Author: José de Jesús García Ruvalcaba
Date: 16:17:42 06/09/99
Go up one level in this thread
On June 09, 1999 at 18:34:53, KarinsDad wrote: >On June 09, 1999 at 17:47:05, blass uri wrote: > >> >>On June 09, 1999 at 16:39:42, KarinsDad wrote: >> >> >><snipped> >> And why would black as a perfect tablebase >>>program play for a draw when it would consider 1.b3 a slightly inferior move for >>>it's opponent? >> >>perfect tablebases do not know what is slightly. >>The only knowledge is for the result for every legal position. >> >>perfect tablebases can tell you to do stupid moves(to give a pawn in KRP vs KR >>and to lose the practical chances for a win). >> >>If the starting position is a draw then only losing moves are considered to be >>inferior by the tablebases. >> >>I understand that you have a different definition of perfect tablebases so what >>is your definition? > >My definition can best be shown by example: > >7k\Q7\7K\8\8\8\8\8 > >White could win with Qg7++, Qh7++, Qa8++, or Qb8++. Qf2 and Qf7 are stalemates. >Other moves can lead to a draw or a win, but not a loss. Therefore, the perfect >moves are the first 4 that I listed. Although other moves may lead to a win, >they are not perfect in the sense that they take more moves and hence, they do >not need to be in the tablebase (in regard to this position). Neither do the >draw moves. Neither does this position if a perfect game does not lead to it. >Neither do 3 out of 4 of these moves. > >The reason I place the minimal number of moves restriction is in order to >minimize the possibilities. > >I do not use the current concept of a tablebase that returns the number of moves >until a draw or a win with no concept of a better or worse move (the program >makes that determination based on ply). I use the concept that some moves are >perfect in the sense that they will lead to the best result in the given >position (assuming that the player continues to make best moves). > >As can be seen by my example, there could be more than one perfect move in a >position. > >Therefore, the perfect tablebase (there would be 2, one for white and one for >black) would not have ALL legal positions. For a given side, it would only have >those positions that can be achieved by it's opponent; assuming that the side >using the tablebase is making perfect moves. > >So, this would drop the maximum number of positions for 60 moves each from >approximately 40^120 to 40^60 positions in the table (ignoring transpositions, >ignoring early draws and wins, assuming that you only need one perfect move for >any given position in the table, and assuming an average of 40 legal moves per >position). Obviously, the real number of positions in the table would be much >smaller than 40^60. > >KarinsDad :) Could you please elaborate your definition of «perfect move» in a drawn position? José.
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