What would be the Elo rating of a computer which plays all optimal moves?

ELO is not an absolute measurement; it is only meaningful relevant to the ELOs of other players. This is because it is only calculated based on performance against other rated players. The "Maximum ELO", which seems to be what you're looking for, is therefore equal to the ELO of a player at such a time when his ELO is so high that he cannot gain any ELO points for defeating the second-highest-rated player.

The answer to your question, then, relies on at least the following two questions:

What is the highest-rated opponent that this theoretical machine could always defeat?
How much higher than that rating does an ELO need to be, in order not to gain any points from a victory?

The problem is this: if you play this machine against itself, the outcome is undefined. If we assume (since we don't know) that Chess is a fair game (Black and White have equal winning/drawing chances), then this machine can't raise its ELO indefinitely by repeatedly playing and defeating another version of itself, because it'll lose half the time and not get anywhere. So without hacking the system (see below), there is an upper bound somewhere.

What that upper bound is, however, is very fluid and somewhat ill-defined, because players' ratings are always in motion, and because rating systems are not equivalent. So to give you a value, let me make a couple of simplifying assumptions.

"Perfect play" is always a victory. (If draws are possible with perfect play from one side, it doesn't change the endpoint, but it does make it take longer to reach the top).
We use the FIDE ELO system, including the k-factor tiers (the k-factor will be 10 in the range we care about).
FIDE only uses integer ELO values.
The highest-rated opponent for this machine is Magnus Carlsen, currently rated at 2881.
Magnus is willing and able to play against this machine as many times as needed for the machine to reach its peak ELO. Between games against the machine, Magnus will play other humans to regain his 2881 ELO rating.

Given these assumptions, the machine will max out at about 3351 ELO1, where if it wins, its ELO will increase by less than half a point (+0.49 to 3351.49), which will be discarded (rounded down to 3351).

If a competitor achieves an ELO above 2881, than the upper bound increases. This fact allows us to pull the following (very silly) stunt, if we so choose:

We have a machine that always wins.
Presumably, we could build another one.
We pit the machine against Magnus until it achieves FIDE ELO 3351.
We disable perfect play on the machine (Machine 1). We set Machine 1 to always lose.
We build another machine, Machine 2, and play it against Machine 1 until it cannot gain more ELO points.
Repeat steps 4-5 with new machines ad nauseam to create a machine with an arbitrarily-high FIDE ELO.

1 I haven't done all the calculations myself by hand. I just plugged the appropriate numbers into this calculator. It's entirely possible that the formula used there differs from the current FIDE rules, but the basic premise is the same even if the numbers are inexact.


I used to keep scoresheets in the past, but it's tedious to keep them. Firstly, you may not recognise the writing that you recorded in hurry during the game. Besides, it is hard to be systematic with them: a single shuffle will make your games jumble up, and it will waste a lot of time.

Therefore, instead of doing it manually, I do it electronically. The main recommendation of mine is chess apps. For me, it's just Droidfish. You can get them on apps stores and it is free. Now comes the fun part. You can input your game by manual, which is playing out moves on your phone in double player mode and save it. You can also play the moves out in programs and get its pgn, then input into your phone using a cable. Either way its good.

Alternatively, chess5.com is a good website to keep your games. And do remember, if you use droidfish, keep a copy of the pgn file of your game in your computer in case your phone breaks.

Have fun


What does an engine do if it has found the shortest mate?

It does what it was programmed to do.  During any Alpha-Beta pruning, the computer would stop searching and just do nothing.
In another game, like an RTS, the computer would constantly go through a todo list.
What should/can I build?
What should/can I produce?
How do I defend/attack?
...
Since a chess AI has only one objective, find the best move, there's no point in searching once it's objective if found.


According to Gnu, which has a page dedicated to Berolina chess, the value of the Berolina pawn is the same as in standard chess, = 1. This is unsatisfactory because they give no explanation of how this evaluation was made.
The evaluations for standard chess existed before computer chess programs and were based on hundreds of years of experience playing standard chess. That doesn't exist for Berolina chess which was only invented in 1926 and is little played.
In the absence of similar amounts of over-the-board games of Berolina I think the best approach to getting an accurate evaluation would be an AlphaZero-like simulation of millions of self-learning games which could provide the empirical data upon which a good evaluation could be made.


What is the average age to become a grandmaster?

Brilliant little data mining project!

I used the wiki list of GMs and wrote a quick and dirty script to extract the data. Feel free to use and expand/alter it, if you are interested.

As it turns out, the average age for reaching GM is just above 28. It is, however, skewed by "old" generation players and players from time before GM title was a thing. It was officially introduced in 1950 and some (old) players were awarded it at the time. It is intriguing to look at average age in different generations of players. And so:

For players born after 1945, the average is slightly above 26 years old.
For players born after 1970, the average is slightly above 23 years old.
For players born after 1975, the average is slightly above 22 years old.
For players born after 1980, the average is 21 years old.
For players born after 1985, the average is just shy of 20 years old.
For players born after 1990, the average is 18.5 years old.

Clearly, on average, people are becoming a GM faster nowadays! The age distribution (for players born after 1945) is as follows:

In case it is of interest, the two countries "producing" GMs on average at lowest age are India and China - both at 21 years old. Countries with most GMs (all time) are Russia (by huge margin), Ukraine, Germany, USA and Hungary.


What do these numbers mean on chess.com?

Those are the times taken for the moves.
So e4 took 0.1 seconds,
e5 took 6.2 seconds and
Nf3 took 7.7 seconds.


Can't apply strategical knowledge in tournament games

Thinking Techniques that I give my students:

What new threat(s) has my opponent's last move created?  How can I answer it?(them?)
Is my King safe?  Is my opponent threatening to checkmate me in the next few moves?  Can I checkmate my opponent?
What threats can I set up?  How?
Have I seen this position, or a similar one before?
If so:  who stands better, and what is the best plan for continuing?
If not:  what are the outstanding features and elements of this position, and what plan(s) and method(s) of achieving it are available?
What is my play?  What specific position would I like to obtain?  How can I achieve my goal?  How can I improve my position?
How many good moves do I have?  Which one is best?  Can I capture material without penalty?  Can I develop a piece?  Can I employ any of the following tactical devices:  pin, fork, skewer, discovered attack, double attack, trap a piece, double check, etc.?
Is it safe to move my piece to the square I'm thinking about?  (Blunder check.)
Did I remember to start my opponent's clock and write down my move.

Notice that there is no mention of the positional elements.  Beginners should be more concerned with the tactical side and how to develop plans.  Strategic plans are formed based upon the position.  By studying games which have similar positions and learning how the masters continued should help you with strategic plans.
There is also plans which can be applied to completely different openings.  A knight sacrifice on f5 can be used in both the closed Benoni system and the open Dragon Sicilian.  By studying good annotated games, I mean the author saying in a simple language what (s)he is thinking, not pages of computer analysis, you will find great insight.


How to play for a win with White without fighting for an opening advantage

One way to play for a win without seeking an opening advantage is to play a system opening. In this answer, I recommended the English Botvinnik System to a player struggling against the Sicilian.

A system opening is where one player develops their pieces to the same squares and has similar plans available no matter what their opponent does.

System openings have the advantage of saving you clock time and giving you a position that you are familiar with, hence allowing you to play for a win.

The problem with system openings is that they ignore the opponent's play and you tend to play with a mind that is half closed. That is, you may miss interesting moves that take advantage of an opponent's mistakes. This is why system openings are not objectively 'the best', i.e. they don't give a theoretical opening advantage.


Why the initial rating of FIDE is calculated that strangely?

I'm wondering what is the rationale behind this?

The rationale is very simple. 5 games is far too few to get a realistic and accurate assessment of a player's strength. That is why a new player's K factor remains at 40 until either they have completed 30 rated games. Additionally it remains at 40 for all players under the age of 18 with ratings under 2300.
Here is the relevant section from the FIDE Rating Regulations effective from 1 July 2017:

8.56 K is the development coefficient.
K = 40 for a player new to the rating list until he has completed events with at least 30 games.
K = 20 as long as a player's rating remains under 2400.
K = 10 once a player's published rating has reached 2400 and remains at that level subsequently, even if the rating drops below 2400.
K = 40 for all players until their 18th birthday, as long as their rating remains under 2300.
If the number of games (n) for a player on any list for a rating period multiplied by K (as defined above) exceeds 700, then K shall be the largest whole number such that K x n does not exceed 700.

A K factor of 40 allows for very rapid changes in rating. Hence the last clause above which seeks to limit the rating change in any one month to prevent see-sawing rating.


Electronic gadget chess opponent for children

This iPad/iPhone app looks promising based on the reviews. I haven't tried it personally though, so I can't attest to its worth.

Here is the website of the developers. You can contact them to find out more about the features that they have. For instance, I couldn't find anything about whether it would speak to your child.


What are some common tactics that arise when black has played h6?

Two basic ideas:

Put a knight on f5; Black will have a hard time chasing it away with g6 without losing material.
Storm with your g-pawn to g5. Especially with the black knight still on f6, Black cannot avoid the opening of some lines.

Both plans would work in some circumstances with the pawn still on h7, but are a lot more effective with the pawn on h6.


Whats the difference between these chess tempo databases

They are currently exactly the same.

Typically, when a website does the old.sitename.com, it is to allow people to temporarily use the old format of a recently-updated website. Over time, they phase out the old one in most cases. The underlying data, such as a database, does not change at all during this transition, just the aesthetics and layout of the webpage.

In this case, it looks like they already phased out the old version, but simply kept the URL for convenience: They are currently exactly the same. To prove this, I did the following:

I opened each page in Firefox (but you could use any web browser), and right-clicked the page, and selected "View Page Source", which shows you all of the data that is used to render the webpage. I selected all the text for each document, and pasted it into a Word document. It was of note that viewing the page source, each one had 2576 lines...exactly the same. Once in Word, each document had 54 pages, and exactly 6017 words.

I then took both documents, "Old" and "New", and used the site copyleaks.com to compare them. As you can see from the screenshot, as I expected from the previous data I mentioned above, they are exactly the same.


How does one respond to 3.d4 after playing the Sicilian?

3...cxd4 is indeed basically forced. Perhaps the single biggest idea of the Sicilian is to exchange your c-pawn for White's d-pawn, leaving you with more pawns in the center. So go ahead and do it!

However, 4...Nxd4 is a mistake, leaving White with much better development after the trade.

