Author: Mike Hood
Date: 13:41:35 03/25/03
I don't think that Chessbase's tablebase engine (which is activated when a tablebase position is on the board) is used optimally in drawn positions. In engine-engine matches it makes no difference, but a different strategy could give better results against human opponents. Let me explain what I mean, using the following position: [D] 8/8/8/7p/2K4P/5k2/8/8 w - - 0 1 Let's assume that the computer is playing White and the human is playing Black. The tablebase engine first does a lookup and recognizes that the position is a draw; then it finds that there are are four "correct" moves that lead to further drawn positions, namely: 1. Kc3 2. Kd3 3. Kd4 4. Kd5 The tablebase engine chooses the first move in the list, Kc3. If the human replies with Kf2 the new list of moves is: 1. Kc4 2. Kc2 3. Kd2 4. Kd3 5. Kd4 The computer will play Kc4, and if the human replies Kf3 we're back at the start position again, and the computer will play Kc3 again, heading for a rapid draw by threefold repetition. Not a mistake? Well, be honest, if you were playing this position as White in your chess club, and you had 20 minutes on your clock while your opponent has 3 seconds, would you want a draw by repetition? Of course not. A better strategy for tablebase engines would be to avoid draws by repetition if at all possible. The algorithm is easy to program: if in a drawn EGTB position several moves are possible, only choose the first move in the list if it doesn't lead to a position that has already been on the board. Otherwise make the next move in the list, etc. This will lead to draws under the 50-move rule rather than by threefold repetition. I chose a very simple example to illustrate this point, but look at the example in http://www.talkchess.com/forums/1/message.html?290545 [D]4K3/7P/6k1/8/8/8/1q6/7Q w - - 0 102 It would be foolish for White to accept a quick draw by repetition in a KQQKQ endgame position.
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