An encore is a period of reopened play used in some rule sets to settle disputes about life and death at the end of the game. An encore is usually played under special rules that differ from normal play as far as repetition and/or passing are concerned. When the encore(s) are finished, the resulting position stays on the board and scoring is done according to the usual rules.
An encore differs from hypothetical play, another way of settling status disputes, in that an encore results in a new position while hypothetical play does not affect the position, only the presumed status of the stones in it.
- Hypothetical Play — Settling disputes by discussion
- ResumingGame — A survey and explanation of how rule sets treat status disputes
- Rules of Go - Second Tutorial — Explains finer details of of various rules including status dispute resolution
- Spight Rules — Where Bill Spight and others discuss his proposal for settling status disputes
- Spight Rules II — The role of ko and superko
- Unremovable Ko — A position which tests status rules
Distinction from hypothetical play
Patrick Traill (2020-08-13): Is hypothetical play the same as an encore? (also asked in Rules of go - second tutorial)
Anon No, once hypothetical play is done the board is restored to previous state (to not mess up scores). Encore is an actual continuation with moves that remain on the board (ResumingGame).
Bill: No. As Anon indicates, some people may make hypothetical play on an actual board, but that is not actual play, and risks making errors in restoring the board. Good players do not do that. In an encore play is resumed.
RobertJasiek: No. Hypothetical play is not an alias for encore. Some encores may have hypothetical play. Some encores do not have hypothetical play. Some encores may not have hypothetical play.
Origin of term
Patrick Traill (2020-08-15): Did you/Bill introduce the term and concept of an encore?
Robert Jasiek Might have appeared first in Mathematical Go Endgames, 1994.
Bill: I picked up the term from Berlekamp, one of the authors of Mathematical Go. It is simply a round of play after play has stopped and resumed. I would keep the reasons for it out of the definition. Some rules allow a player to resume play for any reason. And rules that have an encore may require it. An encore may result in a return to the same position. For instance, under Ing rules a pass is a play, and an encore might simply consist of two consecutive passes. As for the difference between an encore and hypothetical play, logically you could have an encore with hypothetical play or hypothetical play that is not in an encore. Such as a variation in a review. I am not sure that it helps to try to draw a distinction between the two. The distinctions are between hypothetical play and actual play, and between the period of play before play stops and periods of play after play resumes.