When does the middlegame end and the endgame begin? Is there any specific point where the middle-game ends and end-game begins? E.g. after x number of pieces are exchanged, or say 40 moves, etc.

There isn't a clear-cut definition of endgame, or a set of criteria where you could draw a line and say "after this move, we have reached the endgame."

Quoting Glenn Flear in his excellent book Practical Endgame Play - Beyond the Basics:

  The word 'endgame' is widely used and generally implies the final phase of the game  (however long!), assuming that there already has been significant simplification.  If we had to define the word more rigorously in terms of material then opinions vary.  Some specialists consider all queenless positions to be endgames, others those where both sides have limited material, for instance less than queen and rook.

So basically, once the position becomes 'simplified' to the point where more often than not you are using your few remaining pieces (including the King) to try and queen a pawn, rather than organize an attack.  Also included would be the end result of queening a pawn (or winning significant material), i.e. positions where you mate the King with only a few pieces on the board, like King and Rook vs. King.


When a pawn promotes, does the new piece go to the promotion square, or the home square of piece type it promoted to? When a pawn promotes, does the new piece go to the promotion square, or the home square of piece type it promoted to? In other words, if a pawn promotes to a queen, does the queen go back to the square where the queen starts?

The promoted piece replaces the pawn on the square that the pawn moved to (the 8th rank for White, the 1st rank for Black).

From the FIDE Laws of Chess, (emphasis mine):

  3.7.e. When a player, having the move, plays a pawn to the rank furthest from
  its starting position, he must exchange that pawn as part of the same
  move for a new queen, rook, bishop or knight of the same colour on the
  intended square of arrival.


What do the numbers mean at the end of predicted variation opcode in and EPD entry? I'm writing an EPD (Extended Position Description) parser and I have a doubt about what numbers means at end of "predicted variation" opcode.

Look the follow EPD sample:

rq2r1k1/5pp1/p7/4bNP1/1p2P2P/5Q2/PP4K1/5R1R w - - bm Nxg7 BT-2630.1; ce 182; acs 0; acn 106652; pv 1.Nxg7 Kxg7 2.Qxf7+ Kh8 3.Qh7+ Kxh7 4.Rf7+ Kg6 5.Rf6+ Bxf6 6.h5+ Kxg5 (38.748) 112.9; c0 depth=8

As its possible to notice, the opcode pv ends with numbers (38.748) 112.9. That

I started from the article in the Chess Programming Wiki. There I found some related materials, like the PGN specification, that have a more elaborated EPD documentation an some links to EPD entries examples. However, I can't find any explanation about the meaning of the numbers.

Does anyone have some material with a more elaborated documentation about the EPD (or PGN) format?

On a strict reading of the EPD spec, the example shown is malformed; the pv opcode should only contain a list of moves, not any commentary on it, which should be moved to other opcodes.  Indeed the move numbers should not be there either, only raw SAN moves.

I assume that some naive EPD author has simply dumped the output of an engine into it.

Indeed following the discussion from your (fixed) examples link, the first reply seems to agree with me:

  Crafty has an option to clean up epd (called epdpfdr) that produces
  EPD output that most programs can read.  You have a few errors in your
  output below.

…

  No numbers in the pv!
  Like this: Nxg7 Kxg7 Qxf7+ Kh8 Qh7+ Kxh7 Rf7+ Kg6 Rf6+ Bxf6

  Also (a common mistake) is to put ... in the front of the pv when it
  is black to move.  This is not allowed.  You did not do that, but I
  just wanted to mention it.

…

  This stuff:
    (73.507) 130.7;
  is not allowed except in the comments field.


Complete book of chess search I have read a number of chess books by now, which either contained a number of analyzed games, or some tactics. But I am a little underwhelmed with completeness. What I am hoping exists is a really complete book that contains a bit of everything. I am reading silmans A-Z, which gets kind of close. But coming from academia I'm thinking of something more similar to a 2000pg textbook format, which after reading will have provided a relatively complete understanding many chess concepts.

The Steps Method is a graduated series of books that attempts to provide all material necessary to take a player from complete beginner to expert. I have not used it but it has a strong reputation.

To proceed past that, the best thing I can think of is Yusupov's 9-book course (Build Up Your Chess et al), which is around 2700 pages in total and attempts to take a player from about 1500 FIDE to master. I am a bit more than halfway through and give it a great deal of credit for my rise from 1800 to 2000 USCF.

Of course, either (or both) of these series must be supplemented by actually playing games.


How did a pawn appear out of thin air in “P @ e2” after queen capture? I was playing chess against the computer and captured black’s queen.  All of a sudden, a black pawn appears out of thin air, one space behind the captured queen for a total of nine pawns, and moves multiple squares diagonally.

The computer calls this move “P @ e6,” but after half an hour of scouring the internet, I could not figure out what that means.
1. |  h2 - h4 | Nb8 - c6 |
2. |  e2 - e4 |  e7 - e5 |
3. | Rh1 - h3 | Qd8 × h4 |
4. | Rh3 - h4 |   P @ e2 |

How did this happen?

You were playing the chess variant called Crazyhouse. In this variant you can place pieces you captured, as one of your color anywhere on the board, instead of a normal move.
I don't know the software you are using, but on Lichess the variant can be selected in the "Create a game" dialog. There should be something similar in your application.


Swiss Pairing Algorithm I am building a simple Android application for hosting Chess tournaments, I am having some difficulty implementing a Swiss paring algorithm, I need link to an article or a paper that explains how I can achieve that.

I would also like to know any ideas that can help me.
I am following the rules in this Article Swiss Pairing Rules

I am particularly having problem ensuring that

For each player the difference between the number of black and the number of white games shall not be greater than 2 or less than –2.
Each system may have exceptions to this rule in the last round of a tournament.
No player shall receive the same colour three times in a row.
Each system may have exceptions to this rule in the last round of a tournament.
In general, a player is given the colour with which he played less games.

If colours are already balanced, then, in general, the player is given the colour that alternates from the last one with which he played.

Jeremy Bierema has written a Swiss pairing program and put it on Github. You could look at the code there which is in C++.

At any stage in the tournament you have to have a list of forbidden pairings.

The first, obvious entries are pairings that have occurred previously. The second, banning 3 whites in a row, is ww v ww since one of them will have to be white giving www. Similarly bb v bb is forbidden. Then the white/black imbalance, so 2 v 2 and -2 v -2 are forbidden since in each case one player will end up with a 3 or -3 imbalance.

So, for each player you need to keep track of previous opponents, colour sequence and colour imbalance. This gives you the information to know which pairings are forbidden. In the last round you should also perform the forbidden pairing check for colours and pair with this in mind if possible. If not then you can ignore colour restrictions in the last round only.

The "previous opponent" forbidden pairings are cumulative. The "colour" forbidden pairings change from round to round as the players' colour sequences and imbalances change.


Did Reinfeld make a mistake? One of the illustrative games featured in Fred Reinfeld's The Complete Chessplayer is a game between A. Muffang - P. Devos, France-Belgium 1948:

[FEN ""]

1. d4 d5 2. c4 dxc4 3. Nf3 Nf6 4. e3 e6 5. Bxc4 c5 6. O-O a6 7. a3 Be7 8. Qe2 b5
9. Ba2 Bb7 10. dxc5 Bxc5 11. b4 Ba7 12. Bb2 O-O 13. Nbd2 Ne4? 14. Rfd1 Qe7 15. Rac1 Nxd2
16. Qxd2! Bb6 17. Qc3! f6 18. Nd4! Bxd4 19. Qxd4 Nc6 20. Qc5 Rfe8 21. Rd6 Nd8
22. Qd4! Bc8 23. h4 Kh8 24. Bb1! Rb8 25. Qe4 f5 26. Qe5 Ra8 27. Rc7!! 1-0

The point in question is Reinfeld's commentary on move 16, after 16. Qxd2!; he says:

  A pretty variation is 16 ... N-B3; 17 RxN! BxR; 18 Q-B3 (double attack) threatening mate and therefore winning the Bishop on QB6, with the victorious material advantage of two minor pieces for a Rook.

Translated into algebraic, that is 16... Nc6 17. Rxc6! Bxc6 18. Qc3:

[FEN "rn3rk1/bb2qppp/p3p3/1p6/1P6/P3PN2/BB1nQPPP/2RR2K1 w - - 0 16"]

1. Qxd2! Nc6 2. Rxc6! Bxc6 3. Qc3

But what about 18... Qf6?  That not only parries the mate threat, but if now 19. Qxc6, then 19... Qxb2, bishop for bishop, and White cannot even continue with 20. Qxa6? (taking a vital unprotected pawn), for Black can then take White's other bishop - 20... Qxa2.  In fact, any line of play makes it hard for White to rescue the bishop after 19... Qxb2.  20. Rd2??, the only possible move to protect the bishop results in 20... Qa1+! forcing mate in four.  And 20. Bb1, the only possible move of the bishop to safety results in the loss of his QR pawn - 20... Qxa3.

[FEN "r4rk1/b3qppp/p1b1p3/1p6/1P6/P1Q1PN2/BB3PPP/3R2K1 b - - 1 18"]

1... Qf6 2. Qxc6 Qxb2 3. Bb1 Qxa3 (3. Qxa6? Qxa2) (3. Rd2?? Qa1+! 4. Bb1 Qxb1+ 5. Qc1 Qxc1+ 6. Rd1 Qxd1+ 7. Ne1 Qxe1#)

I don't see any way for White to justify the sacrifice of the Exchange with 17. Rxc6, since after 18... Qf6 it looks as if Black can hold his own. (Yes, there is 19. Qxf6 gxf6 20. Bxf6 winning a Pawn, but that doesn't make up for the loss of the Exchange.  And Black can also double White's pawns and steer toward the endgame with 20... Bxf3 21. gxf3.)

Am I right in saying that Reinfeld made a mistake, or am I missing something?

Yes, it does look like Reinfeld made a mistake, but white should still be doing well after 18... Qf6.

White should now play 19. Qc1! hitting the queen and the bishop.  Now black's best continuation is to sacrifice the queen with 19... Bxf3 20. Bxf6 Bxd1

[FEN "r4rk1/b4ppp/p1b1pq2/1p6/1P6/P1Q1PN2/BB3PPP/3R2K1 w - - 1 18"]

1. Qc1 Bxf3 2. Bxf6 Bxd1

One possible line from here is

[FEN "r4rk1/b4ppp/p3pB2/1p6/1P6/P3P3/B4PPP/2Qb2K1 w - - 1 18"]

1. Bxg7 Kxg7 2. Qxd1 Rad8 3. Qg4+ Kh8

and white has a queen and a pawn for the two rooks, but a strong attack because black's king is so weak.

To summarize, it does appear that Reinfeld made a mistake because after 16... Nc6? white can simply play 17. Qc3! and win easily, but even the line he gives should be okay for white.


Arena Software and Mac OS X Does someone know or have tested a way of using ARENA software on Mac OS X?

Maybe using Wine or something similar.

According to the Chessfiles [ref. 1], Arena [ref. 2] can be played on OS X within Wine 1.0 or higher [ref. 3]. Likewise, Arena claims to function within Wine 1.0 or higher.

