Author: Robert Hyatt
Date: 06:49:25 08/11/99
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On August 11, 1999 at 04:23:09, Bruce Moreland wrote: > >On August 11, 1999 at 03:11:25, Shep wrote: > >>On August 10, 1999 at 21:35:12, Robert Hyatt wrote: >> >>>On August 10, 1999 at 19:56:10, Marc Plum wrote: >>> >>>>A while back I ran some multiple engine tournaments within the Nimzo99 >>>>interface. One thing that I noticed was that some programs would make >>>>meaningless underpromotions. That is, in a position where a promoted pawn would >>>>be immediately exchanged anyway, the computer might promote to a bishop or rook >>>>rather than a queen. I had occasionally encountered the same thing in my own >>>>games with computers; I also found a small number of computer games like this >>>>when doing a database search for underpromotions. I don't have any statistics >>>>to present; I'm just noting that this happens not infrequently. >>>> >>>>When a human player does this, he is probably just being whimsical, or it could >>>>be a psychological ploy. I wonder, though, why a computer would do it. Is it >>>>just a random thing? Does the computer reason that losing a bishop is less bad >>>>than losing a queen, even though the resulting position is the same? Or do >>>>computers like messing with people's minds too? >>>> >>>>Marc Plum >>> >>>Actually at times there is a valid reason. If (say) d8=Q is a check, and d8=R >>>is not, then the program can choose whichever one maximizes the evaluation. How >>>could they be different? Remember that one is a check and will extend the >>>search while the other is not. So if searching one extra ply discovers >>>something interesting, then =Q will get played. If searching one extra ply >>>discovers something bad, then we avoid seeing the 'bad' by playing =R. >>> >>>Cute, eh? :) >> >>There might be yet another very clever reason: >> >>If program A sees the promotion, his opponent, program B, will see it too. >>So Program B expects, say, d8=Q and has this information in its permanent brain. >>But Program A sees the promoted pawn will be immediately captured. >>So what would you do here if you were program A? >>Since it is meaningless whether you promote to Rook or Queen, what would you >>promote to? >>A queen, which Program B expects and which will allow it to use its PB info? >>Or a Rook, which takes Program B out of its PB and force it to re-search the >>position?? >>See my point? >> >>I suppose it would be very easy to add such a promotion rule to a program, >>right, Bob? :-) >> >>[I have seen programs which just about always promote to a rook if they see an >>immediate recapture (IIRC, MChess and Hiarcs are some of them). >>This is more than a conincidence... :-] > >It is extremely unlikely that anyone would intentionally do this, I believe. It >would be more complex than you think, it would be a possible source of bugs, and >it would serve almost no purpose. > >bruce Actually, when you think about the SSDF rating list, this does make a lot of sense to do. I don't do it. But I do see oddball underpromotions for the reason I gave earlier. But when you are interested in topping the SSDF list, every little thing helps. Good point, Shep. :)
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