Author: Tony Werten
Date: 00:44:06 08/02/03
Go up one level in this thread
On August 01, 2003 at 22:45:11, Robert Hyatt wrote: >On August 01, 2003 at 05:09:59, Tony Werten wrote: > >>On July 31, 2003 at 18:15:47, Robert Hyatt wrote: >> >>>On July 31, 2003 at 14:23:34, Tony Werten wrote: >>> >>>>On July 30, 2003 at 17:18:12, Rick Bischoff wrote: >>>> >>>>>>> >>>>>>>a. at depth 3- hash table is empty for this position. alpha = -INF, beta = +INF >>>>>>>a. all requirements for null move are met >>>>>>>a. makes null move: int e = -alphabeta(depth - 3, -beta, -beta +1); >>>>>>> >>>>>>>b. now we are at depth 0, alpha = -INF, beta = -INF + 1 >>>>>>>b. we call quies(alpha, beta) >>>>>>> >>>>>>>c. e = static eval is, oh say, 1. >>>>>>>c. e >= beta, return beta >>>>>>> >>>>>>>b. store this position in the hash table as -INF + 1, exact, depth = 0, return >>>>>>>-INF + 1 >>>>>> >>>>>>This is _way_ wrong. How can it be "exact"??? It is impossible for the >>>>>>search to return valid scores outside alpha/beta window as defined at the >>>>>>root. If you are returning an "edge" then it must be an upper or lower >>>>>>edge, not an exact score. >>>>> >>>>>Yes, I know it is wrong-- which is why I was asking the question to begin with >>>>>:-) What I do know is store anything quies returns as exact-- but you are >>>>>telling me I can't do that, right? (Forgive my ignorance!) >>>> >>>>You are correct (despite what the others say), but only if you use the failsoft >>>>version of alphabeta. >>>> >>>>Tony >>> >>>I don't see how he can be correct even with failsoft. If you get a score >>>outside alpha/beta it is _never_ an exact score, it will only be a bound. >> >>No it isn't. If you evaluate and take a beta cutoff, the evaluationscore is >>still exact, has nothing to do with bounds. > >Never heard of "lazy evaluation?" AFAIK lazy eval isn't part of alphabeta. Tony > > >> >>If you evaluate below beta then there are 2 possibilities. In the end, best >>score didn't improve, score is still eval, and eval is exact. >>Second, bestscore did improve, must have been by search, so read from start, but >>now 1 ply deeper. >> >>Tony
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