HOW DOES A SWISS SYSTEM TOURNAMENT WORK?
Most of our competitions are run on a Swiss system basis.  Most people enter them, but never really understand what they are.  Below is the full official guidelines as issued by the English Chess Federation.  

Rules for Seeded Swiss Pairings (Amended April, 2009)

BASIC PRINCIPLE

  1. No player shall play the same opponent twice.

    2. PRIORITIES

  2. When making pairings, the priorities are:-
    1. score
    2. colour
      1. equalise numbers of whites and blacks
      2. avoid runs of the same colour
    3. grade order
    4. float history

    Where alterations from the perfect application of these rules must be made, the principle of minimum disturbance is applied.

    PREPARATION

  3. Ungraded players are allocated an estimated grade using the best information available. This can be amended for particular players in the light of experience during the tournament.
  4. Pairing cards are arranged in descending order of grade. Players with the same grade are placed in order of FIDE title status (GM, WGM, IM, WIM, FM, WFM, no title) and then alphabetically. Pairings for a particular round can sometimes be improved by changing the order of players having the same grade.

    5. MID-LINE

  5. When the players on a score level have been ranked according to rule 4, the cards are divided in to two groups. The higher graded players will be expected either to upfloat to a higher score level or play a lower graded player on the same score level. The lower graded players will be expected either to downfloat or to be awarded a bye or to play a higher graded player on the same score level. The position of the mid-line is chosen so that after any floaters or byes are removed, the number of players above the line equals the number of players below the line. Example: for 61 players in round 1, the mid-line is set below player 30. When the bye has been selected there will be 30 games between top-half and bottom-half players.

    6. BYES

  6. If a bye is required in round 1, it is given to a player just below the mid-line who is not due to receive a pre-arranged bye. For subsequent rounds the bye is chosen, if possible, from the lowest score level, looking first at the larger colour group, working from the mid-line downwards, seeking a player who has not hitherto had a bye or default and who is not due to receive a pre-arranged bye. If this fails, the bye is chosen using the same criteria but working upwards from the mid-line.
  7. The chosen player receives the points given for a win, without colour.

    8. PAIRINGS FOR ROUND 1

  8. Players are paired top half v bottom half in descending grade order with the colour on board 1 being decided by lot, e.g. with 64 players:- 1v33, 34v2, 3v35, or 33v1, 2v34, 35v3.

    9. PAIRINGS FOR OTHER ROUNDS

    SCORE

  9. As far as possible players are paired within their own score level.
  10. Where this is not possible, the minimum number of players are floated by the minimum score difference (see rules 19-24).
  11. The highest score level is considered first, then the next highest and so on.
  12. On each score level, the top half is paired against the bottom half, keeping as close as possible to grade order. Where this is not possible, the players on either side of the mid-line are exchanged by the minimum extent necessary.
  13. This policy is only broken to avoid a blockage near the bottom of the pairings, when as few score levels as possible, working upwards, are disturbed.

    14. COLOUR

  14. Within each score level, pairing cards are sorted into white seekers and black seekers, each group then being arranged in descending order (see rule 4). A white seeker is a player who has had more blacks than whites, or has had equal numbers of each colour, but played last with black. A black seeker is a player who has had more whites than black, or has had equal numbers of each colour, but played last with white.
  15. As far as possible, white seekers play black seekers.
  16. Where there is an excess of one colour group, transfers are made which involve those players with the weakest claim for the original colour. Colour difference is more important than colour alternation.
      1. The greater the difference between the number of whites and blacks, the greater is his claim to be given the correct colour, e.g.WWBW has a colour difference of 2 and would be given black in preference to byeBWW, which has a colour difference of 1.
      2. A player who has just had one colour should be given the other colour. A player who has just had two of the same colour has a stronger claim to the other colour than a player who has not just had a run of the same colour. Even longer runs of a colour give a stronger claim to alternate in the next round, e.g.(1) WWBB deserves white more than WBWB, e.g.(2) BWWB and WBWB equally deserve white.
      3. Rule (ii) is used to distinguish between players who have the same colour difference, e.g. (i) WBWW is more strongly due for black than WWBW, e.g.(2) WWBW is more strongly due for black than WWWB.
      4. Byes are ignored for the purpose of (ii) e.g. WBBbye and WbyeBB are equally deserving of white in the next round.
      5. A player who has played fewer games has greater priority for the correct colour e.g. bye bye W deserves black more than WBW, but less than BWW.

