What is the longest current tablebase mate with a unique optimal line?

Guy Haworth gives an answer to this in his Chess Endgame Records.

[fen "8/8/7p/7n/k7/8/2K5/3R4 w - - 0 1"]

1. Rd4+! {dtc/m/z = -26/-49/-17m} Ka3 2. Kd3! Kb3 3. Rd6! Kb4 4. Kd4! Nf4 5. Rb6+! Ka5 6. Rf6! Ne2+ 7. Kc4! Ng3 8. Rg6! Ne4 9. Kd4! Nd2 10. Rg2! Nf3+ 11. Kc5! Ka6 12. Rg6+! Kb7 13. Kd5! h5 14. Rh6! h4 15. Rf6! Ne1 16. Rf1! Nc2 17. Rb1+! Ka6 18. Rb2! Ne1 19. Ke4! h3 20. Rb1! Nc2 21. Kd3! Na3 22. Ra1! h2 23. Rxa3+! {KRKP: dtc/m/z = -3/-15/-3m} {Nalimov and Lomonosov DTM EGTs} *

Haworth states that this is the longest-known decisive AUMS, Absolutely Unique Move Sequence, known to the author.

This move-sequence arose from White and Black adopting the following strategies. White's strategy is: first, preserve the value, i.e. keep the position won for White; second, maximize DTM. (Why "maximize" and not "minimize"? I don't know, but in the above line White has only one value-preserving option at each move anyway, so it doesn't matter.) Black's strategy is to challenge White to find the unique value-preserving move.

Every move in the above line is optimal for the player's strategy. In the cases of Black's 20th and 22nd moves, there is not one unique option which is optimal for Black's strategy, but for all Black's other moves the move given above is Black's only option which implements Black's strategy of giving White only one option which keeps the position won for White.

Note that the identity and length of the longest decisive AUMS depends on what White's and Black's strategies are. Black's strategy of preferring "restrict White to a unique winning move" seems calculated to enable there to be long AUMSes. If, instead, Black adopts the strategy "maximize DTM", then the game proceeds differently. 18...Ne1 is indeed Black's only option which gives White only one winning move, but it loses in 20 moves. By contrast, 18...Ne3 loses in 32 (i.e. keeps Black alive for 12 moves more); 19. Kc6 then wins in 32, and 19. Kc5 in 34.

Some of the jargon explained:

decisive: ending in checkmate, not in stalemate

AUMS: Absolutely Unique Move Sequence

DTC: depth to conversion (i.e. depth to capture, promotion, or the end of the game)

DTM: depth to mate

DTZ: depth to changing which ply is the earliest at which a 50-move-rule draw may be claimed (i.e. depth to capture, pawn-move, or the end of the game)

value: whether the position is (with best play) won for White, won for Black, or drawn

Upper-case DTC/M/Z refer to white; lower-case dtc/m/z refer to Black.

Depth is measured in plies, where a ply is either a white move or a black move.

Haworth cites Conrady, 2003; van der Heijden #70232, (2010). The relevant entries in his bibliography are:

Conrady H. (2003). Computerschach und Spiele, Vol. 2, No. iv-v

van der Heijden, H. (2010). http://www.hhdbiv.nl/. ENDGAME STUDY DATABASE IV

The longest AUMS I can see in Haworth which ends with the mating move is a 13-ply KNkp mate. Using Nalimov I have extended it back for a further two plies but only by dint of captures.

[fen "8/8/8/1p6/b1R5/8/N7/k1K5 w - - 0 1"]

1.Rxa4! bxa4 2.Nb4! a3 3. Nc2+! Ka2 4. Nd4! Ka1 5. Kc2 Ka2 6. Ne2 Ka1 7. Nc1 a2 8. Nb3#! {Nalimov and Lomonosov DTM EGTs} *


Is there a rule for anti noise earpieces?

But I was wondering what is the rules for that kind of object.

Strictly speaking they are not allowed without the arbiter's permission.

This is what the latest FIDE Laws of Chess state:

  11.3.2.1 During a game, a player is forbidden to have any electronic device not specifically approved by the arbiter in the playing venue.

  However, the regulations of an event may allow such devices to be
  stored in a player’s bag, provided the device is completely switched
  off. This bag must be placed as agreed with the arbiter. Both players
  are forbidden to use this bag without permission of the arbiter.

  11.3.2.2 If it is evident that a player has such a device on their person in the playing venue, the player shall lose the game. The
  opponent shall win. The regulations of an event may specify a
  different, less severe, penalty.


How to calculate the FIDE Percentage Expectancy Table

It's basically just table 8.1a with the columns switched. E.g. the entry in table 8.1b with rating difference 92-98 and expected score (for the higher rated player) of .63, corresponds with the entry (.63, 95) in table 8.1a.

That table is based on the expected score formula mentioned here:

  If Player A has a rating of RA and Player B a rating of RB, the exact formula (using the logistic curve) for the expected score of Player A is

  EA = 1 / (1 + 10 (RB - RA) / 400)

but it's also possible to directly generate table 8.1b from this formula. For example, a rating difference of 92 points (in A's favor) leads to EA = 0.6294.

The inverse formula, calculating the rating difference which corresponds to a certain expected score, is RB - RA = 400 log10(1 / EA - 1).


How can I automatically extract features from a position?

I do not want to hand pick the features as I want the network to learn everything by itself.

There is an AI-Koan concerning this situation:

  In the days when Sussman was a novice, Minsky once came to him as he
  sat hacking at the PDP-6.

  "What are you doing?", asked Minsky.

  "I am training a randomly wired neural net to play Tic-Tac-Toe" Sussman
  replied.

  "Why is the net wired randomly?", asked Minsky.

  "I do not  want it to have any preconceptions of how to play", Sussman said.

  Minsky then shut his eyes.

  "Why do you close your eyes?", Sussman asked his teacher.

  "So that the room will be empty."

  At that moment, Sussman was enlightened.

Think about it.


What are the letters and numbers next to an opening's name on online services?

The Encyclopedia of Chess Openings (or ECO) is a classification system for the opening moves in chess.

Instead of the traditional names for the openings, ECO has developed a coding system that has also been adopted by other chess publications. There are five main categories, "A" to "E", each of which is divided into 100 subcategories.

Here is more info and related questions in case you are interested:

How are the ECO codes for chess openings assigned?

https://en.wikipedia.org/wiki/Encyclopaedia_of_Chess_Openings

Does ECO openings classification have an established more detailed specification - by sub indexes?

And this is the exact same code that you mentioned, covered in another source:

https://www.365chess.com/eco/C22_Centre_game_Berger_variation


How to play against the Allgaier, Horny Defense?

If you type your moves into Google it will actually find games that open that way.  It's quite cool. I use the move numbers as well as the actual moves.  Basically, a copy-paste of the first few moves.  Your game seems to be a ECO "C30".

For your Qh4+ question, I get this link.

The gist is you get this continuation:

[fen ""]
1. e4 e5 2. f4 Qh4+ 3. g3 Qe7 4. fxe5 d6 5. exd6 Qxe4+ 6. Qe2
Qxe2+ 7. Nxe2 Bxd6

And you really don't have a lot to worry about.  In the games in the link above, White developed easily, Black's pawn structure was smashed, and White won pretty easy endgames.


Why does FIDE rate women in different category?

First, let's clear up a misunderstanding.  Women and men are rated on the same scale, with the same formula.  A woman with a FIDE rating of 2400 can be assumed to be equally matched with a man with the same 2400 rating.  FIDE merely defines four titles that are only available for women.  In general, woman can and do participate in tournaments against men.  However, there are a handful of tournaments open only to women, including a Women's World Championship.

The reason for the tournaments and titles is obvious: some women want to participate in such tournaments, and some women appreciate the titles.  Chess is filled with reserved tournaments and not-too-prestigious titles of other kinds - this isn't a "woman-thing".  Every club, state, or national championship is a tournament which sacrifices strength and prestige to encourage the participation of a specific group.  The USCF has titles down to "4th Category", a title which requires hardly more than a heartbeat and a willingness to play in at least five tournaments, obviously to encourage tournament play among those still learning the game.  FIDE correctly calculates that having the WGM, WIM, WFM, and WCM provides motivation for some women and encourages them to improve their game and participate in tournaments.  Given that FIDE exists to promote chess among all populations, including women, providing these title is a no-brainer.

Damning women who participate in such tournaments or accept such titles is as ridiculous as complaining that the Canadian National Championship is tainted by the lack of Americans in the field or considering the USCF Candidate Master title to be a farce because it is easier to obtain than the FIDE Candidate Master.  There is no shame or fraud in competing for these titles, as the requirements are well-known and observers can easily understand exactly how much prestige should be attached to them.  Some of the strongest women players may disdain the women-only titles, but there are many male GMs who disdained their IM or FM norms.  You may choose to learn what you want from their examples.


There are two sections of the FIDE Laws of Chess which are relevant.

11.3.2.1 During a game, a player is forbidden to have any electronic device not specifically approved by the arbiter in the playing venue.

and

11.5 It is forbidden to distract or annoy the opponent in any manner whatsoever. This includes unreasonable claims, unreasonable offers of a draw or the introduction of a source of noise into the playing area

Use of a Kindle or other electronic book is governed by the first. You will have to get the arbiter's permission to read such a device during the game (or even to have it in the playing area) and this is unlikely.
For a traditional book printed on regular paper you just need to do it in such a way that it does not disturb your opponent (i.e. don't rustle the pages, put the book down noisily, etc.) as covered by 11.5. Although you would be well advised to talk to the arbiter first to clear the fact that the book contains no chess related material.
I have seen this done during FIDE rated league matches with no problems but not in large tournaments.


When to (and when not to) play Bxc6 (i.e. BxN) as White in Ruy Lopez?

It is just a matter of taste.  There are pluses and minuses to the move, but the strategic idea is gaining a better pawn structure.
I have played the Exchange 4.Bxc6; the Deferred Exchange 4.Ba4 Nf6 5.Bxc6; and the Double-Deferred Exchange 4.Ba4 Nf6 5.0-0 Be7 6.Bxc6.  All have unique flavors and Black has to know the ideas in each or risks a very bad game.
The Exchange variation was used with success by Fischer.


In my experience, memorization of chess games simply came from improvement. I first realized that I could remember the games of past tournaments when I was around 1600 ELO, and as I improved my visualization became sharper and I could recall games played years ago. My advice to you is to have the games notated and not just read, but play through them regularly. This repeated process of playing the moves of a game will help you retain the information necessary for you to recall the game in the future.


Shogi without Japanese characters (kanji)

I think a turn-based multi boardgame site called brainking supplies information which is close to what you want. http://brainking.com/en/GameRules?tp=69


Converting advantages such as a lead in development or a better position are practices that operate on a higher level (conceptually, at least) than tactics. The most common forms of tactics are those than result in the gain of material or a mating net, much more tangible results than say a weak square or an initiative. Pure calculation and a sharp tactical sense are important aspects of chess, but for the majority of the game they will be largely separate from positional play. Therefore, I would say that this is more supportive of your statement that it is a lack of understanding of principles rather than a weak tactical vision.

Let's address the specific examples that you outlined in your question. First, what does a lead in development entail? There is one main principle that you can utilize - initiative. The initiative is dictating the flow of the game. You can force your opponent to respond to your moves, allowing you to execute whatever plan you want while placing his own goals on hold. In such, it is common for positions where one side has the initiative for that player to launch an attack, given that the opponent is not adequately prepared.

If you can elaborate on the "slight positional advantage" (Minor piece difference? Pawn structure [backwards, isolated, doubled, hanging, passed]? Open files? Weak squares? Space? etc.) that you mentioned in the question, I can recommend other plans that are associated with the appropriate imbalances.


