Endspiel

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Endspiel, a Windows chess program and explanation tool dedicated for simple Endgames, written by Wilhelm Barth in the 90s. Endspiel combines rule-based knowledge with a modified alpha-beta search to generate explanations. The rules cover a large part of the positions of an endgame. For each such position they define a score interval guaranteed to contain the true value. Multiple rules may be applied, resulting in the intersection and narrowing of intervals. Further, an alpha-beta search finds the values for all positions not covered and removes uncertainties left by too wide intervals in rule-scored positions. Thus, the method yields a correct evaluation for every position and. furthermore, the rules governing the position of its successors provide some tutorial insight to the user about the reasons behind the evaluations. Moreover, automatic validation assures that mistakes in the rules will be discovered and then can be eliminated in dialogue .

=Rules= For a specific endgame, e.g. KPK, KQKQ, KQKP, or KPKP, a system of rules is developed, which decides for the positions whether they are won, drawn or lost. The remainder of the positions may be left undecided. The rules may be arranged by decision trees , or they may be examined sequentially until applicable to the position involved. The rules consist of conditions to match and associated score intervals which may express some uncertainty. A winning position obtains the value of (maxval - k), where maxval is a huge positive integer, i.e. minus mate score, and k the minimum of For instance in KPK (BTM), the case of opposition on the same file, white king on the stop square, the interval is defined by value[maxval-8, maxval-4].
 * number of plies on the shortest path to mate, and
 * minimal number of plies ending with an irreversible move on the winning path

=KPKP= In his 1995 ICCA Journal article on KPKP with passed pawns , Wilhelm Barth elaborates on following six rules applied in his Endspiel program, along with several examples.

Symbols:
 * &and; - and
 * &or; - or
 * &#8712; / &#8713; - Element of / Not Element of
 * &#9632;, &#9633; - Square of The White, Black Pawn
 * &#10507; - Black Pawn's Front Span
 * D - Chebyshev Distance
 * &#128721; - Black Pawn's Tele Stop
 * &#9813; / &#9819; - White / Black Pawn's Promotion Square
 * !+ - No Check after Queening

=See also=
 * Chunker
 * KQKP
 * KPK
 * Pawn Endgame

=Selected Publications=
 * Wilhelm Barth, Stephan Barth (1991). Programme für korrekte Schachendspiele und deren Validierung. Institutsbericht, Nr. 34. Institut für Computergraphik, TU Wien (German)
 * Wilhelm Barth, Stephan Barth (1992). Validating a Range of Endgame Programs. ICCA Journal, Vol. 15, No. 3
 * Wilhelm Barth (1994). 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 (German)
 * Wilhelm Barth (1995). Combining Knowledge and Search to Yield Infallible Endgame Programs A study of passed Pawns in the KPKP endgame. ICCA Journal, Vol. 18, No. 3
 * Steven Edwards (1995). Comments on Barth’s Article “Combining Knowledge and Search to Yield Infallible Endgame Programs.” ICCA Journal, Vol. 18, No. 4
 * Heinz Herbeck, Wilhelm Barth (1996). An Explanation Tool for Chess Endgames Based on the Rule Method. ICCA Journal, Vol. 19, No. 2

=External Links=
 * Neues Schachprogramm für Spezialprobleme, October 28, 1996 (German)
 * Computer Chess site (Barth, Herbeck) (Wayback Machine)

=References= Up one level