Author: Tijs van Dam
Date: 02:55:39 02/01/00
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On January 31, 2000 at 19:42:37, Vincent Diepeveen wrote: >On January 31, 2000 at 16:48:41, Tim wrote: > >>Crafty does not use(store and probe) hash table at root. >>How about other programs? >>Is there problem to use hash table at root? > >It depends upon how you write to hashtable, >but in general spoken it is not possible. > >Suppose you get to the same position as the root position somewhre in >your lines, which is very likely. now suppose one day that's with >difference alfa and beta values, so even though you already have it >in the hashtable you might overwrite it with a small depth, say 1 ply. > >then you need to abort your search. searching PV of this ply is not ready >yet. In your hashtable is only a 1 ply search from this position. > >Bad luck. all those plies searched for nothing... I don't understand fully what you mean. Do you, after a search, extract the PV from the hashtable? Then i see your point. But I save the PV when getting a value between alpha and beta anywhere in the search. The problem you are referring to gives me a 1 ply search hash value for the position, while otherwise I would have none at all. So when I have this position again, at least I have a 1-ply-best move to search first. Tijs
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