Author: Uri Blass
Date: 12:02:06 04/10/01
Go up one level in this thread
On April 10, 2001 at 12:04:17, Vincent Diepeveen wrote: >On April 10, 2001 at 10:25:02, Dieter Buerssner wrote: > >>On April 10, 2001 at 08:58:14, Ulrich Tuerke wrote: >> >>>On April 10, 2001 at 07:05:59, Tony Werten wrote: >>> >>>>On April 09, 2001 at 23:40:21, Jon Dart wrote: >>>> >>>>>>On April 09, 2001 at 17:04:09, Vincent Diepeveen wrote: >>>>> >>>>>> An interesting thing is lazy evaluation, as the problems of it are >>>>>> very similar to futility pruning. >>[...] >>>>>> My big question was: what score to return for example if evaluation in this >>>>>> position is e and e+ 3.5 pawns <= alfa ? >>>>> >>>>>> Must one return alpha, estimated evaluation or evaluation+3.5 pawns, >>>>>> when talking about e+margin <= alfa (idem story for e-margin >= beta) ? >>>>> >>>>>I return the estimated evaluation. But I fail to see that it makes a lot of >>>>>difference. If it's below alpha, you're not going to propagate this evaluation >>>>>up the tree, anyway. >>>> >>>>With failsoft alfabeta it easily could. >> >> >>>I think that it is a bad idea to return the estimated eval here because it can >>>result in some root-value far outside the aspiration window. It would be >>>interpreted as a corresponding bound which may cause serious trouble (fail low >>>in fail high verification search for instance). >>>IMO, it's much safer to return the corresponding beta or alpha. In case of >>>traversion of this value to the root this would cause a continous re-search >>>(i.e. over a neighbour region of the original window). >> >>I also have thought about this problem. I am using fail-soft alpha-beta search. >>I agree, that returning alpha or beta is safest. Nevertheless, some limited >>testing has shown here, that returning an estimation solved the testpostions I >>used with less nodes on average. >> >>From my understanding, returning an estimation should work and be theoratically >>sound. In eval, I first check for cases, which I don't want to estimate, like >>pawn endgames, endgames where one side has no pawns, etc. For other cases, I >>more or less compute bound values. >> >>1) material score + highest positional advantage seen for this side >>2) material score - highest positional advantage seen for the other side > >So i would need after a few ply a window > > materialscore + 20000 > > materialscore - 20000 > >pawn = 1000. I think that big positional scores of +20 pawns or even +10 scores in the middle game is a stupid thing to do. 2,3 or even 4 may make sense but I do not believe that +10 is logical. You can talk about fortress position when 2 rooks adavantage are not enough to win but even if your programs knows to evaluate fortress positions correctly these positions are not relevant in the middle game when they are a lot of unblocked pawns. Uri
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