17. If the score level requires a float (or floats) and has an excess of one colour and the linked score level(s) below has (have) an excess of the same colour, they are treated as one score level for the purpose of colour transfers, care being taken not to infringe rule 10.

18. Where colour transfers must be made which involve players having identical colour requirements, players should be chosen who best satisfy Rule 12.

FLOATERS

    1. When there is an odd number of players on the score level being considered, a player must be floated down to the next score level.
    2. The downfloater is chosen from the larger colour group. Work from the mid-line of the score group downwards to the bottom, seeking a player who:-
      1. did not downfloat in the previous round
      2. has no worse a downfloat history than any other player below the mid-line in the colour group of the score level being considered.

      If this fails to produce the downfloater, work from the mid-line to the top, using criteria a) and b).

    3. The opponent for the downfloater is chosen from the opposite colour group. Work from the top downwards towards the med-line, seeking a player who:-
      1. did not upfloat in the previous round
      2. has no worse an upfloat history than any other player above the mid-line in the colour group of the score level being considered.

      If this fails to produce the upfloater, work from the mid-line down to the bottom, using criteria a) and b).

    4. If the chosen upfloater has already played the chosen downfloater, the alternative pairing which best satisfies both rule 20 and rule 21 is chosen.
    5. When the floaters have been selected the players on each score level are paired according to rule 12.
    6. Selected floaters are not altered unless a change reduces the number of a) further floaters, b) colour transfers, or c) exchanges of players across the mid-line.

      7. FINAL COLOUR CHECK

    7. Where two players with identical colour requirements are paired together, the correct colour is given to the higher ranking player. Where two players have the same score, this is the higher-graded player. Where two players have different scores, it is the player with the higher score.

      8. GENERAL

    8. In a long tournament, care must be taken that the priorities are not violated for players on the lowest score levels.
    9. Once a draw has been published, if adjustments or alterations are necessary, they are made so as to produce the least disturbance to the draw.

      10. OTHER FORMS OF SWISS DRAW

    10. SWISS DRAW FOR LONG EVENTS: In Long tournaments, including the British Championship, in Rule 21, the search for the upfloater is made from mid-line to top. The reason for this is to avoid giving a lone leader the strongest available opponent for round after round.
    11. SWISS DRAWS FOR LARGE NUMBERS OF PLAYERS: In short tournaments with large numbers of players, in Rule 20, the search for the downfloater is made from the bottom to the mid-line. This acts as a mild form of acceleration.
    12. RANDOM PAIRINGS: When there are many ungraded players, or when the range of gradings is very small or when pairings have to be made rapidly, random pairings may be used. These use the same principles as above, but without any reference to gradings or the mid-line.

      13. SPECIAL RULES FOR THE BRITISH CHAMPIONSHIP AND OTHER FIDE-RATED EVENTS

    13. The British Championship will not normally start with a bye.
    14. In the British Championship, the highest FIDE-rated player takes white in odd-numbered years.
    15. In FIDE-rated tournaments, the grades of non FIDE-rated players should be used to rank those players. Depending on the nature of the tournament, the rated and non-rated pools of players may be placed in a single rank order, or the unrated players may all be placed below the rated ones.
    16. For FIDE-rated tournaments, the words ‘FIDE rating’ should be substituted for ‘grade’ in rules 1-27.

      17. DISCRETIONARY RULES

    17. In round 1, pairings between relatives, players from the same club, distant local area or foreign country are best avoided. The extent to which such pairings are avoided in later rounds is at the discretion of the arbiter.
    18. Full point byes can sometimes be avoided by the use of ‘fillers’ or cross-pairings between sections. These options may not be appropriate for championship events.
    19. In round 2, pairings between players who received half-point byes in round 1 should be avoided if possible.
    20. In an event where there are grades or FIDE ratings from more than one source, a recognised conversion formula may be used to derive the best ranking of the players.
    21. If two players are paired together but one or both defaults, although the two players are still eligible to be paired together subsequently, this should be avoided, providing priorities (a) score, and (b) colour balance, are not violated.
    22. In the last rounds, for players not in contention for a prize, rule 9 may be relaxed to avoid a colour difference of 3 (e.g. 4 whites, 7 blacks).

FINAL NOTE

These rules are approved by the Chief Arbiters of England and Wales, and the Arbiters’ Council of Scotland. The Chess Arbiters’ Association Website contains a complete guide to these rules.

 

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