Author: Andrea Griffini
Date: 13:34:09 06/16/03
I'm writing a chess program (iigchess on FICS) and I implemented something I've seen described and to which I didn't think myself before, that is doing a scan on all moves when entering a node in the alpha-beta search to see if any of the reachable positions is already in the hash table and its value can justify a beta cut. Doing this after the hash table probe for this node but before doing the move sorting and before starting evaluating the moves seemed to me a possibility to save something, but after implementing it I saw that I was actually getting an *increased* number of visited nodes to reach the same search depth. Does this means there's a bug in my code or that can indeed happen ? My hash table is just a single-probe always-update one, but I suppose that shouldn't be the problem. Also a position in the hash table is considered usable only if the search depth that generated the stored result is not lower than current search depth or if we are in capture search (search depth is expressed in units of one tenth of a ply, depth<0 means capture search). Andrea
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