2001-12-22 last update, 1997-2-1 first day, Robert Jasiek
Copyright: All rights of the author are preserved according to the international law.

Game End Rules


Game end rules formally handle the part of a game after the last move that altered the score. A game end leads to scoring. There are different types of scoring and game phases before.


Game end rules say what to score, how to score, how to prepare the board position before scoring, and how to dissolve infinite or exceptionally long play not properly treated by ko rules. Scoring may have modifications. Special circumstances may lead to special game ends.


Go is a contest about sharing a go board. Play leads to a board position at the game end that is scored. Each player has a score that is measured in points. The difference of scores determines the win and the winning margin. Sharing refers to the grid points of the board. Each grid point is worth one point for scoring. The scoring operation is the sum. Two colours - black and white - share the grid points. It is natural to consider all grid points for sharing. Rules that virtually do this are called area rules. During a game alternating play results in about an equal number of grid points with black respectively white colouring. Rules that use this fact are called territory rules. A further simple scoring method exists. Primitive rules even completely avoid scoring.

Primitive Rules

Instead of determining the winner by scoring primitive rules let the first player without an available move lose the game. Such rules omit passes. Games tend to be very long and are so called pass fights. Their final stage consists of suicides respectively attempts to prohibit those of the opponent. They are important in mathematics.

Stone Rules

The simplest scoring method considers grid points only. Both players fill as many grid points as they can. Only single eye points or small shared spaces remain. The final positions naturally become terminal. To minimize empty grid points it is of great strategical importance to connect own groups.

Area Rules

Basically area rules score the grid points as Generally the score of a player is the grid points of his colour plus all empty grid points that are monochromely surrounded by his colour. The scoring allows moves inside own territory that are free of cost. Thus all removals can be solved by actual play.

Territory Rules

Basically territory rules score only empty grid points but add prisoners: Generally the score of a player is all empty grid points that are monochromely surrounded by his colour plus all prisoners of the other colour (with each prisoner being worth one point).

Since stones on the board are not added to the score, removals are not caused by board plays but left for the confirmation phase in which, however, most removals cannot be logically performed.

Shared grid points

Grid points that are not monochromely surrounded by one colour are called shared points. Counting varies:
  1. not counted
  2. counted for both players' scores
  3. equally shared
  4. proportionally shared : each grid point is shared in proportion to the number of surrounding grid points of a colour
4 is currently used in no rule set. 1 to 3 are equivalent.


Several rule sets have special treatments for special shapes. Some shapes as parts of board positions are called alive or dead or seki or with other names. Severe bearings on scorings follow.


Various counting methods exist. Methods are designed to fit scoring methods. Often application is only possible with particular scoring methods.

According to the rules in use adjustments for handicaps and penality points need to be considered together with common komi. - Proportional sharing needs special arithmetics.

Stone Counting

This can be applied for stone or area rules. All scored grid points are filled with stones. With stone scoring for each group the tax of two eye points is not scored. A single odd number empty point of all shared points is not filled.

After filling two ways of comparison exist. One is point-symmetrical arrangement of all stones on the board. The black respectively white stones are put on the upper respectively lower half of the board and the center grid point possibly becomes the odd shared point. The second way is putting away from the board pairs of two stones of black and white.

The score is the resulting difference of both colours' stones.

Point By Point Counting

This method is mainly used for area rules or in implementations. All scored points are counted. For each counted colour the board is scanned like reading and the grid points scoring for a colour counted directly. The difference of colour counts is the winning margin.

Point By Point Half Counting

In case of a half count only one colour is counted using the point by point method. The count is compared with half of the number of grid points. If there are shared grid points, then comparison refers to half of the difference of the number of board points and the number of shared points. Half komi values are to be used. To gain the normal score the difference is multiplied by two.

Chinese Half Counting

With this method for area rules only one colour is counted. The count is compared with half of the number of grid points. If there are shared grid points, then comparison refers to half of the difference of the number of board points and the number of shared points. Half komi values are to be used. To gain the normal score the difference is multiplied by two.

Unlike point by point counting the board position is rearranged. The empty regions of the counted colour are ordered for eased counting (rectangular shapes). Rearrangement must keep the numbers of surrounded grid points constant, of course. To achieve multiples of 10 (to fit the decimal system) stones of the counted colour can be taken off the board. Also stones of the colour could be added. The value for empty grid points is stored. Then the stones of the counted colour that are then on the board are arranged in blocks of 10 (as far as possible). The stone number is counted and added to the stored empty point number. Then the total value is used for comparison.

