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komei 30 ( +1 | -1 )
King & Rook vs. King and Bishop. I have never been in this situation before, but in a game I am playing at a different site the board is clear except I (white) have K on d2 and a R on d4. My opponent has K on h5 and a B on f7. It is me (white) to move. Is a win possible for me in this position, and generally, can a King and Rook always beat a King and Bishop eventually?

Thanks :-)
fattycunny 2 ( +1 | -1 )
? is you want to cheat ?
komei 13 ( +1 | -1 )
Correction... ...It is my opponent to move, I have just taken his last pawn on d4 last move.

I just want to know if it is possible to win.
caldazar 21 ( +1 | -1 )
It's always possible for you to win.

Generally, King+Rook vs. King+Bishop is a theoretical draw. However, as it would be cheating, you'll have to figure out for yourself whether or not your specific position is actually a draw.
atrifix 12 ( +1 | -1 )
It's possible to win as long as any side has any pawns, a rook, queen, or two pieces (provided they are not two same-color bishops).
chessnovice 6 ( +1 | -1 )
... Two knights and a king vs. a king is also a draw, you know...
atrifix 4 ( +1 | -1 )
Two knights and a king vs. a king can checkmate.
tulkos 3 ( +1 | -1 )
I won a game with a R vs B. Right here on Gameknot!
More: Chess
komei 2 ( +1 | -1 )
Cool! How many moves???
chessnovice 11 ( +1 | -1 )
atrifix I dare you to show me where 2 knights and a king vs. a king can possibly force checkmate.

It cannot be done.
lordnguyenvo 46 ( +1 | -1 )
to chessnovice There are actually a chance for 2 Knights to checkmate the King but only in given position in which the weak player have his King in the corner and the strong side have his King and the Knights block his way out(meanwhile set up a checkmate web).I read this from an endgame book but if you are not convinced then I will try to post it for you.
In real game it will be impossible 'cause the weak side doesn't just run his King to the corner and the strong side can't force him to do so.
atrifix 2 ( +1 | -1 )
OK W: Kg6, Nf6, Ng5
B: Kh8

White moves 1. Nf7#.
chessnovice 46 ( +1 | -1 )
... I agree that it is a POSSIBILITY to mate with just 2 knights and a king, but it relies on multiple mistakes from the opponent. The other combinations atrifix mentioned, the mates are forced. With 2 knights + king vs. king, you have to rely on the opponent's ineptitude. And even then it would be pretty much too difficult.

Thus, two knights and a king cannot mate a king.
chessnovice 42 ( +1 | -1 )
atrifix Indeed you've given the example of how to mate with two knights and a king, but my point is that it's not a forced mate. How did the black king end up on h8? Could it possibly have been pushed there? No.

If you played someone smart enough to take you to an endgame of just 2 knights + king vs. king, I seriously doubt that the person would be dumb enough to walk his king into the corner voluntarily to get mated.
lordnguyenvo 52 ( +1 | -1 )
I dont usually play words but "cannot" sounds like it is impossible.But I think that as long as there is a chance you may consider to use another word?
Maybe there is a position in which the Black King is still in the corner(due to castling) while the hasty White King have already approached and the fantasy position appear.Of course everything usually has to rely on blunder from your opponent 'cause it's really hard to win from a game in which nobody makes any mistakes.
atrifix 99 ( +1 | -1 )
The point is that there is the possibility that two knights can mate a bare king, and so this does not fall under the 'insufficient material to checkmate' category of draws ("The game is drawn when a position has arisen in which neither player can checkmate the opponent's king with any series of legal moves. . .this immediately ends the game.").

If this were the case, then endgames like KNN vs. KN and KNN vs. KB would automatically be declared a draw even though the side with KNN can sometimes force checkmate.

For example:
W: Kg6, Nh2, Nd4
B: Kg8, Pa5

White plays 1. Ne6 a3 2. Ng4 a2 3. Nf6+ Kh8 4. Ng5 and now 4... a1=Q would lose but 4... a1=N! draws by claim of insufficient material to checkmate (even though white could play 5. Nf7# next move).