Caveat: some indicate Arena to be unstable within Wine [ref. 4], some have no problem [ref. 5, 6].

References:

http://www.chessfiles.com/os-x-chess-gui.html
http://www.playwitharena.com/
https://wiki.winehq.org/MacOSX
http://www.open-aurec.com/wbforum/viewtopic.php?f=2&t=6550
http://ubuntuforums.org/archive/index.php/t-377613.html
http://ubuntuforums.org/showthread.php?t=31659


Can a player be forced to neatly center their pieces on the board? Following up on a question regarding piece adjustment after an accident, I was wondering if there is a rule which forces someone to neatly place their pieces on the board?

I am asking in the context of a psychological (nasty) war: if you place your pieces away from the center of the square (but still obviously within the square), the general mess can be unsettling to someone (it would certainly be for me) and give you unfair advantage.

No.
That is subjective and personal.
You may adjust anything during your move.
You cannot make the other player adjust them to your liking.

It would be interesting to see an adjustment battle going on when each player took his clock time to RE-adjust all the pieces to their liking every move. Might not work too well at speed chess:)

I wonder if an arbiter could find another rule about doing something to annoy their opponent if it did happen. And which one would be punished. I hope both of them for being twits.


What are good strategies or principles to prolonging the first stage of a game? Is there a particular strategy or principle you can use to drag out the first stage of a game, namely, to preserve all your pieces as long as possible.

One way I can imagine this being useful, if early on you exchange your bishop for an opponent's knight, having a crowded board would thus become in your best interest, as knights are generally more valuable on crowded boards. (Or so I am told)

So once again, the goal is to lose as few pieces as possible for the longest stretch of time.

Some questions were posed to me for clarification:

Why do you want to avoid exchanges?

To see if it is possible to avoid exchanges without hurting your positioning, or by only hurting it in an insignificantly marginal manner.

What is your goal?

To prolong the game. Perhaps if it were a game of speed-chess, and you wished to run down the clock to play for a draw; this could be a good strategy. Perhaps if you knew your opponent to be impatient, this could be effective against him.

Do you aim for a mating attack?

No.

Do you need a middlegame position that gives lots of maneuvering and has a high chance of dodging the endgame ( maybe you do not like to play endgame )?

Great Question; This would be ancillary.

Is there a particular strategy or principle you can use to drag out
  the first stage of a game?

  One way I can imagine this being useful, if early on you exchange your
  bishop for an opponent's knight, having a crowded board would thus
  become in your best interest, as knights are generally more valuable
  on crowded boards. (Or so I am told)

This entire question is unclear, but I will give it a try to answer. Let us start one by one:

  Is there a particular strategy or principle you can use to drag out
  the first stage of a game?

Now why would you want to do that?

  One way I can imagine this being useful, if early on you exchange your
  bishop for an opponent's knight, having a crowded board would thus
  become in your best interest, as knights are generally more valuable
  on crowded boards. (Or so I am told)

Aha! So you wish to keep the board crowded in order to exploit the "advantage" knight has over a bishop!

Well, it is time to answer:

You can not keep the board crowded unless both you and your opponent "agree" to do so.

He can always try to exchange pieces and reduce the tension if he chooses, and the best thing you can do is to try and stop him by making the exchanges unfavorable for him.

Unfortunately, the opening theory has advanced a lot, and there are ways for both sides to obtain a good game, so the above plan will be very hard, if not impossible, to execute.

Another thing: simply exchanging the bishop for a knight, and trying to keep the pieces on board will not give you an advantage. It will all boil down to the placement of your pieces. By the way, exchanging the bishop for a knight early leaves your opponent with the bishop pair, which may give him the advantage.

I would strongly suggest you to find a resource ( book/online tutorial ) for playing the opening.

EDIT IN RESPONSE TO THE OP's EDIT:

  Why do you want to avoid exchanges?

  To see if it is possible to avoid exchanges without hurting your
  positioning, or by only hurting it in an insignificantly marginal
  manner.

This is not possible, I am afraid. You will have to exchange at some point and here is why:

When amateur wants to exchange pieces, he uses his own to "chase" the opposing one until the exchange has been made.

Master, on the other hand, puts the piece he wants to exchange on the strong squares, thus forcing the exchange. That way the piece becomes annoying and strong and opponent is forced to exchange it or else he will stand worse.

In a strong game, versus strong opponent you will not be able to dodge the exchange.

  What is your goal?

  To prolong the game. Perhaps if it were a game of speed-chess, and you
  wished to run down the clock to play for a draw; this could be a good
  strategy. Perhaps if you knew your opponent to be impatient, this
  could be effective against him.

This is very much possible, but you will need to play typical middlegame positions in order to achieve this. Furthermore, you will need to be the one who dictates the game. This is very important requirement.

You can play positions with an isolated pawn. My answer provides comprehensive coverage of the plans for both sides. Still, let me remind you-side with the isolated pawn exchanges pieces only when it can get a definite, visible-with-the-naked-eye benefit. As long as the board is packed with pieces the advantage is on its side. Side without isolated pawn strives to exchange minor pieces and enter endgame. Again, in the endgame you can prolong the game as much as you want as you will have the advantage. Usually you will be the only one who can play for a win and your opponent usually will have no counterplay but will be forced to passively defend.

Another typical position that has a lot of maneuvering and is slow is Carlsbad pawn structure and it arises from Queen's Gambit Declined after White exchanges on d5 with the move cxd5. White again has lots of plans here, but you would be interested in minority attack. Minority attack creates a weak pawn for Black on c6 and allows White to perform long maneuvers in order to take it ( just don't underestimate Black's mating attack on the kingside! ). This would be ideal choice for you.

You could try French defense with both colors. With White you can try Advance variation, and with Black Winaver sounds good. Again, both positions require long maneuvers.

END OF EDIT:

Best regards.


Looking for an old problem that I can't quite remember I remember seeing a particular chess problem awhile ago on YouTube, but I can't find it. The problem's theme was something about caging in the Turkish king, and the video mentioned it as being old.
Regarding details of the problem, here are two. It ends in a smothered mate with eight black pawns surrounding the Black king. In the course of the solution, all of the Black pawns are forced into place by White.
Here is example I've made of the general concept.
[FEN "8/2pKN3/Q3ppp1/2ppk1p1/4pR2/3P1P2/4N3/8 w KQkq - 0 1"]

1. Qd6+ cxd6 2. Rf5+ gxf5 3. d4+ cxd4 4. f4+ gxf4 5. Ng6#

Does anyone know the problem and its source?

[Title "Carl Ferdinand von Jänisch, Der eiserne Käfig des Tamerlan, 1849"]
    [FEN "4N3/P2p1Np1/3Qp1R1/2pR4/2p1kpp1/b2bp2B/q3PP2/3K4 w - - 0 0"]

1.f3+ gxf3 2.exd3+ cxd3 3.Bf5+ exf5 4.Re6+ dxe6 5.Nf6+ gxf6 6.Rd4+ cxd4 7.a8=B Qd5 8.Bxd5+ exd5 9.Qe5+ fxe5 10.Ng5#

It's problem 59 in Max Lange: Handbuch der Schachaufgaben, Leipzig 1862, p. 79. Google Books.

It was published on p. 427 of the 1849 Schachzeitung. Google Books.

The chess puzzle can also be found with the search term tamburlaine's iron cage, e. g. Suren's YouTube video.


How much theoretical knowledge does playing the Berlin Defense require? Sorry if this question is opinion based, however I think it can be meaningfully discussed.
I am researching the Berlin Defense and am reading contradictory opinions on how much concrete knowledge is required to play it.
Some people claim that

It requires very little knowledge of variations and one can rely almost
entirely on endgame principles
Almost all sensible moves are playable
The game is slow and of positional nature, often drawish

The other side claims

It is one of the most theoretically extensive openings
Plans are often not obvious, but one needs to know what to do in order to not fall into a hopeless position with no improvement possible
Play becomes sharp and concrete, requires knowledge of variations, the better prepared player wins

Where do the differences of opinion come from?

Back in the days of over-the-board chess I use to run themed blitz tournaments over the summer to keep members of our chess club occupied in the off season. In July 2019 I ran one on the Berlin Defense. Only 6 players turned up instead of the usual dozen or so (surely not put off by the boring reputation of the Berlin?) so I ran a 6 player double round robin giving each of us 10 games in the evening. That was the most hard work I'd done for a long time and it had nothing to do with playing in and running the tournament (which I did most weeks) and everything to do with the slippery nature of the Berlin. Every single game was a real struggle.
To help players get in the mood and prepare I usually sent out an email with links to a couple of YouTube videos on that week's opening. That week this video from Yasser Seirawan was one of them. I'd strongly recommend you watch it. I will say that as prep for a one-off game it is not suitable. You will either be very frustrated at the pace and apparent lack of a destination or Yasser's soothing voice will put you to sleep.
However if you are going to make the Berlin your goto defence against the Ruy then it will give you your first and most important idea what the opening is about.
When you are learning a new opening quickly the most important thing is to understand what white's plan is and what black's plan is in the opening. That way you know what you are trying to do and what your opponent is trying to do that you have to stop.
The second most important thing when you are learning a new opening is, as well as knowing the plans, you have to be comfortable in the kinds of positions you will get in the opening. By the way, that's why Kramnik beat the mighty Kasparov to become world champion. Kasparov was deeply uncomfortable in the Berlin positions and Kramnik wasn't.
But in the slippery Berlin nothing is clear as Seirawan demonstrates in his video. What are white's plans? It should be fairly obvious. Here is the starting tabiya.
[fen "r1bk1b1r/ppp2ppp/2p5/4Pn2/8/5N2/PPP2PPP/RNB2RK1 w - - 0 1"]

White has the advantage of a viable kingside pawn majority which should be capable of creating a passed pawn. Black's doubled pawns on the queenside make it relatively easy for white to prevent a black passed pawn there. On the other hand black has the two bishops and the e pawn is really one square too far forward. Life would be easier with the pawn on e4 instead of e5.
One important middle game principle is that any given pawn formation will have an optimal number of pieces. A very cramped black pawn structure will be terrible for black if both sides have all their pieces but perfectly fine for black if several pieces have already been exchanged. Similarly far advanced white pawns are good for white, white controls more space, if all the pieces are on but the position becomes over extended if too many pieces have come off. The e pawn is just a bit too far forward given how few pieces are left. It can very easily become a problem child.
Nevertheless, white's plan is simple and obvious.

Arrange the queenside pawns so that black can never create a passed pawn there.
Advance the kingside pawn majority to create a passed on the kingside
Queen the pawn.

Well, that was simple and obvious to state but the next step is working out which moves to make to put the plan into action and that is where the problems start. And that is where Seirawan's video is so good because it slowly, frustratingly makes it clear just how difficult that is. Lots of plans have been tried over the years and none of them really quite work unless black doesn't know how to counter them.
OK, so white's plan was easy to state but seems very difficult to put into action, but what on earth is black's plan?
Well this is where it gets even more difficult and even more hard work. Black's plan is just to counter and frustrate whatever white tries to do. Again Seirawan's video will help make this much clearer.
OK, let's look at some of the propositions.

