This is a fork of simplech, a checkers engine, from the CheckerBoard software package maintained by Ed Gilbert at https://github.com/eygilbert/CheckerBoard It was written by Martin Fierz in C.
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
name: simple checkers
author: martin fierz
purpose: platform independent checkers engine
version: 1.11
date: 8th october 98
description: checkers.c contains a simple but fast checkers engine and a simple interface to this engine. checkers.c contains three main parts: interface, search and move generation. these parts are separated in the code. if you want to improve on the play of checkers, you will mainly have to improve on the evaluation function; this version does nothing but count material. even though it only counts pieces, this checkers engine will blow away all shareware checkers programs you will find on the internet, with the exception of blitz54, which is written for DOS.
board representation: the standard checkers notation is
(white)
32 31 30 29
28 27 26 25
24 23 22 21
20 19 18 17
16 15 14 13
12 11 10 9
8 7 6 5
4 3 2 1
(black)
the internal representation of the board is different, it is a array of int with length 46, the checkers board is numbered like this:
(white)
37 38 39 40
32 33 34 35
28 29 30 31
23 24 25 26
19 20 21 22
14 15 16 17
10 11 12 13
5 6 7 8
(black)
let's say, you would like to teach the program that it is important to keep a back rank guard. you can for instance add the following (not very sophisticated) code for this:
if(b[6] & (BLACK|MAN)) eval++;
if(b[8] & (BLACK|MAN)) eval++;
if(b[37] & (WHITE|MAN)) eval--;
if(b[39] & (WHITE|MAN)) eval--;
the evaluation function is seen from the point of view of the black player, so you increase the value v if you think the position is good for black.
if you want to program a different interface, you call the function "checkers":
checkers(int b[46],int color, double maxtime, char *str);
in b[46] you store the position, each square having one of the values of {FREE, BLACK|MAN, BLACK|KING, WHITE|MAN, WHITE|KING, OCCUPIED}. OCCUPIED are those squares which do not appear in the above board representation, i.e. 0,1,2,3,9,18,27,36,41-45. color is the color to move, either BLACK or WHITE. maxtime is the about half the average time it will take to calculate a move.
after checkers completes, you will have the new board position in b[46] and some information on the search in str.
initcheckers(int b[46]) initializes board b to the starting position of checkers.
have fun!
questions, comments, suggestions to:
Martin Fierz
[email protected]