How could I have played this opening better?

Some thoughts, mainly about your opening (to be fair, this game jumped right from opening to endgame in short order):

Your first four moves are very good, taking control of the center while developing.
5. e5. General rule of thumb: If you have pawns adjacent to each other and well-defended, you don't want to push one of them (unless you have a good reason! And achieve something concrete with it, say, if you had a bishop on g5). The reason is that by doing so you lose a lot of flexibility. As a pair on the same rank, the pawns control a line of squares of both colors, with no obvious opening to attack by your opponent while at the same time retaining the potential of two different pushes by yourself as soon as you see an opening in the opponent's structure in return. If you move one of them without a clear target, you weaken your own line of defense (as you noticed yourself, the bishop diagonal is now open) and you also commit yourself to one attacking angle, which means that your opponent now doesn't have to worry about the other as much anymore (you cannot easily play d5, so your advance has essentially come to a halt and is not much of a threat to him anymore). Bg5 is a much stronger move here, Bd3 is fine too (development + protection of e4).
6. Nxd5. Actually makes a lot of sense, despite moving a developed piece a second time, as it offers a way to "repair" your pawn structure in the center. A pawn on c4 makes it only half as bad, since then the e4 pawn has regained hope of being mobile again with the support of his neighbour.
7.b3. But then you fail to execute that plan. Why not play 7. c4 straight away? The pawn will be defended adequately by your bishop on f1 and scare back the enemy bishop with a gain of tempo. Why do you need more support of c4? The only way black can attack it once more is by ...b5, and he cannot do so because of Bxb5.
8. Bd2. Makes sense.
9. a3. Allows Black to play 9...Bxf3 10. Qxf3 Bxd2+ and you are forced to retake with your king and strand it in the middle of the board behind a less than optimal pawn structure. Lucky that he played it the other way around.
Moves 10 & 11 are obvious.
12. O-O-O. Not the best choice, in my opinion. Your kingside might look just as weak as the queenside, but the doubled pawn actually offers some interesting possibilities, too. Many pieces have been exchanged already, so you don't actually have to worry about your king's safety after castling short: Bg2 fills the gap nicely (and can exploit the long diagonal where Black is actually weak now that his bishop is gone) and Black cannot bring in more pieces other than the queen anytime soon. Your f-pawn can support e5 from f4 to keep the center closed so that this stays this way and it may even attack on f5 in the future. You, on the other hand, might be able to use the half-open g-file to threaten his king. Black's counter plan will be to open files for his rooks. As this will happen on the queenside or center, castling long happens to have moved your king into future lines of fire. h1 would have been a much safer place to hide.
13. h3. Kinda unnecessary at this point in time, but it's alright, you want to make the rook more mobile.
14. exd6. Obviously, following my commentary on move 12, I don't like this move either. En passant looks fancy and all, but I think your strategy at this point should be to keep the center closed and use your (small, but hey) advantage on the kingside before he can break through on the queenside.
Rest of the game, in short, as it doesn't really concern the opening anymore: After opening the center, his rooks can join the fight, and your inferior pawn structure quickly shines through. Castling long proves to be absolutely inefficient in terms of king safety because of said whole-y structure.


Does this opening have a name? 1. e4 e5 2. Nf3 Nc6 3. d4

It is a Scotch Game. It was played a lot more in the 19th century than in the 20th or early 21st.

"Nowadays," it is considered to be too "easy" on Black, because it offers the early exchange of a pair of pawns and knights, thereby freeing Black's game. Also, the White queen ends up in the middle of the board, where it might end up being chased by Black's pieces.

White does have a microscopic advantage in ending up with a king pawn in the center. Also, the queen in the middle of the board hampers the development of Black's kingside.

For those who like to develop queens early, this is a good game. The exchange of one pair each of knights and pawns greatly reduces the chances of the white queen's being trapped.

What is the best way to free your queen as soon as possible?


The terms are a bit loose. To quote from Wikipedia:

  In chess, the word "piece" has three meanings, depending on the context.

  1) It may mean any of the physical pieces of the set, including the pawns. When used this way, "piece" is synonymous with "chessman" (Hooper & Whyld 1992:307) or simply "man" (Hooper & Whyld 1987:200).

  2) In play, the term is usually used to exclude pawns, referring only to a queen, rook, bishop, knight, or king. In this context, the pieces can be broken down into three groups: major pieces (queen and rook), minor pieces (bishop and knight), and the king (Brace 1977:220).

  3) In phrases such as "winning a piece", "losing a piece" or "sacrificing a piece", it refers only to a bishop or knight. The queen, rook, and pawn are specified by name in these cases, for example, "winning a queen", "losing a rook", or "sacrificing a pawn" (Just & Burg 2003:5)

Source: Wikipedia, emphasis is mine.

From the same article, the term pieces to include pawns has been noted since the late 1980's. Speculating, it may be that commentators did not see the need to distinguish between the terms pieces and men, hence coming into common use. For example, Josh Waitzkin's tutorials in Chessmaster, first made in the 1990's, use the term pieces instead of men. I've seen terminology become more lax over time, e.g. pieces being 'killed' instead of 'captured'.

As for other languages, I am unable to say I'm afraid.


According to this question on quora.com, there are ~486,000 players as of January 2015.  (They reference a FIDE rating list here.)  Not an exact number, but most likely close enough for percentile purposes.

If you're not sure how to calculate a percentile rating, I found this question, which gives the following formula:

R = P / 100 (N + 1)

... where R represents the rank order of the score, P represents the percentile rank, and N represents the number of scores.


Openings Recommendations to Study for Unrated Tournament

I would personally stick to learning a few e4 and d4 variations and maybe the English Opening, though I didn't see it much at lower level play. I am also adding some fun, fairly solid variations if you wanted try the more obscure openings

Ruy Lopez
1. e4 e5
2. Nf3 Nc6
3. Bb5

A personal favorite of mine, especially the Rio Gambit Accepted line 1.e4 e5 2.Nf3 Nc6 3.Bb5 Nf6 4.O-O Nxe4, but in general it can create early control of the center and can lead to a strong position with an active bishop or forcing black to double pawns

Not my preference, but I used to see a lot of the Giuoco Piano

e4 e5  2. Nf3 Nc6  3. Bc4 Bc5

and the Giuoco Pianissimo

e4 e5  2. Nf3 Nc6  3. Bc4 Bc5 4. d3

I wouldn't stress studying this one

Sicilian Defense
1. e4 c5

It's rare for me not to see this opening.

Sicilian Sveshnikov
1.e4 c5
2.Nf3 Nc6
3.d4 cxd4
4.Nxd4 Nf6
5.Nc3 e5
6.Ndb5 d6.

It gives a menacing knight position to white, but allows you to prepare your pieces for development and gains a general grasp in the center

Sicilian Dragon
1. e4 c5
2. Nf3 d6
3. d4 cxd4
4. Nxd4 Nf6
5. Nc3 g6

Can create very aggressive and constricting pawn marches for white and a fianchettoed bishop and free queen for black. This is very aggressive and loads of fun to play

English Opening
1. c4

A very flexible and reliable opening if you are well studied into it.

King's Gambit
  1. e4 e5  2. f4

A sacrificed pawn for quick development. What's not to like

A few others you could also look into are the Pirc Defense, Indian-Defenses, Queen's Gambit, Caro-Kann


Is Bg4+ good in this position in the Alekhine Defense?

[FEN ""]
1. e4 Nf6 2. e5 Nd5 3. d4 d6 4. Bc4 Nb6 5. Bb3 Nc6 6. Bf4 dxe5 7. dxe5 Qxd1+ 8. Kxd1, Bg4+ 9. f3 Bh5 10. g4 Bg6

I think that the position after 10...Bg6 is better for black. The white bishops are not collaborating very well. In fact, the white bishops are virtually useless at the moment. In addition, the white king needs to make a couple of moves to find a reasonable position, if it will find it at all.

Black wants to play O-O-O, e7-e6 and h7-h5. White could very well become crushed here. I think that 6.Bf4 was not the best choice for white, 6.e6 or 6.exd6 should be better.


Analysis of Viswanathan Anand vs Vladimir Kramnik in the 2013 Zurich Chess Challenge?

I'm no pro but I can offer my (potentially incorrect) thoughts.

  I always hear that you should capture toward the center, so was there
  a reason why Kramnik played 5..dxc6 instead of 5...bxc6? I know
  5...dxc6 opens up the file for the black Queen, but that is all I see.

Black gains development of both the queen AND the bishop. It's a free tempi which is important in the early game. I personally choose that much more often than taking with the Knight's pawn.

  Is the point of 6. Nbd2 to develop a piece and to add another defender
  to the e4 square?

Doubt it for e4 nothings bugging that square for a while. I think he wanted to attack e5 or just develop the knight in a fashion where the black bishop couldn't exchange for it?

  Apparently Anand sees his dark squared bishop not as strong and wants
  to trade it withKramnik's dark-squared bishop with the move 11. Be3,
  but Kramnik wants no part of this and rejects the trade with 11...Bb4.
  Can someone elaborate on why Anand wants to trade bishops here and if
  it was good or bad for Kramnik to reject the trade?

I can provide two reasons. If Kramnik takes then white gets to open the file for the rook and has an extra pawn to cover the center. If Kramnik allows Anand to take he has a triple pawn stack. He doesn't like either scenario so flees.

  I don't get the move 12. Nfd2 except that it adds a defender to c4 and e4?

Blocks the bishop pressure on D1, allows white to pressure king side threatening the development of the King's Bishop pawn (which possibly explains the king move as well if he was intending to do that for a while) and the queen.

  Rxa6 surprised me as a beginner.... Was my analysis correct?

I think so. I'm thinking its the game winning move. It's a fork btw. A skewer is like a pin but the piece of greater value is the first attacked in the line.

The resignation might be to do with his lack of options for dealing with the A pawn. He can't immediately take it due to the potential fork by the knight and white has options to both push and defend it. The only long term solution is to blockade it with one of his pieces and all his pieces are expensive. A blockade would then leave him with a queen and a rook against a queen a rook and either a bishop or a knight on the rest of the board.


How do you manually set switches when you are compiling Stockfish in Visual Studio?

This question should be in programming.

These can be put in a top h file, the best being stdafx.h.  Just include "#define DNDEBUG",

They can be added to the command line/compiler commands.  Under VS6, Project->Settings (Alt+f7), there is a box to add project settings under the c/c++ tab.


Could I have improved my position in this pawn up exchange Slav?

Your play was good, and you managed to slowly gain the upper hand from the more or less dead equal opening.  At the end Rxe3 is forced, but after Qd2 I would have definitely considered Re4.  You actually don't lose the exchange:

25... Rxe3 26. Qd2 Re4 27. Nc3 Rc4!

Now at this point you're threatening to take on d4, so 28. Nxe4.  But then you take back on e4 with your g3 Knight and you have White's Queen and Rook in a fork.  You are winning back the exchange and are a pawn ahead.

Overall you played a good game.


What are good UCI-compatible GUIs for Mac?

Wow, I usually wouldn't add another answer like this, but I've been quite impressed by the fork of Scid called Scid vs PC (which is more actively maintained, and has a mac distribution called Scid vs Mac). I found it while looking for mac build instructions for Scid while trying to make scid do a better job of processing stockfish's input. (and by the way, Scid vs PC doesn't fix the stockfish 2.2+ problem, as it still depends on the tcl one line at a time input parsing).


Both 5.Bb5 and 5.Bg5 are reasonable here. Lichess wasn't running multiple move analysis, but it didn't mean the move 5.Bg5 was bad.

