Editing Go (game) (section)

== Competitive play ==

=== Ranks and ratings ===
{{Main|Go ranks and ratings}}
[[File:Go pros and amateurs.jpg.jpeg|thumb|Three Japanese professional Go players observe some younger amateurs as they dissect a [[life and death]] problem in the corner of the board, at the [[US Go Congress]] in [[Houston]], Texas, 2003.]]

In Go, rank indicates a player's skill in the game. Traditionally, ranks are measured using ''kyu'' and ''dan'' grades,{{sfn|Nihon Kiin|1973|p=188}} a system also adopted by many [[martial arts]]. More recently, mathematical rating systems similar to the [[Elo rating system]] have been introduced.<ref name=EGFRating>{{Citation | url = http://europeangodatabase.eu/EGD/EGF_rating_system.php#System | title = EGF Official Ratings | first=Ales | last = Cieply | publisher = European Go Federation (EGF)| access-date=2009-11-06}}</ref> Such rating systems often provide a mechanism for converting a rating to a kyu or dan grade.<ref name=EGFRating /> Kyu grades (abbreviated ''k'') are considered student grades and decrease as playing level increases, meaning 1st kyu is the strongest available kyu grade. Dan grades (abbreviated ''d'') are considered master grades, and increase from 1st dan to 7th dan. [[shodan (rank)|First dan]] equals a [[black belt (martial arts)|black belt]] in eastern martial arts using this system. The difference among each amateur rank is one handicap stone. For example, if a 5k plays a game with a 1k, the 5k would need a handicap of four stones to even the odds. Top-level amateur players sometimes defeat professionals in tournament play.<ref name=EGFDatabase>{{Citation | url = http://www.europeangodatabase.eu/EGD/Player_Card.php?&key=12633346
 | title = EGF Tournament Database | publisher = Association for Go in Italy (AGI) | access-date=2008-06-19}}</ref> Professional players have [[Go professional|professional dan ranks]] (abbreviated ''p''). These ranks are separate from amateur ranks.

The rank system comprises, from the lowest to highest ranks:
{| class="wikitable"
|-
!|Rank Type
!|Range
!|Stage
|-
|Double-digit ''kyu''
|30–21k
|Beginner
|-
|Double-digit ''kyu''
|20–10k
|Casual player
|-
|Single-digit ''kyu''
|9–1k
|Intermediate/club player
|-
|Amateur ''dan''
|1–7d (where 8d is a special title)
|Advanced player
|-
|Professional ''dan''
|1–9p (where 10p is a special title)
|Professionals
|}

=== Tournament and match rules ===
{{See also|Go competitions}}
Tournament and match rules deal with factors that may influence the game but are not part of the actual rules of play. Such rules may differ between events. Rules that influence the game include: the setting of compensation points ([[komidashi|komi]]), handicap, and time control parameters. Rules that do not generally influence the game are the tournament system, pairing strategies, and placement criteria.

Common tournament systems used in Go include the [[Swiss system tournament#McMahon system|McMahon system]],<ref>{{Citation|url=https://www.britgo.org/organisers/mcmahon.html |publisher=British Go Association |title=The McMahon system in a nutshell |access-date=2008-06-11 |archive-url=https://web.archive.org/web/20080518202147/http://www.britgo.org/organisers/mcmahon.html |archive-date=2008-05-18 |url-status=dead}}</ref> [[Swiss system tournament|Swiss system]], [[league system]]s and the [[Single-elimination tournament|knockout system]]. Tournaments may combine multiple systems; many [[List of professional Go tournaments|professional Go tournaments]] use a combination of the league and knockout systems.<ref>{{harvnb|Fairbairn|Hall|2007|loc=''A quick guide to pro tournaments''}}{{page needed|date=May 2014}}</ref>

Tournament rules may also set the following:
* compensation points, called komi, which compensate the second player for the first move advantage of their opponent; tournaments commonly use a compensation in the range of 5–8 points,<ref name=histKomi>{{harvnb|Fairbairn|Hall|2007|loc=''History and Timelines'' "History of Komi"}}{{page needed|date=May 2014}}</ref> generally including a half-point to prevent draws;
* handicap stones placed on the board before alternate play, allowing players of different strengths to play competitively (see [[Go handicap]] for more information); and
* ''superko'': Although the basic ko rule described above covers more than 95% of all cycles occurring in games,<ref name="KoRules">{{Citation | title = Ko Rules | url = http://home.snafu.de/jasiek/korules.html | first = Robert | last = Jasiek | year = 2001 | access-date = 2007-11-30}}</ref> there are some complex situations—[[Ko fight#Complex situations involving ko|triple ko]], ''eternal life'',{{efn|1=A full explanation of the eternal life position can be found on [http://senseis.xmp.net/?EternalLife Sensei's Library], it also appears in the official text for Japanese Rules, see [http://www-2.cs.cmu.edu/~wjh/go/rules/Japanese.html translation].}} etc.—that are not covered by it but would allow the game to cycle indefinitely. To prevent this, the ko rule is sometimes extended to forbid the repetition of ''any'' previous position. This extension is called superko.<ref name="KoRules" />