It requires very little knowledge of variations and one can rely almost entirely on endgame principles

Certainly not! If your opponent knows what they are doing and you don't then you will lose like the slowly boiled frog without ever knowing just what happened.

Almost all sensible moves are playable

True in the starting position of the tabiya. There are no proven plans for white. Black's plan is just to counter what white does. The player who struggles and fights the best will win. Because of the unbalanced nature of the starting position there is no obvious route to a draw for either player. You just have to fight.

The game is slow and of positional nature, often drawish

Well, yes. It is slow and positional to start with but the thing about slow, positional, drawish games is that one slip and they can become tactical and lost very quickly. In the absence of a clear plan for your side you must always be countering your opponent's plans and that is a big weakness for weaker players.

It is one of the most theoretically extensive openings

If you are black then you certainly need to know and be able to counter all the current white plans. If you are white then you need to know what to do if black doesn't correctly counter your plan. That may involve a quick transposition into one of the other plans. You also need to be very well prepared if you are going to try and avoid the draw.

Plans are often not obvious, but one needs to know what to do in order to not fall into a hopeless position with no improvement possible

Exactly so.

Play becomes sharp and concrete, requires knowledge of variations, the better prepared player wins

Again, this is absolutely correct, although it can take some time to reach this stage. Your best way of not being on the losing side is to know the starting plans.
The only real contention is the first claim that knowledge of variations isn't necessary. Perhaps this confusion arose because the variations that arise are generally not tactically sharp variations, at least in the first instance, where one side gets quickly mated or loses material. Instead the variations lead to positionally lost games. The result of not knowing these variations is still the same as not knowing the sharper variations which arise in other openings.


What does "half-K" mean in the USCF tournament rating system? The USCF rating system as described by Professor Glickman includes a factor called K:

  If m < 3, or if the player competes against any opponent more than twice, the "standard" rating formula that results in Rs is given by

  Rs = R0 + K(S - E)

(source, emphasis mine)

Though at one point the K value was calculated for each player from the pre-event rating, it is now defined by one of two expressions depending on whether the tournament is "half-K" or "full-K:"

  The value of K, which used to take on the values 32, 24 or 16, depending only on a player's pre-event rating, is now defined as...

(source: same page as above)

What does it mean if a tournament is half-K (besides that it changes the value of K)? Why would the tournament director choose to make an event half-K?

I also see that the USCF considered removing the half-K option, then did remove it, then considered using it for quick games in some way. However, none of those reports explain what being half-K actually does to a tournament.

As dfan mentioned in his comment, K factor, is a factor for changing convergence speed of ratings. When you win against a strong player, your rating converges to your opponents rating, after some consecutive wins, you will have the same rating with your opponent. K factor simply changes how many games you need to converge we can say. Situations where it is used:

High K used, in first few matches of a player, to let the player reach actual Elo quickly
Low K used, in some tournaments which has non-standard time controls
Low K used, in matches between masters, to stabilize Elo changes.

etc.

There is no absolutely correct K value, it's really open to question how fast it should converge. But when it converges slower, Elo points are more stable. When it converges faster, people can reach their actual ratings faster.

I caused a lot of trouble to people just because of this dilemma. I had an initial rating of 1100(for some riddicilous reason, long story). And at the time my actual strength was about 1500. In time, my strength went up to 1900 but my rating was about 1400. Just because of this, my opponents lost lots of points(unfairly). I remember a game when I was 1300 something, and I won against a 2000 player. He lost a lot of points, and was very sad. If I were 1900, penalty would be much more less.


What rating system does the Play Magnus app use? I played a total of 261 games against the Play Magnus app at different ages. My overall score is 144 wins, 99 losses and 16 draws. My last game was against the 10-year-old Magnus. Prior to the start of the game I was rated 1248. I won the game and my rating increased by an astonishing 133 points, so I was wondering what is the rating system used.

Most weird is that I sometimes draw against a far higher rated Magnus and lose rating points (I once drew 26-year-old Magnus and lost 18 rating points when I was rated only 1486). Is there any explanation for that, or is it a bug in the app?

This is a list of Magnus Carlsen’s ratings at each of his birthdays.

9 years old: 900
Norwegian rating.
10 years old: 1645
Still Norwegian rating.
11 years old: 2127
FIDE rating now.
12 years old: 2250
Magnus became an FM at age 11.
13 years old: 2450
Magnus became an IM at age 12.
14 years old: 2581
Magnus became a GM at age 13, the youngest in the world and the second youngest ever at the time.
15 years old: 2570
Magnus went through his only real slump that year.
16 years old: 2698
Magnus played in his first super tournaments right around this time.
17 years old: 2714
Magnus reached 2700 at 16 as the youngest ever, a record that has since been beaten by Wei Yi.
18 years old: 2786
Magnus was now number four in the world.
19 years old: 2801
Magnus reached 2800 at 18 as the youngest ever. The record still stands.
20 years old: 2802
Magnus became the highest rated player in the world at 19, as the youngest ever.
21 years old: 2826
Magnus solidified his top spot on the world rankings this year, and has held it since.
22 years old: 2848
Magnus was really closing in on Kasparov’s rating record now, and surpassed it shortly after his 22nd birthday.
23 years old: 2870
At this point there was a whopping 70 point difference between Magnus and the second rated player, Aronian.
24 years old: 2863
Magnus peaked at 2882 (unofficially 2889) that year, the highest rating ever.
25 years old: 2850
A minor dip in form.
26 years old: 2853
Still number one by a good margin.

About the app - of course there may be flaws, concerning its system there is no information. Although I don't see any reason why they would deviate from the ELO system (which is used in official FIDE games), whose formulas aren't secret and can be found even on Wikipedia.


How to solve mate-in-N problems Here is a mate-in-4 I have been trying to solve:

[FEN "2r4r/b5pp/q3pp2/8/4QBk1/8/3R1PPK/4R3 w - - 0 1"]

(white mates in 4).  I have been looking at it for about half an hour but not solved it. My question is: what can I do to improve my ability to solve problems like this?

(please don't just give the solution, I can easily find that by computer, but you can't use computers in a game).

Here is what I have tried so far.

Enumerating attacks and checks.

White checks: Qf5+, Qg6+, Qf3+, Qxe6+, B-anywhere+, f3+
White captures: Qxh7
Black checks: none
Black captures: Bxf2

Enumerating other ideas:

Black can play Bxf2 or Qf1 which will cause havoc for a move , so probably the solution is checks on every move; at least the first two
White has to be careful not to let BK run to g6 as then it can move to f7 escaping mate in 4
In several variations below, Kh5 escapes with ...g5 or other pawn cover, so I am looking for tricks involving sacrificing rook to break that pawn cover.

Tree of analysis (have omitted some sub-variations that mate for brevity)

Be3+ Kh5; Rd5+ g5; ???
Bc7+ (or other B moves) Kh5; Rd5+ g5; ????
                             g4+ Kh4; ????
Qf3+ Kf5; Qh5+ (otherwise Kg6) g5; g4+ Kxf4; ????
Qf5+ or Qg6+ or Qxh7 don't go anywhere
Qe6+ Kxf4; Re4+ Kg5; Rg4+ Kh6; ????
f3+ Kh5; g4+ Kh4; ????
    Rd5+ g5; g4+ Kh6; ????

Rd3 Qxd3; Qxd3 Kxf4; no mate
Re3 Bxe3; Bxe3 can't be better than 1.Be3
Rd5 exd5 Be3+: doesnt work
g3: doesn't seem to do anything, Black can wait

Now I have looked at all the checks and some other interesting moves, none of them work, and so to solve the problem online I'd be reduced to just guessing random moves (and then probably being stumped on the resulting mate-in-3 for a while, as if I could solve that easily then I would have realized the first move by now).

But in a real game that is not possible; so where do I go from here?

Is there always a "key idea" to look for (and if so, how do I look) or sometimes do you just have to be able to brute force every possible move no matter how unlikely? I can't even think of any more candidates I haven't checked.

Assuming this is a chess problem, then you want to start by looking at things that show up as problem themes, more than as game themes.  There are a few salient features of the position:

White's queen-bishop battery; it seems very likely that discovered checks from the bishop are likely to be a mating resource.
The white bishop being on a line with the king, thus leaving it vulnerable to a pin from either the Ba7 or the Qa6.
The open h-file, and in particular the possibility of a king-rook battery to deliver mate.
More remotely, the possibilities for interference between the black pieces (e.g., bishop/rook interference on c5).

Given these, I would investigate the possibility of a move like Rh1; this offers up the threat of 2. Be3+ Kh5  3. Kg1 mate and forces black to defend immediately. The most natural defenses are via the aforementioned pinning moves, 1...Bb8 and 1...Qd6, so I'd start looking there.

--

Assuming, OTOH, that the problem is a tactics puzzle more than a 'chess problem' problem, then I'll just point out that your analysis missed one particular bishop check, and you should consider the question of where the bishop can go that covers key squares in the vicinity of the king; not just for a mating net, but also as possible 'drop points' for the queen.


Can you estimate a player's Elo rating using tests? So I wonder if there are specific positional/tactical tests for every rating range, so that in the end the general rating of a player can be decided prior to competition.

Obviously the best test is playing in an actual competition, and most trainers will advise their players to play in as many as possible.

Other than that, there are books that try to do this. I don't know how accurate they can be, but it's likely that they need to be taken with a grain of salt: there is probably too much variance in the concentration level and time taken to solve the problems between different readers that they can't all get good answers. Also, chess skill isn't only related to skill in solving chess positions: confidence, controlling nerves, concentrating deeply for hours, judging when to play for a win and when to be content with a draw, most of those are competition skills that will only be reliably judged by actually playing in a competition.

There are many many books of exercises, and some of those try to do Elo estimation based on how many of them you got correct.

Books that I think that do that (there must be more):

The classic "The Best Move", by Vlastimil Hort and Vlastimil Jansa was probably the first of this type.
Barden's "How Good is Your Chess"
Keene's "Discover Your Chess Strength"
Alburt's "Test & Improve Your Chess" (I think)
Bosch's "The Chess Combat Simulator"
King's "How Good Is Your Chess?" (yep, same title as Barden)
Evans' "How Good Is Your Chess?" (seriously, I'm finding these on Amazon and they have different covers)

There's also this site: The Automated Chess Rating Utility website

Sites like Chesstempo have only tactics puzzles, but they also ask users to enter their FIDE rating and use this to calculate a correlation between Chesstempo and FIDE ratings; inaccurate, but better than nothing.

But again: a rating is an estimate of how well you did in competitions. Estimating ratings some other way seems a bit besides the point -- why not just play in competitions?


Why is `a5` a better move in this position? I was playing with a friend and we come to the following position (me white):

My friend played b5 but computer analysis says that this is a mistake and he should have played a5. Now, I don't see why is that better?

Can anyone help me please understand why?

First, you need to see that in the original position, Black has already a close to winning advantage. Especially the pin on f3 is nasty; it's hard for White to defend the knight now that the bishop is 'offside' and Black can easily attack it with another piece (Qf6).

