Why is a 0x88 chessboard array of size 128 bytes when 0x88 is decimal 136?

0x88 is just the name of the system.  The actual length of the board array is 128.

The name comes from the fact that a bitwise AND can be performed the index of a square (range is 0 to 127) and 0x88.  If the result is non-zero, then the square is not on the board.  This happens because 0x88 is 10001000 in binary and every square on the board will have the form 0xxx0xxx.

Another benefit of the system is that all of the legal squares can be trivially constructed in octal notation.  For example, d4 is 0x33 assuming that 0x00 is the lower left of the board (both d and 4 are the 4th square from the edge, so 3 in a zero-indexed array).

See https://chessprogramming.wikispaces.com/0x88 for more information about this system.


Did the 2018 World Chess Championship feature any theoretical novelties in the Sveshnikov Sicilian?

Carlsen introduced 8... Ne7 (after 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 e5 6.Ndb5 d6 7.Nd5 Nxd5 8.exd5) instead of 8...Nb8. He played this in round 12 and then again in game two of the tiebreak. The line was known before but not played at the highest level and therefore not considered a serious approach by black.
You can find the analyzed games here at chess.com. 12... h5 is given as novelty in this line.


What can I learn from my "80 average centipawn loss" game, which I thought I played well?

You are asking two very different question: How to interpret the number 80, and how to make that number go down :-) I'll focus on the first one.

80 means that on average, you overlooked many better moves. What this says about your playing strength depends on how hard those better moves were to discover. In complicated tactical positions higher values are normal. You may miss many opportunities that the computer can see because it looks, say, 10 moves ahead. So the bar is high.

In calm positions the centipawn loss is lower because there are no tactics (as by the definition of "calm"), so as long as you don't blunder your move cannot be a lot worse than the computer's optimal move.

I've had games with a centipawn loss below 20 and above 100 even though, I'd argue, my playing strength was the same. (My) Chess960 games tend to get into complicated tactical positions quickly, for example, so my centipawn loss in those is higher.

Finally, it's an arithmetic mean so it is susceptible to outliers. Many good moves and one blunder will give the same result as just mediocre moves.

You are probably aware that Lichess offers a tool to evaluate your games based on centipawn loss ("Chess Insights", on your profile page).


How can I prevent games from dragging on?

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

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

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

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

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


How to evaluate my move with UCI engine?

Enable multipv on the engine. When you are at "e2e4 e7e5 d2d4" it will list all possible best moves that the engine considers in order of their evaluation. If you find "g7g6" in this list, then what you have considered is one of the best moves also considered by the engine and you'll obviously have the score associated with "g7g6". So, you will find this information before you make the move "g7g6".


What openings were former and current masters experts in?

Black (1.d4):

King's Indian: Fischer, Radjabov, Kasparov, Gufeld
Queen's Indian: Anand, Karpov, Carlsen
Grunfeld: Svidler, Ftacnik
QGD, Slav: Wang Yue, Sokolov
QGD, Semi-Slav: Shirov, Anand
Nimzo Indian: Kramnik, Ivanchuk
QGD, Classical: Petrosian, Karpov

After typing this, I realized that any answer covering all the common openings played at top level would be ridiculously long. I think you can make things easier for yourself by consulting chessgames.com whenever you want to see top practitioners of any particular opening. For example, typing in "Sicilian, Najdorf" in the search box will give you this page, where you can see which top level players employ it the most. Of course, this doesn't mean that they are the authority on said openings. But, given that the list will almost always include strong GMs (2650+), you can be assured that studying their games in said openings will allow you to learn a lot about those openings, which I assume, is the point of you asking the question in the first place.

Another way of going about this is looking at the player profiles of some of the strongest players of all time (like World Champions, and World Championship contenders), and looking at their opening repertoire.

In the end, "expert" is a very loose term in your question. So really, you'd be safe in assuming that some of the strongest GMs (and some IMs as well, such as Nezhmetdinov) of all time are/were experts in whichever openings they employed the most.


Why does Stockfish website offer many apps to download?

On the Android tablet, you download the version for Android, and for the iPhone you can download the iPhone version.

Stockfish engine's source code is written in C++, and therefore it has to be compiled for the platform (Windows, Android, iPhone, etc.) on which it will run. Thus, you have different "versions" (not in the strict sense) of the same engine.

For Android, I recommend you download the app called DroidFish. I use it myself. It is very convenient.


