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Komi
    Keywords: Go term

In a game of go, Black has the advantage of first move. In order to compensate for this, White can be given an agreed, set number of points before starting the game. These points are called komi. The English term "compensation points" or simply "compensation" is often used as a translation for komi.

A typical value for komi is in the region of 6 points, but numerous different values have been used in practice - see below for details. To prevent a drawn game in the case of jigo, the komi is commonly set to a fractional value such as 5.5 (which is a succinct way of expressing "White gets 5 points compensation and wins in the case of jigo").

With the notable exception of the Oteai, almost all tournaments nowadays, both amateur and professional, use komi. But this has not always been so. In fact, komi was rarely used in professional tournaments before 1937, and its gradual introduction into professional play was not without controversy.

The usual komi in Japan was for some time 4.5 points (specified as 4 points with White winning jigo), although even lower values were commonly used early on. Today the standard komi in Japan is 5.5 points, and this was also the case in Korea until the recent switch to 6.5.[1] The usual komi in China was formerly 5.5, but 7.5 is now standard.[2] The Ing rules also have a komi of 7.5, specified as 8 points with Black winning jigo. Western countries often follow Japanese practice in using a komi of 5.5 points, but tournaments with komi set at 6 or 6.5 are not uncommon. The New Zealand rules specify a komi of 7.

Because of the difficulty of determining a fair komi, a few amateur tournaments have adopted a system whereby players arrive at the komi through some form of bidding - see the section on auction komi below.

The Correct Komi

In theory, the correct komi for a given ruleset is a well-defined concept: it is the number of points by which Black would win given perfect play by both sides. Unless the ruleset allows fractional winning margins (which none of the common ones do), this is necessarily a whole number. Due to the absence of perfect players this number cannot be determined with certainty, but it is possible to make a reasonable guess at it, at least for some rulesets.

When area scoring is used (as in Chinese, Ing, AGA and New Zealand rules), the winning margin without komi is always odd, unless there are an odd number of points in seki. Since seki is fairly rare, and since a komi of 5.5 points has proven insufficient in professional play, and since a komi of 9 is generally considered far too much, it seems likely that the correct komi is 7.

When territory scoring is used (as in Japanese and Korean rules), the score is usually either the same as with area scoring, or one point better for White. This suggests that the correct komi under territory scoring rules is either 6 or 7. (Statistical evidence from professional games suggests 7.)

Auction Komi

Instead of prescribing a fixed komi, a tournament may instead use a system of bidding to determine the komi for each game. There are a number of ways in which this can be done. In all cases, bids are restricted to whole or semi-integral numbers, although whole numbers may be forbidden if jigos would be a problem.

In one system (used in the Japan Strongest Amateur tournament), one player is given the right to choose the komi, and the other then chooses whether to play Black or White.

In another system (used in the annual Furze Platt tournament in England), the players bid against each other in a standard auction, the player who bids the most points taking Black and giving that number of komi.

Auction komi systems have been criticised on the grounds that if they became widespread some players would end up playing Black almost all the time, while others would be White in nearly every game. At present, however, auction komi systems just provide a little extra variety and there seems little danger of them becoming widespread.

Komi in Handicap Games

In handicap games a komi of half a point is often given to White in order to avoid a drawn game.

Komi can also be used in handicap games to compensate for differences in strength that exceed the traditional maximum handicap of 9 stones. Such a komi, given to Black rather than to White, is called "reverse komi" (gyaku komi in Japanese).

Komi can also be used to 'fine tune' a handicap. This is especially useful on small boards, such as 9x9, where a single handicap stone compensates for a much greater difference in strength than is the case on a 19x19 board.


[1] The first significant professional tournament to adopt 6.5 komi seems to have been the 3rd LG Cup in 1998. This was an international tournament, but Korean-sponsored. Some Korean tournaments are still using 5.5 komi in 2002.

[2] Under Chinese rules there is very little practical difference between 5.5 and 6.5 komi, hence the jump directly to 7.5. Note also that in China it's usual to talk of 2.75 or 3.75 zi (子, meaning stone), rather than 5.5 or 7.5 komi.


