Whole number and halves
Conventional ''komi'' in most competitions is a half-integer such as 6.5 points. This is convenient and the prevailing usage for knock-out tournaments, since it makes a tied game (''jigo'' in Japanese) and rematches less likely (a drawn game is still possible under Japanese rules since the Japanese rule prohibiting repeated positions applies only to the simplest possibility, called 'ko'). In a club or friendly game this is not a problem, so a value such as 6 points is just as practical. Within a Swiss system draw, tied games are not convenient and tiebreakers are used. Some argue there is nothing wrong in having a tie. Forbidding a draw may misrepresent one player as superior when there is no difference in skill.History
White is at a disadvantage because Black gets to move first, giving that player sente ("initiative"). Records show that the winning percentage of Black is higher. The importance of playing first was, however, not dealt with by the rules until the 1920s, and then only tentatively. The compensation (''komi'') system was introduced into professional Go inEffects on strategy
Since very minor mistakes can cost one point, discussion of the 'true' value for ''komi'' makes little sense, except at the level of the top-ranked players in the world. These are (in most cases) also the opening-theory experts, and evaluate opening strategies in practical play against their peers. The introduction and then increase of ''komi'' has led to ever more ambitious or aggressive strategies for Black, the first player. In the days before ''komi'', White as second player had to disrupt the smooth working of Black's classical strategies, described sometimes as aiming for a sure win by 3 points. From the introduction of ''komi'' in most pro events, around 1950, Black's older methods had to be reconsidered, since White suddenly needed appreciably less (in pro terms) in secure area. The 3-3 point became an interesting play for White, where previously it appeared experimental, and was developed in particular by Go Seigen and Sakata Eio. In the following decades a mixture of classical and '' shinfuseki'' techniques became normal. The most obvious effect was the replacement of the 4-3 point by the 4-4 point as the most common way to first occupy a corner.Perfect Komi
In theory a perfect value of Komi would make each game result in Jigo (draw) given perfect play by both sides. Since in practice no human or computer can play perfect Go, this value is not known with certainty. However under area scoring rules and in the absence of Seki the perfect Komi can be shown to be an odd integer and statistics from professional and computer play suggest that 7 is the correct value.Local variations
Although 6.5 points is a common komi as of 2007; each country, association, and tournament may set its own specific komi: * In Japan, the usual komi was once about 2.5 points. Some time later, it was raised to 4.5 points. In 1955 the Oza became the first tournament to adopt 5.5. The value of 5.5 became standard over some decades. The Nihon Ki-in increased the komi to 6.5 in 2002, citing Black's 51.855% win rate under the old rule. * In Korea, it used to be 5.5, but is now 6.5. * In China, 5.5 points was common, but 7.5 is now standard. A value of 6.5 would seldom give a different result from 5.5 due to Chinese scoring rules. * In America, American Go association (AGA) official rules used to specify 5.5 points, however they later suggested also experimenting with values up to 8.5 points in both informal games and tournaments in order to gather data to determine the effects of increasing U.S. komi officially. The American Go Association changed komi from 5.5 to 7.5 in August 2004, effective 2005. * The New Zealand rules specify a komi of 7. * For the Ing Foundation (Ing rules) komi is specified as 8 points. Due to the different counting method used by the Ing system, this komi is equivalent to 7.5 points under the Japanese rules.Types
Fixed compensation point system
By far the most common type of ''komi'' is a fixed compensation point system. A fixed number of points, determined by the Go organization or the tournament director, is given to the second player (White) in an even game (without handicaps) to make up for first-player (Black) advantage.Auction komi
As no one can be absolutely sure of the ideal value for komi, systems without fixed komi are used in some amateur matches and tournaments. This is called auction komi. Examples of auction komi systems: * the players do an "auction" by saying: "I am willing to play black against XXX komi" and the player who wins the auction (offers the highest komi) plays black. * one player chooses the size of the komi, and the other player then chooses to play black or white. This version of auction komi becomes equivalent to the pie rule to Go, if choosing the size of the komi is considered to be a move that white player makes before the game would normally start.Pie rule
* One player chooses komi, and the other player chooses whether to play black or white. OR * Black places his first stone, after that white decides whether he wants to play black or white.See also
* Pie ruleNotes
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