Almost all tournament formats will, in various rounds, have groups of players that need to be paired. These may be bands in McMahon or Swiss tournaments, or groups of remaining players in knockout tournament. In the first round of the tournament, this might even be all players. Most methods depend on the group containing an even number of players, so it may be necessary to enlarge or reduce the size of the group if it is odd, by pairing players outside the group, or by giving a player a bye. Once the group is determined, the players can be paired in a number of ways, most of which are based upon ordering the field of players by some criteria, from strongest to weakest. Once the group has been ordered, there are four primary pairing methods: slaughter, slide, adjacent, and random.
To perform the pairing, pair the strongest with the weakest player in the group. Repeat by pairing the strongest player with the weakest player from among those that are unpaired till all players have been paired. If a bye needs to be given, it is generally given to the strongest player.
This pairing aims at getting the strongest players reaching the last rounds, postponing the most exciting games until the end of the tournament.
Slaughter pairings are popular in knock-out tournaments.
Done by dividing the group of players, ordered from strongest to weakest, into two strength ordered sets, one containing the stronger players of the group, the other containing the weaker players of the group. The strongest player of the stronger set is paired with the strongest player of the weaker set. The next strongest player of the stronger set is paired with the next strongest player of the weaker set, till all players have been paired or there is only one player unpaired.
This method also aims to have the strongest players play each other in later rounds, to produce exciting games at the end of the tournament, but tries to avoid the disadvantage of giving the top players a bad SOS due to their first round pairing.
Slide pairings are especially popular in the first round of Swiss tournaments
To perform the pairing, pair the strongest player with the next strongest, then pair the third strongest with the fourth strongest. Repeat till all players have been paired or there is only one player unpaired.
Although this pairing is likely to produce the largest number of exciting games throughout the tournament, it is rarely used because it tends to produce the most exciting games at the start of the tournament, rather than towards the end.
Chooses the pairs within each group randomly.
This method is the only option available when it is impossible, or undesirable, to make a prior sorting of the players by strength.
Suppose a tournament with 8 players in some relevants orders
Opponent under pairing: Fold or Slide Adjacent or Player Slaugther or Cross King-of-the-Hill 1 8 5 2 2 7 6 1 3 6 7 4 4 5 8 3 5 4 1 6 6 3 2 5 7 2 3 8 8 1 4 7
In the 2006 US Go Congress, there were groups for each dan grade, as well as each kyu grade of 6 kyu and stronger. From that point down, several kyu grades were combined to form each prize group.