Both moves (a5 and b5) share the same idea: gaining space on the queenside, with tempo. The move a5 doesn't attack anything but threatens to trap the bishop. The move b5 has a deep tactical refutation involving a (temporary) queen sacrifice:

[FEN "r2qkbnr/pp3pp1/2pp3p/4p3/B2nP1b1/2NP1N2/PPP2PPP/R1BQ1RK1 b - - 0 1"]

1... b5 2. Nxd4!! Bxd1 3. Nxc6 bxa4 4. Nxd8 Bxc2 5. Nc6 Bxd3 6. Rd1 Ba6 7. Nd5

and White has more than enough compensation for the pawn; center control, space advantage, advantage in development and a better pawn structure. (Immediate tactics on c7 look promising but aren't.)

Black is better off trying to hold on to the queen, but he'll have trouble protecting his king from the dangerous bishop-knight battery:

[FEN "r2qkbnr/pp3pp1/2pp3p/4p3/B2nP1b1/2NP1N2/PPP2PPP/R1BQ1RK1 b - - 0 1"]

1... b5 2. Nxd4!! Bxd1 3. Nxc6 Qh4 4. Bxb5 a6 5. Ba4 Bxc2 6. Bxc2 Be7 7. Ba4 Kf8 8. Nd5

This is an unbalanced position with chances for both sides; in any case, much less than Black started out with.


Should aspiring chess players analyze all of their games? Or is time better spent analyzing particular games (like a match between two masters)?

In general, is it better to play more, and analyze a few of those games, or to play less, and analyze most of them, or even play a less, and still only analyze a very few selected games? What is the most professional attitude towards learning?

Should aspiring chess players analyze all of their games?

It all depends on the result of the game.

Every single game that you lost was because you made at least one mistake. If you don't correct your mistakes you will continue to lose to the same kind of mistakes. The only way you are going to stop making the same mistakes, same kind of mistakes is by analyzing your games, identifying what you are doing wrong and correcting it.

Analyzing the games you lost is the one constant of the life of a player who wants to improve.

Analyzing the games you won is nice for your ego but in general does little to make you a better player.

Analyzing the games you drew can be very useful for identifying the "one that got away". If you were winning, or thought you were winning, and the game ended in a draw then it is useful to find out where you went wrong. Either your judgement was wrong and it was always more or less even or you really were winning and you made a mistake that let him get away. This is often a problem in endgames.


What are the advantage of sicilian defense for black? I have seen many players with black prefers Sicilian defense, what are the advantage of the opening?

The sicilian defence is not just one opening, it is a whole family of variations, that are quite different from each other. So this breadth of possible choices surely contributes to the popularity of the sicilian.

The sicilian variations are also usually quite sharp. This makes it easier for black to create winning chances. In the open sicilian (which is usually the main line) black gets the longterm advantage of two centre pawns against one centre pawn and the open c-line. The other defences against e4 don't have quite such a big disbalance.


Could you show me the code(s) of one or more simple chess program(s) written in C#? I am a novice in C#.
I am looking for the code(s) of one or more chess program(s) written in C#.
Preferably, the code(s) should be short, clean, straightforward, very simple, and use only basic things (try to avoid complicated system namespace / library). It does not matter if the program is not very strong.
If you could also provide some explanations of the different parts of the code it would be even better.

The part of the code which interests me the most is the part which stores all the many millions positions at different depths.
Can this be done in a multidimensional array?
I was thinking that maybe the first two dimensions of the array could represent the two-dimensional boards, the 3rd dimension of the array could represent all the possible positions at a depth of 1 ply, the 4th dimension of the array could represent all the positions at a depth of 2 plies, the 5th dimension of the array could represent all the positions at a depth of 3 plies, etc... But perhaps that would be a little too messy.

Although it is written in C, you might want to take a look at Tom Kerrigan's Simple Chess Program (TSCP) which is created for this very purpose—to allow beginners to see what a simple chess engine is made of.


Idea behind sacrifice pawn I would like to know what compensation White gets after the pawn sacrifice 6. b4.

To me, giving back the pawn just for a tempo, i.e. Bb5, does not seem to be enough.

I simply do not agree with your computer there. It is probably a bit of the "horizon effect", which is when a computer plays a bad move because it puts the refutation beyond its ability to calculate, or "horizon".

White played this opening every passively, and really should be looking to break up black's center so he is not smothered, and b4 does not seem the way to do that. It is very short-sighted by white to try and keep c5, especially when it puts him behind in development. Per my computer, (quad-core 2.9Ghz with 24 GB of RAM), there are a bunch of moves there, and b4 is fourth on the list per Stockfish 10 on my computer. The other candidate moves are c4! (the best in my opinion), h3, and even Nb3 since e4 h3 is good for white.

6.b4?! Nxb4 5.Bb5? {h3, c4, or Rb1 are all still better per my beast) Nc6 6.h3 Bf3 7.Qf3 Bc5 8.c4 Nf6 and while white has some compensation for the pawn, it is not enough. Black is slightly better as white may win the pawn back soon, but black remains slightly better placed.

      [FEN ""]

     1. d4 d5 2. Nf3 c5 3. dxc5 Nc6 4. e3 Bg4 5. Nbd2 e5 6. b4?! (6. c4!) (6. h3) (6. Nb3 e4? 7. h3 Bxf3 8. gxf3 {and white is just a pawn up.}) Nxb4 7. Bb5+?! (7. c4!) (7. h3) (7. Rab1 {are all better}) Nc6 8. h3 Bxf3 9. Qxf3 Bxc5 10. c4 Nf6 11. cxd5 Qxd5 12. Qxd5 Nxd5 {Black's pieces are all very nicely placed here, and the Nd2 is passive.} 13. Bb2 O-O-O 14. Rc1? Bb4 {is the tactical justification.}


What is the result of this pawn-endgame with perfect play by both sides? W : Kg2 , Pa2, b2, c2

S : Kb7 , Pf7, g7, h7

White to move

[fen "8/1k3ppp/8/8/8/8/PPP3K1/8 w - - 0 1"]

Houdini's shootout ended in a black win with depth 23 Ply and a white win with depth
 25 Ply.

Analysis of this general endgame appears in Staunton's Handbook, in the section "King and Three Passed Pawns against King and Three Passed Pawns."

In the preceding section of the book, "King against Three Passed Pawns," Staunton provides analysis indicating that a lone king battling the three connected passers in isolation (without assistance from their own king) can stop a promotion by getting to the so-called master square, which are here g3 for White, b6 for Black.

When considering these KPPP vs. KPPP endgames, he asserts a general rule about the kings' starting points for those positions in which one or both kings are within 3 squares of their respective master squares:

  Victory will be in the hands of the party who can first play his King into its master square.

Staunton goes into some detail explaining the general logic behind play, and gives some examples. I won't try to elaborate here, but instead refer the reader to Staunton's text if interested. According to the rule, the OP's position would indeed be a win for White.

Among the examples Staunton considers, one is "Greco's position," which is identical to the OP's but with kings on e1 and e8. According to Staunton, that position was long considered drawn, but analysis given by Szén revealed it to be a win (in accordance with the rule above). Staunton further considers the position with kings on d1 and e8, calling it "Szén's position," and presenting analysis he credits to Evans (consistent with bof's comment to the OP) showing this also to be a win for White (again in accordance with the master square rule).

For those interested in more beyond Staunton: there is a paper by Noam Elkies applying combinatorial game theory to chess endings, and which in particular considers cases where pawn endgames essentially reduce to distinct subgames wherein mutual Zugzwang might arise. It deals with some of these KPPP vs. KPPP endings near the end, including Szén's position and a nice study by Behting:

[fen "1k6/1P6/2P5/P7/5ppp/8/6K1/8 w - - 0 1"]
[White "White"]
[Black "to Win"]


What are some good books on the Caro-Kann which propose a Black repertoire based on positional, strategic, solid, boring and quiet variations? I'm a 1750 Elo player, and 6 months ago I bought the book Grandmaster Repertoire: The Caro-Kann by Lars Schandorff, and I was disappointed.

In my opinion, the repertoire proposed in the book is too sharp and tactical:

Against the Classical he wants to castle on opposite sides
Against the Short Variation of the Advance he wants to play 5...c5
Against the Panov he wants to play 5...Nc6

What I would like is a book suggesting much more positional, strategic, solid, boring and quiet variations:

Against the Classical I want to castle on the same side as White
Against the Short Variation of the Advance I want to play anything but 5...c5
Against the Panov I want to play 5...e6

Please suggest me some books! (And don't hesitate to suggest me more than one book.)

I would suggest The Caro-Kann: Move by Move. The author, Cyrus Lakdawala, is very lucid & seems to play in the style that appeals to you. Specifically:

He advocates same side castling in the classical variation
He gives an alternative to the ...c5 break in th advance variations, namely the ...f6 break
He advocates ...e6 in the Panov

The move by move series goes through top level games with question and answer format. Many of the games covered were played by Karpov, so if you like his style of play, then you'll like the book. Smyslov, the endgame virtuoso, has a significant number of games too, seeing as the first few chapters cover the Smyslov variation of the classical lines.

PS. I have no affiliation with the author - I'm recommending the book because I'm a Caro-Kann player who likes the book.


Is there any way white can win? [fen "1K6/1P3q2/1P6/P7/3k4/8/8/8 w - - 0 1"]

Is there any way that white can win or draw in the above game?

This position has six pieces on the board, and is hence present in a number of chess endgame tablebases.

For example, the Syzygy tablebases show that this position is a theoretical draw, but that there is only one move which guarantees the draw: Kc8. All other moves allow black to force a win.

[FEN "1K6/1P3q2/1P6/P7/3k4/8/8/8 w - - 0 1"]

1. Kc8 Qe8+ 2. Kc7 Qe7+ 3. Kc8

This position is a draw because White is constantly threatening to promote and win, which leaves Black with no choice but to perpetually check White.  The problem with Ka8 and is that Black can pin the White pawn and gain tempo through constant checking, gaining time to advance their king and win.

If this position were to occur in an actual game, the result would likely be unclear as it would be incredibly easy for either blunder, and end up losing.


Having knightmares, what to do? I just hate when my opponent has the knights because most of my blunders happen due to them. I generally like endgames where my opponent doesn't have the knight. I also hate when the Knight enters my territory. So, what to do about this knight phobia? Should I just exchange all the knights in the opening?

The solution is: play better chess. Train your tactical skills so you can better anticipate the opponent's knight's threats (and also make a better use of your own knights). Avoid creating weak squares in dangerous spots of the board where an enemy knight can dominate the position. Pay attention to how stronger opponents play and try to imitate them in the future.
Sure, you can also make inferior trades to eliminate the opponent's knights, but then you are already making a concession and "surrendering" to those knights before they even start putting you in trouble.


Always capture toward the center? [FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Nc3 Bb4 4. a3 Bxc3 5. bxc3 (5. dxc3)

I usually see bxc3 in this position and the main reason given is to capture toward the center, but doesn't bxc3 weaken the queen side and take the option of castling queen side away from white.  What is wrong with dxc3?  Doesn't this open up the file for the Queen and the Bishop's diagonal?

