Author: Robert Hyatt
Date: 08:05:54 03/26/03
Go up one level in this thread
On March 25, 2003 at 16:41:35, Mike Hood wrote: >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: > Crafty has been doing exactly this for many years. It is the "swindle mode" that several others now have as an option. >[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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