Go
It is better to dip your fingers in the coffee than to try to drink the
stones. --Go proverb
This article is about the game of go, for programming language see
[1]golang.
{ I am still learning the beautiful game of go, please excuse potential
unintentional errors here. ~drummyfish }
Go (from Japanese Igo, "surrounding board game", also Baduk or Wei-qi) is
possibly the world's oldest original-form two-player board [2]game, coming
from Asia, and is one of the most [3]beautiful, elegant, deep and popular
games of this type in [4]history, whose cultural significance and
popularity can be compared to that of [5]chess, despite it largely
remaining widely popular only in Asia (along with other games like
[6]shogi, or "Japanese chess"). There however, especially in Japan, go is
pretty big, it appears a lot in [7]anime, there are TV channels
exclusively dedicated to go etc., though in Japan [8]shogi (the "Japanese
chess") is probably a bit more popular; nevertheless go is likely the most
intellectually challenging board games among all of the biggest board
games. Go is a bit difficult to get into (kind of like [9]vim?) though the
rules can be learned quite quickly; it is hard to make big-picture sense
of the rule implications and it may take weeks to months before one can
even call himself a beginner player. To become a master takes lifetime (or
two).
{ There is a nice non-bloated site hosting everything related to go:
Sensei's Library at https://senseis.xmp.net/. ~drummyfish }
Compared to chess (some purists dislike this, see
https://senseis.xmp.net/?CompareGoToChess) the rules of go are much more
simple -- which is part of the game's [10]beauty (see [11]easy to learn,
hard to master) -- though the emergent complexity of those few rules is
grandiose; so much so that to play the game well is usually considered
more challenging than learning chess well, as there are many more
possibilities and mere calculation is not enough to be strong, one needs
to develop a strong intuition; this is also the reason why it took 20 more
years for [12]computers to beat the best humans in go than in chess. Many
say that go is yet deeper than chess and that it offers a unique
experience that can't be found anywhere else; go is more mathematical,
something that just exists naturally as a side effect of logic itself,
while chess is a bit of an arbitrary set of more complex rules fine-tuned
so that the game plays well. The spirit of go is also more [13]zen-like
and peaceful: while chess simulates [14]war (something more aligned with
western mentality), go is more about dividing territory, one could even
see it not as a battle but rather a creation of [15]art, beautiful
patterns (something better aligned with eastern mentality). Also the whole
[16]culture around go is different, for example there is a strong
tradition of go proverbs that teach you to play (there also exist many
[17]joke proverbs).
From [18]LRS point of view go is one of the best games ever, for similar
reasons to chess (it's highly free, [19]suckless, cheap, [20]not owned by
anyone, [21]fun, mathematically deep, nice for programming while the game
itself doesn't even require a [22]computer etc.) plus yet greater
[23]simplicity and beauty.
Solving go: similarly to chess the full game of go seems unlikely to be
solved -- the 19x19 board makes the game state tree yet larger than that
of chess, but the much simpler rules possibly give a bigger hope for
mathematical proofs. Smaller boards however have been solved: Erik van der
Werf made a program that confirmed win for black on boards up to (and
including) 5x5 (best first move in all cases being in the middle of the
board). Bigger boards are being researched, but a lot of information about
them is in undecipherable Japanese/Korean gibberish, so we leave that for
the future.
A famous proverb about go goes like this: what is the most perfect game
man ever invented? Chess! But what about go? Go existed long before man...
TODO: rating, programming, stats, programs and sites for playing, ...
Rules
The rules of go vary a bit more than those of chess, they are not as much
unified, but usually the details don't play as much of a role because e.g.
different scoring systems still mostly result in the same outcome of
games. Here we'll describe possibly the most common rule set.
The game's goal is basically to surround a bigger territory than the enemy
player. The formal rules are pretty simple, though their implications are
very complex.
Go is played by a black and white player, black plays first (unlike in
chess) and then both players take turns placing stones of one's own color
on squares -- a square is the INTERSECTION of the lines on the board, NOT
the place between them (consider the lines to be carved in stone, the
intersection is where the stone stands with stability). The stones are all
the same (there are no different types of stones like in chess) and they
cannot move; once a stone is placed, it stays on its position until the
end of the game, or until it is captured by the enemy player. The board
size is 19x19, but for for students and quick games 13x13 and 9x9 boards
are also used. As black plays first, he has a slight advantage; for this
white gets bonus points at the end of the game, so called komi, which is
usually set to be 6.5 points (the half point eliminates the possibility of
a draw). Komi may differ depending on board size or a specific scoring
system.
Any player can pass on his move, i.e. making a move isn't mandatory.
However you basically always want to make a move, one only passes when he
feels there is nothing more to be gained and the game should end. If both
players pass consecutively, the game ends.
The game considers 4-neighborhoods, NOT 8-neighborhood, i.e. squares that
don't lie on board edges have 4 neighbors: up, right, bottom and left;
diagonal squares are NOT neighbors.
Capturing: a player can capture a group of connected (through
4-neighborhoods) enemy player's stones by completely surrounding them, or
more precisely by taking away all so called liberties of that group --
liberty is an empty square that's immediately neighboring with the group
(note that liberties may lie even inside the group). If a player places
his stone so that it removes the enemy group's last liberty, then the
group is removed from the board and all its stones are taken as captured.
It is possible to capture stones by a move that would otherwise be
forbidden as suicide, if after the removal of the captured group the
placed stone gains a liberty.
[24]Suicide is forbidden: it is not allowed to place a stone so that it
would immediately result in that stone (or a group it would join) being
captured by enemy. I.e. if there is an enemy group with one empty square
in the middle of it, you cannot put a stone there as that stone would
simply have no liberties and would immediately die. Exception to this is
the above mentioned taking of a group, i.e. if a suicidal move results in
immediately taking enemy's group, it is allowed.
