[blind-chess] Chess Article #48 The Swiss System Tournament
- From: Roderick Macdonald <rmacd@xxxxxxxx>
- To: Blind Chess Mailing List <blind-chess@xxxxxxxxxxxxx>
- Date: Thu, 10 Jun 2010 19:51:59 -1000 (HST)
Chess Article #48
The Swiss system tournament
Adapted and Condensed from
Wikipedia, the Free Encyclopedia
The principle of a Swiss tournament is that each player will be
pitted against another player who has done as well (or as poorly)
as him or herself.
The first round is either drawn at random or seeded according to
rating. Players who win receive a point, those who draw receive
half a point and losers receive no points. Win, lose, or draw, all
players proceed to the next round where winners are pitted against
winners, losers are pitted against losers, and so on. In subsequent
rounds, players face opponents with the same (or almost the same)
score. No player is paired up against the same opponent twice
however. In chess it is also attempted to ensure that each player
plays an equal number of games with white and black, alternate
colors in each round being the most preferable, and a concerted
effort is made not to assign the same color three times in a row.
The basic rule is that players with the same score are ranked
according to rating. Then the top half is paired with the bottom
half. For instance, if there are eight players in a score group,
number 1 is paired with number 5, number 2 is paired with number 6
and so on. Modifications are then made to balance colors and
prevent players from meeting each other twice.
The detailed rules of how to do the pairing are usually quite
complicated and often the tournament organizer has access to a
computer to do the pairing. If the rules are strictly adhered to,
the organizer has no discretion in pairing the round. See the link
below for detailed pairing rules from FIDE.
Final scores and tie-breaking
The tournament lasts for a number of rounds announced before the
tournament. After the last round, players are ranked by their
score. If this is tied then a tie break score (such as the sum of
all their opponents' scores) or the Buchholz chess rating can be
used.
Analysis, advantages, and disadvantages
Determining a clear winner (and, incidentally, a clear loser)
usually requires the same number of rounds as a knockout
tournament, that is the Binary logarithm of the number of players
rounded up. Therefore three rounds can handle eight players, four
rounds can handle sixteen players and so on, however it is not
uncommon to have more players than this, and, if fewer than the
ideal number of rounds are played, it can happen that two or more
players finish the tournament with a perfect score, having won all
their games but never faced each other.
Compared to a knockout tournament the Swiss system has the inherent
advantage of not eliminating anyone. That means that a player can
enter such a tournament knowing that he will be able to play in all
rounds, regardless of how well he does. The worst that can happen
in this respect is being the player left over when there is an odd
number of players. The player left over receives a bye, meaning the
player does not play that particular round but receives half-a-
point. The player is reintroduced in the next round and will not
receive another bye.
Another advantage compared to knockout tournaments is that the
final ranking gives some indication of relative strength for all
contestants, not just for the winner of the tournament. As an
example, the losing finalist in a knockout tournament may not be
the second best contestant; that might have been any of the
contestants eliminated by the eventual tournament winner in earlier
rounds.
A Swiss system tournament does not always end with the exciting
climax of the knockout's final however. Sometimes a player may have
picked up such a great lead that by the last round he is assured of
winning the tournament even if he loses the last game. One fairly
common fix for this dilemma is to hold single elimination rounds
among the top scorers. In Scrabble tournaments a player with such
a strong lead will often be paired against the highest-placed
player who cannot possibly finish in the prize-winning zone; this
process is known as Gibsonization after it was first applied to the
US Champion David Gibson in the 1995 All-Stars tournament. He is
the all-time top money winner in the history of Scrabble, and has
made a habit of clinching victory in major events without waiting
for the final round. Because of this, players are said to be
Gibsonized when after winning, they are paired with lower-ranked
players to avoid affecting the ranking of runners-up.
Compared with a round-robin tournament, a Swiss can handle many
players without requiring an impractical number of rounds. An
elimination tournament is better suited to a situation in which
only a limited number of games may be played at once, e.g. tennis.
