Author: Roberto Waldteufel
Date: 22:21:27 06/11/98
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Do you think the PV is actually worth the overhead of gathering it, bearing in mind that the information in the hash table, ie the killer moves stored with each node, effectively allow the PV from the previous iteration to be quickly retrieved in the current search? When I first implemented PV in a standard alpha-beta search without hashing (it was on a machine with hardly any RAM), I found a speed-up of about 40% by following this line first. Later, when I had more RAM to play with, I implemented a hash table, which speeded up the search a bit more. However, with the hash table working, I found that the search didn't need the PV list any more, because it almost always found it from the table, and so now I only bother to return best move at the root node and I find the search increases in speed by another 5-10% or so. Of course there is the risk that a PV node may have been overwritten, but this occurs too rarely to hurt performance as much as maintaining the PV separately did, particularly if the hash table is large. Does anybody else use the hash table rather than the PV in this way? Roberto
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