Either is fine. bxc3 gives you a strong chance to push in the center successfully. It leaves a dangling pawn on a2, but by playing bxc3 you should already have resigned this pawn's fate to some sacrifice for a tempo later in the game. Note you can not play 6. d4 right away since black's response will most likely be 5. ... d5 or 5. ... Nf6 putting pressure on the e4 pawn which is awkward to defend for you at this point. You should most likely respond 6. d3 which dashes any hopes you had for a pawn charge to d4. Also, black can exert pressure on the doubled pawn at c3 which is also a bit awkward for you to defend.

I personally would play dxc3. It is less committing. You no longer have to hope to pry open the middle with your pawn majority, and you have no dangling pawn you have to sacrifice eventually. You've opened up strong lines for all three of your white bishop, your dark bishop and your queen. Note this may seem not that important, but keep in mind your opponent just traded one of his bishops for your knight. If you can open up this game, you will have a strong edge on your opponent. Any attack on your e4 pawn can now be refuted, such as 5. ... Nf6 comes in with a strong pin 6. bg5. Also, it no longer looks silly for your white bishop to travel to d3 to defend e4.


Requesting draw in last two minutes What is the right way to claim a draw in the last two minutes?
Also, is there a procedure to claim a draw after losing on time (I mean if you have a position where you can go for a win if you had time)?

The first point to note that this kind of draw claim only applies when there are no increments. Since digital clocks are almost universal in advanced and normal chess countries it should (I stress "should") rarely arise.

Note also that FIDE proposes to ban analogue clocks and insist on increments in FIDE rated tournaments from 2021, so then the problem should disappear entirely.

There are three cases which can arise:

1) No increments but one or more digital clocks is/are available. In this case the recommended course is for the arbiter to give both sides a 5 second increment, give the claimant's opponent an extra 2 minutes, offer the claimant's opponent a draw which he can decline or accept in the normal way and the game continues to one of the three normal conclusions of win, draw or loss.

2) The player makes a claim that his opponent is not trying to win the game by normal means but just shuffling the pieces quickly to try and win on time. In this case the arbiter will watch the game and if he judges this is correct he will award the draw. He may do this (award the draw) even after the flag has fallen but the claim cannot be made after the flag has fallen and if it is made with just a few seconds left the arbiter will not be able to come to a conclusion and the game will be lost on time.

3) The player makes a claim that his opponent cannot "win by normal means". This is different from "win by any means". For instance if the player is a queen up and crushing his opponent then his opponent might have enough material to win via helpmate but would almost certainly lose if the claimant had enough time.

Another possibility would be if the game was still in the middlegame when, clearly, anything could still happen. In this case the claim would be rejected immediately, the opponent would be given an extra 2 minutes and offered a draw which he could accept or decline.

These are straightforward cases. More problematic would be where the claimant has a rook against a rook and pawn in a theoretically drawn position. This would be the opposite extreme. In this case the arbiter would ask the players to continue and watch the game again possibly until the flag falls. He would then have to judge whether or not the claimant had displayed the required theoretical knowledge to hold the draw. Clearly if the claim is made with just a few seconds on the clock this is not going to be possible and the game is going to be lost.

This same principle applies to all endgame cases where best play would result in a draw but the opponent can win if the player lacks the required theoretical knowledge, even lone king against king and rook's pawn. It should be a trivial draw but the claimant must demonstrate during his time remaining that he has that theoretical knowledge.

Once your flag has fallen no claim can be made even if it is mate in 2.


Can a King and a Knight force stalemate against a lone King? I believe that a King and two Knights are able to force stalemate against a lone King (though obviously not checkmate)... but what about a King and one Knight against a lone King?

I first thought that forcing stalemate would be impossible. So I set up a random position with King+Knight vs King where the lone King was at the edge of the board, and I tried to analyze it.

The result: White can force a stalemate! The trick is the move 3. Kd2!!

[fen ""]
[White "Stalemate in 9"]
[Black "-"]
[SetUp "1"]
[FEN "8/8/8/8/8/k1KN4/8/8 w - - 0 1"]
[PlyCount "17"]

1. Nb2 Ka2 2. Nc4 Ka1 (2... Kb1 3. Kd2 Ka1 (3... Ka2 4. Kc2 Ka1 5. Na3 Ka2 6. Nb1 Ka1 7. Nc3) 4. Kc1 Ka2 5. Kc2 Ka1 6. Na3 Ka2 7. Nb1 Ka1 8. Nc3) 3. Kd2 Kb1 (3... Ka2 4. Kc2 Ka1 5. Na3 Ka2 6. Nb1 Ka1 7. Nc3) 4. Kd1 Ka1 (4... Ka2 5. Kc2 Ka1 6. Na3 Ka2 7. Nb1 Ka1 8. Nc3) 5. Kc1 Ka2 6. Kc2 Ka1 7. Na3 Ka2 8. Nb1 Ka1 9. Nc3

This doesn't prove that a King and a Knight can always force stalemate against a lone King, but it at least shows that it's not completely inconceivable that King+Knight could force the stalemate.

I obviously don't want a "yes/no" answer without any evidence to back it up. I would like either an irrefutable proof or at least some very strong evidence.

One idea is to build an endgame tablebase which takes into account stalemate as a win, which is equivalent to say that White wins when he captures Black's King. There would only need to be 64x63x62 = 249984 positions.

A second idea would be to get a basic engine and modify its code so that it takes into account stalemate as a win, and you can probably also throw away most of the code of the engine to make it calculate faster. Then make it calculate King+Knight vs King in a few positions where the lone King begins at an edge of the board (but not too close to a corner). But this idea would be less convincing than the tablebase.

An exhaustive computer search shows that as expected K+N cannot in general
force stalemate against a lone K.

In fact, the defending King can avoid stalemate as long as it's not on
one of the six-square triangular neighborhoods of the corners
shown in the following diagram

[Title "Danger Zone"]
[fen "kkK2Kkk/kK4Kk/K6K/8/8/K6K/kK4Kk/kkK2Kkk w - - 0 0"]

even on the long edge of each triangle (the twelve White Kings
in the diagram) stalemate can only be forced in a few special positions.
Namely, Kb2 to move can be stalemated by force only from this position

[Title "Mutual Zugzwang"]
[fen "8/8/8/2N5/8/8/1k1K4/8 w - - 0 0"]

and its reflection about the a1-h8 diagonal; and Ka3 to move is
stalemated only if facing a Kc3 and a Knight on one of the squares
b2, c5, b6 that control a4 (the first of these arises at the start of
the stalemate-in-9 shown by Petrosian).

It follows too that each of these four positions is mutual Zugzwang:
the defender get stalemated by force only if on the move.  There are
few enough other Zugzwangs (up to board symmetries) to list them all.
One is the unique losing position of maximal length:

[Title "Mutual Zugzwang"]
[fen "8/8/8/2N5/8/8/8/1k1K4 w - - 0 0"]

Two more are obtained from it by moving the Kings from b1/d1 to
a1/c1 or a2/c2.  Finally, Ka2 against Kc2 and Nb1(b5) are the
shortest mutual Zugwangs.

As Glorfindel suggested, some of these positions are relevant to
the Troitzky ending KNN/KP.  For example, this is a mutual Zugzwang
(in the usual sense of a win BTM and draw WTM), as are each of the
three BTM positions in the main line 1...Kg7 2 Kg5 Kg8 3 Kg6 Kf8 4 Kf6:

[Title "Mutual Zugzwang"]
[fen "8/7k/3N4/1p5K/1N6/8/8/8 w - - 0 0"]
[Title "Mutual Zugzwang"]
[fen "8/7k/3N4/1p5K/1N6/8/8/8 w - - 0 0"]


Can computer analysis really understand human behavior? I just finished a game. I got into a pretty convenient position at move 17 (I play white):

I noticed that in order to checkmate, I only need to remove the black bishop from protecting e7 and then I can get my knight there and checkmate. So, I figured that if I push the pawn on the b file to the c file, there's a good chance my opponent would capture the knight on c3 "for free" and would allow me to checkmate. My plan worked like a charm but the computer analysis tells me that was a blunder.

I do realize that it might not have been the best move if I would have played against a GM. But in this scenarios which we're both around 1400+, this seemed like the most logical move.

So, I wonder how could I really trust an engine if it only plays GM level and doesn't understand the potential move for a human on a specific level.

Here's the PGN for the game with the analysis:

[fen ""]
1.d4 Nf6 2.c4 d5 3.Nf3 dxc4 4.Nc3 e6 5.e4 Bb4 6.Bg5 h6 7.Bxf6 gxf6 { (+0.60 → +1.11) Inaccuracy. A better move was Qxf6. } 8.Bxc4 Nc6 9.O-O O-O 10.Qd3 e5 11.d5 Bg4 { (+0.94 → +2.81) Mistake. The best move was Na5. } 12.Qe3 { (+2.79 → +1.53) Inaccuracy. A better move was dxc6. } 12...Na5 13.Be2 Kh7 14.Nh4 f5 { (+1.48 → +2.08) Inaccuracy. A better move was Bd7. } 15.Nxf5 Qg5 { (+2.31 → +4.92) Blunder. The best move was Bxf5. } 16.Bxg4 Qxg4 { (+5.23 → +9.72) Blunder. The best move was Qxe3. } 17.Qxh6+ Kg8 18.b3 { (+11.64 → +3.66) Blunder. The best move was d6. } 18...Bxc3 { (+4.09 → +318.00) Blunder. The best move was Qg6. } 19.Ne7#

This response will be very critical of OP's attitude to chess analysis, and I realize that it may even come across as somewhat harsh. However, it is assumed below that OP is interested in improving, and thus I feel that some level of harshness is justified here.

Playing for cheap tricks - because that is exactly what 18.b3 is - is not something a computer would do. You will never find an engine that "understands" the "motivation" behind playing such a move. It calculates variations, and notices that the move is just not good.

However, you seem to be under the erroneous impression that this is not a desireable property for the engine under these circumstances. In the example position you give, of course 18.b3 is a bad move in every respect. It is good if and only if black is careless enough to take on c3. The move doesn't threaten anything, and it only gives black time to defend a lost position. As you have other ways of playing that, unlike 18.b3, won't jeopardize your winning chances, the move is correctly classified by the computer as a mistake.

So basically: you get a winning position, and you don't know how to win. Seeing no way to win, you play a move that isn't very good if black just ignores the knight on c3, hoping that your opponent blunders. You don't try to play the best move in the position. And yet you feel like there is a reason to object when the engine picks up on this? Remember that there is an iron clad rule when playing chess, that should always be followed:

NEVER UNDERESTIMATE YOUR OPPONENT!

I would absolutely not put it past a 1400 player to spot that 18...Bxc3 is a bad move in that position. Furthermore, playing in a way that relies on your opponent falling for 1-move traps, because thinking of better ideas is too much of a bother, is no way to improve. And if you don't want to improve, why does this question even need to be asked? There is no other obvious point in reviewing the games that you play.

If you were in a lost position instead of a winning one, then your doubt would have been justified, as sometimes in such a situation, only the cheap tricks have a chance at succeeding. But if you have a good position, you shouldn't bash the computer for criticizing your way of handling the position. In analysis, you should under no circumstances assume that one side will make bad moves. Analysis is about finding the truth - not about making yourself feel better about your play.

