computer chess

Computer Chess

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binkers 21 ( +1 | -1 )
is Q vs R endgame winnable? A while back I played a game where I had Q & K only vs R & K only, and found it seemingly impossible to win. I found the K & R could always stay by one another, and prevent the K/Q from moving in to mate.

is it possible?

atrifix 60 ( +1 | -1 )
Yes KQ vs. KR is a win for the KQ.

In practice, the endgame is usually easy to win because of inaccuracies by the side with the KR; however, playing against perfect defense, it can be very difficult to win. GM Walter Browne drew a computer in a match with the KQ; in the rematch he narrowly avoided a draw by winning the rook on the 50th(!) move. The maximum number of moves required to win the rook is about 35, I believe.

For in-depth study, consult at a tablebase or John Nunn's Secrets of Pawnless Endings. For a basic primer, look at any endgame manual, e.g., Seirawan's Winning Chess Endings, Tarrasch's Game of Chess, Lasker's Manual of Chess, etc.
macheide 31 ( +1 | -1 )
binkers atrifix is right. The definitive explanation about this important end game is precisely in John Nunn's: "Secrets of Pawnless Endings". Why is this ending so important? Because in K+R+P vs K+R endings it is very common that the stronger side sacrifice his rook in order to promote, resulting in a K+Q vs K+R endgame.

binkers 39 ( +1 | -1 )
yes, but TOUGH! found this comment on the web

The endgame Queen vs Rook is still a classic and deceptively difficult to play. Most GMs are not able to win it against the perfect defence of the computer.The endgame Queen vs Rook is still a classic and deceptively difficult to play. Most GMs are not able to win it against the perfect defence of the computer.

and gives and example of actual master play where there was a draw.

atrifix 66 ( +1 | -1 )
Well, GM Walter Browne is an experienced GM and endgame technician. In all probability most GMs could win KQ vs. KR against a computer at this point in time because of the influence of computer-generated tablebases. The Browne match took place in the 1980s, I believe.

At any rate, in practice the ending is usually very easy to win and usually any chessplayer will avoid it if possible. It is not best to keep the rook by the king (even though this was accepted endgame theory until about 20 years ago), and in fact, it is easy to win provided the KR side does this. Moving the rook away from the king at certain points makes it much more difficult for the KQ side to win.
brunetti 74 ( +1 | -1 )
This only from a theoretical standpoint, i.e. looking at tablebases statistics one may find that the win requires more moves in some positions where the pieces are separated.

In practice, over the board, when the player can't check the tablebase, 20 years ago theory is perfectly sound, and separating the two pieces allows, usually, the Queen to win the Rook with a series of checks. So, the best accepted strategy (unless you'ree playing by correspondence, but in that case there's no nedd to continue the game) i s to keep the pieces together (until the stronger side forces the usual zugzwang position where the Rook has to move away, i.e. Kc6+Qd8, Ka7+Rb7: Black must move the Rook, and White will win it after a short series of checks).

binkers 12 ( +1 | -1 )
very interesting theory, but an endgame I will strive studiously to avoid in future!

thanks for all your learned comments.

atrifix 111 ( +1 | -1 )
You *really* should know how to win this ending. It's a very important ending to know and be able to win 100% of the time. As macheide pointed out, this ending can occur even from rook endings--the most common of all endings. Also, studying the ending gives you a better understanding of the pieces and coordination.

A quick basic example:
White rook on c1, king on h1, pawns on b5, a6.
Black rook on a7, pawn on c7, king on f7.

White wins immediately with 1. Rxc7 Rxc7 2. b6 and one of the pawns will queen, resulting in a KQ vs. KR ending. White might have another way to win the position, but it would be extremely difficult and might result in a draw. Practically any strong player would play 1. Rxc7 instantly, securing a routine technical conversion into a full point.

At any rate the ending is usually basic and an extremely important one to know. It's similar to knowing how to mate with a king, bishop, and knight vs. bare king, an easy win provided the stronger side knows the theory. Most serious players will be able to win this ending even with just a few minutes.