Author: Uri Blass
Date: 14:01:16 06/30/04
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On June 30, 2004 at 15:10:51, Robert Hyatt wrote: >On June 30, 2004 at 02:58:11, Mig Greengard wrote: > >>For storage space considerations, some impractical and unnecessary bases have >>been left out of the DVDs. > > >Again, kpppk is not that impractical. Particularly when all 3 pawns end up on >the same rook file... > >But it really doesn't matter whether the ending is easy to win or not. What >matters is to stop searching as soon as possible along a path where the result >is known. having _all_ 5 piece tables makes that happen. Missing files are >less efficient, period... Based on my knowledge yace does not use 4 vs 1 tablebases. I suspect that it may be cheaper to use static evaluation in most 4 vs 1 positions to end the search and not to call tablebases. I suspect that a simple rule that there is a mate in at most 20 moves if the following conditions even in 8 vs 1 and not only in tablebases position may be correct(I did not prove it but I cannot think now of a negative example): 1)the side to move has at least one rook or one queen 2)the opponent has only king 3)the side to move does not control all the squares near the opponent king(to prevent forced stalemate in the next move). 4)in case of a rook the rook controls at least one square that the king does not control(to prevent a possible problem of white rook at h8 white knights at h7 g8 and black king at g7). You can decide to be careful not to use this evaluation when the root position is position when the opponent has only king and you have at least a rook so you will not have problem of not getting progress in a winning endgame because you only have mate in 20 evaluations. The program without tablebases may show score of mate in 24 some plies before trading to the endgame when the opponent has only king and smaller score later but it is not a problem. Uri
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