Author: Robert Hyatt
Date: 20:44:31 10/03/99
Go up one level in this thread
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. > >In discussions about the term, people seem to want to reserve the term to >describe the giving up of material for "uncertain" compensation. The "romantic" >view on sacrifices. But then in the next minute they will apply the term to the >case I describe above. The common thread is: it is a sac if it voluntarily gives >up material which you don't get back or do not get back in an obvious way. >So a sac can be short term and quite calculable. your last phrase "don't get back..." is the key I have been talking about. A computer (in the case of the rebel move) "sees" that it gets the material back, just like in the two examples I gave above with the rook and then with the queen.. but you are right, it is often used vaguely... or incorrectly (IMHO)... > >As for sac'ing to obtain mate, it is semantically arguable that you are getting >your material back and therefore it is not a true sac, but I don't see that as >natural or useful. In common _chess_ usage, it is called a sac and is >practically speaking consistent, when you consider its use to describe giving up >material to obtain a draw. > yes.. which is why I prefer the term "mating combination" rather than "mating sacrifice" as the latter could easily be termed an oxymoron... >> >>Bob >> >> >> >> >>>> >>>>But I like the term 'combination' here... and usually use the term sacrifice >>>>as in 'sacrificing the exchange'... after the rxc3 bxc3 type sac in many >>>>Sicilian variations, black is 2 pawns (the exchange) down, yet gets lots >>>>of compensation for that material, hopefully... Or in sacrificing a pawn >>>>(such as playing a4-a3 to force your opponent to play bxa3 and end up with >>>>three isolated pawns that you hope you can eventually win, and which you >>>>_know_ can not be used to create a passed pawn... >>>> >>>>Mainly semantics... But if we call this a sacrifice, then I see one of these >>>>every 2 games or so... IE QxR RxQ BxR, because after QxR RxQ I am definitely >>>>down 4 pawns, but after the third move I am up a pawn... >>>> >>>>Bob >>>> >>>> >>>> >>>> >>>>> >>>>>>>>Larry - the chess software addict!
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