I'm sure there are dozens of drawn endgames where the 'stronger' side cannot force a win, but my intention was only to clarify the situations which are automatically drawn when a side does not have enough material to checkmate (KNN vs. K does not fall into this category).
chessnovice 67 ( +1 | -1 )
... Your argument that KNN v. K would have to be agreed upon to draw makes sense, though I would be annoyed by someone if they tried to continue a game with me when there is obviously no win coming to them.

I enjoyed your example, too. I appreciate the thought you're putting into this. However, your example is that of KNN v. KP. At least in that, you have the option to restrict the king's movement and continue the game. When it's just KNN v. K, you don't get that option, which is essential for the mate.

But still, case in point. I suppose since there is that very unlikely mistake of being mated by KNN, you can't call KNN v. K an automatic draw...
lukulus 19 ( +1 | -1 )
K+R vs K+B: there depends on corner where weaker's king is. Same color as bishop - lost different - draw.

you can play opposit bishop without pawns. You can arrange mate too:)
desertfox 42 ( +1 | -1 )
I have a game which could reach a B and K against R and K. Its a draw, but the opponent (who beat me in our first game) has a much higher rating and continues to play. A very instructive game.
diversemanx: board #687974. I told him I am ready to play even 100 moves. I am a very patient player.

Desertfox
firebrandx 72 ( +1 | -1 )
Just pointing out:
Here on Gameknot the rules allow for looking up move databases, so it is technically legal here to look up a move set from an endgame database. The K+R versus K+B would fall under the 4-piece database set and could be looked up for the perfect set of moves.

Please note: I have seen some sites not allow endgame databases, claiming it is using a program. To this, I completely disagree. An endgame database by its very definition is not a calculating enging. It is merely a list of moves. A person could simply print out all the moves onto sheets of paper and it would suddenly be legal research again. Like if I were to keep a dictionary of the 4-piece moves, it would be completely clean and legal.

loreta 24 ( +1 | -1 )
Query for more information Has somebody ever seen (and could provide) links to pages on this subject?
I mean K+R+pawns vs K+B+pawns...
.
I know all endgames has their own identification codes (as how beginnings have all thess A00, B46 and so)... Can somebody say about that more?
white_disc 29 ( +1 | -1 )
King-Rook v. King-Bishop I saw a book somewhere...

Is it that the side with the King and Bishop should make the way to a corner ? The book says it will be a draw then.

Anyone can enlighten me on this ?

Thanks alot.



Rgds,
white_disc
bellepheron 8 ( +1 | -1 )
desertfox I am not nearly as good a player as either of you - but I would fancy myself in his position!
clemens 58 ( +1 | -1 )
What?! Endgame tablebases are allowed here on GK? I didn't know that, and I very much object to it. To me, an endgame tablebase is like using a computer since these perfect moves were calculated using a computer, so it doesn't matter whether you have it running "live" or you just use its results.

Opening books are something different, they were compiled by humans, and also, openings can never be as objective as endgames where there is a very clear outcome (win, draw or loss).

I will continue to play my endgames without the help of tablebases.
firebrandx 57 ( +1 | -1 )
But
That's purely a subjective opinion about an otherwise completey inate raw data set. The database could have been done by hand and then you'd have no point. That fact that the move lists were generated by computers does NOT mean it was calculated. The computers merely made listing the moves more efficient than if you did it by hand.

I repeat, endgame database sets are NOT calculated. It is merely the some total of every possible move. If written out by hand, any objection would have no grounds to stem from.

komei 45 ( +1 | -1 )
Hmmm thanks all... ...I think my opponents King is nearer to a corner of opposite colour (black) to his (white square) bishop so shall i draw it now or play 100 moves and hope that somewhere along the line his king goes nearer a white corner? I do not know the opponents rating or if he knows about K&B vs K&R endings (1st time i personally have had this type of ending...) - I would guess he is similar to me 1800-1900 rating (if he were on gameknot...)
loreta 18 ( +1 | -1 )
Wrong "i draw it now or play 100 moves"
You couldn't play 100 moves. By rules you have to checkmate or move a pawn (you haven't them already) during 50 moves. Otherwise - a draw...
clemens 64 ( +1 | -1 )
The endgame tablebases could NOT be done by hand simply because the amount of data is much too large for a human to process. It would take ages.

