Updated Nov 15, 2007 by brainix
Labels:	Phase-Design, Phase-Implementation

Terminology

Chess engine terms and definitions.

Introduction

Details

BitBoard - A data structure, an unsigned 64-bit integer, in which each bit corresponds to a square on the chess board. A single BitBoard can't represent the entire state of the board. A single bit can only hold a value of 0 or 1 - enough to describe the absence or presence of a piece on a square, but not enough to describe the piece's color or type. Therefore, we need 12 BitBoards to represent the entire state of the board: white pawns, white knights, white bishops, white rooks, white queens, white kings, black pawns, black knights, black bishops, black rooks, black queens, and black kings.

Branching Factor - The number of moves that the player on move has in a given position.

Ply - One move by one player. The ply is used as a unit of depth. For example, at the start of a game, a move tree that's 4 plies deep consists of white's possible moves, black's possible responses, white's possible counter-responses, and black's possible counter-counter-responses.

Pondering or Permanent Brain - What the engine does when its opponent is on move. For a more detailed description, click here.

Principal Variation or PV - A series of best moves from the current position to a given depth. The PV always begins with a move for the color on move. For example, at the start of the game, the PV consists of white's best move, black's best response, white's best counter-response, black's best counter-counter-response, and so on.