Author: Rudolf Posch
Date: 08:36:19 04/06/03
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>Wouldn't it be a good idea to hash the 50 move counter when it aproach say 45?
My chess engine RDChess (and many others as I think) stop hashing positions when
the 50 move count reaches a certain limit (RDChess has not a 50 move count but a
100 ply count and stops hashing at a ply count of 81).
That is because without folding in the 100 ply count into the hash key one would
get wrong position values for positions with differing 100 ply counts.
(RDChess draws the position evaluation value from ply 81 until ply 100 nearer to
zero ("draw by 50 move rule")).
So when one folds in the 100 ply count (only when > 80) these positions could be
stored safely in the hash table.
But positions with the same 100 ply counter should be rare on different points
in the search tree, so you will get not many hash read hits for these positions
and I would expect the advantage not be very big (??).
Anyway it should be worth a try !
Rudolf
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