Fruit (chess engine)

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 free and open-source software subject to the requirements of the GNU General Public License and as such 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.

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.

Fruit uses the classical Negascout (principal variation search) 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.

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.