Author: Matthew McKnight
Date: 09:01:19 12/17/03
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On December 17, 2003 at 11:52:33, Alvaro Jose Povoa Cardoso wrote: >Hi, all. >I saw several discussions in the past on hash table replacing schemes, optimal >hash table sizes, wich information to store there, etc. >But I don't remember any discussion about what positions are the best candidates >to store in the HT. >What most of us do is to store positions in wich the best move is a fail high >or, an exact score, wich is correct for move ordering purposes. >I was wondering if someone uses a different criteria for choosing positions to >store in the HT. >When in some middle game positions I see a drop in the hash table hits (below >15%) of my engine I sometimes think if there is a better way to improve the >transposition effect, if such a thing can be done. > >My best, >Alvaro Cardoso I'm not sure if this answers your question, but I use two tables. One of them is the normal, "depth-preferred" table. The other one is an "always store" table. If I am adding a position to the table, but the entry in the DP table comes from a deeper search I leave the deeper information and put this new information in the "always store table," replacing without prejudice. Then in the readPosition() function I first check the depth preferred, and if there is nothing there I look in the always store table. This makes a noticeable difference with HT performance. Matt
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