5.Bb5 doesn't lose a pawn as 5...Nxe4 6.dxe5 dxe5 7.Qxd8+ Kxd8 8.Bxc6 bxc6 9.Nxe5 is better for White.


What are must read chess books every chess player has to read to become an Expert Class?

Some favorites:

Secrets of Modern Chess Strategy
My 60 Memorable Games
The Life and Games of Mikhail Tal
My System
Fire on Board

These books are all famous and very good.

Books by Nunn, Aagaard, Dvoretzky or Yusupov are recommended, though you have to be careful to find those suitable for your level.

The Polgar trilogy is very good and there is an upcoming series by Boris Gelfand. Two absolute top players, but nevertheless very accessible books.

Metachess: I really liked The Seven Deadly Chess Sins and Move First, Think Later.

Still, although I always read a lot of books, I would maintain that playing a lot of tournament games against stronger players is far more important.


xboard is not a UCI user interface, so you'll need to install the Polyglot adapter to make it work. Once you have the Polyglot installed, you'll need to edit the polyglot.ini file. Read here for instructions on how to do it.

Please note Polyglot is not a very professionally made software. You'll only be able to find some old documentation. The whole process is quite technical. If you don't want to spend the time, you might as well consider other user-interfaces.


How do I play against this kind of position with double c pawn?

ad 1: Partially, yes. Ng6 is a good move but it will get surely met by white's g3. That's natural. Still u want to move your knight from f8, this square is for your rook.

ad 2: Of course c5 was a good move. You played the opening correctly!

ad 3: Yes, the natural plan is to prepare f5 break. Something like Ng6, Rf8, Nh7, f5

ad 4: I would say rather equals. White has pair of bishops but c-pawns might be an issue later on. Good position to evaluate players' strength. Good luck!


After playing around in the Lichess's analysis page for some time, I have found a mate in 10. Throwing the moves into chess.com's analysis page provides further confirmation. It has some wholly unique lines, and only a few dualed lines, making it reminiscent of a chess problem, per @Hauke Reddmann's above comment.
[FEN ""]
[Title "#10 After 3 Moves"]

1. e4 d5 2. h3 Kd7 3. Bb5+ Ke6 {Now the helping play is over.} 4. Qg4+ Kd6 5. e5+ Kc5 6. b4+ Kxb5 7. a4+ Kb6 8. a5+ Kc6 9. b5+ Kc5 10. Ba3+ Kxb5 11. Nc3+ Kc6 12. Qa4+ b5 13. Qxb5#


Does swapping the colors of the squares affect the gameplay?

The only difference would be that the players would be playing a mirror image of a normal game.  In fact, if you think about it, the play would be exactly like allowing Black to go first on a normal board.

I don't think this would seriously phase any level of player, simply because good players are able to calculate well enough to cope with the slight change, and bad players don't strategize properly even on a normal board, so it wouldn't make a big difference for them to swap the king and queen.

Intermediate players might be put off a bit, since they may have memorized certain openings which are slightly changed on this new board, but I think the biggest thing to watch out for would be outright forgetting that the King and Queen are swapped and playing accordingly (e.g. accidentally exposing your King, thinking you're opening lines for your Queen).  As long as that can be avoided, I think any "psychological" effects are quite minor.


Is it possible to castle with checkmate?

I can think of two questions you might be meaning to ask, given the wording of your question. Maybe neither of these is what you're after, but just in case:

1. Is it possible to castle out of check or even checkmate? Here the answer is no. If your king is in check, then castling is not a legal move.

2. Is it possible to castle while checkmating your opponent? Here the answer is yes, it is possible, though it does not happen often. For instance, the game Ed.Lasker-Thomas (1912), with its famous queen sacrifice and king hunt, could have finished with a castling mate:

[fen ""]
1. d4 e6 2. Nf3 f5 3. Nc3 Nf6 4. Bg5 Be7 5. Bxf6 Bxf6 6. e4
fxe4 7. Nxe4 b6 8. Ne5 O-O 9. Bd3 Bb7 10. Qh5 Qe7 11. Qxh7+
Kxh7 12. Nxf6+ Kh6 13. Neg4+ Kg5 14. h4+ Kf4 15. g3+ Kf3
16. Be2+ Kg2 17. Rh2+ Kg1 18. Kd2# (18.O-O-O#)1-0


3. Bc4 is one of those fairly regular moves that defer the opening selection of the Scotch Gambit (1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4) and the Danish Gambit (1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4). 3... Bc5? is a well-known mistake because of the Bxf7+ followed by Qh5+ sequence.
That's why Black's move is normally 3... Nc6 or 3... Nf6.


As you noticed there are very few games in the database with this line. That's why it does not make much sense to speak of "more common"/"infrequent" response here.

The move 2. d5 is not good, but not so bad that you can expect to get a huge advantage as black soon. Basically it gives away the first move advantage and gives black an equal position for free. Generally, if your opponent plays an unusual move like this to which you don't see an immediate refutation, stay calm and make normal moves.

Problems with 2. d5 are:

it neglects development (don't move a piece twice if you don't have to)
it weakens the dark squares in the centre
it does not do much; Typically a pawn push like this is meant to limit the opponents options. Here it prevents the knight going to c6, however the knight rarely wants to go to c6 in these kind of openings. Also black has not fixed the position of its central pawns so is free to attack the pawn at wish with c6, e6 ...

Your opening repertoire or your preference for closed vs open positions might influence your decision on how to respond to it.

If you are a King's Indian or Benoni player you could for instance transfer this to a main line King's Indian or Benoni. Or just go for a fianchetto on g7 first, trying to take advantage of the weakened dark squares and don't fix your central pawns yet.

If you don't mind unknown territory, 2 .. c6 seems like a good choice questioning the pawn immediately  and giving you tactics with Qa5+ (and attack on d5) in some lines.

But any other continuation such as 2 ... e6, d6, e5, g6,.... can't be wrong either. I don't understand why you think that e5 was bad. The position you achieved seems quite normal to me.


Draws by game number in championship matches

I am not aware of a study of this kind, but why not make our own? Let us parse some WCC PGNs!

To me, this does not seem to have any definite regularities for when a draw is more likely (also note, that at the very high number of rounds, only a few games are available - there have been only a few very long WCC matches).

EDIT

Recent events only. Looks like more draws overall and slight tendency for more draws towards the end of a match.


Why doesn't SimpleEval's eval change in multiples of 1?

I took a peek at the code given in a comment. It seems to have a small semi-random factor added to the evaluation, probably so it can more easily just pick a move from all the ties that are going to come up. However, the size of the score difference appears to be greater than what could be explained by just this. Also, at move 65 it evaluates the position as -M3 but there is clearly not a mate in 3 from that position.
The false mate clearly shows that there is a bug somewhere.


What's wrong with 4...e5 in the Open Sicilian?

After 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 e5 5.Nb3 Nc6, the position is probably fine for black.

However, after 4....e5, white seems to have a stronger reply: 5.Bb5+. According to the Game Database of ChessTempo, this is also the most popular move. Now, black has two options: 4....Bd7 or 4....Nd7. After both moves, white can put his knight on f5 and obtain a slightly better position.

Therefore, I would say that 4....e5 is a small inaccuracy. However, the ideas behind the move (occupying the center, gaining a tempo) are perfectly fine.

Maybe it is interesting to take a look at:

the Sveshnikov variation: 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 e5
the Kalashnikov variation: 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5
the Classical variation: 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6, and after 6.Be2, 6....e5
the Najdorf variation: 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6, and after 6.Be2, 6....e5

      [FEN ""]
      [StartPly "3"]

      1.e4 c5 2.Nf3 d6 (2...Nc6 3.d4 cxd4 4.Nxd4 Nf6 (4...e5) 5.Nc3 e5) 3.d4 cxd4 4.Nxd4 e5 (4...Nf6 5.Nc3 a6 (5...Nc6 6.Be2 e5) 6.Be2 e5) 5.Bb5+ (5.Nb3 Nc6) 5...Nd7 (5...Bd7 6.Bxd7+ Qxd7 7.Nf5) 6.Nf5


I'm not a long time member here but I was pretty sure that question regarding this opening will show up. First of all, this kind of defense is really great against weaker players, let's say <1800, who don't know how to place their pieces/how to maneuver properly. By doing this, black dodges theoretical conversation, which can be pretty desirable. Since you gave us only two moves of black g6 and b6, I can't provide you lines or variations, no point to consider all possible setups of black pieces. If you want - share a game with us, I'll be glad to point out not-the-best moves. For now I can only give you few tips:

Avoid playing Bd3 and Be3. That's too squeezed. The light-squared bishop should be placed on c4 in most cases. (I assume black plays e6 and d6 not d5. (See, you should be more precise!:)).
You can wait to develop the dark-squared bishop a bit. g5 might be a nice spot occasionally.
As "waiting moves" to use above, you can castle, or play Qe2.
When your opponent plays a6 consider responding with a4 to avoid some b7-b5-b4 followups.
And the most important: do NOT hurry here. Don't go all in too early, in such set-ups black has an easy counter-attack in the center once you commit to go all in on a side. It's serious. I saw many people losing games due to immediate attacks like Be3, Qd2, Bh6, h4 and stuff.


Why ...g6 before ...Bxa6 in the Benko Gambit?

No, there are no real differences between the 2 lines. White has no way to defend the pawn, so black can choose the move order they feel most comfortable with.

You see something similar in the french defence:

[FEN ""]

1. e4 e6 2. d4 d5 3. e5 c5 4. dxc5 Nc6

Black could have regained a pawn straightaway with 4...Bc5, but decided to develop a knight first, seeing as white has no way to defend that pawn.

Edit

I found this explanation of 5...g6 on wikipedia

  The main line continues with the moves 4. cxb5 a6 5. bxa6 Bxa6 followed by Black fianchettoing the f8-bishop. (Black players leery of the double-fianchetto system, where White plays g3 and b3, and fianchettos both bishops, have preferred 5...g6 intending 6.b3 Bg7 7.Bb2 Nxa6! The point is that it is awkward for White to meet the threat of ...Nb4, hitting d5 and a2, when Nc3 may often be met by ...Nfxd5 because of the latent pin down the long diagonal.)

The double fianchetto has fallen out of favour seeing as the king's walk variation gives a good game for white.


It means one of the players resigned or lost on time.  In the game above, White threatens mate on g6 if the black Queen can be deflected from its defense. So White threatens Qxe8 followed by Qxg6#.  If Black plays 37... Qf7, White responds with Qxd7 which threatens the Black Queen and a potential mate on g7. It's a mess that at best ends up with Black being down a ton of material.


How do chess players keep records of their previous games?

There's a plethora of chess software that support saving, querying and updating games played. From the commercial ChessBase to open source equivalents like SCID on PC, ChessX and Tarrasch. They all support database facilities that allow games to be added, searched by tournament, player, position, pawn structure, opening, in some cases even by tactical motif and strategic themes. And with plugins for various chess engines, analysed and blunder-checked.
For a player's own games, if the tournament is run by a good set of arbiters, then the games will make their way to The Week In Chess weekly chess databases that a player can download and open in their chess database software. Players can also enter their own games into their personal chess databases that can be queried, searched, analysed and dissected in the very same fashion.
For online chess playing sites, player's games can be downloaded individually or as a collection and opened in their chess software.
These chess databases and their software are flexible enough to create subsets or aggregates of other chess databases, so a player, or trainer, can typically create their own personal/private databases formed of games or positions that meet their training needs.