Some common 4th moves for Black after 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 are 4...Nf6 (attacking the e4 pawn), 4...e6 (preparing to develop the dark-squared bishop and/or play ...d5), and 4...g6 (planning to develop the dark-squared bishop to g7).


I use the games published by The Week In Chess, which are published in a weekly basis. These games make a superb database, although maybe you'll miss some historical games. It takes some effort to build the database with all games published to the date, but from then on it's easy to keep it up to date.

It is also possible to download the Million Database and then to keep it up to date with TWIC games.


Does 40/100, SD/30 d10 mean that the delay is applied to both time controls?

It looks like the tournament is run by the Continental Chess Association. From my experience playing in many CCA tournaments, the d10 is applied to both time controls.


Why using the queen is not a good idea in this case?

You are missing the knight fork on c2. After 1.Qa4+ Bd7 2.Qxb4 Nc2+ 3.Kd1 Nxb4 you would lose the queen...


Recent full-point-blunder in a pawn-endgame?

Here's an example between players rated 2565 and 2498.  I haven't checked this against a tablebase due to the number of pawns, but the move Kb5 changes the Stockfish 6 evaluation from below -100 (at depth 60) to above +11 (at depth 43), which is pretty convincing.

Black has a straightforward win here by first pushing his a-pawn to distract the White king, then capturing White's queenside pawns, then driving his own b-pawn forward to push the White king back, and finally capturing White's kingside pawns and queening one of his own.

But instead Black played Kb5, and White responded by sacrificing a pawn to get his king to d5 to help queen a pawn.  At first sight White's sacrifice may not look too promising, as Black queens first and still has an extra pawn.  But in fact Black is lost due to the advanced position of White's pawns.

[Site "Prague"]
[Date "2014.11.29"]
[Round "3.3"]
[White "B. Heberla"]
[Black "Z. Pakleza"]
[Result "1-0"]
[FEN "8/1p3p2/pPk1pPp1/2P3P1/3K1P2/8/8/8 b - - 4 54"]

1...Kb5 2.f5 exf5 3.Kd5 f4 4.Kd6 f3 5.c6 f2 6.c7 f1=Q 7.c8=Q Qd3+ 8.Ke7 Qd5 9.Qe8+ Kxb6 10.Kf8 Qxg5 11.Kxf7 Qh6 12.Kg8 g5 13.Qe3+ Kc6 14.Qe4+ 1-0


It's not a ridiculous question. Before discussing your precise example, let's cover some basic grounds:

Purely from an optimal play perspective: having more space translates into having more activity and thus more options for your pieces, and that's really the key point here. The more space your pawn structure provides, the more maneuvering possibilities you will have to re-route your pieces around the board to ever more optimal posts. Moreover, controlling more space also means eyeballing or covering your opponent's important squares, related to concepts such as "dark/light square control" in chess strategy. So it's really about the relative amount of space both sides control. For a trivial example, go to very basic cases, such as first moves, 1.e4: what is the point very naively speaking? Not only it activates some of your pieces, but it also potentially takes away options from black, namely, it stops black from establishing a pawn on either d5 or f5, therefore we say white is a tempo up, because it gets the first say in space control and thus partially dictates the types of subsequent positions.
As for general ways of defining it, not necessarily restricted to optimal play in chess strategy, you can e.g., define space in terms of the number of possible legal moves you have, or the number of squares that are under attack by your pieces, so on and so forth, all compared to the other side.

Your position:

 [title "French defense example:"]
 [Fen "rnbqkbnr/ppp2ppp/4p3/3pP3/3P4/8/PPP2PPP/RNBQKBNR b KQkq - 0 3"]

In your example, there are very clear differences in terms of piece-activity thanks to the advanced white pawns on d4 and e5 in contrast to black's lesser advanced central pawns of e6 and d5:

white has activated both bishops, whereas black's c8 bishop is facing a wall.
white has enabled both knights to be posted centrally on c3 and f3, whereas black's f6 square has been taken away, so the knight is bound to go via the e7 square, but you have both options of f3 and e2!
white's queen has a total of 6 legal possible moves at its disposal, black's queen is restricted to only 3! Specially Qf3, Qd3 and Qg4 all very useful and common moves for the queen, all of which are symmetrically impossible for black, because of the lesser space created by the central pawns (which in turn also disabled the c8 bishop in taking away the g4 square from white's queen!)
Last but not least, although both sides have committed to their central e and d pawns, black's prospect are further limited by the fact that in order to eventually create healthy space for their pieces, they're forced to undermine white's pawn chain with f6 at some point. Meaning black's further pawn development is also being limited here, but white's are not.

Now all is not lost, because space alone doesn't dictate the outcome of the game and all still depends on how you decide to use that space, but the moral here is that having more space means having more choices, both in terms of possible moves and possible strategies to pursue.


Can you resign in a stalemated position?

No. Stalemate ends the game. Nothing further is possible after that.
According to the FIDE Laws of Chess:

5.2.1 The game is drawn when the player to move has no legal move and his king is not in check. The game is said to end in ‘stalemate’. This immediately ends the game, provided that the move producing the stalemate position was in accordance with Article 3 and Articles 4.2 – 4.7.


Why not take the bishop with the knight (Guseinov vs. Bauer)?

There is no hurry. After 8. Bb2 the bishop on b6 is not going anywhere. NxB continues to be available to white until black does something about it like a6. That means that delaying NxB gains a tempo if black has to make a less useful move to try and "save" the bishop like a6. Since recapturing with the a pawn probably gives black a better game it is worth waiting to see if he will throw away this option by playing a6.

Delaying the capture also retains the possibility of playing Nc5 which may be stronger in some circumstances.

Finally an immediate NxB will be met by axN opening the a file for black and allowing the a8 rook to pressure the now weak, backward a3 pawn.

So, in short, delaying the capture retains flexibility. That way white has more and possibly better options. This "maintaining the tension" is one of the things which separates weak and strong players. Weak players are in too much of a hurry to release the tension in a position. Strong players maintain the tension and with it give their opponents more opportunities to go wrong.


How to understand Stockfish’s source code?

I believe the line you quote is about probing KPK tablebase endgame. There are 64 squares for the king, and 24 squares for the pawns (mirrored from file A to D). Nothing special, just how Stockfish indexes the bitbase data structure.

The code is not going to work in Chinese Chess for obvious reason.

  This line of code in this file is not well documented

No, the line was fully documented. Please look at the code file again.

  Please give me suggestions to understand the source code better

In the open source world, if you don't have sufficient coding experience you just can't do anything. You may ask on the Fishcooking forum, but you will still need decent programming experience.


In order to qualify for the title of Grandmaster, a player must
  achieve three Grandmaster norms.

That is not accurate. The regulations for the award of FIDE titles are given here.

There are two ways to become a grandmaster. Achieving norms and reaching a certain rating is one way but there are also Direct Titles. The FIDE handbook defines these like this:

  Direct title (automatic title) is a title gained by achieving a certain place or result in a tournament. For example, winning, or
  achieving a result ≥50 percent in a tournament. On application by the
  player’s federation and confirmation by the Qualification Commission,
  such titles are awarded automatically by FIDE.

The tournaments and achievements which qualify the player for the various titles are given in the Table for Direct Titles effective from 1 July 2017.

For the grandmaster title the following results give the player the right to the GM title:

Last 16 of the World Cup
Winner of the Women's World Championship
Outright winner of any of World S65, S50, U20 championships
Outright winner of Continental Individual Championship

But in any case these regulations are made by FIDE and they change with time.

  Who were the first GMs, and how did they become GMs?

The original FIDE grandmasters were awarded the title via a resolution of the FIDE general assembly in 1950. These players were:

The top players of the day: world champion Mikhail Botvinnik, and those who had qualified for (or been seeded into) the inaugural Candidates Tournament in 1950: Isaac Boleslavsky, Igor Bondarevsky, David Bronstein, Max Euwe, Reuben Fine, Salo Flohr, Paul Keres, Alexander Kotov, Andor Lilienthal, Miguel Najdorf, Samuel Reshevsky, Vasily Smyslov, Gideon Ståhlberg, and László Szabó.
Players still living who, though past their best in 1950, were recognised as having been world class when at their peak: Ossip Bernstein, Oldřich Duras, Ernst Grünfeld, Boris Kostić, Grigory Levenfish, Géza Maróczy, Jacques Mieses, Viacheslav Ragozin, Akiba Rubinstein, Friedrich Sämisch, Savielly Tartakower, and Milan Vidmar.

In 1951 Efim Bogoljubov was added to the list via another vote.

In 1953 something similar to the modern rules was introduced with the world champion and players who qualified for the candidates having the right to the title (if they weren't already) being joined by a variation of the current norm based qualification.

These rules received major revisions in 1957, 1965 and 1970 and may have been tweaked on further occasions.


What is the thought process of a GM playing bullet?

Well, of course in very short time controls one cannot assess all the details prescribed in the answers of that good post. Grandmasters rely mostly on their vast experience, as much as it happens in other fields. But we can say that pattern recognition for tactics and mate threats play a major role. And they also learn to polish their intuition. They can efficiently and quickly prune the decision tree (even if they are wrong, they have the process automated) and they learn to recognize the critical points in which they should take some more time evaluating a position. They will have time saved for that critical moment, if it appears.


How does Magnus create opportunities for his opponents to go wrong?

An interesting question!
I think it was Kramnik who, when asked who the best player on earth was, mentioned some other player. When asked why not Carlsen he replied: Magnus is from another planet!
That such a great player as Kramnik, conquereor of Kasparov, was in awe of Carlsen speaks volumes.
His "sight of the board" is phenomenal as is his ability to detect tactical possibilities.
How does he create opportunities for his opponents to go wrong?
The simple answer is by continuing to play!
He seems to absolutely love playing chess and plays out positions that many other GM's would pass up as too dry and drawish.
He has a superb ability to find resources in any position where other GM's cannot. Sometimes the advantages are only microscopic but Carlsen is willing to steadily seek out and accumulate these and convert drawish positions into winning ones.
Carlsen seems content to just get a playable position out of the opening rather than dominate with superior opening knowledge like Kasparov could do.
If you play through his games he often switches play back and forth from the centre then to one wing then to the other. He keeps sustained pressure on his opponent and squeezes as much as possible out of any position.


Looping through the same lines while solving puzzles

Establish an order to analyse the lines!

I would begin by the most forced moves (checks, mate threats, captures...) and finish with those where the opponent was multiple possibilities. Respect that order strictly so you won't be jumping back and forth.