Catalan opening - plans for white after exchanging on d5

The idea of exchanging on d5 when Black goes for an early ...b6 is usually connected with play on the c-file: Nc3, Bf4, Rc1, maybe Qa4.

In this particular position, after ...Bxd2 Nbxd2, this plan is not available and the pawn exchange is much less promising. Here, you can stand with the main plan of preparing e2-e4 (with 0-0, Qc2, Rd1), or look for an opportunity to exploit the dark squares (Ne5, e3, and someday either f4, Ndf3 or c4-c5).

If memory serves, 6.Qxd2 is a bit more promising than 6.Nbxd2 in this line.


How do you stop white's queenside advance in the Reversed Sicilian?

You don't.

There is no way at this point to stop white from advancing on the queenside. Playing a5 still makes sense, because short term this will give you the open a-file and longterm this will eliminate a potential weakness that white might take advantage of once he breaks through.

Instead of stoping white on the queenside you have to develop play on the kingside or potentially even in the centre to compensate for white's attack.

Here is a nice and recent example:

[Event "World Cup"]
[Site "Khanty-Mansiysk RUS"]
[Date "2011.08.29"]
[EventDate "2011.08.28"]
[Round "1.2"]
[Result "0-1"]
[White "Arman Pashikian"]
[Black "Radoslaw Wojtaszek"]
[ECO "A24"]
[WhiteElo "2616"]
[BlackElo "2683"]
[PlyCount "64"]
[FEN ""]

1. c4 Nf6 2. Nc3 e5 3. g3 g6 4. Bg2 Bg7 5. Nf3 Nc6 6. d3 O-O
7. O-O d6 8. Rb1 a5 9. a3 h6 10. b4 axb4 11. axb4 Be6 12. Nd2
Qd7 13. b5 Nd8 14. Nd5 Nxd5 15. cxd5 Bh3 16. Nc4 Bxg2 17. Kxg2
b6 18. f4 exf4 19. gxf4 Qg4+ 20. Kh1 Ra2 21. Bd2 Nb7 22. f5
Qd4 23. Qb3 Rfa8 24. e3 Qh4 25. Qd1 Nc5 26. Qe2 Ra1 27. Rxa1
Rxa1 28. Be1 Qh3 29. Nd2 Bc3 30. Nf3 Ra2 31. Nd2 Bxd2 32. fxg6
Bxe1 0-1


Is there such a thing as a unique chess playing signature?

Unlikely.  The first several moves of any game by notable players are all book.  Thereafter, people who play notable games are able to play superb offensive and defensive moves.

Now, if you see some crazy sacrifice, you might think Anderssen or Tal is playing this game. Similarly, if you see some superb positional move, you might think Petrosian or Karpov is playing.

But to see a game played by any of the top 20 players of all time and pick out who was moving the pieces based upon their styles, I can't imagine it.  There simply isn't the 'bandwidth' for such an individual signature in chess beyond someone playing more positionally or more tactically; that's pretty broad-brush stuff.


4-2 vs 3-3 (only pawn) endgames arising from Sicilian/Anti Sicilian

King and pawn endgames are much easier than ones where each side also has a rook. The key principles are fairly simple. You want to try and queen a pawn. With pawns on both sides of the board and an imbalance as here there are two key points:

Getting your king to the middle of the board is very important.
The only pawns you are likely to queen are ones on the side where you have the majority. If the kings keep away then the further up your pawns get the easier it is to get a passed pawn and queen. So, don't move pawns on your minority side unless you absolutely have to! Doing so makes your opponent's task easier. Move pawns on the side where you have the majority.

In the position you show after move 27 you are already behind in the race to centralize your king. Whether that means you were already losing I doubt but it does make things difficult and it was your choice. Your king has taken 3 moves to go from g8 to d8. In the same number of moves you could have gone from g8 to d5 and that would have been a very different story.
Your transition into the endgame was very poor. Perhaps 20...a6 was already a mistake. You are breaking rul2 by advancing a pawn on your weak side. Better would have been f6 which as well as being a free move, because it kicks the bishop, frees f7, which is a much better square for your king than f8, and moves a pawn on your majority side.
After 24. Bb6 you are in too much of a rush to get all the pieces off with RxR and Bd8. You exchanged pieces in a way which was good for your opponent and bad for you. Bd8 was particularly bad. Your rook on c8 paralyzes white's queenside pawns.
Suppose instead it had gone something like this after move 20:
[fen "2rr2k1/pp2bppp/4p3/P3q3/3B4/2P4P/1P3PP1/R2R2K1 w - - 0 1"]

