Performance Pairings User Guide

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Introduction and Target Audience

Performance Pairing (hereafter referred to as PP) is a tsh pairing command affording the operator broad control over pairing parameters so as to cover a broad range of tournament configurations and situations, in particular, approaching the end of the event when pairing decisions are the most challenging. PP is most useful in events with large enough fields relative to the number of games that a large number of players may plausibly be in contention for place prizes.

PP is intended to be used with the tsh Pairing Bars to allow fast assessment of proposed pairings.

Syntax

   pp rank-distance number-of-repeats based-on-round rank [division] [p1 p2 p3 .... pN]
  • rank-distance Similar to the corresponding argument to FactorPair, the "optimum rank separation" for pairings.
  • number-of-repeats As for many pairing commands, the maximum number of times previously any resulting pair of players may have met.
  • based-on-roundAs for many pairing commands, the round from which the ranking is taken.
  • rankThe number of "boards" to be paired, starting at the top of the standings, not counting players who already have a pairing. This is a key feature, which allows an arbitrary number of "strata" within a division to be paired independently.
  • division As usual, the division to be paired. Can be omitted if the event has only one division.
  • [p1 p2...pN] Not a list of player numbers, but pairs of players who are ineligible for "unresolved matchups" assignment. If instead of a sequence of pairs the single value "0" is provided, no unresolved matchups will be considered.

How to Apply PP

First, determine how the field should be divided. Generally you will want to group according to the description provided at Performance Pairings. Of course the group will need to be even so the PP command takes this as the number of "boards" to be paired--twice the number of players. This is the "rank" parameter.

The rank-distance parameter is used to control whether the pairings will resemble king-of-the-hill, "top against bottom", or some form of FactorPair.

Generally one will start without a list of "unresolved matchups" exclusion pairs. These exclusions are normally only listed after an initial attempt to pair produces undesirable results as a consequence of pairing players who have not yet been matched.

Unresolved Matchups

The first factor considered is whether any players have not yet played others in the group. For example, if there have been no repeats within the group and the leader hasn't played everyone in the group, a prime consideration is that someone needs to have their 'shot' at the leader before he plays a repeat. Thus the algorithm starts at the bottom of the division and would assign the leader to play the lowest-ranking player he hasn't yet met.

  • Note that if the bottom player of the group has been brought in just to make it even, the pairing may be improper. In this case it's probably best to give the bottom player a "reasonable" pairing before starting PP.

In the case of a group where no repeats have been played, the algorithm would then continue to match as many players as possible without repeats.

The case where all players have played each other is trickier to explain but the idea is that matchups are first 'evened out' to the extent possible.

A simple heuristic is used here, which is guided by ordering players in ascending order of unresolved matches. To get the optimum number of resolutions, a more sophsticated algorithm could be applied.

In non-contender divisions, this feature can be used to minimize the number of repeat pairings.

Rollbacks

If a prospective pairing for a group is deemed unsuitable, it needs to be rolled back. The only way to do this currently is to unpair the entire division. If an upper group has already been paired it will need to be redone. To facilitate this it is helpful to take notes on the commands used previously.

An UNDO command to roll back only the previous pairing command rather than the whole division would be useful but is not currently (2019-05-08) being worked.

Non-Contender Divisions

After pairing contenders with PP, remaining players can be paired by whatever means. KOTH can be used if players can be paired with no repeats.