Move Representation
The representation of a chess game includes representation of positions and moves. Positions represent states of game and moves represent operators which are used to achieve transition from one position to another. Both of these representations must be able to do the following operations:
- make move
- unmake move
- generate a list of all possible moves
- generate a list of all possible capture moves
- evaluate a position
- store moves
- compare positions
- set position
- check if position has been repeated 3 times
- check rule of 50 moves
- check if king is in check
All of these operations must be very time efficient because they take place inside the search algorithm. Efficient presentation of game will therefore exhibit an efficient chess program.
The move is represented by a 16-bit integer value with following bit mask.
0000000000111111 - index of square from
0000001111000000 - promotion piece (optionally)
1111110000000000 - index of square to
First six bits are used for the description of source square, next four for promotion piece type and last six for destination square. Promotion piece type is optionaly.