1. Bxe5 f6 2. Bd4 a6 3. Bb6 Rd6 4. Rxd6 Bxd6 5. Rd1 Rc6 6. Kf1 (6. b4 Bc7) Kf7 7. Ke2 e5

After 5...Rc6 you have a simple plan of bringing your king quickly to the center with Kf7, e5, Ke6. If white tries immediately to kick your rook away from the defence of the bishop by rushing forward the queenside pawns starting with b4 then Bc7 is a good response.


When a pawn reaches the 8th rank, it then must be promoted to a Queen, Rook, Bishop or Knight.
The pawn can capture normally to reach the 8th rank. IE fxg8=Q, but as we know the pawns don't attack pieces whom are directly blocking them so captures straight is not an option.

According the the FIDE 2017 handbook promotions can be done in numerous ways:
4.6.1 the pawn does not have to be placed on the square of arrival,
4.6.2 removing the pawn and putting the new piece on the square of promotion may occur in any order.
4.6.3 If an opponent’s piece stands on the square of promotion, it must be captured.
It is worth noting that incorrectly promoting in Blitz or Rapid games results in a loss by illegal move according to the official rules.


In early FIDE ratings files what does a flag value of "n" indicate?

Going through the January 2002 list, I notice that these "n" marks seem to concentrate on certain countries.  Everyone from Russia, Yugoslavia,  Cuba, and Latvia seem to have this "n" mark.

If you look at the April 2002 list, you'll notice that now everyone from the Philippines also has an "n".  Perhaps the "n" stands for "nation" and designates something about the player's country.


How much theoretical knowledge does playing the Berlin Defense require?

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

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

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

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

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

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

Almost all sensible moves are playable

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

The game is slow and of positional nature, often drawish

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

It is one of the most theoretically extensive openings

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

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

Exactly so.

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

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


Is it beneficial to play themed practice games?

It really depends on what your end goal is. Themed games in a specific opening are good to get familiar with a specific opening, and get a "feel" for the positions arising in the resulting middlegames. So, if you want to learn a new opening, or are having trouble in a certain line, it could be a great way to learn an opening, coupled with studying some opening theory (on the 1500 level the amount of opening theory needed isn't that great, and a few lines together with some basic knowledge of ideas in the opening usually is enough).

However, if you want to become a stronger player all-round, I would say that it's an inefficient training method in and of itself, and should be used as a supplement, rather than your main means of exercise. You will learn more studying tactics and analysing your games, since tactics will be an area any 1500-level player can improve, and practicing analysis is key to being able to improve later on. But of course - play chess! That is probably the single most important means of training available, since it gives you more experience. And playing some of these games in a pre-arranged opening line will not be a waste.


Is there a free online chess repertoire tool?

In addition to the other answers, there are a few sites to consider. These include annotation and comment features as mentioned by the OP.
Listudy.org
Upload a PGN and then you play the computer interactively. You play moves from your repertoire and the computer plays the opponent moves. This is also open source.
ChessTempo.com
Similar functionality in the "Opening Trainer." The interface is a bit different but it tracks what lines you have learned a bit differently which is nice.
lichess.org
As B.Swan has pointed out in a comment.

There are also other related sites worth exploring to understand their capabilities and how they may supplement the resources above.
ChessTree.com
Import/export PGNs. Search databases, get statistics. See opening relationships in a graphical tree.
OpeningTree.com
Import/export PGNs.  Import and analyze a user's openings from a database, PGN, etc, including popular online chess sites.


Have there really been more books published on chess than any other sport?

The below answer is incorrect because it includes newspapers and magazines. If you go under "Advanced search" and do the same search string, you can see that the results reported on the main page include magazines and newspapers. After omitting these, google search does not give a number of results.

It stands to reason that there will be a large number of newspaper and magazine accounts about football.


Longest forced sequence that ends with checkmate and every move is a check

I'm not aware of any resources documenting the specific situation you're asking about. The closest available is probably this page from Tim Krabbé's chess records which documents the longest known series of mutual checks, but not ending in checkmate.

One of the puzzles from the page could end in checkmate via 14.. Qb7# instead of 14...Bxb7+, so this would be an example of a checkmate after 27 consecutive checks. This series of checks could be considered "forced" by the objective of the puzzle.

