Author: Mike Hood
Date: 14:49:07 04/07/02
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On April 07, 2002 at 15:23:23, Sergei Smith wrote: >On April 07, 2002 at 14:18:30, Mike Hood wrote: > > >>Another factor is that tablebases aren't just used when the endgame position is >>on the board. The 5-piece table bases are often used when there are 10 or more >>pieces on the board, if the program's search tree sees a path that exchanges >>pieces. > >Thanks for the explanation, but this blows me off my base : ) >If the position is not in the tablebase how could it be called by the Chessbase >GUI ? >Probably you mean : If the engine sees a way to reduce the number of pieces by >quick exchanges, it would be inclined to resort to a particular database. >Or did I get you wrong ? You got it right. What I mean is that there might be a position with 6 or more pieces where the winning side sees that exchanges can be forced in order to enter a 5-piece tablebase position. Let me give you a very simple example: [D] 6rk/2N5/8/8/8/8/1K5P/Q7 w - - 0 1 There are six pieces, so (if you only have 5-piece tablebases) it isn't a direct tablebase lookup. Let us suppose White plays Qa8. If Black replies with RxQ it's a simple tablebase lookup (KNP-KR) with the result Mate in 25. If Black replies Kh7 or Kg7 White plays QxR, and it's a tablebase lookup (KQNP-K) with the result Mate in 21. That means, by playing Qa8 White forces an exchange to enter a won tablebase position, and the program playing White knows it because it has already had a peak at the two relevant tablebases.
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