From John Fairbairn: A lot of misinformation is being bandied about on the history of komi. I'm not going to write it up here but a few dates culled from the GoGoD database of 17,000 ganes will, I hope, allow readers to infer some of the errors. The table below shows the various possible Japanese/Korean komis and the first date of their use in the database, plus a few comments.

 2:   1935
 2.5: 1935
 3:   1852; first used in a tournament in 1907;
      first used in the Oteai in 1931
 3.5: 1929 (in the Oteai)
 4:   1931
 4.5: 1934
 5:   1890; 1932 in tournament play. There was
      a tournament then called the Hochi Shinbun
      Win & Continue Komi Tournament
 5.5: 1955 (the Oza)
 6:   1978 (Taiwanese Mingren);also 1998 in the
      Korean Promotion Tournament
 6.5: 1984 in Japan (Amateur Strongest Players);
      1997 in Korea(Tong Yang)

I would expect even these dates to be modified with a bit of research, A fuller treatment would cover not just Ing komis, Chinese (now 3.75 throughout), komi and reverse komis, but the use of komi combined with the old B-W-B kind of handicaps. There are also a few examples of 0.5 komi. I have never seen 1 or 1.5

I'm sorry I don't know how to prettify this. JF

SAS: I've tried to prettify your table, maybe not very successfully.
Are you sure that the Tong Yang Securities Cup used 6.5 komi in 1997? The games given [ext] on Jan van der Steen's site are all marked as 5.5 komi - with one exception, which I assumed was a mistake, because it seems unlikely that the komi varied throughout the tournament. (By the way, you're just the person who might be able to identify the mystery Korean player mentioned on the Tong Yang Securities Cup page.)
The Go Player's Almanac states that the 1937 tournament to decide Shusai's last opponent was the first to adopt a komi. It also states that there has only ever been one Oteai game that used komi, and that was in 1958. Is The Go Player's Almanac always this unreliable?
Is the "Amateur Strongest Players" tournament different from the "Strongest Amateur Player" tournament? According to [ext] this page, the 8th Strongest Amateur Player took place in 1999, so presumably they are not the same event.
I've made a couple of changes in accordance with your comments. (You can, of course, edit the text yourself. I deliberately didn't sign it so as not to deter people from making improvements.)

JF: I have now dug out my notes and can modify my statements above slightly.I too have queried there the 6.5 entry for the Tong Yang but have now bestirred myself to check it. It should definitely by 5.5. I also have a query against the 7th TV Asia Cup Final, given as 6.5, but it was in Japan that year, which makes it unlikely. However, the available sources for that event do not mention the komi. For the Amateur Strongest Game, I can neither confirm nor deny. It matters because the result of the game was W+0.5. But the game record gives only 148 moves and I have no other games from that event to compare with.

The earliest games for which 6.5 can reliably be stated are the 4th LG Cup (the international event). Interestingly, in that year the LG company retained 5.5 for its domestic cup, the Techron.

The reference to the Oteai games refers to the final playoffs where komi was used (the "Oteai Select" games).

Of course the Almanac has mistakes but that's only to be expected where a mass of figures and foreign names exist and it's unfair to call it unreliable. I haven't checked the statement quoted. If it's quoted correctly it's wrong. If it says this was the first use of komi in a true even-game tournament where the old B-W-B style handicaps did not apply, it's correct.

The Amateur event was the Hochi Ama Igo Saikyo, which became the Nihon Ama Igo Saikyo (in 1992 I think) and the term numbering was change to reflect that.

The missing Tong Yang runner-up was Chang Su-yeong.

I noticed a comment in my notes that Shusaku once said he would give 5 points to keep Black, but Shuwa said he'd take White with 5 komi. (ends)


Charles Matthews We've become used to komi - to put it another way, pros have been adapting their play to komi since I was born. My feeling though is that the adaptation to Komi Go was somewhat painful or empirical.


See also: Mathematical Bounds of Komi, Fair Game without Komi, Why Chinese Komi should increase by 2 point steps, another explanation.



This is a copy of the living page "Komi" at Sensei's Library.
(C) the Authors, published under the OpenContent License V1.0.