One final note: if you really want to improve using analysis, you shouldn't rely on the computer for analyzing your games. Focus on trying to find the best moves in the position yourself. The computer can never explain the "why" of a position. That is something you need to figure out for yourself most of the time if you don't have the help of a strong human player.


How is it possible that the Lomonosov-endgame-tablebase from 2012 still is the most powerful tablebase? Due to Wikipedia: Endgame tablebase the Lomonosov endgame tablebase is still the biggest tablebase (with a size of 140TB). Now this tablebase was computed in the year 2012 with the Lomonosov 1 (Top500-list November 2012, rank 26). The Lomonosov 1 had 78.660 cores with ~900 TFlop/s (peak: 1.700 TFlop/s). When I have a look on the most recent Top500-List (June 2016) I see that the Lomonosov 2 is ranked 41 in the world with ~2.100 TFlop/s (peak: ~2.900 TFlop/s), the No1-ranked super-computer has 93.000 TFlop/s.
So I wonder why the Lomonosov-tablebase after 4 years still is the biggest tablebase. Shouldn't it be easy with the growing computer-power to calculate an 8-men-tablebase? Or is the step from 7 to 8 just too big? Maybe the size would go up exponentially so that standard-storage-systems just cannot handle this? Would appreciate all information about this theme.

I am a developer currently working on software to compute endgame tablebases. The real bottleneck with calculating positions is not memory per se but the working memory and computing cycles needed to calculate a network for an exponentially-growing set of positions.
The number of positions grows exponentially according to the number of men on the board; this means that the working memory needed (whether it be RAM or hard drive reads, which are less expensive and more scalable but significantly slower) increases proportionately to A^N where A is a scaling constant (somewhat less than 64) and N is the number of men in the tablebase. The Lomonosov Supercomputer used 92 TiB of RAM, which is sufficient for a 7-man tablebase; as dfan said in his comment, the jump is too big.
Furthermore, as more nodes are added to the tablebase the number of calculations increases faster than linearly to the number of nodes. For instance, accessing data in a Binary Search Tree (BST) is proportional to ln(M) where M is the number of nodes in the tree; since M = A^N, to access each node of the tree once, A^N * ln(A^N) operations are needed. There are several steps in the tablebase retrograde evaluation algorithm that scale similarly.
In short, memory increases exponentially and the number of operations increases faster than exponentially as more men are added. Computing has not advanced this far in (at the time of writing) 6 years.
Edit
Since this answer is getting a lot of traffic and I re-read my answer, I feel the need to add some clarification. Endgame tablebases are created with retrograde analysis, so deterministically calculating the outcome of one position requires knowledge of enough possible successor positions. As we know, this graph mushrooms quickly. While retrograde analysis is definitely parallelizable, one needs an enormous amount of working memory. However, it is common practice to allocate only 10s of GB of RAM to a single processor, so positions must be communicated over a network. This would require a lot of bandwidth, and multiple processors contending to make changes to the same table state would create synchronization problems that add overhead. Positions must be stored in RAM because disk read latency is horrendous (on the order of milliseconds instead of nanoseconds for cache or microseconds for RAM). It's possible some amount of pipelining or caching could amortize poor latency, but this is still a hard problem to solve at the required scale.
Tl;dr even with a big supercomputer, modern computer architecture is not amenable to this type of problem.


Is high IQ necessary to become a GM? There is an option in the Swiss Manager pairing program which allows you to download into the program the current list of FIDE registered players (for many individual federations also). Once it is done it gives you a count of the number of players. I just did this and it told me 897,324 players had been found.

The FIDE rating website has an advanced search function. I just used this to search for all GMs. It also gave me the count - 1680.

This means that 100 x 1680 / 897,324 = 0.187% of FIDE registered players are GMs.

Are these GMs also intelligent in the same proportion? So, are they in the top 0.2% of the population for intelligence also? Or are there some GMs who, as we say in England, are "as thick as mince"? (Failed to graduate high school might be one indicator) Have there been any World Champions who have been "as thick as mince"? (Bobby Fischer, I'm looking at you!)

Is there any research which has examined IQ and chess playing ability?

The most comprehensive and recent publication I've found related to this question is The relationship between cognitive ability and chess skill: A comprehensive meta-analysis. It's behind a paywall, but you may be able to find copies of the PDF by googling the title. Also here's a less technical overview of the article from ScienceDaily.

The bottom line is that according to a meta-analysis of numerous studies, there is clearly a correlation between chess skill and cognitive ability, but cognitive ability explains only about 6% of the variance in chess skill (12% if you only consider numerical ability only). There must be other factors as well (e.g., training), some of which could be more important than cognitive ability.

An interesting observation was that intelligence plays a bigger role among lower-level players; here's a relevant quote from the ScienceDaily article.

  The study found that intelligence was linked to chess skill for the
  overall sample, but particularly among young chess players and those
  at lower levels of skill. This may be because the upper-level players
  represent a winnowed distribution of cognitive ability -- in other
  words, they all tend to be fairly bright. (By way of comparison,
  Burgoyne said, consider the world's best basketball players. Although
  there is essentially no correlation between height and points scored
  at that level, that doesn't mean height isn't important in
  basketball.)

I don't have an answer specifically regarding the IQ of GMs or world champions, but this page has an interesting, if unsourced, factoid:

  International team of psychologists have attempted to measure IQ score of Garry Kasparov and after many tedious tests has concluded Kasparov’s IQ to be 135, making him fall into ‘moderately gifted’ category.

(I later found the same claim in other websites, some of which say that the testing was organized by Der Spiegel in the 1980s.)

If this is true, it would mean Kasparov is perhaps in the top 1% in terms of IQ, which is certainly not bad, but seems almost nothing compared to the percentile he occupies in terms of chess skill (top 0.0001% or whatever, depending on how you define "chess player").


Is this opening a joke or serious? I was watching Daniel Naroditsky's speedrun on YouTube and in his 1870 video (https://youtu.be/3UqPa5eV2e0?t=987) his opponent (rated 1889, playing black) played a very bizarre opening by pushing almost all his pawns before developing any of his pieces. It appears to be someone trolling, but they seemed (to me) to play a really good middlegame/endgame. Is this considered a serious opening, or does it seem like more of a joke opening? Or was it a trap that throws lots of players off?
[White "SenseiDanya"]
[Black "ions26"]
[FEN ""]

1. e4 c6 2. d4 d6 3. Nc3 e6 4. Nf3 a6 5. Bd3 h6 6. O-O b6 7. Be3 Bb7

Stockfish 10+ (depth 20) disagrees with the other answer, because it thinks that White's opening here is sound and evaluates the final position as +1.4. I would be very interested to see anyone play as Black starting from that position and beat Stockfish 10+. If nobody can, how can one consider White to have played badly?


Why do some players never accept a draw offer? Some of the people I play against will never accept a draw offer, even in positions that are a theoretical draw.

I know it's a draw. They know it's a draw. But they want to play until:

Draw by stalemate
Draw by insufficient material
Draw by threefold repitition
Draw by the 50 move rule

In a recent casual game (i.e. no arbiter, no clocks), my opponent forced a stupidly long draw (49 moves with no captures or pawn moves, then 1 pawn move to recent the count. Repeat until insane).

My question is, why do some players never accept a draw offer, even in dead drawn positions?

I'm going to assume here you're playing against people you don't know very well in a park somewhere.

While you both know it's a draw, he's assuming that you don't know how to play it out or that you'll lose your patience and make a blunder. After you both have played against each other some time, you'll both know what you can and can't win against each other and he will offer draws out of his own initiative. Unless, of course, your opponent is very stubborn then you just have to put up with it.


What is a base chess engine? For the asmFish 2017 11 05 there is one option as a base bmi2 and popcnt.  What does base mean?  Is it just a weaker version of the correct one or is it the fully capable engine
https://github.com/lantonov/asmFish/tree/executables/Windows

The base version is for everybody, all Windows users. The other versions are built for specific hardwares, and should outperform the base version if you have the hardware.

Try the bmi2 and popcnt versions, if they crash on you fall back to the base version.


Does SCID allow to draw arrows on the board? I figured out that holding shift allows me to highlight a square I click on, but no luck finding the shortcut for arrows. Using SCID Vs. PC 4.9.

I use Scid 4.2.2, which is quite old, but maybe what works there also works in Scid vs PC.

You can open the Comment Editor window, and besides editing the comment and adding things to squares, you can also click and drag over the board to create arrows.

Make sure to store the comment before you enter the next move, or it will be lost!


Kasparov quote on boldness I am looking for a Kasparov quote on boldness. I would like to be something along the lines of this: "I do less tactical training as tournament time approaches. Instead, I do more bold, daring things."

I found a few in an article on chessworld.com called "31 Great Chess Quotes from Garry Kasparov."

“When your house is on fire, you can’t be bothered with the neighbors. Or, as we say in chess, if your King is under attack, don’t worry about losing a pawn on the queenside.”

“If you wish to succeed, you must brave the risk of failure.”

“The highest art of the chessplayer lies in not allowing your opponent to show you what he can do.”


Average ELO of Tradewise Gibraltar Chess Festival 2016? I am wondering what the average ELO of the Tradewise Gibraltar Chess Festival 2016 is? And if it falls to any rating category that elite tournaments usually have?

If I didn't mess up my script the average Elo of the Gibraltar Masters 2016 is 2321.64.

That is category III and nowhere near a super tournament.

But of course if you only look at the top seeds the average is very comparable to super tournaments. (The top nine would be category XXI)

Basically after the first 4-5 rounds you have a full fledged super tournament going on at first 5 boards.


Stockfish on Android Question I recently downloaded Stockfish 10 on my android phone and after unzipping the rar file, there were three separate engine binaries and I am wondering which one would be the strongest one to use.  The three that were in the folder are stockfish-10-arm64-pgo, stockfish-10arm64v8, and stockfish-10armv7.  Which one of these binaries would be the strongest one to use?

Android 32 bits? stockfish-10armv7

Android 64 bits? stockfish-10arm64v8 and stockfish-10-arm64-pgo

stockfish-10-arm64-pgo is faster but also with larger file


How can I prevent games from dragging on? How can I prevent a game from dragging on, taking 60+ moves to get anywhere near finishing?

I mainly encounter this when playing people at or below my level (~1400). This never happens when playing someone better.

I recall reading somewhere that most games should ideally be finished in about 30 moves or so. That seems reasonable.

What can I do to prevent a game from dragging on without giving myself a disadvantage?

Seriously, by checkmating your opponent.  If every game is going on for 60 moves, the bad news is that you don't know how to score the win.  The good news is neither does your opponent.

But by merely recognizing something is amiss, you have gained a huge advantage.

Now, you have to sharpen your game.  The next step is for you to figure out why you can't win sooner.  The moves are there - you know that a GM could win either side of the board pretty much up to the bitter end.  The moves are there.

I don't know if it is appropriate for this site, but post a game (you DO keep notation of your games, don't you??) and we'll look at it.  Post a typical game, regardless if you won it or not.  And don't worry about the quality of the game.  There's always a bigger fish.

