Fruit (chess)
Encyclopedia
Fruit is a chess engine developed by Fabien Letouzey. In the SSDF
rating list released on November 24, 2006, Fruit version 2.2.1 had a rating
of 2842. In the CEGT rating list released on January 24, 2007, Fruit version 2.2.1 had a rating of 2776.
At the World Computer Chess Championship
in Reykjavík
in 2005, Fruit 2.2 scored 8.5 out of 11, finishing in second place behind Zappa.
Until Version 2.1 (Peach), Fruit was an open source
engine. The source of the version 2.1 is still open (under GNU GPL) and contributed much to the development in computer chess in recent years. Some people still work on the old source code and have created variations from the original Fruit.
(PVS) algorithm with iterative deepening to traverse the game tree. It also uses the null-move heuristic
. The original version used a simplistic evaluation function
with a robust search. Later versions have improved evaluation functions.
The board representation is distinct — Fruit uses a 16x16 board.
As of July 23, 2007, Fruit became freeware. The latest version Fruit 2.3 and Fruit 2.3.1 are free to download on superchessengine.com. Fruit 2.3.1 was one of the top 3 free UCI
chess engines.
Toga II is a derivative created by Thomas Gaksch. It has more chess knowledge, multi-processor support, and perhaps a better search algorithm. It is based on Fruit 2.1 and is free. The strongest versions are 1.4 beta5c and 1.4.1SE. Experimental versions of Toga II running on computer clusters have competed in the World Computer Chess Championship (WCCC).
In 2008, forks of Toga II started to appear, like Grapefruit and Cyclone.
GambitFruit is another free derivative of Fruit 2.1, created by Ryan Benitez. It plays a more aggressive style and has more chess knowledge. GambitFruit also incorporates improvements from Toga II. Development of GambitFruit stopped in 2005.
In June 2011, the strong chess engine Rybka
was disqualified from the WCCC, after a lengthy investigation found evidence of plagiarism of Fruit and Crafty
. The author of Rybka has since declined to comment.
An up-to-date ranking of Toga II and Fruit derivatives is found at the CCRL.
Swedish Chess Computer Association
The Swedish Chess Computer Association is an organization that tests computer chess software by playing chess programs against one another and producing a rating list. On September 26, 2008, the list was released with Deep Rybka 3 leading with an estimated Elo rating of 3238. Rybka's listing in...
rating list released on November 24, 2006, Fruit version 2.2.1 had a rating
Elo rating system
The Elo rating system is a method for calculating the relative skill levels of players in two-player games such as chess. It is named after its creator Arpad Elo, a Hungarian-born American physics professor....
of 2842. In the CEGT rating list released on January 24, 2007, Fruit version 2.2.1 had a rating of 2776.
At the World Computer Chess Championship
World Computer Chess Championship
World Computer Chess Championship is an annual event where computer chess engines compete against each other. The event is organized by the International Computer Games Association...
in Reykjavík
Reykjavík
Reykjavík is the capital and largest city in Iceland.Its latitude at 64°08' N makes it the world's northernmost capital of a sovereign state. It is located in southwestern Iceland, on the southern shore of Faxaflói Bay...
in 2005, Fruit 2.2 scored 8.5 out of 11, finishing in second place behind Zappa.
Until Version 2.1 (Peach), Fruit was an open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
engine. The source of the version 2.1 is still open (under GNU GPL) and contributed much to the development in computer chess in recent years. Some people still work on the old source code and have created variations from the original Fruit.
Technical details of Fruit 2.1
Fruit uses the classical NegascoutNegascout
NegaScout or Principal Variation Search is a negamax algorithm that can be faster than alpha-beta pruning. Like alpha-beta pruning, NegaScout is a directional search algorithm for computing the minimax value of a node in a tree...
(PVS) algorithm with iterative deepening to traverse the game tree. It also uses the null-move heuristic
Null-move heuristic
In computer chess programs, the null-move heuristic is a heuristic technique used to enhance the speed of the alpha-beta pruning algorithm.- Rationale :...
. The original version used a simplistic evaluation function
Evaluation function
An evaluation function, also known as a heuristic evaluation function or static evaluation function, is a function used by game-playing programs to estimate the value or goodness of a position in the minimax and related algorithms...
with a robust search. Later versions have improved evaluation functions.
The board representation is distinct — Fruit uses a 16x16 board.
As of July 23, 2007, Fruit became freeware. The latest version Fruit 2.3 and Fruit 2.3.1 are free to download on superchessengine.com. Fruit 2.3.1 was one of the top 3 free UCI
Universal Chess Interface
The Universal Chess Interface is an open communication protocol that enables a chess program's engine to communicate with its user interface....
chess engines.
Derivatives
Although Fabien Letouzey's development of Fruit stopped in 2007 with version 2.3.1, the earlier open source 2.1 version provided the basis for many other programs.Toga II is a derivative created by Thomas Gaksch. It has more chess knowledge, multi-processor support, and perhaps a better search algorithm. It is based on Fruit 2.1 and is free. The strongest versions are 1.4 beta5c and 1.4.1SE. Experimental versions of Toga II running on computer clusters have competed in the World Computer Chess Championship (WCCC).
In 2008, forks of Toga II started to appear, like Grapefruit and Cyclone.
GambitFruit is another free derivative of Fruit 2.1, created by Ryan Benitez. It plays a more aggressive style and has more chess knowledge. GambitFruit also incorporates improvements from Toga II. Development of GambitFruit stopped in 2005.
In June 2011, the strong chess engine Rybka
Rybka
Rybka is a computer chess engine designed by International Master Vasik Rajlich. , Rybka is one of the top-rated engines on chess engine rating lists and has won many computer chess tournaments...
was disqualified from the WCCC, after a lengthy investigation found evidence of plagiarism of Fruit and Crafty
Crafty
Crafty is a chess program written by UAB professor Dr. Robert Hyatt. It is directly derived from Cray Blitz, winner of the 1983 and 1986 World Computer Chess Championships....
. The author of Rybka has since declined to comment.
An up-to-date ranking of Toga II and Fruit derivatives is found at the CCRL.