=== Time control ===
{{See also|Time control|Byoyomi}}

A game of Go may be timed using a [[game clock]]. Formal time controls were introduced into the professional game during the 1920s and were controversial.{{sfn|Bozulich|2001|pp=92–93}} Adjournments and [[sealed move]]s began to be regulated in the 1930s. Go tournaments use a number of different time control systems. All common systems envisage a single main period of time for each player for the game, but they vary on the protocols for continuation (in ''overtime'') after a player has finished that time allowance.{{efn|1=Roughly, one has the time to play the game and then a little time to finish it off. Time-wasting tactics are possible in Go, so that ''sudden death'' systems, in which time runs out at a predetermined point however many plays are in the game, are relatively unpopular (in the West).}} The most widely used time control system is the so-called [[byoyomi]]{{efn|1=Literally in Japanese ''byōyomi'' means 'reading of seconds'.}} system. The top professional Go matches have timekeepers so that the players do not have to press their own clocks.

Two widely used variants of the byoyomi system are:<ref name="Byoyomi">{{Citation | publisher = European Go Federation | url = http://www.eurogofed.org/egf/tourrules.htm | title = EGF General Tournament Rules | access-date = 2008-06-11}}</ref>
* ''Standard byoyomi'': After the main time is depleted, a player has a certain number of time periods (typically around thirty seconds). After each move, the number of full-time periods that the player took (often zero) is subtracted. For example, if a player has three thirty-second time periods and takes thirty or more (but less than sixty) seconds to make a move, they lose one time period. With 60–89&nbsp;seconds, they lose two time periods, and so on. If, however, they take less than thirty seconds, the timer simply resets without subtracting any periods. Using up the last period means that the player has lost on time.
* ''Canadian byoyomi'': After using all of their main time, a player must make a certain number of moves within a certain period of time, such as twenty moves within five minutes.<ref name="Byoyomi" />{{efn|1=Typically, players stop the clock, and the player in overtime sets his/her clock for the desired interval, counts out the required number of stones and sets the remaining stones out of reach, so as not to become confused. If twenty moves are made in time, the timer is reset to five minutes again.}} If the time period expires without the required number of stones having been played, then the player has lost on time.{{efn|1=In other words, Canadian byoyomi is essentially a standard chess-style time control, based on ''N'' moves in a time period ''T'', imposed after a main period is used up. It is possible to decrease ''T'', or increase ''N'', as each overtime period expires; but systems with constant ''T'' and ''N'', for example 20 plays in 5&nbsp;minutes, are widely used.}}

=== Notation and recording games ===
{{Main|Go game record}}
Go games are recorded with a simple coordinate system. This is comparable to [[Algebraic notation (chess)|algebraic chess notation]], except that Go stones do not move and thus require only one coordinate per turn. Coordinate systems include purely numerical (4–4 point), hybrid (K3), and purely alphabetical.<ref>{{cite web|author=Stas Bekman|url=http://stason.org/TULARC/games/go/5-3-Recording-Go-games.html |title=Go FAQ |publisher=Stason.org |access-date=2014-03-25}}</ref> The [[Smart Game Format]] uses alphabetical coordinates internally, but most editors represent the board with hybrid coordinates as this reduces confusion.

Alternatively, the game record can also be noted by writing the successive moves on a diagram, where odd numbers mean black stones, even numbers mean white stones (or conversely when playing with a handicap), and a notation like "25=22" in the margin means that the 25th stone was played at the same location as the 22nd one, which had been captured in the meantime.

The Japanese word [[kifu]] is sometimes used to refer to a game record.

In Unicode, Go stones can be represented with black and white circles from the block [[Geometric Shapes (Unicode block)|Geometric Shapes]]:
* {{unichar|25CB|white circle|html=}}
* {{unichar|25CF|black circle|html=}}

The block [[Miscellaneous Symbols]] includes "Go markers"<ref>{{cite web|title=Go markers|url=https://www.unicode.org/charts/PDF/U2600.pdf#search=Go%20markers|work=The Unicode Standard|archive-url=https://web.archive.org/web/20010603010228/https://www.unicode.org/charts/PDF/U2600.pdf|archive-date=2001-06-03|url-status=live}}</ref> that were likely meant for mathematical research of Go:<ref>{{cite web|last1=Dürst|first1=Martin J.|title=Purpose of and rationale behind Go Markers U+2686 to U+2689|url=https://unicode.org/mail-arch/unicode-ml/y2016-m03/0025.html|website=The Unicode Archives|date=2016-03-10}}</ref><ref>{{cite web|author1=Beeton, Barbara|author2=Avtalion, Ori|title=Purpose of and rationale behind Go Markers U+2686 to U+2689|url=https://unicode.org/mail-arch/unicode-ml/y2016-m03/0074.html|website=The Unicode Archives|date=2016-03-15}}</ref>
* {{unichar|2686|white circle with dot right|html=}}
* {{unichar|2687|white circle with two dots|html=}}
* {{unichar|2688|black circle with white dot right|html=}}
* {{unichar|2689|black circle with two white dots|html=}}

