Author: Robert Hyatt
Date: 18:36:38 09/16/98
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On September 16, 1998 at 18:31:14, John Coffey wrote: >On September 16, 1998 at 18:23:09, Robert Hyatt wrote: >>You apparently misunderstand the concept. "hash tables" (more correctly >>called transposition/refutation tables) store the results of searches at >>nodes inside the tree. so that if I search the move path Nf3 Nf6 Ng5 and >>search some more stuff deeper into the tree, when I get back to the position >>after these three moves I store the search result in the hash table. Then >>when search the moves Nh3 Nf6 Ng5 I reach the same position by different >>moves, but I find the result of the other search from this position and >>don't have to repeat it... > >Thanks for the response. > >Is there a limit to the depth that you will store positions into the >hash table? Does the hash table add much overhead? overhead is nominal, in the 1-2-3 percent range, max. The work it saves is always more than that. Sometimes *far* more. For example, if you take a simple pawn endgame position, without a hash table, you might search 14-15 plies deep in 3 minutes. That same position with hash tables might hit 30-40 plies deep. I don't hash in the capture search, but at all interior nodes I do... > >Back to my other question: Do programs spend more time evaluating the positions >than they do traversing the tree? I can only answer for mine. I spend about 50% of the total search time in the various evaluation function procedures. The remainder of the time is in the usual alpha/beta tree traversal, ordering moves, sorting moves, check detection, etc... > >John Coffey
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