Author: Komputer Korner
Date: 20:31:44 11/24/97
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Didn't Crafty announce a long mate from the tablebases? -- KK On November 24, 1997 at 19:44:44, Robert Hyatt wrote: >On November 24, 1997 at 19:24:55, Willie Wood wrote: > >>All, >> >>I recall reading that some programs, like Ferret, don't use mobility in >>their eval functions, and I would guess that's for speed. I've been >>trying to do without mobility as an experiment, and it's been a bit >>tough to get the bishop to know what it's doing. Anybody have a hint? >> > >I'm not sure what Bruce does. I do mobility for bishops, as there is >not a lot of other things that can tell whether the bishop is a good one >or a bad one... But it doesn't have to be an expensive calculation, if >you use the right data structures. IE mobility is "free" for bitmap >programs... > > >>Another issue is the tree explosion that occurs with check extensions. >>Hyatt mentioned the use of fractional ply extensions on replys-to-check, >>though I don't see how that avoids being arbitrary (my lack of >>understanding). I wonder if there's a good check-pruning method that >>would avoid chasing the king all over the board? >> >>WW > >I have used fractional ply extensions for about 15 years. The idea is >that >a normal check can extend 1 ply, but if there is only one legal way out, >I >let this extend by 3/4 of a ply. The 3/4 is critical, because a single >such extension does nothing (3/4 < 1). but the second such extension >will >trigger an extra ply, as will the third and fourth, then the fifth won't >extend, but the next 3 will. This provides a throttling effect to >prevent >a non-terminating search. Just be aware that following too many checks >is >just as bad as following too few. You want to find the obvious mates so >you >don't get killed, but there is no real need to find a mate in 30. I've >played >in computer vs computer and computer vs human games for almost 30 years >now >and have *never* seen a program of mine announce a mate in 30, nor have >I >ever found a position where such was important. If you go too far, you >waste >time that could be used in other ways...
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