Multiple teams from the same country in Swiss system

There is a tradeoff between making the pairings that "should" be made according to the strict pairing rules, and attempting to prevent collusion.  Imagine this scenario:

Russia 1: 8.5
Russia 2: 8
India:    8
Peru:     7.5

Which is more unfair: to have Russia 1 play Russia 2 and have a possible prearranged result, or to prevent Russia 1 and Russia 2 from competing, causing Russia 2 to play a team with a lower score instead of the strong Russia 1 team?

There are several ways to handle this.  You could switch the pairings only when it does not cause a team to be moved up or down a pairing group. You could switch the pairings in any round except the last two. Or you could not switch them, and watch closely for signs that the players aren't playing seriously.


Biggest Possible Material Advantage But Still Losing

[FEN "QQQQQbBk/QQQQQBQB/QQQQQRBK/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ b - - 0 1"]

1... Bxg7

I'm getting +518 for this.

That could be improved to +520 if we allow a black pawn on the 8th rank instead of the bishop, since this position is obviously already impossible for a number of other reasons.

Edit:
Found a better one.

QQQQQQNk/QQQQQQNp/QQQQQQKN/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ b - - 0 1

This is +530.


How do convert/parse/extract data from a PGN into a spreadsheet/google sheet/excel file?

How do I get this data into a spreadsheet like column 1 is all the dates, column 2 is the corresponding white elo, column 3 black elo, col4 white username and col5 black username?

From the .pgn file downloaded at
https://api.chess.com/pub/player/gmwso/games/2020/12/pgn
I have created a file called chess_games.xlsx and I have inserted the five values you are asking using a python2 script. You need to install chess and openpyxl libraries with pip. The .pgn file is read as a long string.
import pgn
import openpyxl
import os

pgn_text = open('ChessCom_gmwso_202012.pgn').read()

dates = []
welo = []
belo = []
white = []
black = []

whiteLong = []
blackLong = []

def getValues(file):
    test_str = file
    test_date = "[Date"
    res1 = [i for i in range(len(test_str)) if test_str.startswith(test_date, i)]
    test_welo = "[WhiteElo"
    res2 = [i for i in range(len(test_str)) if test_str.startswith(test_welo, i)]
    test_belo = "[BlackElo"
    res3 = [i for i in range(len(test_str)) if test_str.startswith(test_belo, i)]
    test_white = "[White "
    res4 = [i for i in range(len(test_str)) if test_str.startswith(test_white, i)]
    test_black = "[Black "
    res5 = [i for i in range(len(test_str)) if test_str.startswith(test_black, i)]
    for i in res1:
    dates.append(test_str[i+7:i+17])
    for i in res2:
        welo.append(test_str[i+11:i+15])
    for i in res3:
        belo.append(test_str[i+11:i+15])
    for i in res4:
        whiteLong.append(test_str[i+8:i+43]) //The max length of a nickname in chess.com is 35 characters
    for i in res5:
        blackLong.append(test_str[i+8:i+43])
    for value in whiteLong:
        posClose = value.find("]")
        white.append(value[0:posClose-1])
    for value in blackLong:
        posClose = value.find("]")
        black.append(value[0:posClose-1])

def generateExcel(dates,welo,belo,white,black):
    file = 'chess_games.xlsx'
    if os.path.isfile(file):
        wb = openpyxl.load_workbook(filename=file)
    else:
        wb = openpyxl.Workbook()
    ws = wb["chess_games"]
    for k in range (len(dates)):
        ws['A'+str(k+1)] = dates[k]
    for k in range (len(welo)):
        ws['B'+str(k+1)] = welo[k]
    for k in range (len(belo)):
        ws['C'+str(k+1)] = belo[k]
    for k in range (len(white)):
        ws['D'+str(k+1)] = white[k]
    for k in range (len(black)):
        ws['E'+str(k+1)] = black[k]
    wb.save(file)

getValues(pgn_text)
generateExcel(dates,welo,belo,white,black)

Download the output .xlsx file


Why does this puzzle offer f8=R as better than f8=Q?

If anything, promoting to a queen is the better choice, as it forces Black to exchange their rook. For promoting to a rook, Stockfish NNUE actually slightly prefers moving the f5-rook away instead of playing ...Rxf8 (although any continuation gives White a large winning advantage). So at the very least Black is given a choice.
But even if we were certain it's best for Black to play ...Rxf8 if White promotes to a rook, there would still be no reason to say that promoting to a rook is better than promoting to a queen - both lead to the same outcome. What possibly happened is that the site's computer calculated one line further/differently, and arrived at an evaluation that was higher in the line for promoting to a rook. Although since you said the site allows multiple solutions to sometimes be accepted, this seems like a bug in their software.


Where can I get a reliable and user-friendly, but not extravagant, chess clock?

I just saw you asked this couple of months back but adding my answer if others are looking for something in this price-range.

Do you have an iPhone? There are chess-clock apps which are pretty good. This is only for home games, as you don't want the other player scratching too much on your iPhone screen.

You should also search eBay. They are the best bet for low-prized yet pretty good digital chess clocks. Don't buy the cheap analog clocks as they have inherent problems and I have thrown away couple of them before switching to digital clocks. Always compare prices at Amazon before bidding on eBay.

Note: Digital clocks outweigh the cheap analog clocks by miles for under $25.

Pleasing displays
Lots of options for your game (e.g. extra seconds added for each move if you want it).
More lifetime than analog clocks at this price range (fewer mechanical problems).
Their only drawback is they need batteries.
Some digital clocks require little knowledge of how to set the clocks, but reading the manual helps and it is not very complicated.

Lots of good digital chess clocks on eBay (used/new; make sure it is listed as working) and Amazon. Good Luck.


You can use the first 64 bits to encode which squares are occupied, and then encode what's in the occupied squares one by one, using four bits per square for up to 32 occupied squares.
The four bits allow sixteen possible piece types. There are only twelve types of pieces, but this lets us get in some additional necessary information. Here's an example encoding scheme.
0 - white pawn
1 - black pawn
2 - white knight
3 - black knight
4 - white bishop
5 - black bishop
6 - white rook that can't be castled with
7 - black rook that can't be castled with
8 - white rook that can be castled with
9 - black rook that can be castled with
A - white queen
B - black queen
C - white king if white has the move
D - black king if black has the move
E - the king that doesn't have the move
F - a pawn that has just advanced two squares
This should be enough to specify the position (piece locations, player to move, castling rights and en passant, but not fifty-move counter or move number).


Software suggestions to make printed chess exercises for kids

Possible ideas I found when I asked the question on Reddit r/chess

Chessbase + Wordprocessing tool
Lichess + Evernote clipper (or snagit, etc) + Word (Add +blog if you want the answers to be public)

Other useful links that were suggested as comments

Apronus Pgn viewer/editer
Free chess diagrams list


Is there any UCI engine that presents DTZ information from syzygy in analyse mode?

Stockfish has an undocumented, non-standard command "d" which prints, among other things, the DTZ value. Some interfaces, for example, Arena, let the user give commands to the engine manually.


King's indian attack vs defense relationship

They are indeed similar in some ways; as you have noted, the kingside structure that gives the variations their names are identical to each other, and there are some similar themes, such as a kingside attack.

A comparison between them provides a great example of the general difference between White openings and Black openings. Black in the King's Indian Defense has to be very precise and constantly runs the risk of falling one move behind White with potentially disastrous consequences. On the other hand, because White started with the advantage of the first move, when he plays an initially restrained setup like the King's Indian Attack, all he is doing is ceding some of that first-move advantage, and the game does not balance on a knife-edge as much (until maybe later!).

For this reason the two openings proceed along quite different paths, and expertise in one does not necessarily translate to the other.

(To answer the nomenclature question: Indian in chess opening terminology tends to indicate a fianchettoed bishop (one on g2, g7, b2, or b7); the King's part means that the fianchettoed bishop is the one on the kingside; and Black openings tend to be Defenses while White openings can be Attacks.)


What is the most queens that have been on the board in a grandmaster game?

This sounds like a job for Tim Krabbé, who presents two games with six queens: Szalanczy - Nguyen, Budapest 2009 and Anton - Franco, XXI Elgoibar Magistral 2011. I don't know how many of the participants were grandmasters.

There are some other games with 5+ queens at Chess Siberia. Of these, Miton - Benjamin, World Open Philadelphia 2005 definitely features two grandmasters.


How can the moves from this pawn endgame study be found without a computer?

Some of the corresponding squares are quite easy to work out, especially if you write things down (not allowed in a real game).

First of all, it is clear that

a5 corresponds to c6.

Black can move from c6 to g4 in 4 moves. The only square that stops black's invasion and is 4 moves away from a5 is e2, so

e2 corresponds to g4.

The squares on the paths in between need to correspond, so

b4 corresponds to d7,

c3 corresponds to e6,

d2 corresponds to f5.

It then follows that

b3 corresponds to e7,

c2 corresponds to f6,

d1 corresponds to g5.

Hence,

b2 corresponds to f7,

c1 corresponds to g6,

b1 corresponds to g7.

The trickiest part is to show that a3 corresponds to e8. When the black king is on e8, it threatens to go to d7, e7 or f7, corresponding to b4, b3 and b2 for white. Therefore the white king needs to be on a3 or c3, but c3 is the wrong square. Why? Because after a subsequent Kd8 move form black, white would be in zugzwang. Black can still go to d7or e7, so white needs to go to a square adjacent to b4 and b3. Such a square is not available from c3.

So,

a3 corresponds to e8,

and therefore

a4 corresponds to d8,

a2 corresponds to f8

a1 corresponds to g8.

Now the solution can be explained. In the diagram position Black can go to g6, g7 or g8, so white needs to have c1, b1 and a1 available. Therefore 1. Kb2!


I have the same problem, and I think it's caused by two factors:
1- Bad time management.
2- Taking the games (win, loss) and rating seriously.

It happens to me that when I am winning and then I lose on time. I keep thinking of the game, even after I close the app. It's because I keep thinking that I should've played faster here or there. When I lose due to bad position or blunders, or if the position was equal, I run the analysis and keep thinking of the missed chances to win.

I did like what you did. It's been a week or so that I haven't played chess games. I only solve puzzles and do lessons. No online full games. This keeps my mind working (refreshed by the distraction of a different activity) and I don't have to think of what went wrong!


In ChessBase 12, when viewing an Opening Tree, why do all the games always stop near move 26?

"Move 26" (or thereabouts) is the "midpoint" of most chess games.

Your opening tree application appears to working fine in getting you to the  peak or "combustion point" of most games. (That seems to be its purpose.) From there, it's mostly downhill.


Guarding my seventh rank and a king walk assualt

White was slightly better after 23.Rd7. This is one of those cases where you should have gone for activity with 23...Rcd8! Now, if he just doubles with 24., you can trade and then play Rf7; or if 24.Ra7 then Rd3 with active counterplay and better chances, but white is still better.

That said, the reason you won is that white knows nothing about the endgame, and tried to mate you with h4 and g4, and that is not what the position called for. He only weakened his position, and improved your K since there was not going to be any mate on g4 or e4. It required a gradual improvement of the white K, and then the gradual advancement of the q-side pawns.

By the time you started advancing e5-d4, that was generally the right plan, but you should have started with 36...f5 first so the pair could not be blockaded with Rf4.

In any case, you were already cruising by then.


How many legal but unreachable positions exist?

The fraction of all six-man positions that are unreachable from the starting position is very, very small. Removing them would have a tiny effect on the size of a six-man database.

