Rule 1  The organizers reserve the right to disqualify any participant from the competition at any time if the participant is determined by the organizers to have worked outside the spirit of the competition rules. The organizers' decision is final in any matter. 
Rule 2  The organizers reserve the right to change the rules at any time. Any change of rules will announced on the competition website. 
Rule 3  Competition organizers cannot participate. Results from competition organizers who choose to work on the problems will be presented for comparison, without being included in the competition ordering. 
Rule 4  There are no computation time or technology restrictions. While computation time is obviously not unimportant, a fair comparison in terms of computation time is quite challenging, and it could easily lead to disputes that we as organizers prefer to avoid. We also allow to make use of any commercial solver. In this way, we would like to lower the threshold to participate, and reach out to the largest possible research community. 
Rule 5  We do not expect the code to run on our hardware. However, in order to compete for prizes, competitors may be required to show source code to the organizers. This is simply to check that they have stuck to the rules and will be treated in the strictest confidence. 
Rule 6  In order to be considered for the first milestone prize, solutions must be submitted at the latest January 1, 2021. Any solution submitted before this deadline will be automatically considered, unless explicitly requested otherwise. Although advised, participation for the first milestone prize is completely voluntary and has no impact on the final ranking of participants. 
Rule 7  The organizers will select 35 participants as finalists. Their list without any specification of the ordering will be published in May, 2021. Winners, as well as a complete ordering of competitors, will be announced at the PATAT 2021 conference (virtual or live). In order to receive the prizes, the three overall best competitors are required to attend the PATAT 2021 conference and present their successful results. In addition, they have to submit a full version of their papers to the special journal issue of the conference. 
Rule 8  All solutions must be submitted via email to itc2021 at ugent dot be, at the latest on April 30, 2021. This deadline is absolute, and no extensions will be given under any circumstances because to do so would be unfair to other participants. 
Rule 9  The goal is to produce timetables in which all hard constraints are satisfied (i.e., aiming for feasible timetables), and the total cost of soft constraints (i.e., the total penalty of the solution) is minimized. The penalty of a solution with no soft constraint violation is zero. It is guaranteed that a feasible timetable exists but a solution with a zero penalty may not and typically will not exist. The feasibility and total penalty of a solution is determined by the ITC validator. 
Rule 10  Only solutions in the prescribed XML format and submitted via email to itc2021 at ugent dot be will be considered. Submitted solutions must be successfully validated by the ITC validator. The solution is successfully validated when the format of the solution file is correct according to the XML specification and the solution is feasible. 
Rule 11  When submitting solutions to ITC 2021, the same version of the algorithm must be used for all instances. That is, the algorithm should not "know" which instance it is solving  while your particular algorithm might analyze the problem instance and set parameters accordingly, it should not "recognize" the particular instance. The programmer should not set different parameters for different instances although if the program is doing this automatically, then this is acceptable. 
Rule 12  Three groups of data instances will be published during the competition (early, middle, late). The competition consists of constructing alltimebest solutions to all competition instances.  
Rule 13  Solutions submitted within time are scored solely on the total penalty of the violated soft constraints; no other characteristics of solutions (such as the runtime or the number of cores provided with the solution) are considered. For each competitor and each instance, only the best submitted feasible solution is considered.  
Rule 14 
Following the ITC 2019 competition, points are awarded to each solution based on the position among its competitors and the type of the instance (early, middle or late). The top six, eight, and ten competitors will score points according to the scale in Table 1 for each early, middle, and late instance, respectively. When there are two or more solutions tied for the same positions, the points granted by these positions are split evenly between competitors (rounded up in case of fractional points). When a solver does not compute any solution for some instance, it is awarded zero points for that instance.


Rule 15  The ordering of all participants is based on the weighted sum of points for all early, middle, and late instances. The winner is the competitor with the highest total number of points. 
Points are awarded in the same way as in the ITC 2019 competition. The example below is taken from the ITC 2019 website.
Consider the following example with six instances and eleven participants. Instances 1 and 2 are early, instances 3 and 4 are middle, and instances 5 and 6 are late. Penalties for particular solvers and their solutions are (the symbol "—" means that the solver was not able to compute any solution for the instance):
Early  Middle  Late  
Instance  1  2  3  4  5  6 
Solver A  34  40  92  92  10  12 
Solver B  82  64  94  93  13  15 
Solver C  33  36  100  —  31  17 
Solver D  36  32  96  92  12  13 
Solver E  37  30  93  89  9  4 
Solver F  72  29  91  55  10  5 
Solver G  36  30  —  58  10  4 
Solver H  90  65  —  99  37  25 
Solver I  85  35  95  90  11  14 
Solver J  87  —  100  94  34  18 
Solver K  99  70  —  95  36  22 
Points are awarded to each solution. For early instances (1 and 2), six competitors score points. For middle instances (3 and 4), eight competitors score points. For late instances (5 and 6), ten competitors score points.
Early  Middle  Late  
Instance  1  2  3  4  5  6 
Solver A  7  0  11  4  15  12 
Solver B  0  0  6  2  6  6 
Solver C  10  1  2  0  4  4 
Solver D  4  3  3  4  8  10 
Solver E  2  6  8  8  25  22 
Solver F  1  10  15  15  15  15 
Solver G  4  6  0  11  15  22 
Solver H  0  0  0  0  0  0 
Solver I  0  2  4  6  10  8 
Solver J  0  0  2  1  2  2 
Solver K  0  0  0  0  1  1 
Points are summarized for all solvers to give ordering between competitors.
Total points  Order  Final position  
Solver A  49  4  4th 
Solver B  20  8  8th 
Solver C  21  7  7th 
Solver D  32  5  5th 
Solver E  71  12  1st 
Solver F  71  12  2nd 
Solver G  58  3  3rd 
Solver H  0  11  11th 
Solver I  30  6  6th 
Solver J  7  9  9th 
Solver K  2  10  10th 
Ties between solvers E and F are based on the lexicographic ordering of points, i.e., the solver E with points (25,22,8,8,6,2) is the winner and the solver F with points (15,15,15,15,10,1) is on 2nd position. If a tie still exists, and additional set of 5 problem instances will be made available (awarded according to the rules for the late group of instances) untill a winner is decided.