Author: Dieter Buerssner
Date: 12:26:18 04/05/03
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On April 04, 2003 at 20:46:21, Sune Fischer wrote: >Like Dieter said, there are only two real problems with hashing, the repetition >and 50 move rule. >That's because they depend on the path and not only on the position. >I have no fix for this, I'm not sure there is a solution (one that is >efficient), but it doesn't seem to destabilize the search very much so the >effect must be small. For repetition, I think there cannot be an efficient solution. For 50 moves rule it is different. Typically, almost all situations you search, will be rather close to the last pawn move or capture. Typically you will also not have hash entries with 90 ply stored depth :-) In the cases, you approach 50 moves, it is most likely dead draw anyway, or perhaps easy for other reasons. One can use info about the current 50 moves counter and the depth stored in HTs to decide if this HT entry is reliable. Say, you have depth 10 stored and a very high score, but you are already only 5 plies before the 50 moves draw, the HT entry might not be reliable. Youc could use it for move ordering, but using it for a cutoff may yield in a wrong evaluation. Typically even this will make much of a difference, because it is going to be draw anyway. But one can find rules, to avoid that wrong evaluation from hash. Regards, Dieter
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