Use the same criteria also for sorting subvariations (ie: start by the most obvious check, pick an opponent's answer, now calculate checks, threats and captures after that particular answer and so on)


Claiming a 50-move draw with a mating move

Mate ends the game immediately, but the mating move must be made, not just written down. If the player only writes the move down and claims a draw in the correct way, it's a draw (but I doubt it'll ever happen in practice).


How many moves out do the static board evaluations use?

Note that there are two components to the score. First, there's a raw
  score due to some sort of piece scoring system. Second, there's a
  positional evaluation scoring element that considers future moves and
  future pieces that might be taken.

This is wrong. The "piece scoring system" is part of the positional evaluation that is considered at the end of possible lines. It doesn't matter what the pieces are now, it matters what they will be in the future. Therefore the -0.9 is equal to the score after the best move black can currently do, 2...dxe4. It's also equal to the score after the best move white can answer to that, moves other than 3.d3 apparently scored worse. This is called the "minimax algorithm".

At the time static evaluation is done, it looks only at that exact position and doesn't look ahead more moves. The looking ahead part is done by then.

Pawns get different scores depending on where they are. I think that most engines compute some score that says how "endgameish" a given position is, and if it's more endgameish then a pawn gets a bigger bonus for being far advanced, but that's actually guesswork on my part.


In Chess, you use SPSA and CLOP. Those are the algorithms used by Stockfish in Fishtest to tune its parameter. The algorithm worked so well that it made Stockfish be the strongest engine in the world.

Please note that the algorithms are very complicated mathematically. One could write a PHD thesis on this topic. In SPSA, you start from a best guess from the value. Then play games, use those games to derive a better gradient for the next series of parameters.

The maths is very hard, but it all boils down to some statistics - you play games, and use those games to derive a distribution to update the parameters you want to tune.

Please read:

http://talkchess.com/forum/viewtopic.php?start=0&t=50823&topic_view=flat

and

https://groups.google.com/forum/#!searchin/fishcooking/SPSA/fishcooking/WNrxeXAJ6VI/ZkCnRv4I_qEJ


Quiesence search isn't able to handle situations like that - including checks would explode the search tree.  Two iterations later (assuming you're doing iterative deepening), Qxd5 and Bg3+ will take place in the main search, and then quiesence search would be able to find the continuation you described.
Some engines include quiet checks in the first ply of quiesence search - in that case you situation would be resolved in one additional iteration instead of two


Is there a name for a chess variant where you are allowed to capture your own pieces?

In German, we would call this "Schlagschach". The German Wikipedia translates this to "Capturechess".

However, I could not find an English resource that describes this variant.
But there is a thread on chess.com where someone asked about the exact same thing.

Edit: Thanks to @bitchaser who dug that thread more thoroughly and found a link to another page that calls this variant "Self-Eliminator", which states:

  John Gallicano and Steve Mann invented this variant in 1997.

There is also a Java applet on that page, which is not easy to use nowadays, since for security reasons, modern browsers just don't support Java applets anymore.

I hope, this is not too off-topic for Chess.SE, but for those of you, who are interested, here follows a short instruction on how to run the game, nonetheless:

first, make sure you have the tool appletviewer on your PC. If not, you have to install the Java 8 JDK or earlier, since the tool is deprecated since Java 9. Make sure, it's the JDK, not JRE.
second, download the following files of the applet and put them all in the same folder:

https://www.chessvariants.com/play/erf/SelfElim.html (the html code is enough, no pictures, CSS or scripts are required)
https://www.chessvariants.com/play/erf/SelfElim.class
https://www.chessvariants.com/play/erf/EasyChss.class
https://www.chessvariants.com/play/erf/Chsq.class
https://www.chessvariants.com/play/erf/Chmo.class
https://www.chessvariants.com/play/erf/CB10_10.class

last, navigate to that folder and run the following command in a terminal: appletviewer file:SelfElim.html

The applet should pop up and show you the game screen:


Does threefold repetition take into account the side to move?

You quote an extract from the FIDE Laws of Chess which includes the simple instruction "see Article 9.2" yet you don't bother to "see Article 9.2" where your question is answered -

  9.2.1 The game is drawn, upon a correct claim by a player having the move, when the same position for at least the third time (not
  necessarily by a repetition of moves):
  9.2.1.1 is about to appear, if he first writes his move, which cannot be changed, on his scoresheet and declares to the arbiter his
  intention to make this move, or
  9.2.1.2 has just appeared, and the player claiming the draw has the move. Positions are considered the same if and only if the same player
  has the move, pieces of the same kind and colour occupy the same
  squares and the possible moves of all the pieces of both players are
  the same. Thus positions are not the same if:
  9.2.2.1 at the start of the sequence a pawn could have been captured en passant
  9.2.2.2 a king had castling rights with a rook that has not been moved, but forfeited these after moving. The castling rights are lost
  only after the king or rook is moved.

Note in particular "Positions are considered the same if and only if the same player has the move"


Should a player be forced to move a piece that he has picked up after a spectator knocked it off the board?

I am not an arbiter, but here's what the rules say:

Rule 4.3 (emphasis added)

  if the player having the move touches on the chessboard, with the intention of moving or capturing

I think it should be clear to any reasonable person that picking up a piece that was knocked down by a spectator does not imply intent to move.

Perhaps the arbiter went with an overly narrow interpretation of "accident", though, from 4.2.2:

  Any other physical contact with a piece, except for clearly accidental contact, shall be considered to be intent.

I would still argue that picking up a piece that was knocked down is an accident according to the spirit of the rules. Obviously the piece must be "adjusted" since it's not just a matter of centering it a little bit on its square, but of picking it up from the floor. Therefore the intent to "adjust" is implied.

The USCF rules are similar in that they refer to intent to move, but additionally, there is a rule that might have helped in this case: 10H says "there is no penalty for touching a piece that is off the board". The main idea given the rest of the paragraph concerns promotion, but I think it would also apply here. (And I just noticed that the FIDE wording on the rule also says "on the chessboard". I don't know how I missed that the first time!)


Combining AlphaZero methods with Stockfish methods

You are asking the right question but only want to refine your premise slightly. AlphaZero does indeed search "through lots of positions from the current one first," as you have said, only not precisely via alpha-beta pruning. AlphaZero's makers explain it thus:

  Instead of an alpha-beta search with domain-specific enhancements, AlphaZero uses a general-purpose Monte Carlo tree search (MCTS) algorithm. Each search consists of a series of simulated games of self-play that traverse a tree from root state s root until a leaf state is reached. Each simulation proceeds by selecting in each state s a move a with low visit count (not previously frequently explored), high move probability and high value (averaged over the leaf states of simulations that selected a from s) according to the current neural network fθ. The search returns a vector π representing a probability distribution over moves, πa = Pr(a|sroot).

As you know, most opening and middlegame positions make it impractical to search all relevant chessboard futures, so the question is how to prune the search tree. AlphaZero prunes the tree as explained but, for each relevant chessboard future not pruned, evaluates the position by neural net.

Thus, contrary to your premise (if I grasp your premise correctly), AlphaZero judges not only the position actually on the board but also potential future positions.

If you have had occasion to review Stockfish's source code you will have noticed how straightforward Stockfish's evaluation function is. It's fairly simple and very quick. The speed of AlphaZero's evaluation function naturally depends in part on the hardware on which AlphaZero is run but in the absence of exotic hardware AlphaZero's evaluation can hardly be as fast as Stockfish's. Therefore, significantly, as far as I know, Stockfish has the advantage of evaluating more chessboard futures than AlphaZero can. Your premise is right to that extent.

Nevertheless, AlphaZero

searches more chessboard futures than a human master can, and
apparently evaluates each better than Stockfish can.

This is reportedly how AlphaZero plays better than either.

Insofar as AlphaZero's makers have not released their source, it is hard to say too much more, but meanwhile you may have heard of LCZero, a vigorous open-source attempt to replicate AlphaZero's results. If you have not heard of LCZero, also known as "Leela," then you might investigate when you have some time.


KID fiancetto variation - reason for c6 after Nd7

First of all, to sit back and wait isn't a good strategy for black, as white has many useful moves to make: h3, Be3, Qc2, Rfe1, Rad1. If white can get these moves in with black doing nothing, white will be clearly better.

So black has to look for counterplay. Most of black's options involve c6 to activate the queen on the d8-a5 diagonal. If you absolutely don't want to move the c-pawn, then one of the few options left is to play exd4 followed by Nc5 and a5. This is playable, but not popular, as white can place an annoying knight on b5, see Giorgiev vs Ilincic, Belgrade 2000.

Black can also try to play exd4 and Nc5 without a5 (instead Bd7, a6, and so on). The game then can get sharp, but current theory says white is comfortable.

In summary: Black plays c6 to get needed counterplay. The other options to get counterplay aren't quite as attractive.


How to use Arena GUI outputs in a python program

I think using the Arena GUI may be an overly complex way of attempting this.

Instead, go for the Arena engines. Many (all?) implement the UCI protocol, which would allow your application to basically send move information to the engine, and get its responses (under the chosen set of parameters) back.

Some chess engines use other protocols, and not all may be open or freely available.  UCI (see https://www.chessprogramming.org/UCI for more info) is reasonably well known, so you should be able to get answers to any problems you might have.


Why should I try to put knights on weak squares when they can be taken easily?

It is true, that sometimes occupying weak squares with your pieces will just lead to exchanges and no advantage whatsoever. But there is a well known dictum in chess, that "the threat is stronger than the execution".
This means that just threatening to occupy a weak square can severely restrict your opponent's possibilities. Just imagine you brought a knight to c4 and your opponent was set on the idea to either play Nd7xb6 or Nf6-e8 if you dropped your piece into b6 or d6. This would leave him unable to move either knight until you executed your threat. Which in turn would hamper his development, because his bishop cannot move, which in turn means his rooks cannot be connected. And of course you wouldn't oblige him and execute your threat, you would just keep it hanging over his head.

On the other hand, in this specific position, taking the knight on b6 wouldn't solve blacks problems. After you retake with the bishop you actually control the square d8. This is very relevant, because it means that he cannot oppose you with his rooks on the d-line. So, bringing a knight to b6, retaking with the bishop and then taking control of the d-line by doubling your rooks, seems like a valid plan to use the weakness of b6.

Of course these are purely strategic musings, it is always the question whether a plan can be executed tactically.