Here is an example of how rare these positions are. First of all, we can't get into one of these unreachable positions without a bishop and a pawn, so we already have a small subset of the number of total six-man positions. But okay, say that one side is lucky enough to have one pawn, one bishop, and a king. The bishop will have to be in one of its own corners (not the far corners!) and the pawn will have to be diagonally adjacent to it. So only 2 out of the 64 bishop positions could lead to a trapped bishop, and out of those, the pawn has to be in the one spot of its possible 48 positions that would trap the bishop. So even if you have one pawn and one bishop, which is pretty unlikely, the chances of randomly getting an unreachable position are only (2/64) * (1/48) = 1 in 1536.

Let's do one bishop, two pawns, and a king just for fun. If the bishop is in its own corner (2/64 chance), the chance of getting one of the two pawns in the diagonally adjacent square is 2/48 (2 of the 48 squares in ranks 2 through 7 have pawns in them). If the bishop is one of the other spots on the first rank (4/64 chance - c1 and f1 are definitely OK!), both pawns have to be in exactly the right spot (1/48 * 1/47) chance. When I do the math I get a chance of around 1.33% for getting an unreachable position even if you start with this very unlikely great combination of material for generating unreachable positions.

My conclusion, as first predicted in my comment above and now backed up by some math, is that these unreachable positions are an extremely small subset of the set of all six-man positions.


Is it possible for a white piece to deliver check to the black king, but for black's counter move to result in white getting checkmated?

You can find some examples in the following game collection: Games where check is answered with checkmate.

Among those games, Nigel Short vs Alexander Morozevich, Russia - The Rest of the World (2002) is the only one that meets the qualification top players. This was a rapid game.

The most entertaining example is the following:

[FEN ""]
[Event "Philadelphia (m/7)"]
[Site "Philadelphia (m/7)"]
[Date "1945.??.??"]
[Result "0-1"]
[White "NN"]
[Black "Winkelman"]
[ECO "C29"]

1.e4 e5 2.Nc3 Nf6 3.f4 d5 4.fxe5 Nxe4 5.Qf3 Nc6 6.Bb5 Bc5
7.Nxe4 dxe4 8.Qxe4 O-O 9.Ne2 Re8 10.Bxc6 bxc6 11.Qxc6 Rxe5
12.Qxa8 Rxe2+ 13.Kd1 Bg4 14.Qxd8+ Re8# 0-1

There are also some additional examples in Edward Winter's Chess Notes: 4130, 4135.


Please help solve this endgame problem posed by a friend

White is one tempo short of catching the pawn - if White could make two moves immediately it would be a draw as white would just take the black pawn. But they can't, so white has to find a threat which black has to respond to which gains them that move. The only threat they can make is to queen their pawn, and apparently black can stop that with their bishop by moving it to b5. But ... if white can combine moving their king toward the queening square with attacking the bishop, and hence threatening to queen the white pawn, they can gain the tempo. This suggests moving the king towards the queening square via c5, because the king on c5 can attack a bishop on b5 that is stopping the white pawn queen. At that point Black will have to move their bishop or protect it, and white gains the tempo they need. Putting this together leads us to the following - note the move order also means that the black pawn interferes with the Black Bishop's movement, stopping it get to h5 which would be the other square it could use to stop the white pawn queening

[Result "1/2-1/2"]
[FEN "5K2/k7/4P1p1/8/8/8/4b3/8 w - - 0 1"]

1.Ke7 g5 2.Kd6 g4 3.e7 Bb5 4.Kc5 Ka6 5.Kd4 g3 6.Ke3 g2 7.Kf2 Bc6 8.e8=Q
Bxe8 9.Kxg2 1/2-1/2

If you like this kind of thing have a look at The Reti study which is a more famous relation of this problem. It also turns out that this problem was composed by Reti himself.


Black Lion opening plans for White's 5. Bc4 line

The first thing to note is that 9. h3 is a minor mistake if your intention is to play a queenside attack. It is a diversion from your plan. It would make more sense if your plan were to attack through the center with moves like Qe2, Be3, Rd1, de, etc. In that case it would create a safe spot for the bishop on e3 by denying g4 to the black knight. All h3 is does in the plan you play is to accelerate the black kingside pawnstorm by creating a pawn lever for a later black g4.
Instead in the final position above follow Jonathan Rowson's advice and "talk to your pieces". In particular the bishop still at home on c1. Why are you attacking before you have completed your development? Particularly why are you attacking the opposite side of the board to where the enemy king is? Find a plan which involves completing your development by finding a square for the c1 bishop.
One suggestion would be to follow a plan played by Aron Nimzowitsch 100 years ago which involves fianchettoing the c1 bishop with threats of a knight sacrifice on e5 if black plays Nf8. Here are the moves up to where he has a big advantage:
[title "Nimzowitsch - Marco, Gothenburg 1920"]
[fen ""]

1.e4 e5 2.Nf3 d6 3.d4 Nf6 4.Nc3 Nbd7 5.Bc4 Be7 6.O-O h6 7.a4 c6 8.b3 Qc7 9. Bb2 Nf8? (9...g5! 10. Re1 Rg8 11. dxe5 dxe5) 10. dxe5 dxe5 11. Nxe5 Qxe5 12. Nd5 Qd6 (12...Qxb2 13. Nc7++) 13. Ba3 (13. e5 Qxe5 14. Re1 Ne4 15. Rxe4 Qxe4 16. Nc7++) cxd5 14. Bxd6 dxc4 15. Bxe7 Kxe7 16. e5 N6d7 17. Qd6+


Are there endgames which could be forced wins if not for the 50-move rule?

Yes, there are quite a few endgames that require more than 50 moves with best play from the defender.

Wikipedia has a list of material imbalances where it could take more than 50 moves depending on the specific position.  Here are a few examples:

Rook and bishop vs lone rook (often a draw though)
Two bishops vs a lone knight
Two knights vs a lone pawn (the defender must have a pawn)
Four knights vs a lone queen (would never happen over the board…)
Queen and rook vs queen and rook
Two queens vs two queens


Highly non-optimal, but here's one line that reproduces the position. The basic idea is to not capture the existing pieces, but capture pawns. A single pawn capture can free 3 pawns to promote. Here's a sample game.
   [FEN ""]

   1.h4 a6 2.h5 g5 3.hxg6 Nf6 4.g7 h5 5.g8=R h4 6.g4 h3 7.g5 h2 8.Nf3 Nd5 9.
   g6 Nb6 10.g7 Rh4 11.Rg1 h1=R 12.Rh8 Nd5 13.g8=R Rh5 14.R1g5 R1h4 15.Rh6
   Nb6 16.Rg8g6 f5 17.e4 fxe4 18.Nd4 e3 19.Bh3 e5 20.Ke2 e4 21.Qh1 Nd5 22.Kf1
   e2+ 23.Kg2 e1=R 24.f4 e3 25.f5 Bb4 26.f6 e2 27.f7+ Ke7 28.f8=R Rf1 29.Nb3
   e1=R 30.Rf4 Re6 31.Rf3 Rf6 32.Rgg3 Re1 33.R6g4 Ree6 34.Nd4 Kf7 35.Ne2 Bf8
   36.a4 Bg7 37.a5 b5 38.axb6 Nc6 39.b7 a5 40.b8=R a4 41.Raa3 Ra6 42.Rae3 a3
   43.b4 a2 44.b5 a1=R 45.Ra8 R6a5 46.b6 Nce7 47.b7 Nc6 48.b8=R Nb6 49.Kf2 d5
   50.Bb2 d4 51.c4 dxc3 52.d4 c2 53.d5 Qe7 54.d6 c1=R 55.d7 Nb4 56.d8=R c5
   57.Rg2 c4 58.R4g3 c3 59.Na3 c2 60.Nb5 Rd1 61.Ned4 c1=R 62.Nc2 Nd3+ 63.Ke2
   Ne1 64.Nc7 Ra6 65.Ne8 Na4 66.Rhg6 Bb7 67.R6g4 Rff5 68.Rb4 Rh7 69.Ree4
   Rh4h6 70.Qg1 Rhf6 71.Qd4 Ra3 72.Qc4 Rad3 73.Qa2 Rdd6 74.Qa1 Qc7 75.Rff2
   Qc3 76.Ree3 Qa3 77.Rbc8 Qa2 78.Rab8 Qb1 79.Reb3 Rd1d5 80.Ra3 Rb5 81.Qa2
   Rdc6 82.Rdd3 Rg6 83.Qa1 Bc3 84.Qa2 Rgf6 85.Qa1 Rfd5 86.Qa2 Red6 87.Qa1
   Rff5 88.Re4 Rdf6 89.Rb4 Rcc5 90.Rbb3 Rdd6 91.Qa2 Be4 92.Qa1 Rf4 93.Qa2 Bg6
   94.Qa1 Rf4f5 95.Qa2 Rcc6 96.Qa1 Nc5 97.Qa2 Nb7 98.Rd8 Rbb6 99.Qa1 Rc7 100.
   Rde3 Rde6 101.Rd2 Rec6 102.Rbd8 Re7 103.R8d3 Rd7 104.Ref3 Rdd6 105.Nb4 Bd4
   106.Qa2 Rc1c5 107.Qa1 Rcd5 108.Nc2 Bc3 109.Qa2 Ke7 110.Qa1 Ke6


Simultaneously managing attack and defense

Defense isn't something that one does; it is not a tactic. Instead, defense happens when one has ceded the initiative to the opponent. One spends moves patching holes versus attacking the opponent's weaknesses.

(Of course at some point "tactics" and "retaining the initiative" blur. Some fine attacking moves also defend, and some defensive moves free other pieces to attack. It can be a maelstrom when it comes to specifics.)

So consider reading on tempo and initiative.


In this QGD Exchange variation, how should white deal with 6 ...Bg4?

Usually white's aim in this line is to play Qc2 anyway to take away the F5 square from the black bishop. Therefore I dont think Nf3 is a great move. Its better for white to play Qc2 or Qb3 which is also thematic since blacks white squares on the queenside are now weak due to absence of the bishop.


Does this process ever becomes a second nature?

If you are interested in the psychology of learning and improving in chess, I really recommend reading Chess for Zebras from Jonathan Rowson (and/or Move First Think Later from Willy Hendriks, which has a very similar message).
tl;dr: Yes, finding the "best" move continually becomes more and more natural (and thus faster!) while you improve (although even masters never reach the point of perfection).
Rowson explicitly distinguishes between Knowledge (theory learned from books etc.) and Skill (the practiced ability to actually use that knowledge on the board). If you think about learning languages, the former would be knowledge about grammar and vocabulary (you can learn that to a reasonable degree in school), and the latter would be the ability to speak/write fluently (you can only really learn this by constant practice of the language). Someone with only school knowledge will have to consciously think about everything and thus needs more time than a skilled speaker to form sentences - even if he/she knows all the parts!
It works roughly the same way in chess, up to the point that strong masters can often subconsciously "feel" a move within seconds and then "just" have to use their calculation abilities to make sure it actually works.


Arrange 5 non-attacking knights on a 5x5 toroidal board

I noticed a simplification of @RosieF's solution:

  Label the squares with two-number labels as follows:

4,2 0,3 1,4 2,0 3,1
1,0 2,1 3,2 4,3 0,4
3,3 4,4 0,0 1,1 2,2
0,1 1,2 2,3 3,4 4,0
2,4 3,0 4,1 0,2 1,3

  Then two knights may occupy two squares x,y
  and X,Y iff those squares' first numbers x and X are different and
  their second numbers y and Y are different.

Since there are 5 knights and only 5 different numbers in each direction, that means that every x-value must be occupied by a knight, and each of the possible y-values must be assigned to one of those knights.  If we sort the knights' coordinates by their x-value, then list only the y-value, then we wind up with some permutation of the numbers from 0 to 4.  Every valid placement of the knights produces a permutation of the numbers 0-4, and every permutation of those numbers corresponds to a valid arrangement of the knights.