=== Top players and professional Go ===
{{See also|List of top title holders in Go|Go players|Female Go players|Go professional|List of professional Go tournaments}}

A Go professional is a professional player of the game of Go. There are six areas with professional go associations, these are: China ([[Chinese Weiqi Association]]), Japan ([[Nihon Ki-in]], [[Kansai Ki-in]]), South Korea ([[Korea Baduk Association]]), Taiwan ([[Taiwan Chi Yuan Culture Foundation]]), the United States ([[American Go Association#Professional players|AGA Professional System]]) and Europe ([[European Go Federation|European Professional System]]).

Although the game was developed in China, the establishment of the [[Four Go houses]] by [[Tokugawa Ieyasu]] at the start of the 17th century shifted the focus of the Go world to Japan. State sponsorship, allowing players to dedicate themselves full-time to study of the game, and fierce competition between individual houses resulted in a significant increase in the level of play. During this period, the best player of his generation was given the prestigious title [[Meijin (go)|Meijin]] (master) and the post of [[Godokoro]] (minister of Go). Of special note are the players who were dubbed [[Kisei (go)|Kisei]] (Go Sage). The only three players to receive this honor were [[Hon'inbō Dōsaku|Dōsaku]], [[Hon'inbō Jōwa|Jōwa]] and [[Hon'inbō Shūsaku|Shūsaku]], all of the house [[Hon'inbō]].<ref name=jowa.html/>

[[File:GovsShusai.jpg|thumb|left| [[Hon'inbō Shūsai]] (left), last head of house Hon'inbō, plays against then-up-and-coming [[Go Seigen]] in the [[The game of the century (Go)|game of the century]]. ]]

After the end of the [[Tokugawa shogunate]] and the [[Meiji Restoration]] period, the Go houses slowly disappeared, and in 1924, the [[Nihon Ki-in]] (Japanese Go Association) was formed. Top players from this period often played newspaper-sponsored matches of 2–10 games.<ref>{{Citation | url = http://www.msoworld.com/mindzine/news/orient/go/history/newspaper.html | title = History of Newspaper Go | last = Fairbairn | first = John | access-date = 2018-01-06 | url-status= dead| archive-url= https://web.archive.org/web/20110608021318/http://www.msoworld.com/mindzine/news/orient/go/history/newspaper.html | archive-date= 2011-06-08}}</ref> Of special note are the (Chinese-born) player [[Go Seigen]] (Chinese: Wu Qingyuan), who scored 80% in these matches and beat down most of his opponents to inferior handicaps,<ref>{{Citation | publisher = GoBase.org | url = http://gobase.org/games/china/misc/disks/matches.html | title = Go Seigen: Match Player | access-date = 2007-06-14}}</ref> and [[Minoru Kitani]], who dominated matches in the early 1930s.<ref>{{Citation | last = Fairbairn | first = John | url = http://senseis.xmp.net/?KitaniMinoru | title = Kitani's Streak | access-date = 2007-06-14}}</ref> These two players are also recognized for their groundbreaking work on new [[Go opening theory|opening theory]] ([[Shinfuseki]]).<ref name=ShinFuseki>{{Citation | url = http://gobase.org/information/players/?pp=Kubomatsu+Katsukiyo | first = John | last = Fairbairn | title = Kubomatsu's central thesis | access-date = 2008-01-17}}</ref>