In a Swiss system, all players can be playing a round at the same
time.
Variations of the Swiss system
Accelerated pairings
The method of accelerated pairings also known as accelerated Swiss
is used in some large tournaments with more than the optimal number
of players for the number of rounds. This method pairs top players
more quickly than the standard method in the opening rounds and has
the effect of reducing the number of players with perfect scores
more rapidly.
For the first two rounds, players who started in the top half have
one point added to their score for pairing purposes only. Then the
first two rounds are paired normally, taking this added score into
account. In effect, in the first round the top quarter plays the
second quarter and the third quarter plays the fourth quarter. Most
of the players in the first and third quarters should win the first
round. Assuming this is approximately the case, in effect for the
second round the top eighth plays the second eighth, the second
quarter plays the third quarter and the seventh eighth plays the
bottom eighth. That is, in the second round, winners in the top
half play each other, losers in the bottom half play each other,
and losers in the top half play winners in the bottom half (for the
most part). After two rounds, about 1/8 of the players will have a
perfect score, instead of �. After the second round, the standard
pairing method is used (without the added point for the players who
started in the top half).
As a comparison between the standard Swiss system and the
accelerated pairings, consider a tournament with eight players,
ranked #1 through #8. Assume that the higher-ranked player always
wins.
Standard Swiss system
Round 1:
#1 plays #5, #1 wins
#2 plays #6, #2 wins
#3 plays #7, #3 wins
#4 plays #8, #4 wins
Round 2:
#1 plays #3, #1 wins
#2 plays #4, #2 wins
#5 plays #7, #5 wins
#6 plays #8, #6 wins
After two rounds, the standings are:
1 2-0
2 2-0
3 1-1
4 1-1
5 1-1
6 1-1
7 0-2
8 0-2
Accelerated pairings
Round 1:
#1 plays #3, #1 wins
#2 plays #4, #2 wins
#5 plays #7, #5 wins
#6 plays #8, #6 wins
Round 2:
#1 plays #2, #1 wins
#3 plays #5, #3 wins
#4 plays #6, #4 wins
#7 plays #8, #7 wins
After two rounds, the standings are:
1 2-0
2 1-1
3 1-1
4 1-1
5 1-1
6 1-1
7 1-1
8 0-2
Tie-breaking in Swiss system tournaments
Tie-break systems are used in chess Swiss system tournaments to
break ties between players who have the same total number of points
after the last round. If the players are still tied after one tie-
break system is used, another system is used, and so on, until the
tie is broken. Most of the methods are numerical methods based on
the games that have already been played or other objective factors,
while some methods require additional games to be played, etc. The
idea behind the methods based on the games already played is that
the player that played the harder competition to achieve the same
number of points should be ranked higher.
Harry Golombek points out deficiencies in most of the tie-break
systems and recommends a playoff if there is time. If not, he
recommends Sonneborn-Berger and then the player who has the most
wins. For Swiss tournaments, he recommends the Buchholz system and
the Cumulative system (Golombek 1977:322).
Median
The Median system is also known as the Harkness System, after its
inventor Kenneth Harkness. For each player, this system sums the
number of points earned by the player's opponents, but discarding
the highest and lowest. If there are nine or more rounds, the top
two and bottom two scores are discarded. Unplayed games by the
opponents count � point. Unplayed games by the player count zero
points. This is also known as the Median-Buchholz System (Just &
Burg 2003:199-200).
Modified Median
The Modified Median system is similar to the Median system, except:
* Players with exactly 50 percent score are handled as in the
regular Median system
* Players with more than 50 percent score have only their
lowest-scoring opponent's score discarded
* Players with less than 50 percent score have only their
highest-scoring opponent's score discarded (Just & Burg
2003:199-200).
Solkoff
Buchholz system
This system is the same as the Median system, except that no scores
are discarded (Just & Burg 2003:200). Ephraim Solkoff did not
invent this system. He introduced it to the United States in 1950,
but it was used in England prior to that (Harkness 1967:138).