Edit - I'm like a broken record on this, but another way is to run your games through a chess engine.  Every move, both sides.  Set the engine's strength such that it can beat you every game.  See the moves it suggests instead, and when it finds a move markedly better than the one you chose, find out why it made that choice.  Figuring this out is a lot of work, but getting better at chess is not often easy.


Positions in which only a single long sequence of correct moves avoids forced checkmate sequences So for n steps, one player can only choose one out of many moves, because all others lead to forced checkmate sequences. Only one path from the root to the leaves of the game tree avoids a certain loss.
Does this concept have a name? Are there any known positions where this is the case?

To start off, with such a requirement, the sequence would have to end in a draw. Well, more than most likely that is.
There is a similar concept from another question called the "Nunn Convention." It is a term to describe a move by one side that is the only way to draw, with the extra requirement that it isn't the only legal move. That extra requirement is what makes it "Nunn." It isn't quite what you wish for, but it is close.
The Matplus.net thread from which I learned the concept contains the below example. It is the record length of 32 plies for such a "Nunn" sequence. It is from post number 19.
[Title "Geir Sune Tallaksen Østmoe, Matplus.net Forum 8/9/2019, White To Draw"]
[FEN "k1B5/r1p1p2b/nPPP2R1/BN2b1R1/2P2qp1/p7/P3P2P/6Kn w - - 0 1"]

1. Bb7+ Rxb7 2. Rg8+ Bxg8 3. Rxg8+ Nb8 4. Rxb8+ Kxb8 5. bxc7+ Rxc7 6. dxc7+ Bxc7  7. Bxc7+ Qxc7 8. Nxc7 Kxc7 9. Kxh1 Kxc6 10. Kg2 Kc5 11. Kg3 Kxc4 12. Kxg4 Kc3  13. h4 Kb2 14. h5 Kxa2 15. h6 Kb1 16. h7 a2


How can the Danish Gambit be exploited? When dealing with gambits, especially ones where your opponent could have a lot more active pieces to pressure you. Is declining the best approach?

A friend of mine usually always wrecks me with the Danish Gambit, especially whenever I accept and before I know it, she's literally attacking  with way more pieces than I can handle and to be honest it does seem like a solid sacrifice (3 pawns for 2 very active pieces (the bishop pair) while  I literally have nothing to show for the first 3 moves).

Is there a solid way to exploit the fact that white is down 3 pawns? Or even better, what is the best approach to fighting back when the pressure is too much and I'm so behind in development?

The Danish gambit isn't very popular these days because of the Schlechter Defense. The idea is to take the gambit pawns but return them quickly.

  e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4 cxb2 5. Bxb2 d5

5...d5 initiates the Schlechter Defense. The mainline continues 6.Bxd5 (6.exd5 Nf6 closes the position and lets Black develop, still a pawn up) Nf6 7.Bxf7+ Kxf7 8.Qxd8 Bb4+ 9.Qd2 Bxd2+ 10.Nxd2 c5. Black regains the Queen and steers the game to an equal endgame. White has no attack and the position is not even remotely close to tactical, which is psychologically depressing for gambit players.

[FEN ""]

1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4 cxb2 5. Bxb2 d5 6. Bxd5 (6. exd5? Nf6) Nf6 7. Bxf7+ Kxf7 8. Qxd8 Bb4+ 9. Qd2 Bxd2+ 10. Nxd2 c5

The only downside of this defense is, if you keep using it, your friend might not want to play with you anymore.


How to install stockfish on winBoard 4.4.5? I want to install stockfish to winBoard 4.4.5. But winBoard 4.4.5 doesn't seem to have the same protocol as stockfish. Is there a way to do it on windows 10? I would like to install the latest version of stockfish to winBoard 4.4.5.

Stockfish supports the UCI protocol, Winboard supports the Xboard (or CECP) protocol. What you're looking for is a Winboard to UCI adapter, that sits between Winboard and Stockfish and does the translations between the two protocols.
The other alternative is using a chess GUI that supports UCI, e.g. Arena, ChessX, scid. even give Tarrasch a try.


Which openings give a winning pawn-structure in the endgame? For example in the Exchange Variation of the Spanish 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6 dxc6, White gives Black the Bishop pair, but gains a potentially winning pawns-only endgame. Are there other situations where a player may ruin an opponent's pawn-structure thus gaining a (potentially) decisive endgame advantage?

On the other hand, are there openings in which a player may decide to sacrifice his pawn structure in order to get other kind of advantages?

I'm not looking for 'bad' pawn-structures, I'm looking for those which are winning/losing according to theory, if we remove all pieces from the board except the Kings.

Here's a somewhat cheap answer: the Nimzowitsch Variation of the Caro-Kann Defense, given by 1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nf6 5. Nxf6+ exf6. In the resulting position,

if we were to remove all the pieces and leave a pure king-and-pawns endgame, then White would have a winning advantage, because he has a healthy pawn majority on the queenside which can create a passer, while the doubled pawns of Black's kingside majority make it so that White can prevent her from creating a passer. So this is an accurate answer to your question. The only reason I call it "cheap" is because the pawn structure here is just a mirror-image of the Ruy Lopez Exchange structure your question already mentions, but I guess that doesn't make it any less of an example.

I think one reason your question hasn't gotten any answers until now, though, is that for the resulting pawn endgame to really be a winning one structurally, it seems you need this feature that one side can forcibly make a passer while the other side can't, and that means having a workable majority for one side and a "broken" one for the other. That basically requires there to be (1) some doubled pawns for one player, and (2) two distinct sides of the board, in terms of the pawn islands remaining. (E.g. if the white e-pawn and black d-pawn hadn't been exchanged in my example, then the pawn endgame wouldn't yet be a winning one.) And there's actually not so many (truly distinct) ways for that to happen, at least not in realistic ways.

Another common sort of opening that would at least feature a very favorable pawn endgame for one side is those in which one side has an isolated queen pawn. The side that has the isolani could find his king being so tied down to its defense that the other side can force a win. But this won't always be the case, so I wouldn't give that as an answer in and of itself. If you want to find some further openings that at least get part of the way toward what you're after, ones with an isolated queen pawn would be a promising place to look.

All in all, for the reasons I've spelled out, I'm not too optimistic that you'll find all that many (essentially different) examples of what you're after, but I hope this helps.

That said, there is an entire class of openings that provide truly cheap answers to your question: gambit openings. Since these would feature pawn endgames with a pawn deficit (at least), these will generally be lost for the gambiteer's side. I sure wouldn't want the pawn endgame from the Danish Gambit line 1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4 cxb2 5. Bxb2, for instance :)


Tournaments for adults only? Are there any over-the-board tournaments open only to persons over 18?

Everywhere I go it's like a school field trip, more than half the players are from some elementary or middle school, all parents in tow. And as I am in the ~1600 rating range myself, I end up playing nothing but kids and I find it unpleasant.

First of all, it's a no-win situation. If you beat them, you feel like a bully taking candy from a baby.

Most of the time it's fine, but I've had a few very negative experiences, especially:

A kid about 9 years: he played a fantastic opening against me, he was
up a pawn and had a crushing position. He proceeds to go get all his
friends to look at the board, all snickering. Then, I fight back and
when he realizes I'm about to win his rook and take the initiative he
breaks out into tears, like inconsolable. It was horrible. The TD
awarded me the game as forfeit.
A kid about 14 years old: He plays really fast, and I go up a knight
and have a good attack going. It's a complex position but I'm easily
going to be able to finish it. He proceeds to get up, walk around for
20 minutes (game 60 time control), comes back, makes a move, then
gets up again, another 10 minutes, and on and on until he had a few
mins left and then he played to the end (I won easily.) It was
ridiculous. I complained to the TD but he said there's nothing he
could do.

So I can't play tournaments anymore, it's unpleasant. Are there any tournaments that are open to only adults?

There are definitely some, but they are, clearly, not the norm as most organizers want to get the most players they can, and thus, make the most money they can.

Here are a few links of places that have regular adult tournaments. Some of these tournaments have gone by, but if they did them before, they probably would do them again. There are surely more, but I am not going to try to track down every one of them.

Of course, and I am one now, there are also senior events for those over 50; so you have something to look forward to.

Starting a local club that does one game per week, and excluding kids, might also work for you.

I do feel your pain. I got whacked by the number one 8-year-old in the country a week ago. His behavior was totally fine, but kids are always so underrated.

Berkeley, California

Austin, Texas

New Jersey

Tucker, Georgia


What first moves would be advantageous for black? What White moves give away the first-move advantage?


Does your rating express the quality of your play regardless of time control? For instance if I analyze a game played in blitz, move by move, between two 2600s, should I expect the moves to be of the same quality as the moves between two 2600s in classical? Or would worse play in blitz be enough to achieve a 2600 rating, given that every player is playing worse moves due to time pressure?

So if someone who's, for instance, 1600 in classical, 1400 in rapid, and 1200 in blitz, does this mean that they are especially reliant in longer time controls and have a pronounced difficulty in performing under time pressure (more so than other people), or is this drop-off in rating expected, because everyone plays worse under time pressure?

The way ratings are mathematically defined, they don't express the absolute strength of players, but only the strength of players in a pool relative to each other. So there is no meaning in trying to compare blitz rating and standard rating, the way you are trying to suggest.

For the same reason you cannot compare computer ratings with human ratings, because they are calculated from different pools: computers playing only against computers vs humans playing only against humans.

Also for the same reason you cannot really compare ratings on different websites or online ratings with FIDE ratings.

That being said, most of the good players (above say 2600 in standard) are also decent Blitz players and would have a comparable blitz rating.

Still, speaking of absolute strengths, their blitz games would (on average) be worse quality than their standard games.

Giving a concrete example: Ding Liren and Hikaru Nakamura both have blitz and standard ratings in the 2800. So they are equal in strength in blitz (compared to each other) and in standard, but that is because they are equally worse in blitz....


Humans against computers: is it an advantage to humans to have more time or less It's clear to me that humans are at a loss when it comes down to playing against computers. (not only due to the answers to my last question (Humans against computers).

But, would humans (maybe a team of us) have a better chance of winning if we have a longer time per move or a shorter time?

Longer time lets both sides to calculate the variants deeper.

In blitz games (< 5 min) computers are terribly strong and we have no chance. Computer's reaction is too fast and it can compute lots of variants in early few seconds. On the other hand humans are potential to make blunders.

In games with 15-60 minutes engines are strong too, but humans have chances to avoid overlooks, obvious mistakes and they can analyze the position better, but yet it's hard to resist against engines.

In long games, engines can discover more variants, the problem is by processing deep variants the state space tree gets huge and finishing depth N and getting into depth N+1 consumes too long time. In other words, if an engine makes its decision after 4 hours thinking on a position, it's rare for it to change its decision to another move by more 1 hour thinking.

On the other hand humans have more time to analyze positions strategically (the only thing that humans are still better than engines. At least it's comparable to engines)

So my answer is long games can give us a better chance to play better against computers.


Bird's opening versus the Dutch Defence I have played Bird's opening for around a year now, but I don't understand why Bird's opening isn't played as much as the Dutch, even though it is a tempo up. Why is this?

