Title: Rules FAQ Author: Robert Jasiek Frequency: monthly Last Update: 2017-10-13; First Day: 1999-04-12 Distribution: rec.games.go Copyright: free non-commercial usage for promotion 0 CONTENTS 1 Purpose of this Paper 2 Information for Beginners 3 Important Concepts 4 Particular Rules 5 Troublesome Details 6 Tournament Rules 7 Links 1 PURPOSE OF THIS PAPER This paper is a basic reference for important rules terms, rules, and tournament rules. Beginners should read especially Chapters 2 and 3, players Chapters 3 to 5, tournament players and organizers Chapter 6. 2 INFORMATION FOR BEGINNERS 2.1 What Must I Know as a Beginner? The game is played on a grid board. Typically it has 19x19 intersections, but 9x9 are also fine. Two players compete. The first player uses black stones, the other white. The players alternate. A player may play or pass. Playing is putting one's own stone on an empty intersection and removing any surrounded opposing stones. To avoid cycles, a play may not recreate any prior configuration of all stones on the board. Two successive passes end the game. Then the player with more intersections wins. Intersections are his if only his stones occupy or surround them. 2.2 Which Rules do I Need as a Beginner? You can play with short rules as in 2.1. Other rules may be different, but the game is the same, i. e. strategy, tactics, and the score do not change. Extremely rare exceptions confirm this rule. The winner can be determined by area or by territory. Either includes empty intersections surrounded only by own stones. While area adds intersections occupied by own stones, territory adds opposing prisoners instead. All rules, except short rules, have further phases after alternation and before scoring. Towards a game end it is often clear which stones will be removed. The additional phases allow the players to agree on which stones shall be removed. Thereby final removals do not require alternation. Whether you score by area or by territory or whether you remove by alternation or by agreement should mainly depend on which rules are used by people you play with. 2.3 Which Rules Should I Teach? One possibility is to use a board with 9x9 intersections, short rules as in 2.1, and count each player's score by using a finger to scan the board for his intersections. 3 IMPORTANT CONCEPTS While strategy and tactics virtually remain the same, concepts vary in different rules. However, the following gives a comprehensive overview on standard terms. 3.1 Stone, String The physical device that colours one intersection in a play is a STONE. Two intersections of the board are ADJACENT if they have a line but no intersection between them. Two intersections with either black, white, or no stones on them are CONNECTED if they are adjacent or if there is a chain of adjacent intersections of their type between them. A REGION consists of an intersection and any intersections connected to it. A black or white region is called a STRING. 3.2 Surrounded An intersection of one colour is SURROUNDED by another colour if each leaving path reaches the other colour first after the one colour. Hereby it can only be surrounded black by white, white by black, empty by black, or empty by white. A region can be surrounded. For strings there is an alternative notion of no liberty (or breath). A LIBERTY of a string is an empty intersection adjacent to it. Thus a string is surrounded if and only if it has no liberty. 3.3 Removal, Suicide A removal empties the intersections of surrounded stones if there are any. Hereby removal of opposing stones is executed first, if necessary. Rules may either require or forbid removal of own stones. This is called suicide or no suicide. In practice, suicide might be used for so called ko fights or in capturing races. 3.4 Capture, Prisoner Rules that score territory call a removal a capture because all removed stones are seriously kept as prisoners. 3.5 Move, Play, Pass The players have alternate turns. On each turn a player makes a move that is either a play or a pass. A play places one's own stone on an empty intersection. It can then include removal of surrounded stones, if any. A pass merely continues alternation by giving the opponent the next turn. 3.6 Compensation The first move advantage by black can be compensated by compensation points (komi) that are added to the white score after the game end. Komi can be adjusted by 0.5 to avoid ties. Today integer values for komi for 19x19 boards typically range between 5 and 7. For 13x13 boards one should use 8, for 9x9 boards 6; however, there is no real consensus for small board komi values yet. - A weaker player (black) can get the right to place an agreed number of compensation stones (handicap) before white's first play. Rules may allow free or fixed handicap. Free handicap does not apply any restriction. Fixed handicap requires traditional placement on set intersections. 3.7 Phases Normally, a game consists of the phases alternation, agreement, scoring. A game stop is between alternation and agreement, the game end is between agreement and scoring, and after scoring both players accept the counted score as the result. The main part of the game is the alternation phase. Special rules are invoked after it. Typically, two successive passes in alternation are the game stop and start the agreement phase. In it the players may agree on strings to be removed. If they agree, then they remove those strings from the board; this ends the game. Sometimes they might disagree, then no strings are removed but alternation is resumed as if the last game stop did not occur. 