[Title "G. Leathem, Fairy Chess Review, 1938, 28 Consecutive Checks"]
[FEN "K2kn2r/NP1P1PPP/1PPPnNq1/1Rr1Bb1Q/4R3/8/8/8 w - - 0 1"]

1. c7+ N8xc7+ 2. bxc7+ Nxc7+ 3. dxc7+ Ke7+ 4. g8=N+ Rxg8+ 5. hxg8=N+ Qxg8+ 6. f8=Q+ Qxf8+ 7. Qe8+ Qxe8+ 8. d8=Q+ Qxd8+ 9. c8=N+ Rxc8+ 10. bxc8=N+ Qxc8+ 11. Bb8+ Bxe4+ 12. Nd5+ Bxd5+ 13. Nc6+ Bxc6+ 14. Rb7+ Bxb7 (14...Qxb7#)


Having a space advantage means you have more room to navigate your pieces.
Space may allow you to attack on both sides of the board, or attack on one side then switch to the other;  the cramped defender simple can't navigate as well.
You may be able to dominate an open file as it is easier for you to double or triple heavy pieces.
In late middlegame to endgame situations your king can get further up the board.
In your specific game black has a lot of weak squares and is behind in development as well as space disadvantaged.  Your play needs to consider other fundamental elements.  First after 13...Ba6 you shouldn't waste time with 14.Bxa6 which after Nxa6 allows Nc7-d5 with occupation of an outpost.  But rather just continue development with 14.0-0
In the game black continued to play horribly with 15...Qc7 and after 16.Qd3 Nb8 you have various options.  Doubling rooks on the b-file and penetrating the 7th rank will be crushing.  Consider the rook lift Rb1-b3 -- if Black castles trying to get his h8 rook in the fight, the b3 rook can swing to the kingside.
You can also think about occupying d6 with a knight (Ne5-c4-d6).
Wasting time with Ng5 and back like you did is not because you don't know what to do with space, but rather you don't know what to do with your pieces in general.
Target weak squares, coordinate, and invade!


Apart from chess.com, here are a few others:

http://www.queenalice.com
http://www.gameknot.com
http://www.redhotpawn.com
http://www.chessos.com
http://www.chess-mail.com

There are many out there...


I have the same behavior for both parts of your question, and the first behavior (the slowness to populate the reference) is by necessity since it has to search all 8 million games to populate the "Reference" window. The second behavior is just a bug, but I will tell you how to refresh it.

Regarding the slowness of populating the "Reference" pane, I want to make sure that you have done two things:

Gone to File>Activation>Update program, and that you are running the latest build.
And this, which may be exacerbate your problem: Right-click on the Mega 2020 Database, and go to Tools, and "Delete Search Booster". Then "Create Search Booster". I do this every time I add new games.

To refresh the "Reference" pane after coming back to it, just play any move, and if necessary, then go back to the previous move. You can also click on the "Openings Book" tab, among others, and then go back to the "reference", and it will refresh.

I agree that it is not cached, and re-searched, but with the search booster and now that the database has been read into memory, for me, it only takes under a second for the refresh.

P.S. Go into File>Options>Limits, and set the "Cache Size Reference DB" to at least 6GB since right now, it is barely over 5GB. That way, once you read through it once, it will all be cached in memory.


How to reach an open position in the 4 Knights Game without exchanging too much material?

There isn't really anything wrong with what you show as an example in my opinion. White is in the superior position. Just because the queen is attacked once does not mean that you are going to lose a tempo. If Black moves c5 to attack your queen on d4 then that is a blunder in my opinion, and can be countered with qd3. In this position stockfish gives White a +0.64 advantage with 23 moves of depth. So I would say that you are on the right track. Continue to dominate that center, and then look towards exploiting Black's weak pawn on d6 by getting your f rook involved and developing your other bishop. Game on!


Which sites offer good tutorials for novices to improve?

IMHO if you are struggling with the middle-game it makes more sense to study that particularly (as well as the endgame) instead of focusing on openings. I would advise you to learn to record your games in Algebraic Notation in order to learn from your mistakes (preferably with a stronger player). As far as online material you can use I can recommend Novice Nook by Dan Heisman and Modern Ideas in Chess by Richard Rèti


What is black trying to accomplish when playing Bb4 after Nc3 in the opening?

