What is RIF Opening?
The RIF opening rule, named after the Renju International Federation, was the official opening of the Renju World Championships from 1997 to 2007. The first player sets up one of the 26 standard openings, the other player chooses a colour, and Black offers two fifth moves for White to choose from. Once the opening is over, normal renju takes over.
The first player places three stones: Black on the centre point, White inside the central 3 × 3 square and Black inside the central 5 × 5 square. The other player may then swap colours, and whoever holds White plays the fourth stone anywhere on the board.
Black then offers two fifth moves that aren't symmetrical to each other. White picks one of them for Black, plays the sixth stone, and the game goes on as normal renju.
Rule changes
| Rule | Standard Renju | RIF Opening |
|---|---|---|
| First stones | Standard RenjuBlack plays the first stone anywhere on the board, then the players take turns. | RIF OpeningThe first player places the first three stones: Black on the centre point, White inside the central 3 × 3 square and Black inside the central 5 × 5 square. |
| Fourth move | Standard RenjuWhite plays the fourth stone anywhere. | RIF OpeningWhite plays the fourth stone anywhere, after the other player has decided whether to swap colours. |
| Colour swap | Standard RenjuNot used: each player keeps the colour they start with. | RIF OpeningOnce, after the third stone: the other player may swap colours. |
| Fifth move | Standard RenjuBlack plays the fifth stone anywhere. | RIF OpeningBlack offers two fifth moves that aren't symmetrical to each other, and White picks the one that is played. |
| After the opening | Standard RenjuBlack may not make a double three, a double four or an overline. Black wins with exactly five in a row, White with five or more. | RIF OpeningThe same, from the sixth stone on. Forbidden moves also apply to Black's stones and offered fifth moves during the opening. |
History
The Renju International Federation, founded in Stockholm in 1988, adopted this rule at its General Assembly on 2 May 1996 as an upgrade of the older swap opening, which the World Championships had used from 1989 to 1995. The World Championships of 1997 to 2007 were played with it. Because the first three stones must go on the centre point and inside the 3 × 3 and 5 × 5 squares, every game starts from one of 26 patterns, each with its own name.
Over the years, analysis helped more and more by computers showed that only a few of the 26 openings were balanced with two fifth moves, so top games kept returning to the same positions. In 2008 the federation chose the Yamaguchi rule for its title tournaments, and today the RIF rule is used mostly in tournaments for newer players.