You are right, h3 has no immediate purpose. But that's not the point. The idea behind playing h3 is to set up many resources that may be used in the future. I'll list these resources below:

A) Luft. Sometime long down the road, the king may need a luft to prevent a back rank mate. Yes, Caruana doesn't know if moving the h-pawn will be the ideal luft in every possible situation, but usually moving the h-pawn works best. You also mentioned that Caruana would soon have plenty of Luft because Aronian trades his bishop for the three kingside pawns. This is also true, but Caruana had no way of knowing this ahead of time.

B) Possibly playing g4. Notice how Black's knight on f6 is tied to the defence of the d5-pawn. One day, White may play g4-g5, booting the knight from its post and winning d5. This doesn't work in the current position (why else would Caruana play 12.Qe2 instead of 12.g4?), but again it's about the possible future. In some future position, Caruana may find the g4 idea useful. It's likely he will never use it, but it doesn't hurt to have the option ready should the need arise.

In summary of points A) and B), h3 is meant to set up resources that Caruana might use in the future. He may never use these resources, but it's good to have them ready just in case. Playing h3 doesn't hurt his position, so why not?

There's also two more reasons behind playing h3:

C) The bishop on h5 is arguably worse than on g4. On h5, the bishop can only go to g6, where it will be blocked in by White's e4-pawn (provided White can protect the pawn). On g4, the bishop would have been able to retreat along the c8-h3 diagonal.

D) As user1583209 pointed out, by playing h3 White has the option to suddenly break the pin with g4 at any moment. This may be a very useful resource, if White's knight needs to be freed up to do something immediately. Without inserting h3, Black would be able to capture on f3 if White played h3 later on.


Mate could be forced sooner...[the] two bishops [can mate in up to] 19 [moves].

Source: Last paragraph from Daniel's answer to 'With only a king left, how many moves remaining until a draw?', with editing from me, seeing as I am taking just the part relevant to this question.

For a table of maximum number of moves to mate, see Wikipedia, which cites Batsford Chess Endings by Speelman, Tisdall and Wade.


Are there any gambits where I HAVE to decline?

While it's not generally given as part of the explicit definition, the term "gambit" usually refers to an offer of material that can be accepted. If it can't be accepted, then it's a trap.
You can look through chess traps and see that many of them involve apparently giving up material.


Can white do better versus the Sicilian Defense by avoiding an early d4?

All the main lines against the Sicilian are the open Sicilian.  This opening of the center gives white better attacking chances against black's lack of development.

Larsen claims that playing d4 is a positional mistake, allowing black to exchange a less valuable wing pawn for a center pawn.

Spassky played the closed Sicilian with great results.  And there are many anti-Sicilians which claims to give white the advantage.  The Grand Prix is the most fun, but I personally prefer the KIA.

The main difference between the open and closed Sicilians is the number of moves before the attacking begins.  The open offers more tactics right from the start.  The closed allows both players to finish developing before any attack really develops.

The real answer is that neither is necessarily good for white.  Since every line of the Sicilian is so heavily analyzed, the advantage goes to the player with the better knowledge and comfort in the positions.


Would this clock time mode be useful at all?

Perhaps this could be somewhat useful in practice games, but I don't see much point in having a minimum time control in real games. Some reasons (let's assume the minimum is 10 seconds but could be any number):

sometimes you are doing forced moves (or known opening moves) where having to wait 10 seconds would be annoying
conversely, there are situations where you have to think a lot longer than 10 seconds, so here the minimum time would not help at all
you might run into the problem that you end up trying to make moves just after 10 seconds (particularly in time trouble), with the added annoyance that you now also have to keep track of when 10 seconds have passed

Overall I think that you should rather try other methods like sitting on your hands, analyzing your games with respect to time spent on moves (and relation to blunders), etc. to improve your time management. An important factor in improving your chess is also to know when to spend more time and when you can make more or less automatic moves.


Is it ever posible to win if the only pieces left are two kings and a knight?

No, it is not possible to checkmate with a lone knight (K+N vs K).
However, Add another Bishop and you'll be able to Checkmate (K+N+B vs K)

There is a rule in Chess which goes like this "No Mating material = Draw"

So:

K vs K = Draw

K+N Vs K = Draw

K+B Vs K = Draw


Books that help improve your chess without a chessboard?

One book that can mostly be read without a chess board is Willy Hendriks' "Move First Think Later", one of my favourite chess books. It mostly contains puzzles and some interesting musings from the author.

Also, even though you are not looking for a digital solution, I have to add that I find DroidFish (available on Android) to be a nice compact way to read chess books on my daily commute while still having the power of a GM level analyst right there.


To answer your first question, in these structures, white has more space and because of that, he can put his pieces in more advanced positions. Black's king is usually on the kingside in these positions which makes the e5 square a great square for a knight. If the knight was on c5, then black could play b6 and kick the knight out. When the knight lands on e5, f6 would be unwise by black because it greatly weakens the e6 square. Basically, these pawn structures result in more space which means it is easier to maneuver and therefore, start an attack. Also, these pawns are a short term advantage, and without quick action, black could quickly arrange his pieces to attack your d4 (and c4) pawn(s).

Black would benefit with an exchange of light squared bishops because of the fact that the e6 pawn blocks the activity of black's light squared bishop. White's bishop is very strong on the b1-h7 diagonal, therefore, in a majority of circumstances, it is favorable for black to exchange light-squared bishops.


Can Black reach full equality in this game?

Deep Rybka's 4 opening book (with pre-calculated scores on positions in it) gives the position resulting by

    1.d4 d5 2.c4 e6 3.Nc3 Be7 4.cxd5 exd5 5.Bf4 c6 6.Qc2 Bf6 7.e3 Ne7 8.Bd3 g6

a +0.52 score, so definitely some advantage for White. It contains the following continuations:

[fen ""]

1. d4 d5 2. c4 e6 3. Nc3 Be7 4. cxd5 exd5 5. Bf4 c6 6. Qc2 Bf6 7. e3 Ne7 8. Bd3 g6 9. Nf3 Bf5 10. h4 (10. O-O Bxd3 11. Qxd3 O-O 12. h4 (12. b4 Nd7))

and several sub variations.


I think the best way to get yourself acquainted with chess evaluation schemes, is just by looking up the documentations of some of open source (or GNU) chess engines out there, after all such questions have been asked/tackled for many years now, and there are many good answers out there that you need to explore before coming up with your own (hence all the variety of good engines today).

Of course as things stand today, most of chess engines rely on evaluation systems that are (for the most part) heuristics-based. What is important before getting into some of the possibilities is to note that, there's no one single evaluation function that would solve chess, so what we really need (all we can hope for really) is a well weighted combination of many different evaluations, some of the main (usually mentioned) ones:

Pawn structure: if your engine is capable of noticing connected pawns, doubled pawns, blocked pawns, isolated pawns etc, then you're already doing pretty good.
Material: Probably the easiest part to implement, just get a total piece count for both sides and compare. Then compare by piece-type (how many bishops vs. how many knights etc)
King safety: Again pretty easy to implement evaluators such as: open lines/diagonals heading towards the king, likelihood of checks (within next 2-3 moves for simplicity), rights to castle, and so on.
Individual piece evaluation: For each piece type, you should have a different evaluator, that measures its activity, e.g. by counting different possible moves the piece can make (total of 8 for the most active knight as example), openness of diagonals for bishops (also whether own-piece is blocking it or opponent piece, should be weighted differently), available squares for queen etc.
Mobility: A simpler version of the above if you will, i.e. just count the number possible moves each piece can make, and try to maximize it, i.e. the evaluator should add positively to the total evaluation function if from one move to next one (or more) of your pieces is gaining additional move possibilities.
Piece exposure: Just count how many of your pieces can be captured within a well defined ply (within next 2 moves e.g.). Such evaluators bring dynamics into your whole evaluation scheme, as based on them, you will then re-prioritize each of the previously mentioned evaluators (by re-distributing the weights initially assigned), you see it's a lot of fun implementing a chess engine ;)
Central control: Can be simple or very complex, the simple approach would be: defining a set squares that define what you call "center", then count how many pieces can potentially jump to those squares within next 1-2 moves, such approach should give you an estimate for central control.
More advanced features would be: Tempo considerations, to define such concepts in your engine, you need to have already covered all the basic evaluators. Connectivity or coordination of pieces come next, and so on.

Hope the few mentioned elements give you some rope already, of course there's a long way to go, but it's really important to first find out what's already been done and tried before you stumble on your own ideas. There's a must-check website for programming chess engines, have a look, you'll find tons of ideas and implementation suggestions: chessprogramming on wikispaces. If you need further clarifications, don't hesitate! Have fun implementing!


First things first, this is an example of a very poorly played game, so Black gained its edge because of White's tactical mistakes, rather than by taking advantage of their extra space. This is a "fault" often made by chess authors when trying to illustrate a concept. They will explain the events in a game in a way that "fits their narrative" rather than provide an objective analysis, which is this case would lead to conclude that the position is pretty much balanced if not slightly advantageous for White until the horrible 7.Qe2.
It is true, though, that by move 6, White's lack of interest in fighting for the center costed them most of its starting advantage despite Black having lost several tempi with their queen. White could have played 7.Be2 (among others) and still have a reasonable position despite Black's lead in the center due to their extra development.


You're trying to analyze the very equal position with no significant tactical potential. Depending on minor tweaks of your engine settings, you may get a few "good" moves, including Be2, Ba3, c5 -- all approximately equal.

Computers at lichess have limited resources, hence they spot only obvious stuff, and have a limited precision when evaluating moves.

If you move h4 -- you're down about 0.1 pawn, I would not lose a sleep about that, Be2 is good enough and you should not worry what stupid engine says =)

Disclosure: I'm actually running one of the lichess analysis boxes, so I took a deep dive into the details. Here's what I found:

From your screen shot, you're running analysis on your local iPad, which is slow and may take some time to arrive to the good result. It would be much preferable to run the server side analysis, much faster and more precise.
I have found the game in question among your games and analysed it using various engines available. Most of the engines recommend c5 as the best continuation for White. However, for the lichess analysis we use a very conservative settings of Stockfish ("Analysis Contempt" is turned Off), this changes the focus from the active attacking moves to the "safe" defensive ones. And h4 is one of those nice safe moves.

As I have said earlier, it all depends on the minor tweaks of the engine parameters, the score difference is negligible and h4 is no better and no worse than a few other moves -- play what you like and don't worry about what computer says.

