Refutation (chess)
In the game of chess , a refutation means the thwarting of an intention with a counter move or a counter strategy . In the opening theory, the previous evaluation of a variant is turned upside down by a refutation, the refuting move, which has not yet been or insufficiently examined, is often called an innovation .
Chess composition
A refutation in chess composition proves an error in the composer's train of thought and thus completely devalues his idea. When temptations is intentionally designed by the author astray, which in turn each have a (single possible) refutation. Example: Composition in the article by Gerhard Latzel : Seven knight deductions are refuted, only the eighth leads to mate.
|
Analysis chart
White to move holds a draw |
Solution given by the author:
However, the study is refuted by 2.… a5 – a4, according to which Black first receives a queen and wins. The black pawn moves in with a check bid. After that, White must move the king and Black prevents White's pawn promotion with a queen and a king. If White wants to avoid this, he has to make another king move beforehand and is then too slow for a move. |
Computer chess
In computer chess , refutation plays a central role in the effective calculation of variants. In contrast to the minimax algorithm , the principle of refutation is integrated in the alpha-beta search . In principle, two types of refutation can be identified in the alpha-beta search:
- Real rebuttal: The rebuttal move proves that the move currently being examined is weaker than an alternative line that has already been analyzed . The remaining response trains therefore no longer need to be analyzed.
- Refutation in the extended sense (borderline case): The refutation move only proves that the move currently being examined is no stronger than an alternative line that has already been analyzed. In theory, both lines could even be equally strong. To determine this, one would have to examine the remaining response trains. For reasons of time, however, this is not done: you stick to the previously analyzed playback.
The former case is given in the alpha-beta algorithm by the condition α> β, the latter by the condition α = β. Since practically both types of refutation are treated in the same way, the condition is reduced to α ≥ β in summary.
A special abstract case of refutation also arises in the zero move search :
- Zero pull refutation: Zero pull proves that the attracting man maneuvers himself into a worse position without the assistance of the following. Even the inactivity of the pulling party is, so to speak, still strong enough to refute the playing of the pulling party.