Author: Vincent Diepeveen
Date: 05:26:55 02/25/99
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On February 24, 1999 at 12:45:08, Andrew Dados wrote: > >On February 24, 1999 at 11:53:39, Vincent Diepeveen wrote: > >>On February 24, 1999 at 11:27:53, Ed Schröder wrote: >> >>>>Posted by Vincent Diepeveen on February 24, 1999 at 08:03:23: >>> >>>>I know however that i must have had wrong collisions, probably the fact >>>>that i don't store true values hides collision probs from me, as i >>>>cannot have true values in my program; if a score is true then alfa >>>>gets improved and then score is again <= alfa, so i use only 1 bit >>>>to see whether it's >= beta or <= alfa. >>> >>>I don't understand the above. You say, "i cannot have true values in >>>my program" and then "if a score is true then..." which I interpret as >>>you use true score after all? >>> >>>My best guess is you only use alpha (and not beta) to mark the >>>score in the hash table. Correct view? >>> >>>Can you tell why Diep can't use "true scores" in the hash table? >> >>This is something theoretical Ed, >>ASSUME we have true scores in search. >>Now try to prove that to false. >> >>We assume that we have true scores. >>then alfa becomes the true score, >>however score <= alfa, so >>conclusion is falsum. >> >>so the score is <= alfa, which is a bound. >>therefore i only store using 1 bit in hashtable. >>a score is either <= alfa or >= beta, but never alfa < score < beta, >>that cannot happen in DIEP as i improve alfa with the result of the search. >> > >Hmm... but if score=alpha and score<beta then you have it exact, correct? >Andrew if score == alpha then score is <= alfa, so it's a bound then. you only get a true score when alfa < score < beta however as soon as i get a score back then i improve alfa with the score, so then always the score <= alfa. On the other hand if score gets one ply further a fail high then it might be here <= alfa, so score == alfa. So score == alfa says nothing except that it is a bound. In the case that we backup alfa initially, then we can after searching the moves compare and we see that alfabackkuped < alfa < beta Now we say that alfa = score is a true score. This is the *only* way to find a true score However this doesn't work for DIEP. Somewhere this goes wrong. I don't see extra speed up either because of this. I just waste a few million bits extra doing this in my hashtable. In the case of MTD this even isn't possible. >>>Ed
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