3.8 Recreation The position is the pattern of black and white stones on the board. Without extra rule a position might be repeated infinitely. The easiest rule to prohibit this says: A play may not recreate a position. This refers to positions after completion of plays, i.e. after possible removals. The rule is called "superko". - Some rules use concepts different from superko. They combine a "2-play rule" with a "long cycle rule". The first says: Two successive plays may not recreate a position. The second says: If a position is recreated after more than two moves, then the game ends either immediately or, as a variant, as soon as the players agree, with the result "without result". In practice the 2-play rule is sufficient for almost all cases. It handles the relevant standard pattern of two adjacent intersections. For superko this is just a special application. 3.9 Scoring The score is the result after the game end as defined by the rules. There are two different scoring methods: area scoring and territory scoring. Rules use one of them. Both give the same result in almost all cases and both evaluate the difference of the black and the white scores. A player's AREA score is the sum of intersections with own stones and of empty intersections surrounded only by own stones. Simply speaking, a player's TERRITORY score is the sum of empty intersections surrounded only by own stones and of prisoners of opposing colour. With both scoring methods empty intersections that are not surrounded by either black or white are neutral. 3.10 Counting A score must be determined by some mechanical procedure in practice; this is called counting. There are various methods. Some rules prescribe one. A possible method is to use one's finger to count point by point. Other methods rearrange a lot of stones on the board. 4 PARTICULAR RULES Rules vary extremely. However, in practice they often give the same result. 4.1 Short Rules Examples of short rules are the Simple Rules or the Tromp-Taylor rules. They have no game stop and no agreement. Both are superfluous since necessary removals may already be performed in the alternation. Two successive passes end the game that is scored then. Short rules use area scoring, superko, and suicide. Further settings are left for tournament rules. 4.2 American Rules These are used by the American Go Association. They use situational superko, no suicide, and 7.5 komi. They permit free or fixed handicap. Their most remarkable feature is to allow one of area scoring or territory scoring. Herefore pass stones (one prisoner compensates each pass) and white moving last always ensure the same result, regardless of the applied scoring method. 4.3 Chinese Rules These are used in continental China and sometimes in other countries. Area scoring and no suicide are used. 4.3.1 Official Chinese Rules In practice, ko rules roughly amount to a 2-play rule and a long cycle rule. The mentioned superko is overridden. The counting is a sophisticated half counting, where empty intersections and then after rearrangements stones of one colour are added to be compared with half the non-neutral intersections. The komi as a half komi is 3.75. In full counting, counts and komi would be twice as big. 4.3.2 Simplified Chinese Rules Positional superko is used. A counting method is not prescribed. The full komi should be 7.5. 4.4 Japanese Rules The differences mainly affect handling of late game phases but often do not alter scores. Japanese rules use some traditional territory scoring that attempts to exclude so called sekis. No suicide applies. The core of the ko rules is a 2-play rule and a long cycle rule. Typically, komi is 6.5. Fixed handicap should be used. The counting is a sophisticated rearrangement of empty intersections and filling-in of prisoners. 4.4.1 Game Finishing Process A game finishes with the following process: 1) So called dame (neutral points) and defensive moves (necessary connections etc. due to occupied dame) are filled. 2) The hypothetical analysis, which presumes perfect play, determines so called life or death of each string and the scoring intersections. 3) Without making any approach moves, dead stones are removed from scoring intersections and added to the prisoners. 4) The score is counted. (2) and (3) do not allow to play out life and death since actually filling intersections costs points in Japanese rules. 4.4.2 Official Japanese Rules There are the Japanese 1989 Rules, which are used in Japan and elsewhere, and the World Amateur Go Championships Rules, which are used in some particular tournaments. Korean rules are similar to Japanese rules but have a very different text and differ in rare positions. Official Japanese rules are very incomplete and have messy late game phases. E.g., the Japanese 1989 Rules allow filling of dame during alternation, after it, or both and have a so called ko-pass-rule for the hypothetical analysis. Now professional Japanese rules are explained precisely by a rules expert's interpretation called "the Japanese 2003 Rules". 4.4.3 Simplified Japanese Rules As a recent invention, they are not used yet. They are complete and have clear late game phases. Filling of dame is done during alternation. 