Author: José de Jesús García Ruvalcaba
Date: 10:29:23 01/19/00
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On January 19, 2000 at 09:48:11, Steve Coladonato wrote: ><snip> > >>>Dave, >>> >>>Thanks. From this and also what Michel posted, I gather that a TB is some kind >>>of ordered list based on some criteria that, once a root position is reached, is >>>searched repeatedly for the next move. And it's structure is not like that of a >>>tree. >>> >>>Steve >> >>The tablebase is a giagntic, collision-free hash table. You have a hash >>function that takes a board position (where all the pieces are, whose move it >>is, is castling legal, et cetera) and tells you the spot in the hash table that >>contains the data you need for that position (who is to win, and in how many >>moves.) >> >>It is possible to have an ordered list, and use binary search to find >>information on the position you are interested in, but hashing is faster for >>looking up stuff, because no searching is involved. You can find more >>information on "hashing" in books that deal with computer algorithms. It is a >>general technique that is often used when data retrieval must be fast, and >>certain other constraints are met. >> >>Dave > >Dave, > >OK. Now, if the information for the position also contains the best move, It does not. Tablebases only store scores, not moves. >the >program would make that move and then do a hash lookup on the position arising >from the opponent's move. Not quite. After receiving the opponent's move, it does a one ply search and chooses the move which leads to a higher score (I am assuming we are on a root tablebase position). >The assumption is that once a TB position has been >reached, all possible subsequent positions are in the TB. > Most programs assume this, and thus have problems when there are some tablebases missing. >Am I any closer? > >Steve
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