Submissions are scored on the log loss:
$$
\textrm{LogLoss} = - \frac{1}{n} \sum_{i=1}^n \left[ y_i \log(\hat{y}_i) + (1 - y_i) \log(1 - \hat{y}_i)\right],
$$
where
n is the number of games played
\\( \hat{y}_i \\) is the predicted probability of team 1 beating team 2
\\( y_i \\) is 1 if team 1 wins, 0 if team 2 wins
\\( log() \\) is the natural (base e) logarithm
The use of the logarithm provides extreme punishments for being both confident and wrong. In the worst possible case, a prediction that something is true when it is actually false will add an infinite amount to your error score. In order to prevent this, predictions are bounded away from the extremes by a small value.
Submission File
The file you submit will depend on whether the competition is in stage 1 (historical model building) or stage 2 (the 2020 tournament). Sample submission files will be provided for both stages. The format is a list of every possible matchup between the tournament teams. Since team1 vs. team2 is the same as team2 vs. team1, we only include the game pairs where team1 has the lower team id. For example, in a tournament of 64 teams, you will predict (64*63)/2  = 2,016 matchups.
Each game has a unique id created by concatenating the season in which the game was played, the team1 id, and the team2 id. For example, "2015_3106_3107" indicates team 3106 played team 3107 in the year 2015. You must predict the probability that the team with the lower id beats the team with the higher id.
The resulting submission format looks like the following, where "pred" represents the predicted probability that the first team will win:
id,pred
2015_3106_3107,0.5
2015_3106_3110,0.5
2015_3106_3113,0.5
...