Answering the second part of your question, here's my analysis:

Bd3 seems to be "the best", with h4 and Be3 sharing the second place. Actually, while analysis was running, 4 or 5 top pretenders constantly swapped their places, sometimes h4 was on the top. Probably, if I run the analysis deeper, there will be a few moments when any of the top 5 moves will be declared "the best".

All in all, the analysis is not exhaustive, and it does not guarantee to give you the "absolute best move". The main purpose of the analysis was to spot your mistakes (8. h3? was clearly a mistake, losing 0.5 pawn), and propose something better, not necessarily the best.

Here's the analysis @ depth 24, h4 is way below.


It is not an answer, but an extended comment.

A great question, and a very interesting functionality proposal.

I don't know if such a tool exists - however if I were to implement it I'd consider analysing the same position using different strength settings. For example, if the move is only found by the top strength, it is a good candidate for !!. It is more or less easy to implement, but may require some effort tuning up.


Which common response against 1.e4 did Magnus Carlsen say is a bad opening? And what was Carlsen's exact quote?

I think the answer is the French Defence.

A quote of Carlsen can be found here: http://www.reddit.com/r/chess/comments/1do05q/annotated_chess_game_in_french_defence_by_carlsen/

I copied the quote:

  The French Defence. In my younger years I used to consider it at best a second-rate opening, and I once even lost a bet with one of my friends, and as a result had to play 1... e6 in all my games with Black in a Super-GM tournament. Fortunately my friend was greedy, and took money instead. I believe that both 1...c5 and 1...e5! are better choices, but since I desperately wanted to win this game (I was trailing the leaders Kramnik and Shirov by 1 point at this stage) I decided to try something new.

Carlsen wrote this quote in his comments of the game Karjakin-Carlsen, Wijk Aan Zee 2010. See annotations of the game Ivanchuk-Carlsen in following report:
http://www.chessvibes.com/?q=reports/masters-final-r5-leader-ivanchuk-loses-to-carlsen-nakamura-beats-vallejo


Plan against QGD Janowski variation (3...a6)

Indeed, the line is relatively rare, but the move 3....a6 seems to become more and more popular the last couple of years. Even Magnus Carlsen has played it twice in blitz recently, against Aronian and Grischuk.

The move 4.cxd5 is the most popular move and arguably the only way to fight for an advantage. After 4.Nf3, black has the choice to transpose to a favorable version of the QGA by 4....dxc4. As the knight is already on c3, black avoided the most critical lines of the QGA.

After 4.cxd5 exd5, in Mamedyarov-Vallejo Pons, white went for the aggressive 5.Nf3 c6 6.e4!? dxe4 7.Ng5 Be7 8.Bc4. Now, 8....Bxg5 would be a mistake as white regains the piece by 9.Qh5, with a strong initiative. Instead, black played 8....Nh6, defended correctly after 9.Ngxe5 Nf5 and made a draw.

Another try to spice up the game is 5.Qb3!?, which was played recently by the Russian top GMs Nepomniachtchi, Matlakov, Vitiugov and Svidler. After the logical 5....c6, white obtains a dangerous initiative after 6.e4 dxe4 7.Bc4 Qe7 8.a4! (to prevent ...b5), which was played by Svidler. In the three other games, after 5.Qb3, black continued with 5....Nc6. After 6.Nf3 Bb4 7.Bf4, white is probably slightly better, as the black knight on c6 is somewhat misplaced.

      [StartPly "6"]

      [FEN ""]
      1.d4 d5 2.c4 e6 3.Nc3 a6 4.cxd5 (4.Nf3 dxc4) exd5 5.Qb3 (5.Nf3 c6 6.e4 dxe4 7.Ng5 Be7 8.Bc4 Nh6 (8...Bxg5 9.Qh5) 9.Ngxe4 Nf5) 5...Nc6 (5...c6 6.e4 dxe4 7.Bc4 Qe7 8.a4) 6.Nf3 Bb4 7.Bf4


A chess problem: White to play and mate in two

This is a fairly simple one:

   1. Qd8+ Bxd8 2. Re8#


What is the earliest queen move in any strong, modern opening?

The definition is still a bit ambiguous, but here's what I found.
The absolute soonest to move the queen is probably the French Defense: Chigorin Variation which begins with 1.e4 e6 2.Qe2.
The Scandinavian with 1.e4 d5 2.exd5 Qxd5 looks like the most common way to move the queen on move 2. I found a game by GM Aleksandr Rakhmanov in 2019 at standard time controls, which ended in a draw.


Training tactics - doing more easy puzzles or fewer, but deep, puzzles?

I would say it really depends on your skill level. If, like me, you're a relatively weak player, playing lots of "easy" and "medium" puzzles is probably more beneficial. You want to train yourself to recognize patterns and interactions that are likely to come up in a game. In that case, seeing lots of different tactics is probably best.

As you get stronger, the basic tactics from "easy" and "medium" puzzles will be almost always seen by both players (you still need to recognize them because if you miss your opponents simple fork, you're going to have a bad time). Focusing on harder puzzles will help you find those more complex patterns and tactics in your games. In this case, both lots of tactics and complete understanding of every puzzle is probably the desired outcome.

I've listened to GMs talk about puzzles where they look at it for hours and when they have a "solution" they still don't actually know if it's solved until they consult an engine, the puzzle creator, or their coach. (Compared to a simple forced mate in X puzzle).

Additionally, it's all about where your strengths and weaknesses are. If you're really good at a particular type of tactic, de-prioritize continued training of that tactic and focus instead on your weaknesses.

Most people have a bias where they would rather do 5 puzzles they're good at and 1 they're bad at, which is fine if you're doing it purely for entertainment, but if you're trying to improve, reverse the ratio.


These codes are the extended ECO codes by SCID, and have no meaning outside it.

When classifying the games you can enable or disable the extended ECO codes to force SCID to use the standard ones, if you prefer so.

There's a short explanation of the reason for the extended ECO codes here: https://sourceforge.net/p/scid/wiki/TheECObrowser/


It depends what level you're talking about.  At the top level with super GMs, it's more or less out of fashion in serious games.  They either choose the Berlin or some other main line (like the Closed Spanish).

In the -2000 section though, it's still a viable opening.  If you know it well enough then it's a good weapon to catch your opponents off guard.  I would recommend learning another line to play against the Spanish though, so that you can alternate between it and the Jaenisch.  If someone were to spend a serious amount of time preparing for you, they could cause some problems.  If you have multiple lines though, it makes preparation much more difficult.

I looked up the Jaenisch's stats in the Mega Database, and it actually stores fairly well.  White only scores slightly over 50%, and this is a normal stat for most main lines.  Also, some top level guys have played it before (Aronian, Radjabov, Carlsen, Ivanchuk).  While they don't play it regularly, it's still a testimony to the viability of the Jaenisch.


Help for beginning player to start learning openings

It's important to know the main openings and their ideas, but there are some don'ts here.

Don't study obscure or excessive lines under the impression that not knowing these rare lines will result in poor play (it doesn't).
Don't study opening moves without understanding the ideas behind the moves.
Don't fall into the trap of learning hundreds of opening lines in order to gain an advantage of 0.2 pawns, only to drop a piece to a simple tactic in the middlegame. One of the best coaches in the world for beginners, National Master Dan Heisman, said:

  It does not matter who gets the advantage out of the opening if one of the players is likely to lose a piece to a simple tactic in the middlegame. Losing a piece from an advantageous position will almost always result in a lost position. So study tactics, not openings, until you almost never lose pieces to simple tactical motifs.


Does Google's new quantum computer mean we will soon have a more powerful AlphaZero?

TLDR: No

Reasoning: Quantum Computers in the short to medium term only have some very specific things efficiently (factoring and discrete log and a few others). The algorithm google showed "quantum supremecy" on is basically simulating a random quantum circuit to generate random numbers, which is

about as favorable an algorithm as you could imagine
completely useless as an algorithm since there are plenty of simpler random number generators
probably not even quantum supremecy achieved IBM paper

For general tasks, quantum computers achieve a quadratic speedup assuming a large enough quantum computer (compared to exponential or more speedup for the demonstrated problem). Furthermore, to even run a basic chess evaluation function on a quantum computer you would need at least an order of magnitude more qbits than state of the art (probably way more, but I'm hedging).

Overall, quantum computers now are at about the same stage as computers were in the 1800s. It will be a while before they are useful for anything, and chess is highly unlikely to be something they are ever used for seriously.


Why did Capablanca win a majority of games playing as black?

In Megabase 2016, Capablanca played 791 games as White and won 52.6% of them, and played 406 games as Black and won 48.5% of them, so he didn't win more as Black but it was surprisingly close.

The discrepancy between number of White games and Black games was surprising, so I broke out his simultaneous displays (in which he would generally be playing White). In his simuls, he played 304 games as White and won only 40.8% of them, and played 26 games as Black and won 34.6% of them.

When we subtract out the simul games, he won 292/487 = 60.0% of his games as White, and 188/380 = 49.4% of his games as Black.

In conclusion, I suspect that the unique aspect of his play was that he didn't try that hard in simuls.


Is there a software where we can query historical games to find patterns without inputting the exact chess position?

As Brian mentioned, CQL (Chess Query Language) is the most capable tool for the job.  The current version of CQL at the time of this writing is 6.0.5 and the current website is http://www.gadycosteff.com/cql/.  The site provides lots of examples and comprehensive documentation.  Below are queries that will find games matching your three examples to give you an idea of what CQL looks like in practice.
More than 10 checks in a game
cql()
initial sort "total checks" find all check > 10

This will find all games where check was delivered (by both sides) more than 10 times in a game.  The matching games will be sorted in descending order by the number of checks delivered (the first game in the output will be the one with the most checks) and will contain a start-of-game comment with the number of checks that appeared in the game.  For example, here is a game from lichess.org that was found using this query with 81 checks.  By default, the query will also add a comment to each move that matching the find filter (i.e. each move that is a check).  The find filter is described in detail here.
Consecutive checks
The CQL website provides many examples.  The consecutive-checks.cql example finds games with 5 or more consecutive checks.  The query provided there is:
cql(input heijden.pgn)
sort "number of consecutive checks"
  line 5 100 nestban
    --> check+

The sort filter will again cause the games to be sorted by the number of most consecutive checks.  A comment will be inserted for each checking move in the longest line of checks for each matching game.  Documentation for the line filter used in this query is found here.
Winning side has King crossing middle rank
The following query will find all decisive games where the winning side's King moved to the opponent's side of the board at some point.  The first time the King crossed into enemy territory will be commented.  The query is written from the perspective of White (the filter result 1-0 means White won and Ka-h5-8 matches a position where the White king is present on ranks 5-8) but matches for both White and Black using the flipcolor query (the flipcolor query is described here).
cql()
initial
flipcolor { result 1-0 find Ka-h5-8 }


What motivated Kasparov's comments on the Anand-Gelfand match?

