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Computer Chess

(Barth, Herbeck)

At the Algorithms and Programming Methodology Group (now called Algorithms and Data Structures Group), a special program for playing chess endgames based on a newly developed theory has been implemented.

This program uses the strict rules-search method (Barth and Barth, 1991, 1992). It is essential that part of the positions of the endgame considered have to be treated by rules, without it being necessary, however, to find rules for all positions; indeed, some positions may be left undecided. Thus, the finding of simple rules not overburdened by exceptions is facilitated.

For every position covered by the rules, they define an interval guaranteed to contain the true value. For example: "If White is to move and can capture the black Pawn the value is in [draw,win]." Note that many positions of the endgame may be ignored by the system of rules; for others an uncertainty may be left (as in the example just given). All deficiencies are supplemented and all uncertainties are removed by an appropriate alpha-beta-search. Herbeck (1995) uses the B* Algorithm.

Thus, granted an appropriate amount of time, the program will find the best possible result and a corresponding move for any position of the endgame under consideration. Failing enough time, it will produce an interval showing the knowledge found before curtailment. Yet, the interval is guaranteed to contain the true value of the position. An automatic validation component guarantees the rules to be free of errors (e.g. if some strange board configuration has been overlooked by the programmer). So far, almost all four-piece endgames have been implemented.

The fact that the rules seem quite natural to the average chess player makes interaction with the program much more interesting. In particular, the user may ask for an explanation to be displayed, and will be able to understand the plain text answer. This allows a "computer-aided teaching" approach.

Example: Reti's endgame problem

[Image of Reti's endgame problem] In this famous endgame problem dating from 1921, White is to move and finds a rather surprising way to prevent the black pawn's promotion, finally reaching a draw.

If moving 1.Kg8 or 1.Kh7, the program quickly finds that after 1....Kb6 Black has the possibility to both lead its pawn to promotion and hold the white pawn, i.e. Black wins. However, within a few seconds it also states that White will be able to reach a draw by moving 1.Kg7.

The solution and arbitrary variants can interactively be followed and evaluated, and often the program will comment a position and explain what it leads to.

Related Publications

W. Barth: Combining Knowledge and Search to Yield Infallible Endgame Programs
A study of passed Pawns in the KPKP endgame.
In: ICCA Journal, Vol. 18 (1995), No. 3, pp. 148-159.
W. Barth: Computerschach
- Ein korrektes Programm für das Endspiel König und Bauer gegen König und Bauer
- Unterteilung von Endspielen in Klassen
- Behandlung der Stellungswiederholung bei der Intervallbewertung
Institutsbericht Nr. 36, Institut für Computergraphik, TU Wien, Februar 1994.
W. Barth, S. Barth: Validating a Range of Endgame Programs
ICCA Journal, Vol. 15 (1992), pp. 132-139.
H. Herbeck: Eine Erklärungskomponente für Endspiele im Computerschach unter Verwendung der Regelmethode
Dissertation, TU Wien, Technisch-Naturwissenschaftliche Fakultät, 1995.
H. Herbeck: Solving Chess Endgames using the B* Algorithm and the Rule Method
Abstract, CSGP Workshop, Chinese University Hongkong, May 1995.
H. Herbeck, W. Barth: An Explanation Tool for Chess Endgames Based on the Rule Method
ICCA Journal 19, 2, pp. 75-82, 1996.

Software

There is an implementation of the rule-based endgame program as described above for MS Windows (3.1 or greater). The package is available here. See the text files in the respective directories for explanations. The site also contains some unpublished papers.

Lecture

The overhead slides for a lecture held by Prof. Barth in 1996 and 1997 (in German) are available in WinWord 6.0 format from here.


Algorithms and Data Structures Group | Inst. of Computer Graphics and Algorithms | TU Wien

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Last modification: 2006-09-28, 11:53