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Subject: Re: Q for programers

Author: Louis Fagliano

Date: 15:25:42 04/29/02

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On April 29, 2002 at 14:01:23, Joe McCarro wrote:

>If I were playing someone over the board and they seemed to give me a
>possibility to play Bxa1 snatching the rook I would think long and hard before
>doing that. I'd figure as long as this isn't a trap I will win the game.  Let me
>take my time to just make sure its not a trap. I wonder if this couldn't be
>programmed in.  Anytime the other player makes what on the surface appears to be
>a blunder (e.g., drops over a pawn) the computer could spend extra time working
>out the position before moving.  If it ended up it was in fact just a blunder
>presumably the computer should still be able to win despite the extra time spent
>looking for the tactical shot.  If it found it wan't a blunder the computer
>might avoid taking the poison.  Do the programmers do anything like this?  Would
>this in fact be helpful or would it have disadvantages as well?

This depends on whether Bxa1 loses a whole rook or whether White can immediately
recapture the bishop and be "only" the exchange down.

If the bishop cannot be immediately recaptured and White is a whole rook down
then there are two possibilities:

1. White blundered away a whole rook and has no compensation.

2. Grabbing the rook is a tactical trap and White gets a powerful attack in
return for the rook.

If No. 2 is true, then computer programs, who are very good in tactics, would
all spot the compensation for the rook immediately and no extra time would be
necessary to decide to take the rook.

The second possibility, where the bishop can be immediately recaptured and White
is only the exchange down is a lot more dicey.  There are lots of positions
where a player greedily grabs the exchange in a position where there are no
immediate tactics to regain the exchange.  But then as the game slowly
progresses he may find out that in the specific resulting position, the
opponents two bishops are stronger than his own rook and bishop.  This can be
due to control of key squares, or the creation of a passed pawn where the two
bishops completely neutralize the enemy rook and bishop's ability to stop the
passed pawn.  In the long run, Black may be forced to give back the exchange and
maybe more in order to stop either a passed pawn or the creation of a passed
pawn, or even a mating attack occuring twenty moves after the exchange is
sacrificed.

They key is "in the long run".  In losing a whole rook, White better have
immediate tacical possibilities or he's lost.  If only the exchange is lost,
White may have long term positional and strategic pluses that a computer program
would never see even if it did take a lot of extra time.



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