Kasparov's reason for that statement may be no deeper than this:

The current rating list does give a concrete, factual basis for his assessment, though it is certainly something with which others might disagree. Current world #2 Levon Aronian, for one, made a point of contradicting Kasparov:

  "I don’t think [what Kasparov said] is true. The player that made it through a very tough Candidates’ Tournament and the player that has held the title for so long are, by rights, the strongest players in the world."

Ultimately, how one defines the "strongest" players is clearly a subjective matter. As for what underlying personal motivations Kasparov might have for saying what he did, we shouldn't speculate; so if that really is what you're after, then I concur with the current vote to close the question. But if you take the rating list to satisfy the "why" of your question, then it seems OK to me.


I would like an iPad app for annotating my games

Stockfish works well for this purpose; and it's free software.


Can the Scotch Game really give White chances to get an opening advantage?

I like your question a lot. Though I don't play either side of any 1. e4 e5 openings, it got me thinking about the motivations behind playing the Scotch Game. Though you were clearly happy with the answer you accepted, I'm adding another answer because I don't personally understand how that one addresses the question as you asked it, and I think some further thoughts might be useful for others who come upon the question. So here's an alternative way of looking at things.

To answer your question, yes, against a peer, the Scotch Game really does offer chances of obtaining an opening advantage; Kasparov's record using it against his peers, including Karpov, is a case in point (even though, yes, he is Kasparov and we are not). The Scotch Game will not lead to an opening advantage against equal play by your opponent, but that is no different than with any opening. For example, that is just as true for the Scotch Gambit which Tony's answer recommends as an alternative. (And, incidentally, if the opponent declines the Scotch Gambit, you can just end up in the Italian Game anyway. If we're dismissing out of hand the "standard positional play" in the Scotch Game as offering no hope for an advantage, as expressed in Tony's answer, then I don't know why we wouldn't do the same for the Italian Game. No reason has been given for dismissing either.)

Regarding Kasparov's assertion that only the Ruy Lopez and the Scotch Game are "serious" attempts at obtaining an opening advantage for white after 1. e4 e5 2. Nf3 Nc6, it is safe to say that he was speaking in terms of what he considered to be a serious attempt where he lived, i.e. the very highest echelon of the chess world. I am of course completely unqualified to confirm or dispute Kasparov's opinion on that matter; judging from the frequency of which openings appear after those moves, it does seem that that is the consensus among top players.

In any case, while I won't compare or contrast the Scotch Game with those "lesser" alternatives, I will try to give you a bit of an answer to your question as to what kind of an advantage white can seek in the Scotch Game. As stated above, I don't typically play either side of this opening, and even if I did, I'm not a strong enough player to really be trusted. So I decided to look up John Emms' introductory book Starting Out: The Scotch Game; the thoughts below come from the beginning of that book, and all opinions expressed here are those of Emms, not myself. (If you find any of this explanation enlightening, then consider it a good advertisement for the rest of his book.)

After 3. d4 exd4, white has induced black to give up the center, and we have this pawn structure:

[FEN "4k3/pppp1ppp/8/8/4P3/8/PPP2PPP/4K3 w - - 0 1"]

This structure is already inherently better for white, with greater control of the center and more space for the pieces. Since black typically wants to avoid 4... Nxd4 5. Qxd4, which centralizes white's queen in a nice way, white often ends up exchanging the knights himself with Nxc6, when black has two choices for recapturing. If ...dxc6 is played, then we have the following pawn structure, which is also typical of the Exchange Variation of the Ruy Lopez.

[FEN "4k3/ppp2ppp/2p5/8/4P3/8/PPP2PPP/4K3 w - - 0 1"]

Here white's structural superiority offers a significant advantage in the long-term. For instance, most king-and-pawn endings in this structure are wins for white, because of the ability to create a passer on the kingside, while black cannot do so on the queenside. Everything's not as simple as that, of course, as black can develop pretty painlessly and so has good short-term prospects; but white's structural advantage is the basis for his optimism.

If black instead recaptures via ...bxc6, then her central control is improved, and ideas of playing ...d5 are in the air. White often pushes with e5, and we have this structure:

[FEN "4k3/p1pp1ppp/2p5/4P3/8/8/PPP2PPP/4K3 w - - 0 1"]

Now white has even more space, and the e5 pawn cramps black's position. Black will try to free her position with a ...d6 or ...f6 pawn break, and white will try to prevent this, or make it as disadvantageous as possible.

In none of these scenarios does white obtain an advantage by force (though again, that's just chess for you), but we see that white has structural pluses which offer hopes for an advantage (especially in the long-term) in the Scotch Game. Here's a review of both Emms' book and a similar one by Gary Lane; if you want more guidance on this opening, that review, at least, is positive about both books.


How is a computer programmed to play chess?

Chess programming is full of "rules of thumb" that can be applied to your own chess.  There are many aspects to chess programming... but the most prominent are tree search and a heuristic evaluation.  Here are some ideas that you might be able to apply to your games:

Minimax Search: The basis for adversarial search formalized... I'd hope the principle here was intuitive.
Evaluation: A computer scores a position by combining metrics about material balance, king safety, activity, and pawn structure.  This goes into a strategic understanding of any given position.
Iterative Deepening: The applicable idea here might be to consider your list of candidates first, prior to expending to a deeper level of analysis.
Killer Moves: An amazing move discovered in one line of your analysis might be applicable in other lines of analysis... consider it early in the process.
Null Move Pruning: You can better understand your opponents intentions by considering what moves they would make if you were to skip your own turn.
Quiescence Search: When you reach the end of some analysis, make sure everything is still ok if you were to resolve the tension in the position.
MVV-LVA: This one is obvious, but in considering capture patterns, usually a good idea to identify the most valuable victim, and take with the least valuable attacker.
Alpha Beta Search: You can stop considering a line when you find the first refutation to it, rather than continuing to search for a better refutation.


Looking for analysis or games of top players in less known, perhaps a bit dubious but aggressive lines in the Ruy Lopez from Black's point of view

There are a couple of games between AlphaZero and Stockfish. The authors of the book Game Changer about AlphaZero, GM Matthew Sadler and WIM Natasha Regan, analyse the opening phase of these two games in this YouTube video.
Here are the opening moves from the two games, first with AlphaZero playing black and coming up with a new idea, castling queenside and pushing the h pawn.
[Title "Stockfish vs AlphaZero"]
[fen ""]

1.e4 e5 2.Nf3 Nc6 3.Bb5 f5 4.Nc3 fxe4 5.Nxe4 Nf6 6.Nxf6+ Qxf6 7.Qe2 Be7 8.Bxc6 bxc6 9.Nxe5 Bb7 10.O-O O-O-O 11.d3 Rde8 12.Nc4 h5 13.Qe3 h4 14.Qh3 Kb8 15.Bd2 d5 16.Bc3 d4 17.Bd2 Bc8 18.Qf3 Qxf3 19.gxf3 Be6

And then with AlphaZero playing white and again getting very aggressive
[Title "AlphaZero vs Stockfish"]
[fen ""]

1.e4 e5 2.Nf3 Nc6 3.Bb5 f5 4.d3 fxe4 5.dxe4 Nf6 6.O-O d6 7.Bc4 Bg4 8.h3 Bh5 9.Nc3 Qd7 10.Nd5 O-O-O 11.Qd3 Kb8 12.a4 Ne7 13.Ng5 Bg6 14.Nxf6 gxf6 15.Nf7 Bxf7 16.Bxf7 h5 17.a5 a6 18.Qb3 Nc6 19.Be3 Bh6 20.Be6 Qg7 21.Bd5 Qd7 22.Ra3 Bxe3 23.fxe3

Then there are these two YouTube videos where GM Melik Khachiyan analyses some of his games in the Schlieman -
Part 1
Part 2
Finally Kingscrusher analyses the historic game Bobby Fischer vs Milan Matulovic - Herceg Novi Blitz 1970 on his YouTube channel.


In the Pirc, bringing a dragon pawn structure fails

Yeah, seems like black just blundered a pawn with c5.
Probably you just mixed up the variation and you really wanted to play:

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
1. d4 d6 2. e4 Nf6 3. Nc3 g6 4. f4 Bg7 5. Nf3 c5

That is quite a common variation, I looked at 6.dc Qa5 7.Qd4 for white a while back, if I remember correctly. So maybe you should just check your book again, it's unlikely they made such a mistake.


Is there a name for this variation ? (or just this setup in general)

You are right that it doesn't fit the description for the Barry Attack or London system. In neither system does white fianchetto his kingside bishop like that.

The black side looks characteristic of the Gruenfeld Defence. There are many ways for white to respond to the Gruenfeld. I haven't seen this one but that doesn't mean much since I rarely play the Gruenfeld as black.


Caro-Kann continuation for Black in this position

I'm wondering about the purpose of 13... Qd6. Seems a waste of time to me. What's wrong with grabbing the pawn? White's 13. Qh5 is a simple mistake.

And about the point that "draw with Black is as good as a win" - it is not. You should aim for a win with both sides and also ignore rating gaps. I've given up the habit of looking at my opponent's rating before the game. Just play.


How many games of optimal chess are there?

