Author: blass uri
Date: 21:06:54 10/05/99
Go up one level in this thread
On October 05, 1999 at 11:40:27, Lanny DiBartolomeo wrote: >On October 05, 1999 at 11:15:35, blass uri wrote: > >>On October 05, 1999 at 10:23:46, Lanny DiBartolomeo wrote: >> >>>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. IE we (as humans) gamble on things all the time. But >>>>would it be the same as saying "I'll flip a coin and if it is heads I win, and >>>>if it is tails you win" if I rig the coin so there is _no doubt_ that it will >>>>end up heads when I want? >>>> >>>>That is the minor point here... computers don't sacrifice in the traditional >>>>way usually. There are exceptions like the famous chaos sacrifice vs chess >>>>4.x where chaos didn't see any materian coming back, but thought the position >>>>justified the Nxe6 sac anyway... I see a number of those in Crafty. More than >>>>I really want to see. But they do come close to the definition of a sacrifice >>>>as nothing "real" is won back, just some intangible positional things that may >>>>well not be enough to win with. >>> >>>Yes,even then, did chaos choose the move against a better move as related to its >>> score,if it saw a move that left its score at +1.00 or the move it made at >>> -1.00 did it go for the -1.00? I think a real sac in a computer is if it >>>chosses a move against its score, or else it is still going on raw calculation. >> >>A serious human does not do sacrifices by your definition. >>Sacrifice is the same as something that you believe that is clearly wrong by >>your definition. >> >>Uri >Not buy my definition, if you read the threads of which a true sacrafice is made >then, A.there cant be material gain by it.B. there has to be a gamble. >A computer program under this definition cant provide a "true" sacrafice >because it would go against its evalution of the position,if it sees that it >gives up a knight and the score still remains the same, it has not done a "true >" sacrafice, if its score goes up it is not a true sacrafice either, my point is >because of the logical functions of a computer program by the definition of >"real" sac presented in the threads, then it is not possible (when it comes to a >chess program) to give up material meaning taking a negative score in hopes that >it may bring it to a + score in the long run. When humans give up material and hopes that it is going to bring them back in the long run they use positional knoledge and evaluate the position after the sacrifice as positive evaluation inspite of the fact that the opponent has material advantage. They do not prefer position with negative score relative to positional with positive score. Another case is when their evaluation of the position is based also on some selective search and the selective search show positive score they are again may have positive score and not negative score. In both cases it is a sacrifice by definition. Uri
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