted to your setup. Note that multiple (backup) servers can be specified: they are queried in order to try to successfully authenticate. After successful authentication against the LDAP server(s), PHP sessions are used to track login into DOMjudge.

Fixed team authentication

This method automatically authenticates each connection to the team web interface as a fixed, configurable team. This can be useful for testing or demonstration purposes, but probably not for real use scenario's.

Adding new authentication methods

The authentication system is modular and adding new authentication methods is fairly easy. The authentication is handled in the file lib/www/auth.team.php. Adding a new method amounts to editing the functions in that file to handle your specific case.

4.4 Providing testdata

Testdata is used to judge the problems: when a submission run is given the input testdata, the resulting output is compared to the reference output data. If they match exactly, the problem is judged to be correct. For problems with a special compare script, testdata should still be provided in the same way, but the correctness depends on the output of the custom compare script. Please check the documentation in judge/compare_wrapper when using this feature.

The database has a separate table named testcase, which can be manipulated from the web interface. Under a problem, click on the testcase link. There the files can be uploaded. The judgehosts cache a copy based on MD5 sum, so if you need to make changes later, re-upload the data in the web interface and it will automatically be picked up.

Testdata can also be imported into the system from a zip-bundle on each problem webpage. Each pair of files <path-to-file>/<filename>.in and corresponding *.out found in the zip-bundle will be added as testdata. Furthermore, when the file domjudge-problem.ini exists, then problem properties are read from that file in INI-syntax. All keys from the problem table are supported, so an example contents could be:


probid = hello

name = Hello world!
allow_submit=false
color=blue

Testcases will be added to those already present and imported properties will overwrite those in the database. A completely new problem can also be imported from a zip-bundle on the problems overview webpage; in that case, note that if the file domjudge-problem.ini is not present, a default value is chosen for the unmodifiable primary key probid (as well as for the other keys).

4.5 Start the daemons

Once everything is configured, you can start the daemons. They all run as a normal user on the system. The needed root privileges are gained through sudo only when necessary.

4.6 Check that everything works

If the daemons have started without any problems, you've come a long way! Now to check that you're ready for a contest.

First, go to the jury interface: http://www.your-domjudge-location/jury. Look under all the menu items to see whether the displayed data looks sane. Use the config-checker under `Admin Functions' for some sanity checks on your configuration.

Go to a team workstation and see if you can access the team page and if you can submit solutions.

Next, it is time to submit some test solutions. If you have the default Hello World problem enabled, you can submit some of the example sources from under the doc/examples directory. They should give `CORRECT'.

You can also try some (or all) of the sources under tests. Use make check to submit a variety of tests; this should work when the submit client is available and the default example problems are in the active contest. There's also make stress-test, but be warned that these tests might crash a judgedaemon. The results can be checked in the web interface; each source file specifies the expected outcome with some explanations. For convenience, there is a link judging verifier in the admin web interface; this will automatically check whether submitted sources from the tests directory were judged as expected. Note that a few sources have multiple possible outcomes: these must be verified manually.

When all this worked, you're quite ready for a contest. Or at least, the practice session of a contest.

4.7 Testing jury solutions

Before running a real contest, you and/or the jury will want to test the jury's reference solutions on the system.

There is no special feature for testing their solutions under DOMjudge. The simplest approach is to submit these solutions as a special team. This method requires a few steps and some carefulness to prevent a possible information leak of the problemset. It is assumed that you have completely configured the system and contest and that all testdata is provided. To submit the jury solutions the following steps have to be taken:

Note that while the contest time is changed to the current time, anyone might be able to access the public or team web-interface: there's not too much there, but on the scoreboard the number of problems and their titles can be read. To prevent this information leak, one could disconnect the DOMjudge server, judgehosts and the computer used for submitting from the rest of the network.

Furthermore, you should make sure that the team you submit the solutions as, is in a category which is set to invisible, so that it doesn't show up on the public and team scoreboard. The sample team "DOMjudge" could be used, as it is in the "Organisation" category, which is not visible by default.


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