It is indeed a little silly to play ...Bb4 on move 2 here. That said, it often gets played a little later, and the main idea is to pin the knight on c3 (after the d-pawn has moved), so that it no longer protects the pawn on e4, which can now be attacked by a knight on f6, say.

In the particular line you gave, by the way, the bishop is doing just fine on b6. You spent time kicking it to a place where it's aiming right at the weak pawn on f2 and beyond to your king on g1 once you castle.


For players under 1800 USCF/FIDE, Dan Heisman's blog is an extremely helpful source. He has lots of information on:

Thought process: how Hope Chess can cause losses
Time Management: how to manage your time in order to be able to think as much as possible when the game gets complicated.
Practical tips for different situations: when you're way ahead, it's a different game; when you're losing, complicate the position to try to get your opponent to make a mistake; when your opponent is in time pressure, don't blitz him, etc.
Correcting misconceptions: player not recapturing because then he would get doubled pawns (safety is a 100, pawn structure is a 1), players loses because he didn't "see" something when in fact he didn't look out for it (thought process), player making a quick move in a critical position (hand-waving), Player playing a quick move because all moves look bad (acquiescing), Player rejecting move based on shallow or superficial analysis (quiescence error) . . . The list goes on, check out his blog!


What is the strength of the Shredder Chrome app?

This is a response from the maker of shredder. Hope it helps!

  We are using a different Shredder version on the Chrom App so this is
  very hard to tell in Elo, even for us.

Best regards
Stefan Meyer-Kahlen


When a pawn promotes, does the new piece go to the promotion square, or the home square of piece type it promoted to?

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

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

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


What are the scales of the numerical evaluations of the strongest engines based on?

There is nobody in the world can answer you confidently. It requires deep source-code level understanding of the engines. However, some of the engines you mentioned are close-source, which means it's simply not possible to get an answer for all engines.

However, I can answer about Stockfish, which I have studied. Stockfish doesn't attempt to optimize evaluation score just to make it consistent to what a human thinks. Stockfish has a framework for parameter tuning (SPSA) but the overall purpose is to increase strength. The score reported from Stockfish is no way consistent and tuned to what a grandmaster expects. Stockfish tends to report a score larger than Houdini in absolute term. This means, Stockfish is less conservative and therefore a stronger engine than Houdini.

Think like this, in a position where you have two chocies, one a simple draw that exchanges all pieces and the other is a queen vs three minor pieces. Both scenarios are considered theoretically drawn. Houdini would have reported zero or close to zero for both scenarios. While this is theoretically correct, the scheme doesn't encourage the engine to try harder for the queen vs thee minor pieces scenario where the engine has better chances to outplay a weaker opponent.

On the other hand, Stockfish, by being less pessimism, will have no trouble finding the queen vs minor pieces scenario. This is one of the reasons Stockfish has been proven a stronger engine than Houdini in all rating list.

In short, the score reported from Stockfish and lots of other engines is meaningless. They just guide the engine to make the best decision but it doesn't mean much other than that. Houdini's evaluation has been tuned, most likely for marketing purpose - you sell an engine better if it meets the users' expectation. But meeting a chess user expectation doesn't mean it'll make the engine play better, as Stockfish has proven, it makes the strength worse.

Therefore, there is no such thing as scaling in chess engine scoring. Some engines do, like Houdini, but this is just a trick to make you buy it. Chess engines don't need a scaling scheme to play strong.


French :: exchange variation - but not quite

The game has transposed to a standard exchange variation, a variation pretty well explained on Wikipedia.
You could try a setup with 4... Bd6, 5... Ne7, with the idea that if white puts his best  bishop on Bd3, you can play Bf5 to change it off. Black is very comfortable.

The move 4... Bb4+ is not to be recommended, since it only helps white, giving them the free move 5.c3.

3...Qxd5 should be avoided since in the Scandinavian positions that arise, it is important to develop the c8 bishop before playing e6.


How do I make a chess engine make moves in Arena?

In Arena 3.0, the "analyze" button does not make moves, it just tells the engine to analyze. (it should present you the analysis in the GUI itself).  if you press the "edit" button the engine will responde to your move.  the third relevant button is the "demo": it will tell the engine to play both sides until the end of the game.


While I don't use Babas chess, I'm sure Chessbase and Arena support multi-pv.


Of course FIDE have tournaments in the US.