TL;DR
The answer is that it depends on whether we solve chess for White, Black, or a Draw. If one of the first two, probably very, very many. If instead chess is drawn, then we don't know, and it's not clear how we would go about figuring this out without actually solving chess in the first place.
Pedantic setup
First, the general strategy is the same as the one pursued by Shannon's number. Estimate the number of optimal plies available in a given position, O, and estimate the number of unforced plies in an optimal game of chess, p. The number of optimal games of chess is given by the expression O^p.
Define a winning ply as a ply that either (i) wins the game, or (ii) leads to a board state in which, no matter their opponent's reply, a winning ply exists. Similarly define a drawing ply. Finally, a losing ply is defined as a ply that, if made, leads to a board state in which her opponent has at least one winning ply. Note that because chess lasts a finite number of moves, these options are exhaustive. If all plies from a position are losing, then the player to move is in zugzwang.
Weakly solving chess entails being able to show that there exists either a winning or drawing ply from the starting position, or conversely that White is in zugzwang. Solving chess entails knowing that some particular ply is winning or drawing, or some particular reply from Black is winning.
Finally, note the the definition of optimal says nothing about what to do if a position is losing. The losing player is free to do whatever they wish, because within the context of optimal play, all plies are equally bad.
If White is winning
Suppose that we solve chess for White. Since White has access to a winning ply, all of Black's 20 legal replies are losing. Thus, there are at least 20 games of optimal chess. This argument applies recursively to each resulting board state, and the number of optimal games grows quite quickly. Even if White has access to only one winning ply on each of her turns, Black always has access to all legal plies from the position. We could stipulate that optimal play in a losing position is to resign, in which case there is either 1 optimal game of chess — the winning ply from the starting position — or 0, because no one ever agrees to a game. For comparison, think about whether you would agree to a game of Tic-tac-toe.
All that remains is to estimate the length of an optimal game. Strictly speaking, knowing this number requires solving chess in the first place. However, it seems quite unlikely to me that the average optimal game is short. Arguments to this effect are difficult, however. As pointed out by @wimi in the comments, if Chess is solved for White than the very short game — 1. e4 e5 2. Qh5 Ke2 2. Qe4# — is an optimal game.
For the purposes of this answer, suppose that an optimal game lasts 30 moves. Derive a lower bound by assuming that White only ever has one winning ply. Effectively, her turns don't contribute number of optimal games, since she only every has one option. As argued before, Black has access to all legal plies in any position. The number of legal plies in a position is estimated to be about 30. Thus, a conservative lower bound on the number of optimal games is 30^(30) = 2x10^44. Different estimates of the length of an optimal game will lead to correspondingly different answers.
It gets a tricky if we place further restrictions on optimal play. For instance, you could stipulate that if one is in a losing position, the optimal ply is the one that extends the game the longest. This raises the exponent of the estimate, since games last longer, but it also knocks down the number of optimal moves available in a losing position, since they won't all extend the game the same amount. The interaction between these two is unpredictable.
If White is losing
Exactly the same situation as before, but the positions reversed. This time, no matter which of the 20 opening moves she makes, White is guaranteed to lose.
If White is drawing
Suppose instead  that chess is drawn. Based on the rate of draws seen at high level computer play, I deem this the most likely. This means that there exists at least one ply for White for which there exists at least one drawing reply, and all other plies are losing. How many drawing plies are there in the opening position? Strictly speaking, we don't know. We don't even know if there is one, and figuring this out would be a major advancement in our knowledge of the game.
For instance, it could be the case that there is only one drawing ply from the starting position, and all others are losing. Further, this could be true of all resulting positions, in which case there is 1 optimal game of chess. I think this is unlikely, but strictly speaking it is possible.
Instead, it could be the case that all of White's opening plies are drawing, and all of Black's replies are as well. Then there are probably many games of optimal chess. Of course, this has to stop being the case at some point, as evidenced by the existence of both the Scholar's Mate and the Fool's Mate, so a more precise estimate is difficult.


I play blitz there every day for many hours. My rating periodically oscillates between 1850 and 2050, which is a span of 200 points. This has little to do with my varying strength because it depends mostly on which opponents I happen to run into. This phenomenon puts a certain constraint on your idea of a conversion table.

I added two more comments to this answer. See below.


Is it ethical to force a draw via perpetual check?

There is a rules in chess called Threefold repetition rule. This rule states that you can claim a draw if you are about to repeat the the position for a third time. This subsumes a situation called perpetual check which also leads to a draw.

So what you did in your game wasn't a case of extortion or abusing a flaw in the game - it was completely by the rules and everyday thousands of games are drawn in exactly that fashion.

PS: You also could have stopped the mating threat by playing Rc7, this would have given you a winning position as far as I can see. So by resigning you actually would have turned a winning position into a loss.


in Sinquefield Cup how is white player determined?

In round-robin tournaments, the schedule is known in advance. A very common schedule for 10 players starts with the following games in the first rounds:

Round 1: 1-10 2-9 3-8 4-7 5-6
Round 2: 10-6 7-5 8-4 9-3 1-2

(see this Wikipedia article for more details)

Which player corresponds with which pairing number is determined before the tournament. Traditionally, this is just some kind of lottery, where each player is assigned a random number. It seems this was also the case for Sinquefield 2015:

  Pairing numbers will be drawn randomly at the Sinquefield Cup

For another Grand Chess Tour tournament, Norway Chess 2015, they had a blitz tournament the day before. The winner of that tournament could pick a number first. Because with an even number of players, you play an odd number of games,  the winner could pick a number, say 1, that would give him white in 5 games and black in only 4. The runner-up of the blitz tournament could pick next, and so on.


Is there a copy of Troitsky's analysis of KNN vs. KP online anywhere?

Troitsky's analysis of the endgame K+NN v K+P was published in the German magazine Deutsche Schachzeitung in 19 installments between 1906 and 1910. They all can be read online. I am not aware of an English translation. A Russian book featuring his full analysis was published during Troitsky's lifetime. Apart from that, I don't know of any other source.

Permalinks of the five relevant Deutsche Schachzeitung volumes follow below. In case that I missed an installment, serve yourself in the TOC at the beginning of each volume.

To access the full text you need to connect from a US IP address. If you are located elsewhere, use a VPN and set the USA as your country of origin.

Deutsche Schachzeitung 1906 (vol. 61)
permalink: https://hdl.handle.net/2027/njp.32101072325978
pages 129, 161. 193, 257
Deutsche Schachzeitung 1907 (vol. 62)
permalink: https://hdl.handle.net/2027/njp.32101072325960
pages 1, 97, 161, 225
Deutsche Schachzeitung 1908 (vol. 63)
permalink: https://hdl.handle.net/2027/uc1.a0002788768
pages 1, 101, 197, 293
Deutsche Schachzeitung 1909 (vol. 64)
permalink: https://hdl.handle.net/2027/njp.32101072325945
pages 33, 97, 161, 225, 321
Deutsche Schachzeitung 1910 (vol. 65)
permalink: https://hdl.handle.net/2027/njp.32101072325937
pages 65, 129


Ideas to improve chess books usability in the XXI century

I've long felt that scripting short systems of moves in their chess notation would be very helpful as a teaching tool as well.  There are many, many projects out there that can replay a set of instructions, and it would make it much easier to not only show how to set up some of the basic openings, but also explore their ramifications in response to different positions.


Checkmate overrides the 50 move rule.

Fide Handbook Article 9.3:

  The game is drawn, upon a correct claim by a player having the move, if:

  a. he writes his move, which cannot be changed, on his scoresheet and declares to the arbiter his intention to make this move which will result in the last 50 moves by each player having been made without the movement of any pawn and without any capture, or

  b. the last 50 moves by each playerhave been completed without the movement of any pawn and without any capture.

The player making the move that mates could claim a, but he of course won't do it because he is about to win. The player losing does not have the move after the checkmate, so he cannot claim the draw.

This interpretation is also confirmed by Geurt Gijssen, in his column An Arbiter's Notebook from 2006:

  Regarding your remark about the 50-move rule: only the player on move is
  entitled to claim a draw, but he is not forced to claim it. So if the 50th move produces checkmate – the checkmate stands.


Can Black save this Knight vs Bishop endgame with a pawn down?

I think it is good to notice the possibility of different fortresses, like the one you mention, and of course the wrong coloured bishop for the h-pawn. But to turn reaching such a fortress into a "plan" is way to early in this position.

I think fxg3 was probably ok. At the first glance it looks ugly that now there are white prospects for a passer on the d-line and on the h-line, but your g and f-pawns can actually deal with the white g and h-pawns. Against g4 and h5 you should play f6 and against h4 and g5 (like in the game) you could have played g6. These setups prevent an h-passer.

But maybe 10.f6 was still ok. Then you certainly should have played 11…fg 12.Kg5 Nf8 which prevents the intrusion of the white king. But even here h5-e4-e5-h6 and Kf6 might just win for white.

An engine will be able to come up with better lines, but my feeling is that

Keeping your pawns compact.
Keeping the white king away.
Preventing a h-passer.

might have earned you a draw. (Coincidentally you violate all these guidelines with the move e5, after which you are surely completely lost.)


A disagreement between me and my chess engines

I think that Black is doomed after Qh6 but the engines do not even recommend it as a correct move. Is there something I am missing here?

Yes. The only reason black can't take your queen on h6 is because the g7 pawn is pinned by your rook on g3. If black could take that (even losing the queen to do so) with tempo (i.e. so you don't have time to play Qxh7#) then your queen is lost and with it
the game.
Here's how:
[FEN "2r2rk1/5ppp/1p6/p3q3/1n5R/1P1P2RP/1P1Q2P1/7K w - - 0 1"]

1. Qh6 Qe1+ 2. Kh2 Qxg3+ 3. Kxg3 gxh6

and you are a rook and a knight down and completely lost.


Using the tree window in SCID on a subset of games in the database

Yes. In the tree window, there is an "All Games" checkbox. Unchecking this will make the tree window use the filtered games instead of all the games.


Where is the neural network used in MCTS?

Neither AlphaZero, nor Lc0 (an open source project based on the AlphaZero paper), use MCTS in its pure form, because they do not perform game rollouts - the search is simply called MCTS because the way that it expands its tree is similar to MCTS.

Here are the main differences:

MCTS performs random rollouts to a termination condition (e.g. win, draw, loss) at leaf nodes to estimate to value of that node, whereas AlphaZero and Lc0 simply use the neural network to estimate the win value. They do not perform rollouts.
MCTS uses UCT to decide which node should be expanded. AlphaZero and Lc0 use the output of the neural network as an additional parameter in their versions of UCT: the neural network generates a probability associated with every possible move in the position, which allows the neural network to control the expansion of the search tree to some degree.

Lc0


Is there a winning strategy for Losing chess?

One useful tactic is to try, as far as possible, to leave exactly one of your units en prise. That forces your opponent to capture that unit next. So to a large extent you're in control (and are losing units). By contrast, if you were not so careful as to which units of yours were en prise, then if ever two or more of them were, then your opponent can choose which of them to capture next, and thus keeps more control.