4.4.4 Verbal Japanese Rules They are used for informal games in many countries and undefined, except that the game finishing process is used. In a tournament without any official rules of play, disputes are not solved due to the rules but with a referee. 4.5 Ing Rules Ing rules use area scoring, suicide, 8 komi with black winning ties, and free handicap. 4.5.1 Official Ing Rules The ko rules are a mess but somehow resemble superko. Details could fill books. The late game phases are specified insufficiently. The peculiar counting method requires 180 stones of each colour throughout the game, fills any stones on the board after the game end, and leaves exactly one empty intersection, which determines the winner. The official rules are used in professional Taiwanese and some sponsored tournaments. Taiwanese amateurs have their own rules. 4.5.2 Simplified Ing Rules Positional superko is used. A counting method is not prescribed. The late game phases are specified clearly. The simplified rules are used in EGF tournaments that are said to use Ing rules. 4.6 New Zealand Rules Area scoring, suicide, situational superko, 7 komi, and free handicap are used. 4.7 Go Server Rules Every go server has its own and often complicated rules, if any, so they cannot be given in detail here. Concerning "IGS rules", territory scoring, no suicide, a 2-play rule, fixed handicap, three game stopping passes, and captures in an agreement phase are used. Details about agreements and long cycles are not specified and lead to adjourned games in case of doubt. Komi is suggested but may be altered. Counting is automatic. "Yahoo" has territory scoring, no suicide, a 2-play rule, two game stopping passes; long cycles and disagreements are not handled properly. On "email servers" players must agree on any rules. - Typically territory scoring on a go server means that neither points in any sekis are excluded nor pass stones are used. Thus while the Japanese seki exception is abandoned, disagreements about removals may lead to games without result since playing out can cost points. 4.8 International Rules The international mailing list go-rules has proposed international rules, however, none are adopted yet. The core rules of play shall be clear, complete, and correct. Currently alternative texts are offered for suicide, recreation, and scoring. Especially unification of scoring methods is advocated. 4.9 EGF Rules The EGF uses the Simplified Ing Rules with 8 komi (black wins ties) in Ing sponsored tournaments and the Nihon Kiin 1989 Rules with 6.5 komi in Japanese/Korean sponsored tournaments. If significantly the European Go Championship has both kinds of sponsors, then boards 1-16 use the Nihon Kiin 1989 Rules and boards 17+ the Simplified Ing Rules. However, time settings depend on ranks. 5 TROUBLESOME DETAILS 5.1 Colour Choice In even games typically the colours are randomly chosen. In handicap games black receives the handicap stones. - A manual method for randomly choosing colours is called nigiri. The older player hides a number of white stones taken from the bowl, the opponent takes one or two black stones to guess the parity, and the parity of the number of white stones is revealed. If the opponent guesses right, then he takes black, else he takes white. 5.2 Pass Stones Some rules use pass stones. A passing player adds one own stone to the prisoners. As a consequence, captures before the game end can be resolved in alternation without any loss because any not answered approach move is compensated by one pass stone. With traditional territory scoring that uses no pass stones definition problems arise due to this missing option. Modern territory scoring or equivalence scoring use pass stones. 5.3 Equivalence Area scoring and territory scoring are close because either intersections occupied by own stones or opposing prisoners are used. Essentially, every prisoner is a stone removed from some intersection. For area it scores one point less for the stone's player while for territory it scores one point more for his opponent. This is equal. Exact equality for the entire game must also consider passes by using pass stones and an equal number of moves by requiring white to pass last. This is done by equivalence scoring. 5.4 Meaning of Agreement Removals Removals in an agreement phase under area scoring are fair because they may as well occur in alternation. Removing a stone due to agreement includes its then empty intersection and all adjacent empty intersections in the score. Removing a stone by means of alternation includes its then empty intersection and all adjacent newly occupied intersections in the score. - With traditional territory scoring this is not possible since stones on the board do not score. Thus final captures must occur after the game end due to attempted definitions in the rules. 