You can find them on the FIDE website here - https://ratings.fide.com/tournament_list.phtml?moder=ev_code&country=USA


Well for starters I advise you to try out Daniel King's Power Play series, it helped me take my chess to the next level at the time.

Also, rule number 1 when learning anything about chess. Never do it on a PC or something that's not physical... Always, always, always have a real chess board when practicing tactics and end game... Openings are more about memorizing so it can be done without a real chess board, but even then I still prefer a real board.

There's of course a reason for this... Having physical contact with the pieces has a bigger impact on your mind, it helps learn and even memorize certain aspects of the tactic. This is of course also scientific, having an actual physical contact with things has a much bigger impact than something that isn't. If you ever download the Daniel King series (he's an english GM) he will also advise the same thing :)

However, it would obviously be a waste if you didn't learn something from the book you have! So first off, don't expect this to end fast, this will take time... unlike learning from a teacher or someone who speaks... Learning chess from a book takes time.

First off you will need to take your time and understand every single move, one of the hardest things to learn from chess books are tactics... Those have a lot of annotations and many variations (especially if you look at some rook lifting tactics, f4 pawn push, h4 push etc...). After you are done with the first chapter in the book, if you completely understand what's going on, you will most likely handle the rest fine if you take it at a good pace. Rushing things won't get you anywhere so take your time.

If you have any further questions feel free to ask, I'll answer to the best of my abilities.

A good endgame book to learn from is Domination in 2,545 Endgame Studies By Kasparyan... I bought the book and I can tell you, it's a piece of gold.


I think f6 is an uninspiring move.  It doesn't force anything, blocks the Knight on g8, and exposes the King.

365chess.com says that Black's win percentage is wretched after f6; in fact it's the weakest reply with Black winning only about 16% of the games.

Good continuations include the trade of Knights in the middle with 5. Nxd4 Nxd4 6. Qxd4 or 5. O-O.

Stockfish sees

[fen ""]

1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4 f6 5.O-O Nge7 6.Nxd4 Nxd4 7.Qxd4 Nc6 8.Qd1 Ne5 9.Bb3 Bc5 10.Nc3 c6 11.Na4 Be7 12.a3 b5 13.Nc3 a5 14.Qh5+ g6 15.Qh6 Bf8 16.Qe3 Ba6 17.Rd1 Qc7 18.Qf4

...with a pawn-plus advantage to white.

Here's a sample game from 2001, Wolfgang Kuhn is White, Heinrich Lehr is Black.  I don't know the strength of these players.

[fen ""]

1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4 f6 5. O-O Nge7 6. Nxd4 Ne5 7. Be2 N7g6 8.  f4 Nf7 9. Nc3 Bc5 10. Be3 c6 11. Na4 Qe7 12. Nxc5 Qxc5 13. Nf5 Qf8 14. Qd3 d6  15. Nd4 Bd7 16. Rad1 O-O-O 17. Qb3 Qe7 18. Bc4 Rhf8 19. Be6 Rde8 20. f5 Nge5  21. Bxd7+ Nxd7 22. Ne6 c5 23. Nxf8 Nxf8 24. Bf4 Qxe4 25. Qxf7 1-0


What's the difference between movetime and the Slow Mover option?

When you pass movetime to an engine via UCI, you're telling it to override any time management algorithms it might have, and to instead spend exactly x milliseconds analysing the position.

When playing games, the UCI movetime parameter typically isn't specified. Instead, the engine is told how much time each player has left on their clock (and the increment, if any). This allows the engine to decide how much time to use with its own time management.

The Slow Mover option is used to tell the engine how you would like it to manage time. It only means something in a game situation (i.e. when movetime isn't specified). Higher values will tell the engine, broadly, to use "more time", but it does not control the exact amount of time that is used.


White has some nasty threats involving the loose a8-rook and c7 pawn. After 13...g6:

[FEN ""]
[StartPly "26"]

1. Nf3 c5 2. e3 Nc6 3. c4 Nf6 4. d4 d5 5. cxd5 Nxd5 6. e4 Nf6 7. d5 Nxe4 8. dxc6 Qxd1+ 9. Kxd1 Nxf2+ 10. Ke1 Nxh1 11. Bb5 b6 12. c7+ Bd7 13. Ba6 g6 14. Bb7 Rc8 {Saving material} 15. Bf4 {Defending the passed pawn} Bg7 {Carrying on with the planned fianchetto} 16. Bxc8 Bxc8 17. Nc3 {White will be able to take the trapped h1 knight soon or even play Ra1-d1-d8#}

However, playing 13...e6 allows the black king to attack the c7 pawn, preventing white cramping down like this.

