Silli System

The Silli System makes it possible to run one competition with so many entrants that a full round robin would be impractical. Instead of making every person play everyone else, a formula assigns each player a limited set of opponents drawn from the whole field.

How opponents are distributed

Entrants are placed in one or more closed circles, where the numbering returns to the first player after the last. The formula selects opponents at specified distances in that order and distributes the colors. The result is described as semi-random because initial placement affects the pairings, but the opponents are not chosen freely at random. Once the principles and formula are fixed, the allocation is determined.

• It is not a round robin, because each player faces only part of the field.
• It is not a Swiss system, because opponents are not recalculated round by round according to current scores.
• The formula can be designed to limit shared opponents and spread pairings across a very large field.

Because players do not face exactly the same opposition, the final standings may need tie-breaks that reflect schedule strength. The International Correspondence Chess Federation, abbreviated ICCF, uses Buchholz in this setting. Buchholz adds the scores earned by a player's opponents, while cut variants remove one or two of the lowest opponent scores.