Author: Robert Hyatt
Date: 19:45:11 08/01/03
Go up one level in this thread
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?" > >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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