Author: Robert Hyatt
Date: 08:23:31 01/30/99
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On January 30, 1999 at 09:59:38, Steve Maughan wrote: >I have a couple of question regarding hash tables - can anyone help? > >1 I see in the Crafty code that the flag for a hash entry can be "value is >worthless". What is the condition for storing this type of entry? > that's an entry that has been 'cleared'. IE the score/bound is totally no good because something changed at the root that caused the piece/square tables to be recomputed... which means scores will change. I set the type to 'worthless' because the 'move' stored in such a position is still good for move ordering, but the score/bound is not. if I just cleared the entire entry, I'd lose the move ordering stuff the table contains... this way I just lose the score. >2 Is it advisable to store the a) the side to move b)Enpassant square c) >castling right in the hash code? ie assign a random value that is XORed for >these conditions. you _must_. I do it by dynamically updating the hash signature when I make a move that makes an enpassant possible, and updating it again when I make a move that makes the EP capture impossible. Ditto for castling. If you don't do this you will get matches that are wrong, and results that are wrong. > >All help appreciated. > >Steve Maughan
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