Even if you play the Dutch a tempo up, you don't have great chances of gaining an advantage (especially if your opponent is completely satisfied with just equalizing). As White you typically want to maximize your chances of getting some edge, and a better way to do this is by controlling more of the centre with 1.e4/1.d4, or perhaps developing a piece with 1.Nf3. The Bird's still a fine opening, but not very challenging.
In addition to this, Black doesn't necessarily have to play 1...d5 (even though it's the most popular move). He could go for something like 1...c5, 2...Nc6, 3...g6, 4...Bg7, 5...e6, etc, playing similar to how he would against the Closed Sicilian. If at any point White decides to push e4, then we've actually got some kind of Closed Sicilian where Black is fine. And if White doesn't push e4, it's kind of odd - after all, in the Bird/Dutch isn't one of the main goals to push e4/...e5?


Helpmate of arbitrary length One of the FIDE rules states that if someone's flag falls, and there exists a legal sequence of moves such that the other player mates the first player, then the position is a win for the second player. This got me thinking whether this rule can theoretically be hard to enforce for arbiters, i.e. whether it is possible that the arbiter cannot (easily) decide whether a game is winnable for one side or not:

  Do there exist "hard" chess puzzles where the objective is to find a sequence of moves of any length, with both sides helping, so that one side wins? So essentially helpmate puzzles, but without specifying the number of moves until mate? Or is it always rather straightforward to determine whether, from a given position, there is a sequence of moves leading to mate?

Perhaps one way to make the job for the arbiter difficult is to not keep track of previous moves, and then present a position to the arbiter (when the flag falls) where it is difficult to prove whether one side can legally castle or not, or take en passant or not etc. - if such positions can only be won when say en passant is available, the arbiter (or the second player claiming a win on time, rather than a draw) would have to construct a proof game to show that the game can indeed be won.

In any case: I cannot come up with examples which are hard helpmates of any length, but I am in no way an expert when it comes to helpmates. Any thoughts or comments are appreciated!

Edit: This question is not about what is sufficient mating material, but about whether positions exist for which it is hard to decide if a mating sequence exists. This is more in the territory of artificially constructed helpmates/proof game problems than about simple, realistic adjournment situations for arbiters.

I don't remember where I first saw this kind of trick:

[Title "Could White (or Black) possibly win this?"]
[FEN "8/1p4p1/1Pp3p1/k1P3p1/1pP3Pb/1P4p1/6P1/7K w - - 0 0"]

Yes, the Kingside is necessary!

[Title "White mates in 19 (with Black's help)"]
[FEN "8/1p4p1/1Pp3p1/k1P3p1/1pP3Pb/1P4p1/6P1/7K w - - 0 0"]

1.Kg1 Ka6 2.Kf1 Ka5 3.Ke2 Ka6 4.Ke3 Ka5 5.Ke4 Ka6 6.Ke5 Ka5 7.Ke6 Ka6 8.Kf7! Ka5 9.Kxg6! Ka6 10.Kf7 Ka5 11.Ke7 Ka6 12.Kd7 Ka5 13.Kc7 Ka6 14.Kc8 Ka5 15.Kxb7 g6! 16.Ka8 Ka6 17.b7 Ka5 18.b8=Q Ka6 19.Qa7#

Black could mate a few moves later after (say) 19.Qf4 Ka5 20.Qf2 gxf2 etc.

P.S. It turns out the I first noticed this trick in a help-stalemate
problem by Tivadar Kardos (see my comment below).  Looking at that
problem and some of his others suggests this improved setting of the
same idea:

[Title "White's turn.  Could either side possibly win this? (NDE after T.Kardos)"]
[FEN "5brk/4p1p1/3pP1P1/1B1P2p1/3p2p1/3P4/4K1P1/8 w - - 0 0"]


What is a good line against the King's Indian Defense for blitz play? I am looking for a line as White against the King's Indian Defense to play in blitz.  With the short time I find it hard to play the lines where White might be winning on the queenside, but has to endure an attack on his king.  I've looked at the Smyslov line, but I don't understand what White is trying to do there.  I would consider pure English type lines or Reti if there is a good recommendation.

I think a good way of preventing Black's kingside play is the Makogonov (or Makagonov) variation:

[fen ""]

1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.h3

This is more strategical than tactical, and most of the times prevents Black's ..f5 by playing g4 with White! Not to attack, but to restrain.

After 5..0-0 you can choose:

either a setup with 6.Nf3,
or first develop the queen's bishop (6.Bg5), keeping the option open of playing Nf3 or Nge2.

For the first setup, reply all games played by Chessexplained, he has a tremendous score with this variation, explaining plans while playing: https://www.youtube.com/user/Chessexplained/search?query=makogonov. I especially liked

https://www.youtube.com/watch?v=wqNBR4wejCU (playing on two wings),
https://www.youtube.com/watch?v=ca0tTOOhb6A (explaining some theoretical ideas) and
https://www.youtube.com/watch?v=cJk-NejbiHQ.

For the second, more flexible, setup, read John Watson's "A strategic opening repertoire for White".

Good luck!


What percent of chess games contain a blunder? To specify the question a bit:

I consider a blunder a move which worsens the position by 3 pawns (300 centipawns) or more. I think this is a pretty good base mark, since a strong computer will generally judge sacrificial moves accurately.
Lets only consider amateur (<2100 rating) games, since beyond this, such blunders are very rare

A breakdown by rating would be very nice

EDIT: In consideration of the numerous comments I've decided to tighten the bolts some more on this question.

Addendum 1: The question is asking how many games out of a pool of games will contain a blunder. Not how many moves within a game are blunders.

Addendum 2: It seems 100 centipawn shifts are common even in master level games, so I have upped the ante to 300 centipawns, these would be blunders that outright lose the game.

Addendum 3: I am not asking for how many games are won or lost through a blunder (this is basically impossible to determine), but just how many contain at least one.

I happen to have a dataset with 25000 games with stockfish evaluations after every move. I just did a little blunder search and these are my findings:

Blunders from an equal position (-1.00 < eval < 1.00) are very rare, even among weaker players. That is not particularly surprising, because we tend to leave the equality region in little steps during the opening and the blunders come when we are under real pressure and low on time.

Elo: 1500: 100cp Blunder every 45 moves.
Elo: 1600: 100cp Blunder every 46 moves.
Elo: 1700: 100cp Blunder every 50 moves.
Elo: 1800: 100cp Blunder every 52 moves.
Elo: 1900: 100cp Blunder every 55 moves.
Elo: 2000: 100cp Blunder every 59 moves.
Elo: 2100: 100cp Blunder every 64 moves.
Elo: 2200: 100cp Blunder every 69 moves.
Elo: 2300: 100cp Blunder every 74 moves.
Elo: 2400: 100cp Blunder every 78 moves.
Elo: 2500: 100cp Blunder every 82 moves.
Elo: 2600: 100cp Blunder every 85 moves.
Elo: 2700: 100cp Blunder every 85 moves.

Really big blunders >300cp from an equal position are even more rare. Which also isn't particularly surprising, after all even if you blunder a full piece you usually get a little something in return.

Elo: 1500: 300cp Blunder every 223 moves.
Elo: 1600: 300cp Blunder every 241 moves.
Elo: 1700: 300cp Blunder every 274 moves.
Elo: 1800: 300cp Blunder every 299 moves.
Elo: 1900: 300cp Blunder every 335 moves.
Elo: 2000: 300cp Blunder every 352 moves.
Elo: 2100: 300cp Blunder every 381 moves.
Elo: 2200: 300cp Blunder every 421 moves.
Elo: 2300: 300cp Blunder every 446 moves.
Elo: 2400: 300cp Blunder every 479 moves.
Elo: 2500: 300cp Blunder every 509 moves.
Elo: 2600: 300cp Blunder every 525 moves.
Elo: 2700: 300cp Blunder every 530 moves.

If you leave out the requirement of an equal position, the numbers go way up. As opposed to the relevancy ….

Elo: 1500: 100cp Blunder every 9 moves.
Elo: 1600: 100cp Blunder every 9 moves.
Elo: 1700: 100cp Blunder every 10 moves.
Elo: 1800: 100cp Blunder every 10 moves.
Elo: 1900: 100cp Blunder every 11 moves.
Elo: 2000: 100cp Blunder every 12 moves.
Elo: 2100: 100cp Blunder every 13 moves.
Elo: 2200: 100cp Blunder every 14 moves.
Elo: 2300: 100cp Blunder every 14 moves.
Elo: 2400: 100cp Blunder every 15 moves.
Elo: 2500: 100cp Blunder every 16 moves.
Elo: 2600: 100cp Blunder every 16 moves.
Elo: 2700: 100cp Blunder every 17 moves.

And the bigger blunders:

Elo: 1500: 300cp Blunder every 23 moves.
Elo: 1600: 300cp Blunder every 25 moves.
Elo: 1700: 300cp Blunder every 27 moves.
Elo: 1800: 300cp Blunder every 29 moves.
Elo: 1900: 300cp Blunder every 32 moves.
Elo: 2000: 300cp Blunder every 34 moves.
Elo: 2100: 300cp Blunder every 37 moves.
Elo: 2200: 300cp Blunder every 40 moves.
Elo: 2300: 300cp Blunder every 43 moves.
Elo: 2400: 300cp Blunder every 46 moves.
Elo: 2500: 300cp Blunder every 48 moves.
Elo: 2600: 300cp Blunder every 49 moves.
Elo: 2700: 300cp Blunder every 50 moves.

Those numbers are a little higher than in the linked blog, that's probably because stockfish likes to throw out big numbers compared to other engines.

To confer to the addendum and the final phrasing of the question (i.e. percentage of games with a 300cp blunder.):

Elo: 1500: 62 percent of the games contain a blunder.
Elo: 1600: 58 percent of the games contain a blunder.
Elo: 1700: 53 percent of the games contain a blunder.
Elo: 1800: 50 percent of the games contain a blunder.
Elo: 1900: 47 percent of the games contain a blunder.
Elo: 2000: 45 percent of the games contain a blunder.
Elo: 2100: 41 percent of the games contain a blunder.
Elo: 2200: 37 percent of the games contain a blunder.
Elo: 2300: 33 percent of the games contain a blunder.
Elo: 2400: 29 percent of the games contain a blunder.
Elo: 2500: 25 percent of the games contain a blunder.
Elo: 2600: 24 percent of the games contain a blunder.
Elo: 2700: 24 percent of the games contain a blunder.

With the requirement of an equal position:

Elo: 1500: 13 percent of the games contain a blunder.
Elo: 1600: 12 percent of the games contain a blunder.
Elo: 1700: 10 percent of the games contain a blunder.
Elo: 1800: 10 percent of the games contain a blunder.
Elo: 1900: 8 percent of the games contain a blunder.
Elo: 2000: 8 percent of the games contain a blunder.
Elo: 2100: 7 percent of the games contain a blunder.
Elo: 2200: 5 percent of the games contain a blunder.
Elo: 2300: 6 percent of the games contain a blunder.
Elo: 2400: 4 percent of the games contain a blunder.
Elo: 2500: 3 percent of the games contain a blunder.
Elo: 2600: 3 percent of the games contain a blunder.
Elo: 2700: 3 percent of the games contain a blunder.