Author: Tord Romstad
Date: 07:20:28 04/14/04
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On April 14, 2004 at 10:03:04, Alvaro Jose Povoa Cardoso wrote: >Hi, >I've been playing with the following history heurist variant: >Along with the PieceType-From-To formulation I added 8 bits that correspond to >the rightmost 8 bits of the hashkey. >So the new index to the history table is as follows: >HashKey-PieceType-From-To >HashKey is only 8 bits as said before. The idea is to try to match as much as >possible the moves that failed high with the 'true' posições where that happened >since in the classic hitory heuristic aproach we have little or nothing that >says that those history moves found at the current node where previously stored >in the exact same position as the current one. In other words history moves >don't mean they came from the same position. It is exactly this I'm trying to >avoid. >However when I tryed this idea it failed miserably with much higher node counts. >My question is why did this failed? >Is this a wrong idea from the very beginning? It failed because it happens very rarely in the search tree that exactly the same position arises again, and because in these rare cases, you usually have a hash table move which is more reliable anyway. The very idea of the history heuristic is that a move which has worked in many different positions of the search so far is also likely to work in many future positions. Tord
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