Author: Alvaro Jose Povoa Cardoso
Date: 10:19:55 12/17/03
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On December 17, 2003 at 12:01:19, Matthew McKnight wrote: >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 Thanks Matt, but my question is more in the line of how do we choose positions to try to store in the HT. I don't remeber seeing a discussion about that here. Currently we choose a position with a best move that caused a fail high or an exact score (above alpha). I wonder if that is all we can do. Regards, Alvaro
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