Pairings

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Here is an excerpt of the tsh manual, edited slightly for specificity to this event, giving the pairing algorithm used after the initial three-round round robin. Note that pairings are based on the preceding round’s standings at the beginning of a session and in Round 31, and on the second preceding round’s at other times.

Sort players according to standing in the specified round.
Repeat while players remain unpaired.
- Count Gibsons based on wins and spread. To try to catch a Gibson, a player is assumed to be paired repeatedly with that player, and to win all his/her games with a spread of +250 in one round, +175/round in two rounds, or +150/round for more rounds.
- Pair any Gibsons. If the number of Gibsons is even and positive, pair them with each other KOTH but minimizing repeats and consecutive repeats; else if the number is odd, pair all but the lowest ranked one in this way, then pair the last one with either the highest-ranked player in the lowest prize band (if nonempty) or the lowest-ranked player overall, in each case choosing only from the candidate opponents who have played the Gibson least often. If the number of unpaired players is odd, give an odd Gibson the bye.
- If the number of unpaired players is now odd, give a bye to the lowest ranked among the players with the fewest byes.
- Determine the highest prize band that is still being contended.
- Count how many contenders there are to reach that prize band. Add one if odd. Cap at four times one less than the number of remaining rounds, or two in the final round.
- Determine the minimum number of repeats necessary to pair all the contenders with each other with no other constraints.
- If all remaining players are contenders
  - pair them Swiss (top half plays bottom half in order, avoiding repeats and pairing players due to play first vs. playears due to play second) with that many repeats permitted.
- Else (some players are out of contention)
  - Divide the contenders into leaders and nonleaders, minimizing the number of leaders as long as the subgroup of leaders and the subgroup of nonleaders can each be paired amongst themselves without exceeding the minimum repeats for the whole group of contenders.
  - Pair the leaders by repeatedly matching the top player with the lowest ranked player who can catch him/her, while not exceeding the minimum repeats and where possible avoiding consecutive repeats.
  - Pair the nonleaders Swiss, not exceeding the minimum repeats, and where possible minimizing repeats, avoiding consecutive repeats and matching players due to start with those due to reply.