How can you say they are not calculated? Maybe you are under a misconception as to how endgame tablebases are created. It is the exact same process that a chess engine uses to find the "best" move in any given position, and it is done by a computer. The only difference to using a chess engine in a normal position is that the variation tree is shallow enough to allow the computer to reach a conclusive result, as opposed to the vague rating in decimal pawn plusses or minuses you get in normal positions.
firebrandx 105 ( +1 | -1 )
Ahh
By the very same token, opening books are also calculated the same way in terms of what the computer sees them as (which is raw data). Also you should be aware that large portion of the "human created" openings were actually refined by checking with computers. Many GMs not only admit to this, but also admit to coming up with new lines to add to the opneing book by using the computer.

My misconception as you put it is based on scientific fact, where as yours is based on an ideal. Whether or not it would take humans "ages" to write down the moves lists is completely moot because it can eventually be done. Much like the opening books being 500 years of preparation mind you. From a scientific standpoint, opening books and endgame books are no different. They are simply raw data. How they originated is your only foundation, which is ironic seeing as how both were made with the help of computers. You can't have your cake and eat it too (or however that saying goes).
firebrandx 72 ( +1 | -1 )
One more thing:
Just want to point out one last thing,

I assume that you would have no objection to the database if it had been written out by hand. My question to you is:

Why would anyone waste the time to do that when the data is already there? Your argument causes a paradox in that the database would be fine if written out by hand, yet it is forever too late to do that. Everyone would simply copy the already available data. I could by example claim I had an army of humans write down all the moves. Since the data would be EXACTLY the same as the generated data, there would be no way to tell the difference. Yet one would be more "pure" than the other. That I disagree with the logic of.

clemens 104 ( +1 | -1 )
Well, so opening books were double-checked and enhanced with computers, but all that under human supervision. You cannot possibly write a computer program to automatically create an opening book suitably for competition against humans.

I don't think it is a "moot point" that the amount of work to be done is astronomically large. Already the tablebases for 6 pieces take up many, many gigabytes of memory. IT CANNOT BE DONE BY HUMANS. By your line of reasoning, I should also be allowed to use a chess engine: since there is a finite (albeit immensely large) amount of moves which can be played in a game of chess, ultimately it is possible to analyze the game out, that is, it is theoretically possible to come up with the objectively best move in every position. Where is the difference? Only the depth of analysis, and you claim it to be insignificant.

And please, drop your condescending attitude of you holding the objective, scientific truth; your opinion is as subjective as mine is. It is really not good discussion style.
firebrandx 108 ( +1 | -1 )

Before I begin, I'd like to remind you that you were the one to start with the attitude by calling my point a misconception. I merely returned the favor by addressing what I feel of your view in that I believe it is based on ideal, rather than scientific fact.

Now, let's address what you've said:

First you admit opening books were enhanced with computers, but then you say that they cannot totally be made by computers without human supervision. Here's the pickle: an endgame database can be done entirely by humans as well as an opening book. A computer was used simply to make the process easier and faster (much like a giant opening book is now).

2nd, you are using and unfair comparison when you claim my line of logic would allow the use of a computer engine for normal moves. You are forgetting that A computer has to assign a point-value system to each move and return the best one by it's own preference, rather than by solution. This is completely different from a database and is totally unfair to use that against me.





clemens 27 ( +1 | -1 )
As for your last comment: as I said, you could not gather enough humans to write down the moves for 6 pieces before the world ends, not even mentioning the problems in organizing such a feat. Therefore, you could not credibly claim to have done so.
firebrandx 63 ( +1 | -1 )

So it would be up to you to decide just how much humans could write down? Are we allowed to write down a 3-piece list? 4? 5? A 3-piece list could be done in short order by hand, so you'd have to start judging what you would and wouldn't allow as "humanly" possible to have been written. This opnes up a can of worms.

