Stockfish is 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...

 chess engine, developed by Tord Romstad, Joona Kiiski and Marco Costalba and licensed under the GNU General Public License

GNU General Public License

The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....

 version 3. The current version 2.1.1 (as of May 8, 2011) is available as C++

C++

C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...

 source code, and also has precompiled versions for Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

, Mac OS X Snow Leopard, and Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 32-bit/64-bit. The program uses the 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....

 protocol and can therefore be operated under various graphical interfaces. It can use up to thirty-two CPU core

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

s in multiprocessor

Multiprocessor

Computer system having two or more processing units each sharing main memory and peripherals, in order to simultaneously process programs.Sometimes the term Multiprocessor is confused with the term Multiprocessing....

 systems. The maximum size of the transposition table

Transposition table

In computer chess and other computer games, transposition tables are used to speed up the search of the game tree. Transposition tables are primarily useful in perfect information games, meaning the entire state of the game is known to all players at all times....

s is eight gigabytes. Stockfish implements an advanced alpha-beta search and uses bitboard

Bitboard

A bitboard is a data structure commonly used in computer systems that play board games.A bitboard, often used for boardgames such as chess, checkers and othello, is a specialization of the bitset data structure, where each bit represents a game position or state, designed for optimization of speed...

s.

In various computer chess rankings Stockfish 2.1.1 is second or third behind the top gratis program Houdini and the commercial program 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...

.

The program originated from another open source program by Romstad named Glaurung. Stockfish was forked from the 2.1 version of Glaurung; the latest Glaurung version 2.2 was released December 2008 but is no longer developed.

External links

• Website
• Interview with the programmers (March 28, 2010)