Japanese Territory Counting

Naturally this is only valid for territory rules. Together with Japanese rules point by point counting is scarce. For Japanese territory couting it is essential to keep any prisoner captured or removed from the board before the end of the game together with possible pass stones.

The empty territory regions on the board of both players are conveniently rearranged. The numbers of surrounded grid points must be constant. Single empty grid points can be tranferred between regions of the same colour. All prisoners of a colour are filled into empty regions of the colour as far as possible.

The remaining empty grid points of black respectively white are added. Remaining prisoners are substracted. Both colours' sums are compared as difference.

Fill-in Counting

Fill-in counting requires area rules and an equal number of black and white stones throughout the game of which the sum is the number of board points or the number of board points minus one.

Fill-in allows a clear use of scoring by sharing the board between two colours. The winner and the winning margin are obvious at a glance. The method reduces possibilities of counting mistakes. However, proper means are necessary for easy handling of stone numbers. Bowls are used to keep all unplayed or captured stones of one colour.

All stones are filled on the board. First shared empty grid points are filled equally sharing them. If there is a single odd empty grid point, it remains unfilled. Then own stones are filled in empty areas surrounded by own stones only. Then half as many stones as compensation points exist altogether (if divisable by two, this is generally the case) are put as stones of the colour giving the points in an empty surrounded area of the other colour. Finally remaining stones are filled as so called losing stones in the remaining empty area of the opponent. Compensation stones and losing stones must be positioned separately. (If compensation stones do not have enough space to be put in opponent's area, then a proper number of opponent's stones become losing stones by placing them in area of the player with compensation points. If, on the other hand, not enough stones as compensation stones are available, then the number is completed by taking stones from the board.)

The winning margin in favour of the opponent of the losing stones' player is twice the number of losing stones plus possibly one point for an empty grid point adjacent to losing stones.

Game Phases

A simplified game phase structure is:
  1. setup
  2. alternation
  3. stop
  4. confirmation
  5. end
  6. counting
A setup is used for placement of handicap stones or in special rule sets. The alternation phase is the main part of the game consisting of alternating moves of black and white. A move is a board play or a pass. Mostly with two successive passes the game stops. Then in the confirmation phase removals due to rules or the players' agreement take place. If this is done, then the game ends. This means that without fail counting is to be performed.

The phases alternation, end, and counting are sufficient for a game. Simple area rules, e.g., know this. Else in a confirmation phase removals due to the players' agreement or with the aid of life and death rules occur. Some rule sets allow resumption of alternation phase or partition the confirmation phase into different phases.

The alternation phase is identical in most rule sets. Only very few do not know passes. All other phases have different rulings in the various rule sets.

Another phase structure shows the type of board plays made during the phases:

Examples are available.

Classification of Rule Sets

The main classification of game end rules is done as to their scoring class and usage of game phases. The following are the most important game end rule types: Examples are available.

Primitive, stone, and simple area rules omit stop and confirmation phases. In agreement rules confirmation is done by agreement of the players. In life-death rules confirmation happens due to rulings.


In the alternation phase a single pass by one player signals that he thinks he cannot alter the score by a board play. The first pass play of a game (except passes during the setup) has in some cases an effect on the rules. In most cases two passes played successively by both players are required for a game stop. Sometimes this is equal to the game end. A confirmation phase can be structured using further occurances of (mostly two successive) passes and often its end is formally indicated by two successive passes.

Pass Stones

A few rule sets allow both area and territory scoring while giving the same count. This is enabled by an adjustment value. An often applied means is the use of pass stones.

As long as during alternating play no passes occur the numbers of played stones of each colour remain equal (with white having moved last). Furthermore, for each prisoner removed from the board the other player is to play exactly one stone on the board. So while one occupied point of one colour is added to an area's score, one prisoner point for the score of the same colour is added to a territory's score.

If one player passes and the other moves with a board play, then the territory score is not directly affected, but the area score alters by one in favour of the player not passing. To keep the balance the passing player gives his opponent a pass stone as a prisoner if territory rules are used. Thus also with territory rules the net effect is one point in favour of the player not passing.

Rules with pass stones need to take care of an odd number of moves. E. g., this is possible by forcing white to move last. In handicap games different measures might be necessary depending on the rules.


Komi are compensation points added to the white score. Komi can be used to make even or handicapped games fair, to include penality points or adjust or replace pass stones.

In even games without komi black wins by far most of the games. In professional play a komi of 5.5 and of 7.5 has given black a chance of roughly 53%. So maybe 9.5 komi might be more appropriate. The broken values avoid tied games.

Chinese counting evaluates only half of the board. Therefore komi must be half of normal values: 2.75 instead of 5.5, e. g.