You can see why I have a problem with that. Just how much humans could write down is a completely hypothetical scenario. I ague that if we have to resort to imagined scenarios in order to disregard raw data, then opening books should not be allowed either.
clemens 104 ( +1 | -1 )
What I said was that you MIGHT be under a misconception; from what you said, it was not obvious that you clearly understood how such a tablebase is created. Let's however not split hairs here, that is not the point of our discussion.

While you might argue that both an opening book and an endgame tablebase can be created by humans (see my above posts for my stance on this), you admit that an endgame tablebase can be created by a computer ALONE, while an opening book cannot (unless the game is analyzed out, of course, which will never happen). To me, this sounds like a good characteristic to determine what may be used in ongoing games and what not.

Also, I don't think it was an unfair comparison. The computer's analysis is a better approximation of the "perfect" solution than what I can come up with, but it is still sub-optimal. Why, however, should it be legal to use the perfect move (which, according to your logic, exists, and may therefore be used, regardless if I found it myself or not), but not the possibly WORSE move produced by the computer?
clemens 29 ( +1 | -1 )
"A 3-piece list could be done in short order by hand..."

In "short order"?! Sit down and try it. You will then appreciate the amount of calculation that goes into an endgame tablebase. Consider that the amount of work rises exponentially with every piece you add.
clemens 22 ( +1 | -1 )
There is a very simple way to find out if humans can do something: to try it. This is no "imaginary scenario". As you yourself said, much of our current opening books were created in that manner over hundreds of years.
macheide 41 ( +1 | -1 )
What a long post for something... so simple. K+R vs. K+B can win ONLY under very special circumstances. Except for these, this ending is a draw. K+2N vs. K?, please, it's a draw!, unless you help your opponent to mate you. Paradogicaly, K+2N vs. K+P can win if the pawn is not very advanced because your opponent has extra forced tempos that you can use to win without stalemate him. These are elemental things, canonical endgames. What's the problem? I don't understand.

Regards,

macheide.
mercy 49 ( +1 | -1 )
Secrets of pawnless endings Komei , this ending is generally a draw. It would be wrong for me to tell you how to win or draw but... I dont see nothing wrong with pointing you in the right direction. Try "Secrets of Pawnless Endings" by John Nunn. Excellent book!! In fact, a priceless book for anyone playing serious Chess via internet. It has won and drawn many endings for me that would have been otherwise beyond my grasp.

Doris
desertfox 50 ( +1 | -1 )
Loreta and Bellepheron Loreta, are you teaching me the chess rules? I said 100 moves to emphasize my patience, that's all.
Bellepheron, in French there is a saying "Qui vivra verra". Black has the advantage, but it is not enough for a win. Reminds me of my game with hadenough. He had a rook against two knights and a pawn for me. He scarificed his rook for my pawn and had a theoretical draw, although I was two pieces up. Don't look only at the material situation, that's the mistake computers make, they get a material short term advantage but in the long run it serves them in no way.

Desertfox

bellepheron 53 ( +1 | -1 )
desertfox Perhaps, you are right.

But at my skill level, and that of most of my opponents, I think that game is far too early to call a draw! It would almost be like calling a draw before the first move since the positions are 'equal'!

I would hope to catch my opponent in a tactical mistake, were I in his position. Whereas in yours I would gladly accept a draw!

In a way I do not look forward to achieveing such a high level of skill, because I enjoy the thrill of discovering how the game will go, as I piece it together...
andersdanielsson 33 ( +1 | -1 )
K, R and pawns vs K, B and pawns I'm playing a game right now (board #737470) where white has KRPPP and black has KBPPP. I'm struggling to draw in that game. Feel free to look at it. However the game is not over yet so please don't comment. I'll return when the game is over.