Gomoku

• The game is played on a square field ("board"), drawn by vertical and horizontal lines. Intersections of lines are called “points”. The most common is a field measuring 15 × 15 lines.
• Two sides play - “black” and “white”. Each side uses chips ("stones") of its own color.
• Each turn, the player puts a stone of his color in one of the free points on the board. Black makes the first move to the central point of the board. Further moves are done in turn.
• The goal of the game is to be the first to build with stones of your color a continuous row of five stones in a horizontal, vertical or diagonal direction.
• If the board is full and none of the players has built a row of five stones, a draw may be declared.
• Most rule options have one or another additional restriction for one or both players. So, in almost all cases, the construction of a row of more than five stones (the “long row”) is either prohibited or does not bring victory. More rule options are described below .

It is believed that the game was created in China and is at least two thousand years old. Around the 7th century, it was brought to Japan. The modern name comes from the Japanese word homokunarabe , which means "five pieces in a row." Initially, it was played on the field for go (19 × 19) without any restrictions; Now this version of the game is known as gomoku without limits (freestyle gomoku). Later, the rule of prohibiting winnings using the “long row” was added, and this game is now called “homoku”. In 1899, Tenryu Kobayashi proposed a new name for the game “ renju ” (“string of pearls”).

At the end of the 19th century, Japanese professionals came to the conclusion that the “free” version of the homoku player who makes the move first (black) has an advantage, with an optimal game, sufficient to win. This was strictly proved a century later, in 1994 by Victor Allis ^{[1] [2]} . But at the end of the XIX century, the Japanese Professional Renju Association reduced the size of the board to 15 × 15 and introduced “fouls” - restrictions on some black moves. In 1903, black was forbidden to build 3 × 3 forks, in 1936, at the proposal of Rokusan Takaki, 4x4 forks and the construction of a long row were also forbidden (white can build a long row, but he does not bring victory). It is these rules that are now considered the rules of the "classic renju." They remained unchanged for more than 50 years, but by the end of the 20th century it became clear that they could not completely compensate for the advantages of the first player, which was formally proved in 2001 by Wagner and Virag ^[3] . In 1998, the International Renju Federation ( RIF ) introduced opening rules for the first five moves, and expanded them in 2003.

Also in the 1980s, attempts were made to modify homoku without using fouls. In 1981, Japanese renju professionals G. Sakata and V. Ikawa showed ^[4] that in a game on a 15 × 15 field without fouls with a win when building a series of exactly five stones with the optimal game, the first player always wins. In 1980, Muscovite V. Sapronov published a series of articles on classical renju in the journal Science and Life, in which, among other things, he proposed a version of the game without fouls with a central forbidden square (see below). This variety of rules in the USSR was called “sapronovka” or “free renju”, and in the international version - “pro-homoku”.

Homoku international rules adopted later use a 15x15 board and opening rules with the possibility of exchanging sides: after the third move in the game, the second player (playing white) has the right to either continue playing with his stones or exchange colors with the opponent. There are alternative varieties of opening regulations.

A radical solution to the problem of equalizing chances was proposed in the Connect6 game created at the turn of the 20th – 21st centuries: here, on each move, players put not one, but two stones in a row on the board, and only the first move of Black is made by one stone. The winner is the one who builds a row of six or more stones. There are no artificial restrictions on moves like fouls or regulated principles. At the moment, this game is still very young and insufficiently studied, but so far there is no reason to believe that any of the parties in it initially has an advantage.