The ko rule states that one mustn't make a move that returns the board to
the immediately previous state; this basically applies just to the
situation in which the enemy takes your stone and you would just place it
back, retaking his capturing stone. By the ko rule you cannot do this
IMMEDIATELY, but you can still do this any further following round. Some
rulesets extend this rule to so called superko which prohibits repetition
of ANY previously seen position (this covers some rare cases that can
happen).
Territory: at any time any EMPTY square on the board belongs either to
white (no black stone can be reached from it by traveling over neighbors),
black (no white stone can be reached from it) or none (belongs to
neither). Squares that have stone on them aren't normally considered to
belong to anyone (though some scoring systems do), i.e. if you surround a
territory as white, only the VACANT surrounded squares count as your
territory. The size of territory plays a role in final scoring. An
alternative to territory is area, which is territory plus the squares
occupied by player's stones and which is used under some rulesets.
Prisoners are enemy's stones that are OBVIOUSLY in your territory and so
are practically dead. I.e. they are inside what's clearly not their
territory and with further play would clearly be captured. Obvious here is
a matter of agreement between players -- if players disagree whether some
stones are obvious prisoners, they simply keep playing and resolve the
situation.
Scoring: scoring assigns points to each player when the game is over, the
one with more points win. There are multiple scoring systems, most common
are these two (players basically universally agree the scoring system has
almost no effect on the play so it's probably more of a convention):
* Chinese (area scoring): more [25]KISS, the score is just each player's
area (surrounded empty square PLUS squares occupied by the player's
stones), plus komi for white. { This one seems to me like a better
option for beginners and also for programming, it's just simpler and
makes you not afraid of putting stones anywhere. ~drummyfish }
* Japanese (territory scoring): At the end of the game we count the
score for black as the size of black's territory PLUS one point for
each stone black has captured PLUS one point for each white prisoner
(a would be captured stone) in black's territory. Score for white is
computed analogously but we also add the komi compensation.
Handicaps: TODO.
Implications of rules and basic of strategy/tactics: The very basic
observation a beginner has to learn is that of life and death and
especially so called eyes -- an eye is simply an empty square inside a
group of stones, and it can easily be deduced that if a group has at least
two eyes, it can't be taken by the opponent (the eyes have to be SEPARATE
though, two empty squares next to each other aren't two eyes). One eye
isn't enough to keep the group alive -- the opponent can still surround
this group and then take it by placing one stone in the eye, so two eyes
are necessary. From this it follows that players try to make groups with
these two eyes and more tactics follow from it -- for example if it's
clear a group can no longer form two eyes, usually the player just stops
wasting more time on it and lets it be sacrificed. This is the number one
"implied" rule and many, MANY more follow, but here is not a place to
recount them all: for more please refer for example to the Sensei's
library.
Example: the following is an example of the end state of a beginner game
on a 9x9 board:
_________________
9 |. # . . # # # O .|
8 |# . # . # O O . O|
7 |. . . # # O . O .|
6 |# . . # O . O . O|
5 |# . # O O O . . .|
4 |. # # # O O . . .|
3 |. . . # # O O . .|
2 |. . . . # # O # .|
1 |. . . . # O O O .|
'-----------------'
A B C D E F G H I
Here black's (#) territory is 23, and black made 9 captures during the
game, giving together 32 points. White's (O) territory is 16 and he has
one black prisoner (H2), giving 17 points; furthermore white made 6
captures during the game and gets 5.5 (smaller value due to only 9x9 board
size) bonus points as komi, totalling 28.5 point. Therefore black wins.
TODO
Play Tips
TODO
Go And Computers, Programming
See also https://senseis.xmp.net/?ComputerGoProgramming and
https://www.chessprogramming.org/Go.
Board representation: a straightforward representation of the go board is
as a simple [26]array of squares; each square can be either empty, white
or black, that's 3 values that can be stored with 2 bits, which allow
storing 4 values, leaving one extra value to be used for some other
purpose (e.g. marking illegal ko squares, estimated dead stones, marking
last move etc.). 1 byte allows us to store 4 squares this way so we need
only 91 bytes to represent the whole 19x19 board. On computers with enough
RAM it may be considered to store 1 square in a single byte or int, making
the board take more space but gaining speed thanks to data alignment (we
don't need extra instructions for squeezing bit from/to a single byte). Of
course we furthermore have to keep track of extra things such as numbers
of captured stones.
TODO
Stats
Some [27]interesting stats about go follow.
The longest possible game without passes has
4110473354993164457447863592014545992782310277120 moves. The longest
recorded professional game seems to be mere 411 moves long (Hoshino Toshi
vs Yamabe Toshiro, 1950). There are 2.08168199382 * 10^170 legal positions
on a 19x19 board, 3.72497923077 * 10^79 for 13x13 and 1.03919148791 *
10^38 for 9x9. The number of possible games is estimated from 10^10^100 to
10^10^171. An average high-level game lasts about 150 moves. Average
branching factor is 250 (compare to 35 in chess).
See Also
* [28]chess
* [29]game of life
* [30]hex game
Links:
1. golang.md
2. game.md
3. beauty.md
4. history.md
5. chess.md
6. shogi.md
7. anime.md
8. shogi.md
9. vim.md
10. beauty.md
11. easy_to_learn_hard_to_master.md
12. computer.md
13. zen.md
14. war.md
15. art.md
16. culture.md
17. joke.md
18. lrs.md
19. suckless.md
20. public_domain.md
21. fun.md
22. computer.md
23. minimalism.md
24. kys.md
25. kiss.md
26. array.md
27. interesting.md
28. chess.md
29. game_of_life.md
30. hex_game.md