5.5 Practical Scoring Differences Since area scoring and modern territory scoring using pass stones are equal, correct play is the same for both. Apart from Japanese rules exceptions like not scoring empty intersections especially in asymmetrical coexistences or like a pass-for-ko-rule, traditional territory scoring can make a different winner in practically ca. every 10000th even game. This is so rare because of a parity feature combined with a scarcely odd number of intersections that are in coexistences but do not score for area at the game end. With area scoring a komi change from 1.5, 3.5, 5.5, ... to 2.5, 4.5, 6.5, ... almost always would not change the winner. So altough occupying the last empty intersections that would otherwise not score just before a game stop gains one point each, alternately doing so leaves a total advantage of at most one point. Due to the parity feature the player to get it is predetermined when this occupation starts. More importantly, one final ko is worth 1 point under traditional territory scoring but 2 or rarely 4 points under area scoring. Rare one-sided points in coexistences provide only area. Other practical differences are even rarer. Cute players include the stones in their endgame value counts during the middle of an area scoring game. 5.6 Stone Scoring In ancient times stone scoring was popular. Only stones on the board are scored. Thus empty intersections surrounded by own stones are filled until necessary so called eyes remain. Disconnected stones require more eyes in total, the so called group tax. 5.7 Old Ing Scoring Old Ing rules allowed fractional scores by assigning points to neutral empty regions due to the percentage of black and white stones surrounding every region. 5.8 Primitive Rules They do not have passes. Alternation ends when a player loses due to no legal play. Games can be extremely long and include special strategies, so called pass fights. Primitive rules (also called no pass rules or Conway rules) can be useful in mathematics. 5.9 Tradition Historically, exceptions arose, which some like as such especially together with Japanese style rules. So called sekis are excluded from the score. Special positions, termed precedents, have special rules. Modern Japanese rules have generalized a lot of them by a pass-for-ko-rule. After the game stop or after the game end and particularly in hypothetical play a stone captured in a possible 2-play cycle may not be recaptured unless before a pass is made that specifies the particular 2-play cycle. 5.10 Positional / Situational Superko Positional superko prohibits a play that recreates a position. Situational superko refers to the situation, i.e. to the position together with the right to move. So a play is prohibited if it recreates a position while the same player has the right to move. In practice the differences are extremely rare. 5.11 Handicap Recompensation With area scoring handicap stones beyond the first provide a potential extra area of one point per handicap stone. Komi for white may consider this. Recompensation, H-1 points for H handicap stones, is virtually only used together with American rules. 5.12 Mathematics Go is a complete information game, i.e. at every move each player knows the entire game situation. Hence theoretically an algorithm could determine perfect play. However, due to the complexity of the game with N intersections, for which it is provably impossible to devise a polynomial time solution, perfect play or ideal komi are unknown. What one does know is that in a game without komi the first player wins or ties and that perfect play is independent of set komi. Many other propositions have been discovered, some of which describe the relation between area and territory scoring, solve tiny endgame positions or cyclical behaviour. - Go is a very complex game! According to John Tromp, the number of legal positions is: 208168199381979984699478633344862770286522453884530548425 639456820927419612738015378525648451698519643907259916015 628128546089888314427129715319317557736620397247064840935 For positional superko, no passes, and no resignation, the number of possible games is smaller than N**L(N) because L(N) also restricts the maximal number of moves per game and there are at most N possible intersections per move. (The sign ** is a text file notation for "to the power".) - Extremely modest estimates look like 10**N, which is based on an assumption of 10 reasonable intersections per move. A popular estimate for 19x19 go is 10**761, which must have originated from a typo and should be 10**361, if at all... These types of estimates are so popular because humans cannot even imagine the suggested number of atoms in the universe, 10**80. For comparison, 3**361 is ca. 10**172. 6 TOURNAMENT RULES 6.1 Special Game Ends If the score considering the komi is zero, then the game is a tie and should be treated as 0.5 won games for each. Special rules or undue behaviour like sincere lateness might result in a referee declaring a win by forfeit, 0:0, or 1:1, whichever is most appropriate. 6.2 Tournament Systems A tournament might consist of several stages, of which each has a seed and a system. A seed appropriately restricts participation, e.g. due to qualification. The most important systems are match, league, knockout, Swiss, McMahon. There are many others and hybrids. A system must fit the aims of a tournament. A sufficient number of rounds, a proper seed, and colour variation ensure a fair determination of the best player. - A match takes place between two players that either play a set number of games to see who wins more or a maximal number of games to see who wins a predetermined number of games first. In a league a small, usually even number of players performs a round-robin tournament, so that in each round all players play and every two players play against each other, one game e.g. A knockout preferably starts with a number of players that is a power of two. Losing players are eliminated, winning players continue until the winner remains. - In a Swiss system before each round each player's achieved number of wins is used to pair players with equal numbers as far as possible. So all players play all rounds