There are many variations of the rules designed to compensate for the advantage of the first player, and, accordingly, many names for the resulting new games. The following game options are known and used in Russia:

• Five in a row. The game is played on an endless field, either on a piece of paper in a cage, or on a gobana . No fouls. Building a long row (6 or more pieces in a row) brings victory.
• Gomoku. It is played on the board 15 × 15, less often 19 × 19. No fouls. The construction of a long row is not prohibited, but it is not a victory.
• Gomoku with a common central stone. The game according to the rules of gomoku on the board is 15 × 15, but the first stone (central) is considered black with the move of black, and white with the move of white. The rules of the game are symmetrical. The author is K. Kotsev ( Bulgaria ). In Russia, the game has not received distribution ^[5] .
• Three-dimensional homoku. The game is conducted according to the rules of homoku, but not in a plane, but in three-dimensional space. The goal is to build the "five" diagonally, horizontally or vertically in the plane and in space. The distribution game has not yet received ^[5] .

• One of the options for the game involves putting on the square vertical knitting needles of chips with a hole. Accordingly, an additional rule appears: the filling of the third dimension (knitting needles) occurs not in an arbitrary order, but strictly from the bottom up.

• Gomokunarabe. Playing on the board 15 × 15. The goal is to build the "five". None of the rivals can make a 3 × 3 fork; each player is given 35 stones; if black, having used all his stones, did not build the “five”, then it is considered that they lost. The game is very popular in Japan as a means of leisure ^[5] .
• International homoku. It is played according to the Gomoku rules on the 15 × 15 board with the following opening rules: the first move to the center of the board, the second and third move anywhere, after the third move (black) the second player (playing white) has the right to change color .
• Free Renju. Other names are “sapronovka”, “homoku with the central forbidden square”, “pro-homoku” (international). In the West, this particular kind of game is called “5 in a row” . A game according to the rules of homoku (no fouls, a long row does not bring victory) on a board measuring 15 × 15 lines. An additional rule: Black's second move (third move in the game) must be made outside the central square 5 × 5.
• Penta. Five in a row on a 19 × 19 board. The game starts at the center of the board. The first player to walk is to set white stones. A row of two stones, covered on both sides by enemy stones, becomes "prey" and is removed from the board. Black's second move is made outside the central 5 × 5 square. The winner is the one who first built a series of 5 or more stones, or the first to capture 5 loots. Penta is a simplified version of the Japanese Ninuki Renju game, common in Japan in the first half of the 20th century.
• Kerio Penta. Board game 19 × 19. White goes first. Players take turns to go anywhere on the board. A row of two or three stones, covered on both sides by enemy stones, becomes "prey" and is removed from the board. To win, you must build a series of 5 or more stones, or score 15 “booties”.
• Karo. The Vietnamese version of the game, also known as Gomoku +. A game according to the homoku rules on a 15 × 15 board with the only restriction: the winning five stones must not be blocked at both ends ^[6] .
• Renju . Playing on a 15 × 15 board with the prohibition for black to build a long row (is a loss for black), as well as to build 3 × 3, 4 × 4 forks and any derivatives from them (3 × 3 forks that do not lead to victory, i.e. force black to make a forbidden move in one of the branches, are allowed). The rules for setting the first five moves are also negotiated in the form of opening rules.
• Swap (from the English. Swap: change, exchange - means a possible exchange of color stones between the players at the beginning of the game). The gomoku variant on the 15 × 15 field, which differs only in the opening stage. At the beginning of the game, the first player places 2 black and 1 white stone on the board (without installation restrictions). After that, the second player chooses what color he will play and either makes the next move with a white stone or gives white stones to the first player.
• Swap two (from the English. Swap - change, 2 - two shift options). The gomoku variant on the 15 × 15 field, which differs only in the opening stage. It is used in world championships since 2009 and in other, less significant competitions. At the beginning of the game, the first player places 2 black and 1 white stone on the board (without installation restrictions). After this, the second player has three possibilities:
  • choose black color, that is, without setting stones, pass the turn to the first;
  • choose a white color, that is, put a white stone and pass the turn of the move;
  • or put two stones, black and white, giving the right to the final color to the first player.

