Pairings and Tiebreaks
"How do the pairings work?"
When a large number of players play four rounds of chess, a single player can only face a small fraction of the field.
Tournament pairings are used to match up players in a way that allows a fair and balanced competition.
The system used to do this is called the Swiss System. It determines whom you play and what color
you get in each round.
In the first round, the field is arranged by ratings, top to bottom, and the top half paired against
the bottom half. If there is an odd number of players in a section, the player at the bottom will be asked to sit out the round, and will be given a full point "bye."
In the next round, winners and losers are put in separate pools and paired top to bottom in each pool.
This continues in the following rounds,
with players of like scores paired against each other (sometimes scores may differ slightly).
If you lose to a more experienced player in an early round, you should meet someone closer to your playing strength
in the later rounds.
"How do the tiebreaks work?"
To see a description of various tiebreak methods,
see this Wikipedia article..
The tiebreak methods currently used by the NSCF, in order of priority, are Modified Median, Solkoff,
Cumulative, Cumulative of Opposition. If two players are tied on the first tiebreak (Median), then the next tiebreak is applied (Solkoff). If still tied, move on to the third, and so on.
Here's a sample section of a tournament result table showing tiebreaks:
SwissSys Standings. Columbus: Championship
# Name ID Rtng Team Grd Rd 1 Rd 2 Rd 3 Rd 4 Tot TBrk[M] TBrk[S] TBrk[C] TBrk[O]
1 Spitzer,Jacob A 12821038 1567 QUAKE 5 L3 W8 W4 W2 3.0 8 8.5 6 20.5
2 Li,Edward 12924964 1185 ORANGE 6 W4 W6 W5 L1 3.0 7 8.5 9 21
3 Segall,Ethan R 12906644 1191 CIDER 4 W1 D5 D6 W7 3.0 6.5 7.5 7.5 19
4 Ayton,Treva 13032482 1269 IYMS 7 L2 W7 L1 W6 2.0 4.5 8.5 4 22
5 Rosenberg,Kevin 12933557 1419 WARD 3 W8 D3 L2 H--- 2.0 3.5 6.5 5.5 16.5
6 Warren,Justin N 12757651 1497 FARRA 8 W7 L2 D3 L4 1.5 6 9 5 22.5
7 Schwalbenberg,Matthew 12896706 1133 IONAG 7 L6 L4 W8 L3 1.0 4 7 2 16.5
8 Bogaty,Michael 12883771 1117 FOX 3 L5 L1 L7 B--- 1.0 3 6 0 14
|The column titles should be self-explanatory.
"ID" is the USCF ID; "Rtng" is the USCF rating as it is shown in the most recent official supplement.
Some important notes follow:
- In calculating the TBrk[M] (Modified Median) tiebreak, opponent's scores are summed counting unplayed games as a half point only, with some scores dropped according to the following rules:
- For players with positive scores (>2.0), the lowest opponent's score is dropped.
- For players with negative scores (<2.0), the highest opponent's score is dropped.
- For players with even scores (2.0), both the highest and lowest scores are dropped.
- If an opponent has received a full-bye during the tournament (indicated by B--- in the result table) , his score for that round is counted as a half-point when calculating TBrk[M] and TBrk[S]. Thus, in the above result table, player 1 is awarded only .5 points for the score of player 8 when TBrk[S] is calculated. This gives him a TBrk[S] total of 8.5, not 9. (TBrk[S], or Solkoff, is the sum of opponent's scores with no scores dropped.)
- For TBrk[C] (Cumulative), subtract a point if the player has had a full-point bye in any round.
- Some people have been confused by the final tiebreak, TBrk[O] (Cumulative of Opposition). To find it, simply add the values in the TBrk[C] column for the opponents you have faced.
- If two or more players are tied for first on all tiebreaks, the tournament director may arrange a speed playoff. If you are one of those players, and you have left the premises before the playoff can be arranged, you forfeit your right to the first place trophy.
- When you view the USCF ratings report, please note that it orders players by post tournament rating for similar scores, while the NSCF awards trophies in tiebreak order as indicated in the Individual standings (see the NSCF results page). The USCF rating process does not retain the tiebreaks used to award trophies at the tournament; ratings are based on the player's score and his opponent's ratings, never on tiebreaks.
"Why did I get three whites and one black?"
When pairing players, the computer program that does the pairings must balance various considerations. For example, equal scores are considered before equalization of colors. For this reason, a player will often find that he has been allocated more of one color than another. This is normal and should balance out over a number of tournaments. Please do not complain to the tournament director about this.
What the computer IS instructed to avoid, however, is three straight whites or blacks in a row for the same player. You should alert us of this if it happens and we will see if it can be remedied.
"Why was I paired against a player on my own team?"
As with the color imbalances, this is sometimes unavaoidable. In small sections or sections with many players on the same team, it may be necessary.