The total number of valid arrangements of the knights is thus 5!, or 120.


chess.com Analysis "Accuracy" - What score is computer like for a given rating?

I'm a 1400-1500 rated blitz player on chess.com. Looking through my archives, I see that just this month I had a 34 move game, at a 3 2 time control, where I was rated at a 97.4% accuracy. And I know I wasn't cheating.

When I look at my recent daily games (where I'm rated higher, around 1900) I see a 46 move game where I was rated at 99%.

You can't tell anything from a single game.


How to limit lines in scid vs pc in annotate mode?

In Scid vs PC, after you turn on an engine, a window with analysis opens. In that window you can see icons like Stop Engine, Add Move, Add Variation etc. (see picture below).

Among them, there is a small box with a number (marked by a red circle in the picture below), namely the number of lines suggested by the engine. Adjust that according to your preference. If I understood your question correctly, that should solve your problem. Just for the sake of completeness, I have the version  4.13 of Scid vs PC.


Spoiler-free chess replays for the 2013 Candidates tournament

If you use Scid, then you can turn on the option "Hide next move". That also hides the result of the game. The option is intended for training purposes (solitaire chess, also known as "guess the next move").

You can download a PGN file of the games, and open it with Scid. Don't open the game list window (because it shows results), but first turn on the hide next move option and then choose "Next game" (ctrl-down).

That's one way.


What is the main aim and object of the kings pawn opening?

Generally the goal of the opening is to develop the pieces (knights and bishops in particular) to active squares and to gain space for operation of the pieces (usually achieved by occupying the center with pawns).

If we are talking about the kings pawn opening, i.e. any opening that starts with 1. e4, there is little to say besides:

white aims to occupy the center with a pawn on e4
white makes space for the development of the light squared bishop on f1 (and potentially the queen)

Note that the game after 1.e4 could develop in all kinds of ways of very different character. Many of these openings have their own name (Sicilian, Ruy-Lopez, French, Caro Kann...), their own aims and objectives. Really I'd struggle to call a single move like 1. e4 an "opening".

Also often you will find that proper openings like those mentioned above will be listed by their name while the name King's Pawn Opening is reserved for all the rest, i.e. for games that don't follow any of the established openings.


openings for white which don't involve a central pawn push

Since, you're already familiar with the King's Indian Attack and are looking for a solid line, I recommend playing the Nimzowitsch Larsen Attack, by first playing 1. Nf3.

Normally, the Larsen Attack starts directly with 1. b3, but after 1...e5, I wouldn't describe the resulting positions as "solid" for White, but rather more "dynamic".

  [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

  1. b3 e5 2. Bb2 Nc6 3. e3 Nf6 4. Nf3 (4. Bb5 Bd6 5. Na3 $5 Na5 $5)
 (4. c4 d5 5. cxd5 Nxd5) (4. d4 exd4 5. exd4 d5) 4... e4 5. Nd4 Nxd4 6. Bxd4 Be7 *

1. Nf3 avoids the 1...e5 line, while at the same time maintaining the flexibility of transposing either into the King's Indian Attack or the Nimzowitsch Larsen Attack.

You can get positions similar to the Colle System (very solid and easy opening for White to play, without needing much preparation). Here, I give some sample lines where you can play the Nimzowitsch Larsen attack (often transposing to Colle), or, if you don't prefer certain types of positions, transposing back to King's Indian Attack (although rare).

     [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

     1. Nf3 Nf6 (1... g6 2. e4 c5 3. d3 Nc6 4. g3 Bg7 5. Bg2 e6 6. O-O) (1... c5 2.
     b3 d5 3. e3 Nc6 4. Bb2 Bg4 (4... a6 5. d4 Nf6 6. Bd3) 5. Be2 (5. h3 Bxf3 6.
     Qxf3 a6 7. d4 e6 8. Nd2 Nf6 9. Bd3 cxd4 (9... Nb4 10. dxc5 Bxc5 11. O-O) 10.
     exd4 Nb4 11. O-O Nxd3 12. Qxd3) 5... Nf6 6. O-O e6 7. c4 (7. d4 cxd4 8. exd4
     Bd6 9. Nbd2 O-O 10. c4) (7. Ne5 Bxe2 8. Qxe2 Nxe5 9. Bxe5 Be7 10. c4 O-O 11. d3
     ) 7... Be7 (7... d4 8. Nxd4) 8. cxd5 Qxd5 9. Nc3 Qd7 10. Na4 b6 (10... O-O 11.
     Bxf6) 11. d4 cxd4 12. Nxd4 Bxe2 13. Qxe2) (1... d6 2. d4 Bg4 3. Nbd2 Nd7 4. h3
     Bh5 5. b3 Ngf6 6. Bb2) (1... d5 2. b3 Nf6 (2... Bg4 3. Bb2 (3. Ne5 $5 Bh5 4. d4
     Nd7 5. Nd3 e6 6. Nf4 Bg4 7. h3 Bf5 8. e3 Ngf6 9. Bd3 Bxd3 10. Nxd3 Bd6) 3...
     Bxf3 4. exf3 e6 5. g3 Nf6 6. f4 Be7 7. Bg2) 3. Bb2 Bg4 4. e3) 2. b3 d5 (2... d6
     3. d4 g6 4. Bb2 Bg7 5. e3 O-O 6. c4) (2... g6 3. Bb2 Bg7 4. e3 (4. g3 $5) 4...
     d5 5. d4 O-O 6. Nbd2 Bf5 7. Bd3) 3. Bb2 e6 (3... Bg4 4. e3 e6 5. h3 Bh5 6. c4
     c6 7. Be2 Nbd7 8. O-O Bd6 9. d4) 4. e3 c5 5. d4 Nc6 6. Bd3

EDIT:

This is a funny yet practical suggestion. If you really want to take the Black players out of their preparation, then why not try Anderssen's opening? (lol)

     [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

     1.a3!?

Indeed the great Anderssen himself, in his match with Morphy (the greatest player of that era), tried this opening and scored one win, one loss and one draw, which is not a bad result at all against a player of Morphy's caliber.

Objectively speaking, the opening doesn't offer White any advantage, but it doesn't make White's position worse either. White essentially plays as Black, as though Black had played an extra move 1...a6. As you know, the move 1...a6 is quite useful in openings like the Ruy Lopez, Najdorf Sicilian, Benoni, Benko Gambit, Slav, etc. White's aim therefore is to play as Black and try to get into these type of positions to make sense of the move 1.a3. Practically, this move is worth a try if you want to disrupt Black's preparation or like playing certain positions as Black where 1...a6 is useful.

I give some sample lines where White tries to get into the desired positions mentioned above.

      [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

      1. a3 d5 (1... c5 2. c3 (2. b4 $5 cxb4 3. e4) 2... d5 3. d4 e6 (3... Nc6 4.
      dxc5 $1) 4. Nf3) (1... Nf6 2. Nf3 d5 3. e3 g6 4. c4) (1... e5 2. c4 Nf6 3. d3
      Nc6 4. Nf3 d5 5. cxd5 Nxd5 6. e4) 2. Nf3 Nf6 3. e3 c5 4. c4 d4 5. b4 *


What's an ideal game for teaching a new beginner?

I vote for the Opera Game. It showcases the very basics of strategy (controlling the center, getting the pieces developed ASAP, and attacking the king), and ends with a fantastic combination to force checkmate.

This is one of the most well-known games ever played, and it has been covered by nearly everyone online, so you can definitely find a good overview of this game in many youtube videos. If you watch a few yourself, (such as https://www.youtube.com/watch?v=MKvUQpQWie0) you should be able to present it as a story to your kid too.


Why does it seem that one drops more rating points when losing than gaining when winning?

I suspect it's a result of you not really knowing the rating of the player you're playing. Posted rating for a player in a tournament is typically already out of date. You can see it in more detail by checking the actual rating report of the event you played in (http://www.uschess.org/datapage/event-search.php) and you can see what the real rating of the player you played was at the start of the event. Keep in mind it changes with every round.


Who is best at Fischer Random chess, humans or engines?

You have to understand, that a top ten player is superior to an engine in the opening, because he used engines to analyze openings for many years, and because engines usually don't have an opening book on the level of the preparation of a top player.

In chess 960 you basically take away the opening book for both players and at the very top this actually benefits the engine.

So I think there can be no doubt, that engines would be similarly superior in chess960 as in normal chess. But the only Human-Engine match I know of was still won by the human player: Peter Svidler vs Baron, 1,5:0,5 in the year of 2005.
Of course the big jump in engine strength only came with Rybka in the very same year 2005.


All right, so I found the following query for the pawn structure in the diagram above:
(match  ;query for IQP white
      (position
         :and (
            (position Pa2 Pb2 Pd4 Pf2 Pg2 Ph2 pa7 pb7 pe6 pf7 pg7 ph7)
            (position
            :piececount P[c2-7,e2-7] 0
            :piececount p[c2-7,d2-7] 0 )
         )
      )
)

For black though, I wanted to search for any IQP position, so I used this query:
    (match ;query for IQP black
      (position
        :and (
          (position pd5)
          (position
            :piececount P[a2-7] 1
            :piececount P[b2-7] 1
            :piececount P[c2-7] 0
            :piececount P[d2-7] 0
            :piececount P[e2-7] 1
            :piececount P[f2-7] 1
            :piececount P[g2-7] 1
            :piececount P[h2-7] 1

            :piececount p[a2-7] 1
            :piececount p[b2-7] 1
            :piececount p[c2-7] 0
            :piececount p[d2-7] 1
            :piececount p[e2-7] 0
            :piececount p[f2-7] 1
            :piececount p[g2-7] 1
            :piececount p[h2-7] 1
      )
     )
  )
)

Lame, but at least it works :)


What are the best books on (A) General Theory, (B) Calculation Process/Improvement?

Chess principles:

Aron Nimzowitsch's My System  [Essential. Good for beginners as well]
School of Chess Excellence series 3 - Strategic Play by Mark Dvoretsky. [Intermediate level]
Grandmaster Preparation - Strategic Play by Jacob Aagaard [Advanced. Aagard's books have tough puzzles which will be very hard for Beginners.]

Pawn Structures: [You can read the theory and games to understand the principles. Not very technical, so should be equally understanable by Beginners. At the same time, intermediate/advanced level player will be better able to participate with the book using analysis.]

Winning Chess Middlegame by Sokolov
Winning Pawn Structures by Alexander Baburin

Calculation:

Think like a Grand Master - Kotov [Good for all levels. But beginners will find the technical parts difficult]
Secrets of Chess Training by Mark Dvoretsky. [Advanced. dot. A difficult book since it dwells on analysis and getting better at the technical aspects]
Other authors: Jeremy Silman, Andrew Soltis (The Inner Game of Chess?)
[I have all the above books in my library, and have read them in parts at least, but I don't have the books of Soltis and Silman. Never read them, But I heard good feedback about them. Worth a try, I guess.]


Simply put, Kxc3 loses a piece or the exchange after Rc8.

[fen "1n3rk1/5pp1/4p2p/8/q1N1QP2/Pnp4P/1PK2PP1/3R1R2 w - - 0 0"]

1. Kxc3 Rc8 2. Rd6 {or any move} Na5 3. Rd4 Qb3+ 4. Kd2 Nxc4+


In Hand and Brain chess, is the stronger player generally preferred to be the hand or the brain?

