Author: José de Jesús García Ruvalcaba
Date: 11:27:21 01/18/00
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On January 18, 2000 at 14:17:33, Steve Coladonato wrote: >On January 18, 2000 at 13:52:22, Dave Gomboc wrote: > >>On January 18, 2000 at 10:40:30, Steve Coladonato wrote: >> >>>Are tablebases basically a set of finite positions that have pointers to >>>subsequent positions (most probably positions leading to a win)? And if so, is >>>the basic algorithm to go to the next position that in turn will have a pointer >>>to a "won" position? I am also concluding that once a program starts to use a >>>tablebase, it no longer does any "real" processing, just pointer evaluation. Is >>>this basically it or am I way off the mark here? >>> >>>Thanks. >>> >>>Steve >> >>You're on the right track. The tablebases are the set of positions, accompanied >>by the number of ply it will take to win (or lose)... or if the position is a >>draw (or simply impossible to reach by the rules of the game, e.g. both kings in >>check), it notes that too. Once the root position (the position on the board) >>is in tablebase land, the only processing you do is to see, hmm well I had a >>mate in 51, so let's try all of the moves that are legal here and see which one >>is a mate in 50... aha, it's Rg6, let's play that. Of course, if two or more >>moves led to mate in 50, you could choose any of them. >> >>"Pointer" has a specific computer programming meaning, and it wouldn't be >>correct to say that the positions have pointers to the successor positions, but >>if you are thinking in general terms about the number of plies until checkmate >>values as "pointers" that show how to continue playing, it's all good. >> >>Dave > >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 That is correct, but tablebases are more productive when probed in the search (and not only in the root). Imagine crafty spoting a tablebase win after a ten plies search (i.e. the root position is not in tablebases, but some critical ten plies deep position is). José.
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