The Diagonal Tournament Format was developed on this site based on the tournament experiences since 2011 and used for two years now (2021 and 2022).
Format description finished October 2022.
If all the players are ordered by rating in a Round Robin table, then broadly speaking the outcomes of all the games in the NE and SW parts of the table are known beforehand, since the games are played by players with a large difference in rating.
Only the outcomes of games on the NW-SE diagonal part of the table are unknown, since the games are played by players of nearly equal strength.
So this format concentrates on those latter games and skips the rest.
Experience with the diagonal format.
The games are remarkably well played all across the board. Opponents of neighbouring strength have an opportunity to show their very best and probably have more fun too, and no matter where they are on the rating scale the games are certainly interesting to watch.
The format handles any number of players, a large number as easily as a small number.
No matter where a player is on the rating scale, the format treats everybody the same.
All players meeting their nearest neighbours to both sides functions like one long continuous group of 3-5 players all way through from top to bottom, with every player in the middle of his group.
The tournament is like one long Final. The whole rating scale is immediately activated, and top players meet from the very start. This makes it possible to test players of the whole rating scale very thoroughly. The winner 2021 fx. played against 6 topmost players before the title was won.
It also makes it possible to carry out the whole tournament in a relatively short time.
Since all the players are activated with decisive games from start and all results are carried over to next rounds, the players have fewer opponents at a time and thus more time for the games.
When a player lost games corresponding to losing to two opponents, he is eliminated.
Since two games must be played against each opponent, one black and one white, a defeat to two opponents corresponds to four lost games.
When the tournament has finished, the tournament result can be calculated for all the players, i.e. their Performance Ratings.
All players are ordered in a row by their ratings for this variant (possibly by maximum ratings).
First half of the row, each player plays against the next player in line.
Second half of the row, each player plays against the next two players in line.
The difference is due to that the opponents in the first half-row are roughly double as strong as the opponents in the second half-row.
This gives the last three players X, Y and Z respectively 4, 3 and 2 opponents.
The setup in this end is changed a bit, so that X, Y and Z each will have 3 opponents.
Now player A has 1 opponent, and players J, K, L and M in the middle of the row have 2 opponents.
Games are added for A-J, K-X, L-Y and M-Z.
The numbers of opponents are now 2 2 2 ... 2 2 3 3 3 3 4 4 4 ... 4 4 4
Players with two or more losses in Round 1 are eliminated.
The rest of the players are set up for Round 2 the same way as described for Round 1.
It is avoided, however, that players who already met in Round 1 meet again in Round 2.
Players with two or more losses in Round 2 (incl. the losses from Round 1) are eliminated.
The few players left are set up as a ring:
Fx. players A, B, F and H would be set up as
A-B-F-H plus A-H.
It is again avoided, if possible, that players who already met, meet again.
Continuing with new rounds by this method until a winner is found.
Eventually only one player is left, the winner.
In case all players were eliminated in the last round:
The player with the fewest losses won.
If there are more players with the same fewest number of losses:
Direct comparison of the games of the tied players.
The player who won with the shortest game length, is the winner. (If a game was resigned, the number of moves it would take to finish the game, is added.) If the game lengths differ by less than 10%, they're considered equal.
Or new rounds between these players until the winner is found.