Books/resources on Scotch (as white) and Petroff (both sides but mainly as black)

I can only make recommendations for the Petroff Defence, as I have never played the Scotch:

The Petroff: Move by Move by Cyrus Lakdawala. An engaging author using a question and answer format in annotated games
Petroff Defence by Alexander Raetsky and Maxim Chetverik. This book is more orientated towards Black's point of view, but the explanations are accessible to the club player
thechesswebsite YouTube video on the Petroff Defence


What is the correct placement for the King and Queen on the chessboard?

Each player has a white square on their near right corner. The queen goes on the square of her own color; as a result, the kings and queens face each other.

rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1


In general there are two scenarios in the opening where one side might want to exchange one of their bishops for a knight.

The knight controls key squares in the center which are being
contested. In the Nimzo, for instance, the knight on c3 controls e4.
White would really like to put a pawn there. Pinning and then
exchanging that knight makes the e4 pawn push far less likely.
Similarly in the Dutch black sometimes plays Bb4 to pin the knight on c3 to weaken white's control of e4 and will swap if a3 or O-O is played.
Where one side has control of most of the space on the board that normally gives them an advantage because they have more room to manoeuvre their pieces and can switch the point of attack more easily. The side with less space, conversely, often struggles. However there is balance between space and number of pieces. More space with lots of pieces confers an advantage. Reduce the number of pieces and the pawns defending that space become overextended as the few remaining pieces struggle to defend them. Similarly a cramped space with lots of pieces becomes a comfortable one when pieces are exchanged. So, again, in those positions it is often worth one side exchanging a bishop for a knight.


Can I win this Rook and Pawn vs Bishop endgame?

This position is in fact drawn (which you can confirm e.g. by looking the position up in an online endgame tablebase). The key for Black's defense is to maintain the bishop on the b1-h7 diagonal, which prevents White from doing things like (1) moving the king to g6 (for threatening an eighth rank mate) or (2) pushing the pawn to h7 to threaten checking the black king out of h8 and queening the pawn. Black is able to keep the bishop on this diagonal, or at least be able to come back to it after moving away, and this keeps White from making any progress.

Here is just one line illustrating how White could win if Black were to go wrong with the placement of the bishop. After 1...Ba4?? White has a won position, but only by the move 2.Rg2! which keeps the bishop from returning to its defensively optimal diagonal. And that's the idea behind White's play in the rest of the line given: keep the bishop from coming back to that diagonal (e.g. with 4.Re2, 5.Rd2, 10.Re5 denying the bishop's return) until it's too late and the pawn push has already been arranged.

[fen "5K1k/6R1/7P/8/8/8/2b5/8 w - - 0 1"]

1.Kf7 Ba4?? 2.Rg2! Bb3+ 3.Kf6 Bd5 4.Re2 Bc4 5.Rd2 Bb5 6.Rd4 Bc6 7.Kg5 Bb5 8.Rd8+ Kh7 9.Rd5 Bc6 10.Re5 Ba4 11.Re7+ Kh8 12.h7 Bc2 13.Kh6 1-0


This only really applies to over the board games (since online chess servers prevent illegal moves).
In a standard time control game, under USCF rules, when the illegal move is noticed by one of the players, a few things happen.  First, the illegal move must have been made within the last 10 moves.  If not, then the current position stands, and play continues.  Assuming that the move is recent, the position is restored to the position immediately before the illegal move.
Then, the player that made the illegal move now must make a legal move with the same piece (if one exists).  If there are no legal moves, then the player is free to make any move.  This is due to the touch move rule.  Finally, if the offending player has pressed the clock, a two minute "bonus" is added to the opponent's clock to compensate them for any time lost and to penalize the offending player.
Here is the relevant passage from the USCF rulebook:

11A. Illegal move during last ten moves. If, during a game, it is found that one of either player's last ten moves was illegal, the position shall be reinstated to what it was before the illegal move. The game shall then continue by applying Rule 10, The Touched Piece, to the move replacing the illegal move. If the position cannot be reinstated, then the illegal move shall stand. Move counters on clocks that have them may by readjusted.
11D. Illegal move. If, a player completes an illegal move by pressing the clock, in addition to the usual obligation to make a legal move with the touched piece if possible, the standard penalty specified in rule 1C2a applies (i.e. two minutes added to the opponent's clock).

In blitz chess, the rules are different.  According to the WBCA (World Blitz Chess Association) rules, a player who makes an illegal move loses the game instantly.  This rule is frequently enforced in casual games too.  The most common way that this occurs is that one player doesn't notice that they are in check and makes a move that doesn't get out of check.  Then the checking player simply captures the king and claims a victory.
Because blitz is a much faster pace game, the illegal move must be noticed within two moves.  If it is not, then the current position stands and play continues.
At no point is the game cancelled due to an illegal move.  Pretty much once a game starts and both players make a move, a result of win, loss, or draw will be recorded.


Kramnik - Karjakin in the FIDE Candidates 2014, was 8...f5 correct?

8...f5 is no novelty. It is a well known line and has been played successfully before by strong players like Adams, Salov and Karjakin himself.

8...f5 is absolutely the correct move in the position, because it practically forces White to either surrender his strong central pawn on e5 or give up his strong light squared bishop for Black's knight on b4. I demonstrate a line below showing what happens if White tries to avoid both these possibilities with 9. Bf3.

   [FEN "r1bqkb1r/ppp1p1pp/1n6/4Pp2/1n1PB3/4B3/PP3PPP/RN1QK1NR w KQkq f6 0 9"]

   1. Bf3 f4! 2. Bxf4 Qxd4 (2... Bf5!?) 3. Qxd4 Nc2+ 4. Kf1 Nxd4=

Thus, in the above position, White is practically forced to concede one of the two advantages.

Normally, White players preferred to play 9.exf6 for "obvious" reasons like the light squared bishop is stronger than the knight on b4 and is White's most valuable piece in launching a kingside attack.

Thus, in this position the move 9. a3!? must have come as a complete shock to Karjakin. It has never been played before at Grandmaster level and was only played once before in Janczarski,M (2335)-Bartel,M (2273) Warsaw 2013 (source here).

   [FEN "r1bqkb1r/ppp1p1pp/1n6/4Pp2/1n1PB3/4B3/PP3PPP/RN1QK1NR w KQkq f6 0 9"]

   9. a3!?

Whether 9.a3!? is good or bad is a different question. It seems to me that after

   [FEN "r1bqkb1r/ppp1p1pp/1n6/4Pp2/1n1PB3/4B3/PP3PPP/RN1QK1NR w KQkq f6 0 9"]

   9. a3 N4d5 10. Bf3 Nxe3 11. fxe3 g6 12. Ne2 Bh6!

Black is perfectly fine.

Conclusion: 8...f5 is correct!


Does 4.Ng5 in Two Knights Defense have a name?

I think the name for 4. Ng5 is Knight Attack. There isn't a specific name, because it leads to more specific openings, like the Fried Liver Attack, Polerio Defense 4. Ng5 d5 5. exd5 Na5 (trying to prevent the sacrifice), the Traxler Countergambit 4. Ng5 Bc5, and more. It's just like how 1. e4 e5 is called the open game. There isn't a specific name for it, because it will lead to more specific opening.


Is there any position where not promoting(illegally) would be the best move?

Here is an example:

[fen "8/4P3/8/4p1p1/2p3Pp/p4p1K/k1p2P1P/8 w - - 0 1"]

1. e8 leads to stalemate next move, while all legal promotions lose to 1... c1=Q followed by 2... Qf1#.


Do not know if it really suits you but on http://www.theweekinchess.com/twic you can download a lot of PGN files. I once saw an explanation how somebody used this to create an opening book out of it. I could not find one big file with all games but there are quite a lot of files that date back to 25/06/2012. You can always make 1 big file out of it.


Actually the King's Indian has seen a recent rise in popularity. For a few years now, players like Nakamura and Radjabov have revitalised the opening. And if you take a look at the very recent top level games it is striking how many top players gave it a try: Nakamura, Jobava, Grischuk, Giri, Radjabov, Kasimdzhanov, Bacrot and quite consistently Ding Liren, just to name a few.

Those are all games from 2015 and the list reads like a who's who in top level chess. So there certainly is no big theoretical issue, that would dissuade black from playing the King's Indian.

One of the hottest lines right now is the 6.h3 line (white's choice in most of the games I linked), apparently Aronian introduced some tricky ideas for white in this variation (according to Seirawan).

I have heard this Kramnik-Bayonet-story before, but I'm not sure how close it is to the truth. Kasparov himself said, that he stopped playing the King's Indian because it became too much work to keep up with two ultra-sharp black defences (The other being the Najdorf). A few years ago the Bayonet-variation was still widely played (Nakamura scored some impressive wins against it), but for now the focus seems to have shifted to 6.h3.


Best pseudo-chess game for kids to learn the basic?

If your just looking for instructions, here is the wiki on mini chess.  Make sure you checkout the external links.

To take Andrew's comment a bit further, I will give my own experience with my 3.5 year old.  This is what he knows now with limited time.  He can name all the pieces and he can set the board up, but that is about it.  If I ask him to move the bishop, he will swipe it across the board, but that is OK.  He does not have the concept that it is a game for two people and I am black or white (every piece is his :) ) Your 5 year old probably will get a better grasp on mini chess, but 3 may be too young for it.


Can black win in this KR vs. KN endgame?

No, this is a draw. These kind of positions can be checked with an online database, e.g. this one.

In general, King+Rook vs. King+Knight is only a win for the side with the Rook if the other King is cornered or separated from its Knight, as also described in this answer. Just play around a bit with the endgame database to get a feeling which positions are drawn and which ones are won. Black to move wins in this particular position only because of some short term tactics (Rf1+ and Re1+ wins the Knight).


Can there be two bishops on white tiles? If not, can my queen be capture and then promoted so I can win the game?

Your only problem here is logistical. You can promote your pawn to any piece except the King, even if that means you have two bishops on the same colour squares, or two (or more) queens on the board; but according to the official rules, you must replace it physically with a piece of the correct shape and colour. What to do if no such piece is to hand?

In a tournament, the organisers will make sure to have spare pieces available for such contingencies; but in a home game, improvisation is the norm. For instance, if one of your Rooks has been captured, you can turn it upside down and call it a Queen. In this case, you can just say "that pawn is now a Queen", which ends the game immediately with checkmate.


If the app first displayed checkmate in that position, then it miscalculated.

But as Phonon noted, the app could have displayed checkmate in a previous (future) position, and then you went back a few moves. In that case it's not a miscalculation per se, but just a bug in the UI.