In Russia, the homoku game is traditionally known under the names “Tic Tac Toe” and “Five in a Row”. The Explanatory Dictionary of the Living Great Russian Language by V. Dahl of the 1861 edition mentions the game in Heriki Oniki, although it is not known whether the game on the 3 × 3 board ( Tic-tac-toe ) or a larger board (Gomoku) was meant .

Since 2016, homoku as a discipline has been regularly presented at festivals held in Moscow, Larix ^[7] in January and Hinode ^[8] in April.

In 2011, an updated homoku committee of the International Renju Federation ( RIF ) began its work, the purpose of which is to determine the development strategies of this game in the world.

Chairman of the Committee

From 2011 to 2018 - Attila Demján (Hungary);

Since 2018 - Ilya Katsev (Russia)

Committee members:

• Alexander Bogatyrev (Russia)
• Pavel Laube (Czech Republic)
• Stepan Tesarik (Czech Republic)
• Piotr Malowiejski (Poland)
• Lukasz Majksner (Poland)
• Madli Mirme (Estonia)
• Zoltan Laslo (Hungary);
• Attila Demján (Hungary);
• Ants Soosyrv (Estonia)
• Peter Jonsson (Sweden)

According to homoku, as well as regular renju Russian and international tournaments are held. In the USSR , and then in Russia, championships for personal championships have been held since 1984 , team - since 1985 .

Since 2013, tournaments have been regularly held in Russia in Moscow, St. Petersburg and Tyumen. The average duration of tournaments is 2-3 days, in connection with which the dates for long tournaments mostly coincide with several consecutive holidays, in accordance with the production calendar of the Russian Federation.

In Moscow, tournaments are held in January and February-March. In St. Petersburg in January and May. In Tyumen in November and March-April. The champion of Russia is determined annually at a tournament in June held in one of these cities.

Russian homocock championships have been held regularly since 2014. Their winners were:

In May, in St. Petersburg since 2014, the Russian Cup Homoku Cup has also been held.

Holders of the Russian Cup in Homoku:

Full-time world championships were initially held under the auspices of the RIF in parallel with the Renju Championships, but due to objective problems with the composition of the tournament and the debut unbalance of the game, they ceased to be held. In recent years, with the advent of the debut rules of swap2, the homoku world championships are again held in parallel with the world renju championships. The results of the World Homoc Championships in the table below.

Because of the simplicity of homoku rules, there are a large number of programs for playing against a computer (artificial intelligence).

Since 2000, traditionally in April, Gomocup competitions ^{[29] have been held} among various programs for the game, which, however, have become competitive enough to play on equal terms with humans, only in 2010. The total number of programs taking part in this competition is about 50, as well as dozens of their various versions, changing every year.

Gomocup winners since 2010 ^[30] :

Also worth noting are the programs that participated in the Gomocup that can compete with strong homoku players, such as Renjusolver author Wen Xiangdong (China), Goro author Viktor Barykin (Russia), Tito author Andrey Tokarev (Hungary), Slowrenju author Hao Tianyi (China) , Hewer author Tomas Kubesh (Czech Republic).

Of those who did not participate in Gomocup competitions, but which is a fairly competitive program, the Fiver program of Chinese developers should be noted.

Full-fledged official homoku matches in the “man versus artificial intelligence” format were not held until 2017, with the exception of the match that took place on May 9, 2016 after the end of the 2016 Russia Cup Gomoka draw. By prior agreement with the author of the strongest program in 2016, Sun Kai, the winner of this tournament was to play a match against the Yixin program. The match of 2 games in the presence of judges and live broadcast on the Internet with a temporary control of 60 sec + 45 sec for each Yixin move against Alexander Bogatyrev ended with the score 1-1 ^[32] . In 2017, Yixin successively defeated Konstantin Nikonov 3-0, Pavel Makarov 1-0 and Rudolf Dupsky 2-0 ^[33] .

• Renju
• Tic Tac Toe
• International Renju Federation

• International Renju Federation website
• World Homoku Site