Fill-in counting allows easy handling if komi can be divided by two. Furthermore, an odd board size and rarely occuring odd numbers of odd sekis most often lead to an odd winning margin. Thus the difference between smallest black respectively white wins is two. So different komi can only be distinguished properly if they differ by at least two. Altogether fill-in komi should be 2, 4, 6, 8,... with black winning ties.

Similarly and due to black's 50% chance to get an extra board play area rules with other counting mechanisms need 1.5, 3.5, 5.5, 7.5, 9.5, ... komi.

Handicap stones besides the first in area rules add just by being placed on the board one point to the black score each. This can be adjusted by proper komi.

Special Game Ends

Void Game

A void game is a game ending without result. This can be caused by cyclical play of infinite character if ko rules do not prohibit it, extremely long move-sequences similar to cyclical play, or disagreements aiming at a game end between players that are allowed by the rules.

To name a few examples: If ko rules only treat basic ko, then the ko stones of a triple ko can be captured endlessly. With improper ko rules and n basic kos on the board about two to the power of n moves might occur before a first repetition of the board position. This could need millions of years. So a referee might want to intervene and adjudge the game as void. If removals in the confirmation phase are to be resolved by mutual agreement, disagreements are likely to occur and result in a void game.

Constant Game End

Good ko rules achieve short move-sequences for all kinds of ko positions. Still some exceptional cases allow extremely long move-sequences. To ensure a game end after a reasonable move number all rule sets should include a constant game end rule: What should be the constant value? So far the record for a 19x19 game is about 425 moves. However, ko play easily might exceed this. For each basic ko capture a ko threat is played. Thus at least double the number of grid points might be necessary to fill the whole grid. So the minimal value must be roughly 750. 1024 is chosen for easier complexity calculations. If some ko threats within kos shall be possible, then such a higher or even a greater number is appropriate.


Insufficient performance during the alternation phase might make it almost impossible to gain a winning score at the game end. In such cases a player has the option of immediately ending the game with his loss by announcing resignation.

Lack of Time

If under set conditions the allotted time is exceeded by a player, then this causes his immediate loss and ends the game.


A misbehaving player violating rules or human conventions forfeits a game. This means his loss and the game end. In tournaments it is the task of referees respectively tournament directors to judge in such cases.


Suspension is a game end without result and due to extraordinary circumstances or based on some tradition. Natural forces are one example. In Japan the higher ranked player was traditionally considered to have the right of suspension at any time.

Terminal Positions

All board positions at a game end are called terminal. In a strict mathematical sense a more restrictive view is possible. Game theory is interested in positions allowing clear decompositions of the grid as to scoring and unalterable scores. In practice some rule sets allow scoring for any position, others have a strong desire to score only certain classes of positions. You will get a good idea of terminal positions by looking at examples.


Some - mostly former - rule sets had exceptional preferences. The following cannot be expected complete.

Group Tax

Ancient Chinese rules had a group tax. For each independently living group on the board two points were deducted from the score. This had historically evolved from stone scoring. Obvious fill-in encores were omitted and the tax kept. This explains the existence of Japanese rules, in which games are shortened and territory is counted but logical scoring got lost.

Korean Removals

Old Korean rules, that used territory scoring, followed the removals of opposing dead stones during the confirmation phase by removals of own stones so that own empty regions are enlarged but still completely safe. A maximal number of superfluous stones surrounding empty regions could be taken off the board. This requires further hypothetical analysis of possible play and has a severe effect on strategy and tactics in the alternation phase.


History has breeded rule sets owning precedents. These are special board positions being used as exceptional rulings. Many are owed to traditions. Game end rules have not been spared. Famous examples are bent-4-in-the-corner, three-points-without-capturing, and ten-thousand-year-ko.


Simple area rules, agreement area rules, and territory rule sets shall be compared.

Simple Or Agreement Area Rules?

Simple area rules have concise rule texts and a simple game structure (alternation, end, counting), but they need a few extra moves to remove stones from the board before the end. Agreement area rules often allow a short confirmation of removals, but their texts are longer, the game structure is complicated by stop and confirmation phases, and with the players' disagreement the extra moves for removals are also needed.

Possible agreements in most cases are a compromise for all who want to avoid the elegance of simple area rules. People preferring agreements argue removal moves blot the position. So they keep blotting it with hypothetical play instead and are afraid of being forced to use a minute for a game end in alternation.

Area Or Territory Rules?

Area rules are concise, simple, and logical. The only disadvantage is that more points are counted. Territory rules are long, complex, and illogical. (If they are logical, then because of having approached area rules.) The arguments clearly favour area rules.