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Handbook | C. General Rules and Recommendations for Tournaments | 04. FIDE Swiss Rules | 04.1. Swiss System Based on Rating | A. Introductory Remarks and Definitions

A. Introductory Remarks and Definitions

A.1 Rating

It is advisable to check all ratings supplied by players. If no reliable rating is known for a player the arbiters should make an estimation of it as accurately as possible before the start of the tournament.
(to convert German Ingo or British BCF use rating = 2840 - 8 x INGO = 600 + 8 x BCF)

A.2 Order

For pairing purposes only, the players are ranked in order of, respectively

  1. score
  2. rating
  3. FIDE-title (IGM-WGM-IM-WIM-FM-WFM-no title)
  4. alphabetically (unless it has been previously stated that this criterion has been replaced by another one)

The order made before the first round (when all scores are obviously zero) is used to determine the pairing numbers: the highest one gets #1 etc.

A.3 Score brackets

Players with equal scores constitute a homogeneous score bracket. Players who remain unpaired after the pairing of a score bracket will be moved down to the next score bracket, which will therefore be heterogeneous. When pairing a heterogeneous score bracket these players moved down are always paired first whenever possible, giving rise to a remainder score bracket which is always treated as a homogeneous one.
A heterogeneous score bracket of which at least half of the players have come from a higher score bracket is also treated as though it was homogeneous.

A.4 Floats

By pairing a heterogeneous score bracket, players with unequal scores will be paired. To ensure that this will not happen to the same players again in the next round this is written down on the pairing card. The higher ranked player receives a downfloat ( ), the lower one an upfloat ( ).

A.5 Byes

Should the total number of players be (or become) odd, one player ends up unpaired. This player receives a bye: no opponent, no colour, 1 point. A bye is considered to be a downfloat.

A.6 Subgroups

To make the pairing, each score bracket will be divided into two subgroups, to be called S1 and S2.
In a heterogeneous score bracket S1 contains all players moved down from a higher score bracket.
In a homogeneous score bracket S1 contains the higher half (rounding downwards) of the number of players in the score bracket.
The number of players in S1 will be indicated by "p", indicating the number of pairings to be made.
In both cases S2 contains all other players of the score bracket.
In both S1 and S2 players are ordered according to A2.

A.7 Colour differences and colour preferences

The colour difference of a player is the number of games played with white minus the number of games played with black by this player.
After a round the colour preference can be determined for every player.

  1. An absolute colour preference occurs when a player's colour difference is greater that 1 or less than -1, or when a player played with the same colour in the two latest rounds. The preference is white when the colour difference is << 0 or when the last two games were played with black, otherwise black. In this case the (obligatory) colour is already written down on the score card. (This rule is not in effect when pairing players with a score of over 50% in the last round).
  2. A strong colour preference occurs when a player's colour difference is unequal to zero. The preference is white when the colour difference is < 0, black otherwise.
  3. A mild colour preference occurs when a player's colour difference is zero, the preference being to alternate the colour with respect to the previous game. In this case the colour difference is written down as +0 or -0 depending on the colour of the previous game (white or black respectively).
    Before the first round the colour preference of one player (often the highest one) is determined by lot.
A.8 Definition of "x"

The number of pairings which can be made in a score bracket, either homogeneous or heterogeneous, not fulfilling all colour preferences, is represented by the symbol x.
x can be calculated as follows:
w = number of players having a colour preference white.
b = number of players having a colour preference black.
q = number of players in the score bracket divided by 2, rounded upwards.
If b >> w then x = b-q, else x = w-q.

A.8 Transpositions and exchanges
  1. In order to make a sound pairing it is often necessary to change the order in S2. The Rules to make such a change, called a transposition, are in D1.
  2. In a homogeneous score bracket it may be necessary to exchange players from S1 and S2. rules for exchanges are found under D2. After each exchange both S1 and S2 are to be ordered according to A2.

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