and some time the best player will emerge. However, with greatly varying strengths too many rounds would be needed. So Swiss is only useful for particular events or handicap tournaments. McMahon is the refinement of Swiss. Before the start of the tournament all players are classified in rank groups, with ranks R from 0 to T. This means that one assumes a preceding Swiss tournament where every player has already won R games. Then in the McMahon tournament the strongest players, who deserve the rank T, compete for the top places. In practice, one uses a bar B, that is 1 or 2 ranks below T, so that all ranks above B are contracted to B and also players slightly weaker than the top players get their chance. All players in a McMahon play roughly equal opponents; if they win or lose, then the opponents will be stronger or weaker. 6.3 Tie Breakers Tie breakers can refine pairings or results. Typically the first criterion is the number of wins (or McMahon points); all further criteria, if any, are tie breakers. They attempt a refinement where a low number of rounds and a tournament system do not guarantee sufficient distinction between players' achievements. However, they must be applied with care since they are only marginally better than coin tossing. Examples of tie breakers are direct comparison, which acknowledges the winner of a game between two players in question, and SOS, which is the Sum of Opponents' Scores. - The possible degree of quality of tie breakers is subject to discussion. It depends on tournament system, whether only the top or all players shall be distinguished, and other factors. An alternative to the usage of tie breakers for the final results ordering is issuing shared places for all players with the same number of wins (or McMahon points). - One must fairly assign tie breaker points for opponents missing in some round; enforcing participation is preferable especially for top players. 6.4 Pairing Pairings must be fair, precise, and consider prior achievements during a tournament. One should consider colour balance and no pair twice, one might also aim at avoiding a pair of players from the same club or country, depending on a tournament's intentions. Pairings might be done manually in small tournaments; for most tournaments pairing programs should be used. These can create fair pairings convincingly, some even watch global balance. 6.5 Thinking Times The age of killing each other by greater endurance has gone. Clocks are used to count each player's remaining thinking time. Typically, every game has a basic time and overtime periods. Exceeding a time limit loses a game. Basic time might be 9 hours for a professional top game, 10 minutes for a lightning game, or something in between that fits a tournament's intentions. An overtime period requires a fixed number of moves within a predetermined period, e.g. 1 move within 60 seconds. A move is finished by pressing the clock. - Many variants or other time systems exist, e.g., increasing numbers of moves in further overtime periods, penalty points for entering further periods, full usage of every overtime period, thinking time working like an hour glass, etc. 6.6 Tournament Rules Every tournament uses an announced set of tournament rules. They especially specify the used set for the core rules of play, the tournament system, tie breakers, the pairing method, the winning criteria, compensation methods, thinking times, direction, jurisdiction, adjournment methods, penalities for being late, etc. Tournament rules often deal with details. Not everything can be predicted, so a sportsmanlike spirit is mentioned. Finally, it should be clear which of several rule sets takes precedence. 6.7 Tournament Organization A regional tournament can be organized by a club. Big events can be held at the request of an association or federation, who also supervise. A tournament organization is responsible for providing a venue and playing material. It must be distinguished from the tournament director and his assistant directors, who perform the particular tasks of pairing, collecting results, and ensuring smooth running. Shared power furthermore demands independent referees. 6.8 Jurisdiction Before the start of a tournament valid instances of a jurisdiction as well as the persons to be referees must be clear. Typically, for a tournament itself there is one referee as the first instance and a body of three referees as the second instance. For very peculiar cases a federation could have a third and final instance. Some tournament rules replace the second instance by a single person, called chief referee; to avoid confusion he ought not to judge as the first instance. Players should respect the referees' tough job of mediation or decision; referees should seriously enforce the rules. 6.9 Prizes The first places of a tournament invoke major prizes. E.g. the first, second, third places might get 3/6, 2/6, 1/6 of the available money. In a tournament with many weaker players it is a good idea to provide some prizes for all other players that win most rounds as well. While prizes can be money, books, trophies, etc., one should remember that money is most universally accepted and trophies serve the media better than the winners. - On a related topic, a side event lottery must give equal chances to all participants. This is only achieved by using one lot for each. 7 Links Most rules information, links, short rules: http://home.snafu.de/jasiek/rules.html