Cumulative
To calculate this, sum the running score for each round. For
example, if a player has (in order) a win, loss, win, draw, and a
loss; his round-by-round score will be 1, 1, 2, 2�, 2�. The sum of
these numbers is 9. This system places more weight on games won in
the early rounds and the least weight on games won in the final
rounds. The rationale for this system is that a player who scored
well early in the tournament has most likely faced tougher
opponents in later rounds and should therefore be favored over a
player who scored poorly in the start before subsequently scoring
points against weaker opponents (Just & Burg 2003:200-201).
Cumulative opponent's score
This sums the cumulative scores of the player's opponents (Just &
Burg 2003:202).
Result between tied players
If the tied players played each other, if one of them won then he
finishes higher on tie-break (Just & Burg 2003:201).
Most games with the black pieces
The player that had the black pieces the most times finishes
highest on tie-breaks (Just & Burg 2003:201).
Kashdan
Invented by Isaac Kashdan, this system awards four points for a
win, two for a draw, one for a loss, and zero for an unplayed game.
If players with no unplayed games tie, the one with fewer draws
finishes higher on the tie-break (i.e. a win and a loss is better
than two draws) (Just & Burg 2003:201).
Sonneborn-Berger (Neustadtl score)
Neustadtl score
Add the scores of every opponent the player beats and half of the
score of every opponent the player draws (Just & Burg 2003:201).
The system was named after William Sonneborn and Johann Berger, but
it was invented by Oscar Gelbfuhs (Harkness 1967:137). The system
is the main tie-breaking system in round robin tournaments, but is
also used in Swiss tournaments. It is also called the Neustadtl
score.
History of the Sonneborn-Berger system
What we call the Sonneborn-Berger system was not invented by
Sonneborn or Berger, and it was not originally designed for tie-
breaking. It was invented by Oscar Gelbfuhs about 1873 to be used
as a weighted score in round-robin tournaments. It would be used
instead of the raw score for final places. In 1886 Sonneborn
criticized the system and suggested an improvement that would give
a better weighted score. His suggestion was to add the square of
the player's points to the amount calculated as above. In 1887 and
1888 Berger studied Gelbfuhs' system and the suggestion of
Sonneborn. This improvement became known as the Sonneborn-Berger
system.
When the system is used to break ties between equally-scoring
players, adding in the square of the player's raw score does no
good, so the Sonneborn improvement is omitted. However, the system
has retained the Sonneborn-Berger name (Harkness 1967:136-37).
Opponent's performance
This method uses the average performance rating of the player's
opponents. The "performance rating" of a player is basically the
rating he would receive if he had started the tournament without a
rating (Just & Burg 2003:202).
Average rating of opposition
The average rating of the player's opponents (Just & Burg
2003:202).
Time of Loss
Among tied players, the player whose first loss came last gets
priority. If player A's first loss was in round 4 and player B's
first loss was in round 2, player A gets priority. This was a
tiebreaker used by POP in 2004-2005.
Tardiness
If a player arrives after the first round is paired, the player
loses priority. This tiebreaker is currently used by POP.
Speed play-off games
The tie is broken by one or more games played with fast time
control, or Fast chess.
Single fast game
FIDE rules provide for a single fast decisive game. Black gets five
minutes on the clock whereas White gets six minutes but must win
(i.e. a draw counts as a win for Black). The player who wins the
draw of lots may choose which color he wants.
Coin flip
As a last resort, ties are broken by a random process such as a
coin flip (Just & Burg 2003:203).
USCF recommended order
The U.S. Chess Federation (USCF) recommends these as the first four
to be used: (Just & Burg 2003:199)
1. Modified Median
2. Solkoff
3. Cumulative
4. Cumulative opponent's score.
The USCF recommends having a comprehensive list of the systems to
be used in order, such as this one used by a state organization:
1. Modified Median
2. Solkoff
3. Cumulative
4. Result between players
5. Most games with the black pieces
6. Kashdan
7. Sonneborn-Berger
8. Coin flip.
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