Not a definitive answer, but I'm posting my comment based on the upvotes it received.
It depends. GMs have different opinions.
GM Hikaru Nakamura has said it really depends on the situation. Additionally, he has commented that when the Brain, he often suggests moves that aren't correct because he is factoring in the likely Hand response to his move.
GM Aman Hambleton stated the stronger ELO player should be the Hand generally because they will find good moves in most cases, and be able to identify a plan for a position much easier.


The FIDE rules say this about castling:

  This is a move of the king and either rook of the same colour along
  the player’s first rank, counting as a single  move of the king


If the aim is to award the title only to world class players, I can
think of some much easier system to select them, e.g. you must have
been rated in the top 100 of the world at one point. This would tie
the title to a single, easily-understood number. I notice some of the
lower titles already use this criterion (e.g. Candidate Master)

The comparison with the Candidate Master title is a telling one. The CM title is not highly regarded. This has been covered in two previous questions here - How respectable is the CM title? and Is a candidate master considered a master?

Why are the requirements for becoming a GM so complicated?

They are indeed complicated. Here is the link for the FIDE Title Regulations effective from 1 July 2017. One additional requirement, which I don't see listed here, is that the tournament organizer must send a file with the PGNs of all the games for the tournament.
The reasons they are so complicated is that they have evolved over time to deal with the corrupting influences of money, politics, rating manipulation and cheating.
Money
One of the ways of getting the GM title is to be World Champion. Here is what Wikipedia says about the early period of world championships:

From 1886 to 1946, the champion set the terms, requiring any
challenger to raise a sizable stake and defeat the champion in a match
in order to become the new world champion.

So, no money - no match. As the article says, this had a profound effect on who got to play for the title:

This requirement makes arranging world championship matches more
difficult, for example: Marshall challenged Lasker in 1904 but could
not raise the money until 1907;[37] in 1911 Lasker and Rubinstein
agreed in principle to a world championship match, but this was never
played as Rubinstein could not raise the money.[38][39] In the early
1920s, Alekhine, Rubinstein and Nimzowitsch all challenged Capablanca,
but only Alekhine was able to raise the US$10,000 that Capablanca
demanded, and not until 1927

OK, you might be thinking, those kinds of considerations belong to a bygone age. Well, try telling that to Shirov who, perhaps, should have been World Champion in 2000 instead of Kramnik:

Soon after the 1995 championship, the PCA folded, and Kasparov had no
organisation to choose his next challenger. In 1998 he formed the
World Chess Council, which organised a candidates match between Alexei
Shirov and Vladimir Kramnik. Shirov won the match, but negotiations
for a Kasparov–Shirov match broke down, and Shirov was subsequently
omitted from negotiations, much to his disgust. Plans for a 1999 or
2000 Kasparov–Anand match also broke down, and Kasparov organised a
match with Kramnik in late 2000

Politics
This is what the Wikipedia article has to say on this:

Title awards under the original regulations were subject to political
concerns. Efim Bogoljubov, who had emigrated from the Soviet Union to
Germany, was not entered in the first class of Grandmasters, even
though he had played two matches for the World Championship with
Alekhine. He received the title in 1951, by a vote of thirteen to
eight with five abstentions. Yugoslavia supported his application, but
all other Communist countries opposed it. In 1953, FIDE abolished the
old regulations, although a provision was maintained that allowed
older masters who had been overlooked to be awarded titles

There was more political interference in the 1962 Candidates tournament which selected the challenger for the 1963 World Championships. Here is what the article says:

What makes this tournament famous and often-discussed is the
allegations of Soviet collusion. The three top finishers (Petrosian,
Geller and Keres) drew all twelve of their games against each other,
in an average of only 19 moves.[15]
Soon after the tournament, Fischer publicly alleged that the Soviets
had colluded to prevent any non-Soviet – specifically him – from
winning. His allegations were twofold: first, that Petrosian, Geller
and Keres had pre-arranged to draw all their games; and second, that
Korchnoi had been part of the drawing pact in the first half of the
tournament, and been instructed to lose some games to them in the
second half.[16][17][18] (In the first two cycles Korchnoi drew all
his games with Petrosian, Geller and Keres; in the third cycle he lost
to all of them; and in the final cycle he lost to Petrosian but drew
with Keres and Geller).
The first allegation, of the drawing pact, is generally assumed to be
correct.[18] All of the three players involved have since died, but
Yuri Averbakh, who was head of the Soviet team, confirmed it in a 2002
interview.[10] He offered the rationale that Keres was the oldest
competitor and wanted to conserve energy, and that Petrosian and
Geller were good friends with a history of drawing with each other.
The second allegation, of Korchnoi throwing games, is more
doubtful.[18] Korchnoi defected from the USSR in 1976, and never
alleged he was forced to throw games. Dominic Lawson calls the
allegation "preposterous", noting that the main beneficiary of
Korchnoi's losses was Petrosian, whom Korchnoi detested

Rating Manipulation and Cheating
There is an interesting Wikipedia article on this. For those who like their chess dripping with blood there is the story of infamous mother-killer Claude Bloodgood:

Bloodgood organized chess games within Powhatan Correctional Center in
Powhatan, Virginia, which were by necessity with fellow inmates.3
Many of these inmates were taught the game by Bloodgood, and thus
began as unrated and inexperienced players. Bloodgood obtained USCF
memberships for them. Some accused Bloodgood, with his intimate
knowledge of the rating system, of rigging their ratings. The
accusation was that he arranged for new prisoners to play rated games
against other prisoners, who would deliberately lose, thus giving the
new inmate an inflated USCF rating. Bloodgood, it is further alleged,
then played rated games against the new highly rated prisoner, and
each time he won, gained a few more rating points. This continued for
several years, and by 1997 his rating rose to 2759, making the
59-year-old Bloodgood the second highest rated player in the nation,
only behind Gata Kamsky.

OK, but that was USCF rating not FIDE. That could never happen with FIDE ratings, surely? And certianly not for titles? Well, check out this article from TWIC (The Week in Chess) from 8th March 1999. Here is an extract:

Respected Grandmaster and chess journalist Ian Rogers also felt moved
to comment on the event in the Canberra Times Chess Column for March
7th. He too was almost breathtaken by the number of norms scored in
the event and the calculated level of planning required for titles and
rating fraud on this scale. I quote, with permission, at length below.
"The Grandmaster tournament which took place in Rangoon in the first
two weeks of February took months of planning but succeeded in
creating six Grandmaster results and eight IM results, an astonishing
success rate. (Two or three title 'norms' are needed for a player to
be awarded the GM or IM title.) Some of those scoring Grandmaster
results had struggled to score 50% in the South-East Asian zonal
tournament only a month earlier! Corruption extended not only to the
tournament itself - with seven highly rated locals losing all their
games to their compatriots - but also to a series of events held in
1998 which provided extremely high world rankings for all those
required to be 'victims' in the February tournament. All seven of the
no-hopers in February were unrated in January 1998, yet on the January
1999 FIDE list had rankings higher than Australian Grandmaster Darryl
Johansen."
"The following game is not atypical of their play, with the heavily
'outrated' Mas winning one of the easiest games of his career: Rangoon
1999 White: H.Mas Black: Thein Dan Oo 1.e4 c5 2.f4 d6 3.Nf3 Nc6 4.Bb5
g6 5.0-0 Bg7 6.Bxc6+ bxc6 7.d3 Rb8?! 8.Nc3 Nf6 9.Qe1 0-0 10.b3 d5?
11.e5 Nd7 12.Ba3 Re8?! 13.Na4 Rb5 14.e6 Nf6? 15.c4 Ra5? 16.exf7+ Kxf7 17.Ne5+ Kg8 18.Nxc6 1-0 Mas, the honourable Malaysian IM who performed so creditably in Sydney in January, was not one of the favoured many
who scored title results. His opponent, rated 2539 - a near-GM
ranking, managed only 4 points from 14 games. There is no suggestion
that any of the foreign visitors were involved in anything other than
pre-arranged draws - they simply took advantage of the extraordinarily
overrated opposition. However the local players in Rangoon probably
knew the results of many of their games before the event began and if
an 'accident' occurred to one of those destined to score a title norm

e.g. a loss to a foreign player - their compatriots pitched in and provided some extra points or half points. Unusually for a corrupt
tournament, the foreign invitees were not needed to help out the
locals, since the enormous rankings of the weakest players meant that
the scores required for title results were relatively low."

"From the point of view of the organisers, the event was so successful
that it is likely to be repeated in a few months time, before the
ratings of the tailenders are adjusted on the July FIDE rating list.
After one more such tournament, Burma could have 4 Grandmasters and
half a dozen IMs; after a few more such tournaments they could have
more Grandmasters than any country in Asia! Publicity may encourage
the Burmese to become more discreet in future but FIDE is highly
unlikely to take any action. Their actions in past cases would
indicate that the world body tacitly approves of a 'developing' chess
nation acquiring titled players, whatever the ethics involved."


Chesss training-Can’t find the proper white move

The answer is 1.Rf8+, as Cleveland commented. You remove the defender of the queen on g4 (that is, the rook on g8) by distracting it.

[FEN "2k3rr/pbpp4/1pn1p3/8/2PPB1qp/2N1P2Q/PP4P1/2R2RK1 w - - 0 1"]

1.Rf8+ Rxf8 {1...Nd8 2.Qxg4 Rxg4 3.Bxb7+ Kxb7 4.Rxh8} 2.Qxg4

Wins the black queen in exchange for a rook, which means that white is winning. If black doesn't take the rook and instead blocks the check with 1...Nd8, white exchanges queens with 2.Qxg4 Rxg4, then exchanges bishops on b7 with check (3.Bxb7+ Kxb7) because the bishop was attacked twice, and then wins the rook on h8 (4.Rxh8).

As for training tools, workbooks that explain a tactical theme and then give a number of exercises is the usual way, e.g. the Steps Method. A good website like that is Predator at the Chessboard, where a tactic like this could fit in chapter 5.2.


Modified move-order in the KID 4. ..0-0. What is the point and how to react?

In the vast majority of the cases, 4....d6 and 4....0-0 transpose into each other.

However, with 4....0-0 black keeps the option of playing c6 and d5. Recently, this idea has been played by GM Jobava, known for his original approach in the opening: Lupulescu-Jobava, So-Jobava and Vitiugov-Jobava.

About the last game, chess.com comments "Just giving away the g6-pawn. This reporter is at a loss". The engines do not approve Jobava's opening, but somehow he was able to create enough counterplay and to draw the game.

As you play the Sämisch, it makes sense to start with 5.Be3, as Ng4 is not possible. Clearly, 5....d6 6.f3 would transpose to your repertoire. After 5....c6, white has two popular ways to seize the initiative and to obtain an advantage: 6.e5 Ne8 7.f4 d6 8.Nf3 (e.g. Parligras-Fier) and 6.f3 d5 7.cxd5 cxd5 8.e5 Ne8 9.h4 (as in Vitiugov-Jobava). The former should result in a slight but stable advantage for white, while the latter leads to sharper play.

      [StartPly "7"]

      [FEN ""]
      1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 O-O (4...d6) 5.Be3 (5.f3) c6 (5...d6 6.f3) 6.f3 (6.e5 Ne8 7.f4 d6 8.Nf3) d5 7.cxd5 cxd5 8.e5 Ne8 9.h4


Sense of Humor
There are several real but somewhat silly openings that gets its name. Sodium Attack (1. Na3), Ammonia opening (1, Nh3), Meadow Hay Gambit (1. a4 e5 2. Ra3 Bxa3), Picklepuss Defence (1. e4 h5 2. d4 Nf6).
No one will actually play these in tournaments or something, they serves no useful purpose (except maybe training), but they're funny. Similar to code golf.
Coca-cola is very likely just something that sounds humorous.


