Appendix I: Bucholz and Sonneborn-Berger Tie-breaks for Unplayed
Games
As far as the Buchholz and Sonneborn-Berger system is concerned, Vega follows the rule of 80th
FIDE CONGRESS 2009 Kallithea, Greece – Minutes of Swiss Pairings Programs Committee
Meeting:
7. Handling of unplayed games in Swiss tournaments
The committee agreed unanimously to handle unplayed games in Swiss tournaments as
follows:
There are two points of view:
a. For the player himself who gets a result by default or is absent
b. For the opponents in other rounds of the player who gets a result by default
a. The new style Buchhloz uses a virtual opponent to calculate the Buchholz score for a
result by default. A virtual opponent has the same points at the beginning of the round
and the result by default of a player is treated as a normal result, so a loss by default
(by absence) is a win for the virtual opponent and vice versa. For each next round the
virtual opponent gains half a point.
b. For reducing the consequence for the opponents when calculating Buchholz, each
result by default of a player is counted as a half point (draw) for the Buchholz of the
player’s opponents.
Examples:
1. In a 9 round swiss the player A achieves 6 points including a default win in round 3.
After round 2 A had 2 points score.
The contribution of round 3 for A is 2 + 0 + 6 x 0.5 = 5 points Buchholz
The contribution of A for his opponents’ Buchholz is 5.5
2. In a 9 round swiss the player B was absent in round 7 and scored 6 points after round
9. After round 6 B had 4 points.
The contribution of round 7 for B is 4 + 1 + 2 x 0.5 = 6 points Buchholz
The contribution of B for his opponents’ Buchholz is 6.5
NOTE: The previous example apply only to Buchholz calculation. In case of SonnebornBerger the player that lost to forfeit get no tie-break points
(http://www.chesscafe.com/text/geurt174.pdf pag 4).
In Round Robin tournament the unplayed games are considered as really played
(http://www.chesscafe.com/text/geurt176.pdf pag 1).
The user can choose whether to adjust the score of the unplayed games (consider them as draw)
before applying the Buchholz and Sonneborn-Berger. This is done via the adjusted score for Buc
and S-B checkbox.
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