ChessHackDoc.tioga
Russ Atkinson, March 3, 1986
Russ Atkinson (RRA) March 3, 1986 1:43:25 pm PST
CHESS HACK
CEDAR 6.0 — FOR INTERNAL XEROX USE ONLY
Chess Hack
-- automated beginner's chess
Russ Atkinson
© Copyright 1986 Xerox Corporation. All rights reserved.
Abstract: ChessHack is a simple chess playing program that plays a beginner's level of chess at moderate speed. ChessHack is also a useful tool for browsing in chess games.
Created by: Russ Atkinson
Maintained by: Russ Atkinson <Atkinson.pa>
Keywords: chess
XEROX  Xerox Corporation
   Palo Alto Research Center
   3333 Coyote Hill Road
   Palo Alto, California 94304

For Internal Xerox Use Only
1. Interacting with ChessHack
Running the program
Just bringover -p ChessHack, then type ChessHack to the commander. An icon titled "ChessHack" will be created. Open the icon to reveal the chess board.
Making moves
To make a move, click down on the left mouse button when the cursor is over the piece want to move, move the cursor to the position you want the piece to occupy, and lift up on the left mouse button. If the move is legal, the program will make the move, otherwise it will not make the move. Taking en passant is indicated by moving the pawn on square to the left or right. Castling is indicated by moving the king two squares to the left or right.
To get the computer to choose a move, click the Auto button. The choice of mouse button will determine how hard the computer tries: left is easiest, right is hardest, and middle is in between. Of course, the harder the computer tries the longer it will take. To get the computer to continuously make moves, hold down the CTRL key while clicking Auto.
The buttons
There are a number of buttons at the top of the ChessHack viewer. These are used to control the display, to invoke the automatic player, and to browse within the chess game.
STOP! — Click this button to stop the progrm when it is automatically making moves or when replaying a game.
Reset — Click this button to reset the game to the initial state, except that the game history will be retained.
Refresh — Click this button to refresh the display. This will even refresh the display while the program is considering moves, but you may not like what you see.
Replay — Click this button to replay the game. This is like the fast forward browsing mode on a VCR. Clicking STOP! will stop the replay.
Step — Left-click this button to step backwards in the game history. Right-click this button to step forwards in the game history.
Stack — Left-click this button to save the game history at the current point. Right-click this button to restore the game history from the stacked version.
Auto — Click this button to make the computer choose a move. Left-click will make the computer move fast, right-click will make the computer try harder, middle-click is in between. Holding down the CTRL key while clicking will cause the program to keep on making moves until the STOP! key is hit.
Invert — Clicking this key causes the display to invert the board. Initially, white is at the bottom of the display, and clicking Invert causes black to be at the bottom.
Dump — Clicking this key causes the current game state to be dumped into the file indicated by the selection. The working directory is inherited the CommandTool when the program is started. An empty selection uses the name Dump$.chess.
Load — Clicking this key causes the current game state to be loaded from the file indicated by the selection. The working directory is inherited the CommandTool when the program is started. An empty selection uses the name Dump$.chess. The 24th game of the recent Karpov-Kasparov match is available as Game24KK.chess.
2. Notes on the algorithm
In choosing a move at the outermost level ChessHack performs two passes. The first pass is a three-ply exhaustive enumeration of the legal moves. The second pass is a deeper evealuation of the best eight (sometimes more) moves found in the first pass. Captures, checks, and the like will cause the search to be substantially deeper.
<<More to come.>>