Author: blass uri
Date: 01:26:17 10/04/99
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On October 03, 1999 at 23:44:31, Robert Hyatt wrote: >On October 03, 1999 at 23:17:29, Ricardo Gibert wrote: > >>[snip] >>> >>>my webster's defines 'sacrifice' as 'voluntarily giving up something of >>>value'. I have a hard time saying 'I will sacrifice a ten-dollar bill if >>>you will give me a 20 dollar bill in return...' >>> >>>:) >> >>Ok, you got me. I neglected to explicitly state I was refering to the _chess_ >>version of the term. >> > > >then here is a 3-move sequence. Sacrifice or combination? > >RxB, NxR, RxN. > >RxB obviously dumps a rook for a knight. or if you look to the end of the >combination it wins two pieces for a rook which is a significant advantage. > >Sacrifice or combination? > >How is that different from QxP+, RxQ, RxR#?? > >Dumping a queen for a pawn? Or winning the king? > > >>> >>>But I don't object to the term being used.. I just think that for a computer, >>>the concept 'sacrifice' is wrong. It is just a perfectly computable >>>combinational tree search... >> >>You can give up a bishop to obtain a draw by perpetual check and because you >>never get the material back, it is a called a sacrifice. I know it seems trivial >>and is not what people generally have in mind when they use the term >>"sacrifice", but I do believe it's use in such cases is fairly universal. > > >in the case of a computer, it isn't 'sacrificing'. It _sees_ that it can >draw or that it can win. IE it isn't giving up _anything_. A human might >toss a bishop 'thinking' (but not sure) than he can force a perpetual. But >a computer either 'proves' that it can force it, or it won't ever go for the >move in the first place. Not truth. Some programs use also selective search. I believe that Fritz evaluates positions based on some average between The evaluation based on selective search and the evaluation based on brute force search. If the selective search show perpetual check and the brute force does not see it then Fritz (in a bad position) might 'think' that he have chances to do a perpetual check without proving it and play for it. I saw a case in the past when Fritz5(16 bit) did a wrong sacrifice against Shredder(I am not sure if shredder2 or shredder3). Shredder did not find the right defence and Fritz won this game. Uri
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