How a Computer Plays Chess
The chess program is made up of three parts – move generator, search function, and the position evaluator. The first part generates all the possible moves for every given position. The second part which is the search function looks for the possible moves. It replies by trying to find an ideal continuation. The position’s score is given by the third part and it consists of the material score and positional score. If you can get a checkmate, the score is quite high.
Whenever the computer has to move a chess piece, it will first generate all the possible moves. The computer will pick one move and after that, it will generate all the opponent’s replies. By now, the computer is already thinking two plies deep. The computer will then evaluate the position and take note of the score. The computer will unmake the opponent’s move and will try another good move. The process will repeat until the computer has played the ‘root’ move. This is a basic and simple program.
Other chess programs out there make use of better techniques like the quiescent search, iterative deepening, opening books, endgame databases, and hash or transposition tables.
In the quiescent search, the chess program will aim to end in positions where there no captures or the so called quiet positions.
Iterative deepening does not begin with the utmost search depth. It starts its search 2-ply deep. When this is not finished, it will move on to 3-ply, 4-ply, and upwards. This will continue until the computer is able to decide on a good move. The previous searches can be used in some instances even if the existing search is still not finished.
Some chess programs already have an opening book and so the computer already knows the right chess opening to execute. The openings are preprogrammed and so the opening moves are instantaneous. You can learn man openings from this program and your next games will no longer be boring. Since the computer plays variations, human players will learn a lot of strange and unique openings for their advantage.
With the endgame databases, the chess program contains simple endgames. It will simply search the databases for the right move or ending and is executed promptly.
The Hash or transposition tables contain A key, Score, and depth. The bigger the table, the more info can be reused (hence, the program will be better). Scores are indexed through the ‘key’. Compare the keys so that you can ensure that you’re looking at the right data. If the data is not the same, you can’t use it since it is for a different position.
Computer chess programs vary and because of this, you can’t expect the programs to be the same. Some programs are basic while others are complex. It’s up to you to pick the program that will best suit your playing level. With so many chess programs to choose from, you may find it hard to pick the right one but with the help some websites, you may be able to determine the best programs available today.