Prohibited pairings
Prohibited pairings keep players, or teams in a team tournament, from meeting each other: members of the same club, the same federation, the same affiliation, or any group you put together by hand. They are an option of the Swiss systems, individual and team.
Setting them up
Click Prohibited on the pairings screen. The badge on the button shows how many groups apply to the round.
- Avoid pairing by builds the groups automatically: every player (or team) sharing the chosen attribute, for instance the same club, ends up in the same group. The Constraint next to it applies to all these groups; None turns them off (groups are kept to be turned on later).
- Manual groups let you add groups of your own, for instance members of the same family. Each manual group has its own constraint.
The constraint is Strict, Soft: relaxed from the bottom of the standings or Soft: avoided as much as the pairing rules allow (see below).
Once a round is paired, the groups used to pair the round are frozen: the modal shows the groups that were used for that round, and changing the setting only affects the rounds still to be paired.
Constraints
A strict constraint is always enforced. If the round cannot be paired without breaking it, Sharly Chess refuses to pair the round and tells you so.
A soft constraint is kept as far as possible. The two soft constraints differ in what gives way when it cannot be kept:
| Constraint | What gives way |
|---|---|
| Soft: relaxed from the bottom of the standings | the leaders always stay apart; when that is not possible for everyone, the lowest-ranked players are the first who may meet a member of their group. Keeping the leaders apart comes before score groups, colours and floaters. |
| Soft: avoided as much as the pairing rules allow | members of the same group stay apart only if no Swiss criterion (colours, floaters…) suffers; otherwise they meet, whatever their ranking. |
The groups of a round can mix the three constraints.
Soft: relaxed from the bottom of the standings
When the field cannot be paired with every one of these constraints in place, some of them are relaxed, just enough for the round to be paired, following one simple principle: an unavoidable clash goes to the players doing worst, never to the leaders.
How the constraints are relaxed
Before each round, Sharly Chess looks at the standings entering the round, tie-breaks included. In the first round, when nobody has played yet, the standings are simply the initial ranking.
It then picks a cut-off N, and protects the players (or teams) ranked 1st to Nth:
| Pair from the same group | Allowed? |
|---|---|
| both members ranked within the top N | no |
| one member within the top N, the other below | no |
| both members ranked below N | yes |
A protected player keeps all their separations, including against the players who have been released. Releasing a player does not let them meet anyone from their group: it only lets them meet another released player from their group. A clash can therefore only happen between two players at the bottom of the standings, never between a leader and a weaker player from the same club.
Sharly Chess chooses the largest N for which the round can still be paired, so the fewest players possible are released. If every soft constraint can be kept, nobody is released at all.
The cut-off is worked out again every round, from the current standings. A player released in one round may be protected in the next after a good result, and the other way round.
After the round is paired, the Prohibited modal lists the players (or teams) that were freed from their soft constraints for that round.
Effect on the pairing
The constraints that survive are handed to the pairing engine as strict prohibitions, before it applies the usual Swiss criteria. Keeping the protected players apart therefore takes priority over keeping everyone in their score group: a player may meet an opponent from a lower score group because every player of their own score group is a protected club-mate.
The engine itself then applies the FIDE criteria unchanged among the pairings that remain possible: score differences, colours, and the usual tie-breaks between equivalent pairings.
A worked example
A team Swiss over three rounds has ten teams. Six of them, A1 to A6, come from the same club, A; two, B1 and B2, from club B; C and D from two other clubs. Club A and club B are each a group relaxed from the bottom of the standings.
Round 1. Six club A teams and only four teams from other clubs: at least one match between two club A teams is unavoidable. Protecting everyone is impossible, and so is protecting everyone but A6, the lowest-ranked team (A6 could only meet a protected A team). The largest possible cut-off releases the two lowest-ranked A teams, A5 and A6, who play each other; every other A team meets a team from another club.
Round 2. The standings entering the round are:
| Rank | Team | Points |
|---|---|---|
| 1 | A2 | 3 |
| 2 | A1 | 3 |
| 3 | A3 | 3 |
| 4 | B1 | 3 |
| 5 | A6 | 2 |
| 6 | A5 | 2 |
| 7 | D | 1 |
| 8 | A4 | 1 |
| 9 | C | 1 |
| 10 | B2 | 1 |
- Protecting the top 6 would leave five club A teams (A2, A1, A3, A6, A5) for only four outside opponents: impossible.
- Protecting the top 5 works: A2, A1, A3 and A6 each meet a team from another club, and B1 is kept apart from B2.
- A5 and A4 are released. A4–A5 is the only club A match allowed, and the pairing uses it.
A6 drew in round 1 and moved up to 5th, inside the cut-off; A4 lost and dropped to 8th, outside it. That is why A4 meets A5 rather than A6, even though A4 has the better initial ranking.
The top score group (A1, B1, A2, A3) shows the effect on the pairing: it holds three protected club A teams and a single outside team, so only one of them can play B1. The other two meet teams from the score group below: the result is B1–A3, B2–A1 and C–A2.
Soft: avoided as much as the pairing rules allow
This constraint is the pairing engine’s lowest-priority criterion. The engine first applies every FIDE criterion: score groups, floaters and colours. Only among the pairings that these criteria rank as equally good does it pick the one with the fewest pairs from the same group, ahead of the order in which the rules would otherwise try them.
Keeping a group apart therefore never makes the pairing worse on any criterion: if the only way to avoid a club match leaves a player without the colour they are due, or makes more players float, the club match is played. The standings play no part either: an unavoidable clash can fall on the leaders as well as on the players doing worst. Nobody is released, and the Prohibited modal does not list anyone after the round is paired.
For example, six teams play the first round of a Swiss: A1, A2 and A3 from club A, B1 and B2 from club B, and C1, ranked A1, A2, B1, C1, A3, B2. The standard pairing would be A1–C1, A2–A3 and B1–B2. Since nobody has played yet, the rules rank the pairings of the top half against the bottom half as equally good, so the constraint picks A1–C1, A2–B2 and B1–A3: no club match.
In the TRF export, these groups are written as SCS records, an extension read by the pairing engine of Sharly Chess. Other programs, and FIDE pairing checkers, ignore them: they may report a round where the constraint changed the pairing as a deviation.
If you prefer another pairing that the regulations allow, you can always adjust the round by hand: see Managing pairings.