Author: Robert Hyatt
Date: 06:29:50 10/20/00
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On October 20, 2000 at 00:02:19, Dave Gomboc wrote: >On October 19, 2000 at 09:33:48, Robert Hyatt wrote: > >>On October 19, 2000 at 05:57:30, Pham Minh Tri wrote: >> >>>I see some chess programs retrieve information based on color (side to move), >>>this means only half of hash table is useful. I wonder if we could retrieve >>>useful data from opponent part of hash table (I think when we implement Alpha >>>Beta function, it is easy to convert information between two sides). >>> >>>Pham >> >>The problem is that in many positions, side to move is critical. And it would >>be wrong should you do what you suggest. >> >>In endings it would be fatal. > >I think he means everything, e.g. rotating the board 180 degees and flipping the >colours of all the pieces. Essentially, always hash the position from the >perspective of the side to move, and assume that they are player A. Sounds >costly. > >Dave How could you do this? The score in the hash entry was derived after a long search that was based on the current side to move. Which means that it could be a zugzwang problem that makes the current side lose since he _must_ move. This same identical position, with the other side to move would have a totally different outcome. And I don't see any way to correct this position other than searching so that the zugzwang problem can be found... In the middlegame, it would probably be semi-workable, maybe. But in endgames, it would lose badly.
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