Is there a chess program that can detect if someone has left the game?

Lichess (http://lichess.org) has some ability to detect when your opponent has left the game. When that happens, it gives your opponent a brief chance to rejoin, then allows you to claim a victory or a draw if they do not rejoin. If Lichess detects that your opponent has left, it will show a counter counting down the seconds until you can claim victory. The amount of time on the counter seems to depend on the time control and other factors. If Lichess does not detect that your opponent has left, but they decide to run out the clock, Lichess will not allow you to claim a victory, but will still automatically penalize your opponent with a ban after repeated offenses.
Note that none of this happens in correspondence chess, as temporarily leaving the game is normal in that time control.


What is the record for the most pawn double-steps in a professional game?

This is clearly contrived, but it was an actual tournament game so it wins that record. :)

  [Title "Danny Jazmati-Marcel Harff, NRW-ch U12, 2002"]
  [FEN ""]

1. a4 a5 2. b4 b5 3. c4 c5 4. d4 d5 5. e4 e5 6. f4 f5 7. g4 g5 8. h4 h5 9. Ra2 Rh6 10. Rh3 Raa6 11. Bd2 Be7 12. Bc3 Bf6 13. Nd2 Ne7 14. Nb3 Ng6 15. Ne2 Bb7 16. Kf2 Nd7 1/2-1/2


Does Magnus Carlsen have any openings/opening variations named for him?

In the old days variations were named after players who did serious theoretical work and/or played one line consistently over a longer period.

As openings got more and more analyzed it got increasingly more difficult to find new variations comparable to those old masters. Nowadays the top players might find a novelty around move 20 or so. If you want, you could call those lines variation and credit them to the player. I am sure some websites do just that, but personally I see a big difference between say the Najdorf variation and those side lines.

So yes, probably somebody somewhere called something a Carlsen variation, but whether you consider it a variation is up to you. Also, perhaps it needs some more time until a line is called variation and maybe in 10 years people will agree to call a line Carlsen variation.


Are there statistics on the results of armageddon games at the GM level?

The earliest Armageddon games I can find go back to the Women's World Chess Championship 2001, and the FIDE World Championship in 2002, which GM Ruslan Ponomariov won. This is probably a fairly complete list since Armageddon really only lends itself to knock-out tournaments or matches, and the question did ask primarily about GMs and Armageddon. There might be the occasional country championship that goes to tiebreaker, which I did not find, similar to when GM Irina Krush lost to IM Anna Zatonskih in 2008 for the U.S. Women’s Championship in a controversial finish.

So, while these stats may not be 100% complete, they can give a good idea about the overall statistics.

I am amazed by the results of this: Out of the 48 games I found, 24 were 1-0, 15 were 0-1, and 9 were ½-½. If you look at that both the 0-1 and ½-½ count as wins for black, then the result was exactly 24-24. Seemingly quiet a fair tiebreaker system.

Here is the data I used to compile this estimate.

FIDE World Chess Championship 2002

This was the only FIDE World Championship to use Armageddon during the period of when Kasparov broke off with the title until it was unified in 2006. Prior to this, in 1998 and 2000, they continued playing additional blitz games, and in 2005, FIDE reverted to a double-round-robin tournament.

GM Zoltan Gyimesi defeated GM Stuart Conquest 4-3 in round one. Gyimesi had white 1-0.
GM Emil Sutovsky defeated GM Alonso Zapata 4-3 in round one. Sutovsky had white 1-0.
GM Lazaro Bruzon defeated GM Liviu-Dieter Nisipeanu 4-3 in round one. Bruzon had white 1-0.
GM Jaan Ehlvest defeated GM Ilia Smirin 4-3 in round three. Ehlvest had white 1-0.
GM Alexey Shirov defeated GM Veselin Topalov 4-3 in round four. Shirov had black 0-1.

Chess World Cup 2005

GM Yuri Shulman defeated GM Vadim Zvjaginsev 3.5-3.5 in round one. Shulman had black ½-½.
GM Predrag Nikolić defeated GM David Navara 3.5-3.5 in round one. Nikolić had black ½-½.
GM Sergey Erenburg defeated GM Zviad Izoria 4-3 in round one. Erenburg had black 0-1.
GM Evgeniy Najer defeated GM Shakhriyar Mamedyarov 4-3 in round two. Najer had white 1-0.
GM Yuri Shulman defeated GM Vadim Zvjaginsev 3.5-3.5 in round two. Shulman had black ½-½.
GM Sergei Tiviakov defeated GM Oleg Korneev 4-3 in round two. Tiviakov had white 1-0.
GM Loek van Wely defeated GM Alexander Moiseenko 4-3 in round two. van Wely had white 1-0.

Chess World Cup 2007

GM Michael Roiz defeated GM Varuzhan Akobian 4-3 in round one. Roiz had white 1-0.
GM Konstantin Sakaev defeated GM Nikita Vitiugov 4-3 in round one. Sakaev had black 0-1.
GM Zhou Jianchao defeated GM Andrei Volokitin 4-3 in round two. Zhou had white 1-0.
GM Kiril Georgiev defeated GM Rustam Kasimdzhanov 4-3 in round two. Georgiev had white 1-0.

Chess World Cup 2009

This year, by some accounts a mistake, the tiebreaker was changed to four rapid games, then up to five pairs of blitz games, and only then, Armageddon. Not surprising, but there were no Armageddon games, however, GM Varuzhan Akobian did defeat GM Pavel Tregubov 9-7, just one game short of Armageddon.

Chess World Cup 2011

Starting this year, they went back to the previous tiebreak format, but with two shorter 10+10 rapid games added after the 25+10 rapids.
GM Yuri Drozdovskij defeated GM Alexander Motylev 5-4 in round one. Drozdovskij had white 1-0.
GM Leinier Domínguez Perez defeated GM Igor Lysyj 5-4 in round three. Domínguez Perez had white 1-0.

Chess World Cup 2013

GM Evgeny Tomashevsky defeated GM Alejandro Ramírez 5-4 in round one. Tomashevsky had white 1-0.
GM Julio Granda defeated GM Hrant Melkumyan 5-4 in round one. Granda had black 0-1.
GM Daniil Dubov defeated GM Ruslan Ponomariov 5-4 in round two. Dubov had white 1-0.

Chess World Cup 2015

GM Gabriel Sargissian defeated GM Mateusz Bartel 4.5-4.5 in round one. Sargissian had black ½-½.
GM Michael Adams defeated GM Viktor Láznička 5-4 in round two. Adams had white 1-0.
GM Hikaru Nakamura defeated GM Ian Nepomniachtchi 5-4 in round three. Nakamura had black 0-1.

Chess World Cup 2017

GM Levon Aronian defeated GM Maxime Vachier-Lagrave 5-4 in the semi-finals. Aronian had white 1-0.

Chess World Cup 2019

GM Anish Giri defeated GM Evgeniy Najer 5-4 in round two. Giri had black 0-1.
GM Yu Yangyi defeated GM Nikita Vitiugov 5-4 in the quarter-finals. Yu had white 1-0.

Women's World Chess Championship 2001

Note: I could not confirm the format with 100% accuracy. I am reasonably guessing that this used the same format as the men, and the women in 2008, which I could confirm. In addition, the brackets had the 4-3 results as in the men’s tournaments.

GM Zhu Chen defeated GM Maia Chiburdanidze 4-3 in the semi-finals. (no data)

Women's World Chess Championship 2004

GM Peng Zhaoqin defeated IM Joanna Dworakowska 4-3 in round one. Pend had black 0-1.
WGM Ketino Kachiani defeated WGM Nguyễn Thị Thanh An 3.5-3.5 in round one, Ketino Kachiani had black ½-½.
IM Tatjana Vasilevich defeated WGM Xu Yuanyuan 4-3 in round one. Vasilevich had black 0-1.
IM Lilit Mkrtchian defeated then WGM Monika Soćko 4-3 in round one. Mkrtchian had white 1-0.
Then WGM Kateryna Lagno defeated then untitled Ekaterina Atalik 4-3 in round two. Lagno had black 0-1.

Women's World Chess Championship 2006

None.

Women's World Chess Championship 2008

IM Elisabeth Pähtz defeated WGM Ilaha Kadimova 4-3 in round one. Pähtz had white 1-0.
GM Monika Soćko defeated WGM Sabina-Francesca Foisor 4-3 in round one. Soćko had white 1-0.

Women's World Chess Championship 2010

Then IM Harika Dronavalli defeated then IM Mariya Muzychuk 4-3 in round three. Harika had black 0-1 (on time in a lost position!).

Women's World Chess Championship 2012

This was the first year of the extended tiebreaker with the rapid 10+10 games added.
Then IM Mariya Muzychuk defeated WGM Cristina Adela Foișor 4.5-4.5. Muzychuk had black ½-½.

Women's World Chess Championship 2015

GM Tatiana Kosintseva defeated WGM Mary Ann Gomes 5-4 in round one. Kosintseva had black 0-1.
Then WGM Aleksandra Goryachkina defeated IM Lilit Mkrtchian 5-4 in round one. Goryachkina had white 1-0.

Women's World Chess Championship 2017

IM Anastasia Bodnaruk defeated WGM Mitra Hejazipour 5-4 in round one. Bodnaruk had white 1-0.
GM Tan Zhongyi defeated GM Anna Ushenina 4.5-4.5 in round two. Zhongyi had black ½-½.
IM Nino Khurtsidze defeated then IM Nino Batsiashvili 5-4 in round two. Khurtsidze had black 0-1.
GM Tan Zhongyi defeated GM Harika Dronavalli 5-4 in the semi-finals. Tan had black 0-1.

Women's World Chess Championship 2018

GM Kateryna Lagno defeated WGM Natalia Pogonina 5-4 in round three. Lagno had white 1-0.

US Women’s Championship 2008

Then IM Anna Zatonskih defeated IM Irina Krush 3-2. Zatonskih was black, and white flagged, 0-1.

https://en.chessbase.com/post/us-women-s-armageddon-reactions-from-our-readers

World Chess Armageddon Series 2019

Nepomniachtchi -Karjakin 0-1
Radjabov-Karjakin ½-½
Radjabov-Dubov 1-0
Radjabov-Kramnik ½-½

https://www.chessbomb.com/arena/2019-world-chess-armageddon-series


getting started to develop entire chess application

When you want to write a chess application such as playing against a chess engine, you'll definitely need to learn the UCI protocol. You won't go anywhere unless you master it. Stockfish, Houdini, Komodo and a dozen of other chess engines use it. Please google "UCI chess protocol" for more details.

This is probably out of scope. Anyway, there is no reason why you can't use an XML format. You might want to look up ajax, because this is how most of the web sites use to create an asynchronous behaviour.
It's not a good idea to use a simple HTML page, because you'll force the user to reload the entire page everytime you want to update the board. You'll need something asynchronous, such as an ajax call.

Please check and talk with lichess. They have a chat channel that you can use to talk with the programmers. Those guys know everything.


A script that can create a chess tree from an EPD file

Not exactly. Both Chess Position Trainer and Chess Openings Wizard (the successor of Bookup) can create a tree manually or importing a PGN, export the positions to EPD, and import the evaluations from EPD, but won't create positions from an EPD, so they can't create trees from EPD.


There are many elements that a computer looks at to determine how the computer plays.  A more defensive computer would place more value on the pawns around the king.  A more attacking computer would place more value on retaining pieces, to maintain the attacking possibilities.  The choice of opening and the central pawn structure affects the overall playing style.
Galahad chess and Chessmaster had to option to change around two dozen of these evaluation values.  Beowulf read these values from a config file, but they weren't easily modified.