For much of the 20th century, Go continued to be dominated by players trained in Japan. Notable names included [[Eio Sakata]], [[Rin Kaiho]] (born in Taiwan), [[Masao Kato]], [[Koichi Kobayashi]] and [[Cho Chikun]] (born Cho Ch'i-hun, from South Korea).<ref>{{Citation | publisher = GoBase.org | url = http://gobase.org/games/jp/ | title = List of Japanese titles, prizemoney and winners | access-date = 2008-06-11}}</ref> Top Chinese and Korean talents often moved to Japan, because the level of play there was high and funding was more lavish. One of the first Korean players to do so was [[Cho Namchul]], who studied in the [[Kitani Dojo]] 1937–1944. After his return to Korea, the [[Hanguk Kiwon]] (Korea Baduk Association) was formed and caused the level of play in South Korea to rise significantly in the second half of the 20th century.<ref>{{Citation | url = http://www.usgo.org/news/index.php?%23_id=102 | title = KBA Founder Cho Nam Chul passes | first = Janice | last = Kim | publisher = American Go Association | access-date = 2008-06-11}}</ref> In China, the game declined during the [[Cultural Revolution]] (1966–1976) but quickly recovered in the last quarter of the 20th century, bringing Chinese players, such as [[Nie Weiping]] and [[Ma Xiaochun]], on par with their Japanese and South Korean counterparts.<ref>{{Citation | url = http://www.societies.cam.ac.uk/cugos/tesuji/weiqi_chinese_culture.html | title = Weiqi in Chinese Culture | last = Matthews | first = Charles | access-date = 2007-06-04 | archive-date = 2007-11-30 | archive-url = https://web.archive.org/web/20071130002057/http://www.societies.cam.ac.uk/cugos/tesuji/weiqi_chinese_culture.html | url-status = dead }}</ref> The [[Chinese Weiqi Association]] (today part of the China Qiyuan) was established in 1962, and professional dan grades started being issued in 1982.<ref>{{cite web|url=http://sports.sina.com.cn/go/2016-07-22/doc-ifxuhukz0789072.shtml|title=中国围棋职业段位制的历史|author=朱宝训|publisher=[[Sina.com.cn]]|date=22 July 2016|access-date=7 January 2018|language=zh}}</ref> Western professional Go began in 2012 with the American Go Association's Professional System.<ref>{{cite web|url=http://www.usgo.org/aga-professional-system|title=AGA Professional System|publisher=usgo.org|access-date=3 March 2015}}</ref> In 2014, the European Go Federation followed suit and started their professional system.<ref>{{cite web|url=http://www.eurogofed.org/proqualification/|title=1st European Pro Qualification 2014|year=2014|access-date=11 January 2015}}</ref> [[File:Changho-Dinerchtein.jpg|thumb|South Korean player [[Lee Chang-ho]] plays against Russian player [[Alexandre Dinerchtein]], seven-time European Champion and one of the few non-East Asian players to reach [[Go professional|professional]] status.]]

With the advent of major international titles from 1989 onward, it became possible to compare the level of players from different countries more accurately. [[Cho Hunhyun]] of South Korea won the first edition of the Quadrennial [[Ing Cup]] in 1989. His disciple [[Lee Chang-ho]] was the dominant player in international Go competitions for more than a decade spanning much of 1990s and early 2000s; he is also credited with groundbreaking works on the endgame. Cho, Lee and other South Korean players such as [[Seo Bong-soo]], [[Yoo Changhyuk]] and [[Lee Sedol]] between them won the majority of international titles in this period.<ref>{{Citation | publisher = GoBase.org | url = http://gobase.org/games/nn/ | title = List of International titles, prizemoney and winners | access-date = 2008-06-11}}</ref> Several Chinese players also rose to the top in international Go from 2000s, most notably [[Ma Xiaochun]], [[Chang Hao (Go player)|Chang Hao]], [[Gu Li (Go player)|Gu Li]] and [[Ke Jie]]. {{As of|2016}}, Japan lags behind in the international Go scene.

Historically, more men than women have played Go. Special tournaments for women exist, but until recently, men and women did not compete together at the highest levels; however, the creation of new, open tournaments and the rise of strong female players, most notably [[Rui Naiwei]], have in recent years highlighted the strength and competitiveness of emerging female players.{{sfn|Shotwell|2003|p={{page needed|date=June 2020}}}}

The level in other countries has traditionally been much lower, except for some players who had preparatory professional training in East Asia.{{efn|1=[[Kaku Takagawa]] toured Europe around 1970, and reported (''Go Review'') a general standard of amateur 4 ''dan''. This is a good amateur level but no more than might be found in ordinary East Asian clubs. Published current European ratings would suggest around 100 players stronger than that, with very few European 7 ''dans''.}} Knowledge of the game has been scant elsewhere up until the 20th century. A famous player of the 1920s was [[Edward Lasker]].{{efn|1=European Go has been documented by Franco Pratesi, ''Eurogo'' (Florence 2003) in three volumes, up to 1920, 1920–1950, and 1950 and later.}} It was not until the 1950s that more than a few Western players took up the game as other than a passing interest. In 1978, [[Manfred Wimmer]] became the first Westerner to receive a professional player's certificate from an East Asian professional Go association.<ref name=wimmer>{{Citation | url = https://www.britgo.org/bgj/04112.html | title =Wimmer, Kerwin, Make Professional Shodan | publisher = British Go Association | access-date = 2008-06-11}}</ref> In 2000, American [[Michael Redmond (Go player)|Michael Redmond]] became the first Western player to achieve a 9 dan rank.