N.B. Not checked by an engine. These are just my first impressions.


How do you 'calculate' compensation in chess

Introduction:

Your goal in the chess game, is to win.
Having more points is good, only when it helps you win the game (e.g. check-mate your opponent)
If sacrificing material improve your chances to win the game, then it is the right thing to do.

Compensation in Wikipedia

Compensation includes:

Better pawn structure.
The "two bishops", which refers to having bishops of both colors while your opponent does not. Almost all modern players consider having both bishops as an advantage, although historically there has been great debate as to how much of an advantage they constitute. The two bishops are most likely to show their power in the endgame.
Better piece activity and/or better development (common in gambits).
Having the enemy king open to future attack, either due to a loss of pawn cover or being trapped in the center of the board is often excellent compensation.
Passed pawns are often decisive in the endgame.
Connected and/or protected passed pawns are even more deadly.
Control over key squares, diagonals, files, or ranks.

Summary:

There are several types of compensation.
The answer to Is the sacrifice worth the compensation? might depend on two factors:

Is the compensation very straight forwards? (if so - it is clear to be good)
The specific player profile  (e.g. some players prefer open positions, and some closed positions) - if the new position after the sacrifice will be more suitable for the player - he'll have clear plan how to continue/win


What is the best way to improve visualization?

In my experience at first you should just work on chess as much as you can, especially on combinations. If you get comfortable with visualizing positions that result from the combinations you will notice to be able to also follow positions in chess books.
Then it's time to read endgame books. At first you will not be able to follow the moves too deep, but since the positions are simple you will be able to follow it for a while, that's useful for your endgame, and soon you will notice that it's getting easier to follow even deep lines.


After a blunder, is it better to resign or keep playing?

First, I would try and keep a very straight face, and maybe your opponent will "trust" you, and overlook the blunder. It has happened before even with very strong players.

That said, if the opponent takes it, you should probably decide based on your level of skill and your perceived level of skill of the opponent, and if the position is messy.

For example, if you are playing a master, and the position is just a clear piece down, you should probably resign. If you are playing an 800-player, then it is very possible that you can play on despite your error.

What I mean by "messy" is if the position is a tactical mess even without the piece, it is more likely that your opponent can still make an error, but if it is just a clear piece down with no tricks, as in the position you gave, then you may as well resign if your opponent is a reasonably decent player.

Lastly, is it a blitz game, or an over-the-board tournament game? (I know in this case, you said it was casual.) If it is blitz, it really does not matter as much either way since it will be over soon; but if it is OTB, it matters more, but your opponent also has that much more time to figure things out.

In the end, there is no right or wrong answer, and you have to evaluate the circumstances, and do what you think is best at that moment.

Do keep in mind that if it were a tournament game, that playing it out may also tire you for the next game.


What is the most sound, yet still sharp, gambit?

The Evans Gambit is probably one of the most sound. It's still occasionally played at GM level and most of the critical lines are rarely if ever tested.
The Vienna Gambit and Blackmar–Diemer are probably playable. The Scotch gambit is playable although I wouldn't be surprised if there isn't a forced draw.
With black the Benko is probably sound and the Budapest is playable. Black has fewer sound gambit options since black starts out a half tempo down. Giving up a pawn for a move just gives you an equal position but you're down a pawn.
I'll add though that virtually any opening is playable below 2000 level and certainly in rapid or blitz. In fact, you could probably get to around 2300 with any normal openings.


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


Term for checking piece whose opponent daren't capture it

I'd use the term you already mentioned, "rambling rook", for this (at least when it's a rook). Tim Krabbé claims to have invented it:

If the term 'Rambling Rook' sounds unfamiliar, this could be because I invented it. In Russian it is beshenaya ladya, in Dutch dolle toren, both meaning 'crazy rook.' There is no English term, and I thought a little alliteration would be in its place.

Here are a couple of usages, showing that the term is quite widespread:
Rambling Rooks, compiled by SwitchingQuylthulg on chessgames.com

Rambling Rooks
Witness rooks selflessly throw theirselves at the opponent's mercy again and again... until there is no choice but to take them and accept draw by stalemate.

Can you stop the rambling rook? by user Sleafar on our sister site Puzzling Stack Exchange:

The rook can't be taken, because black couldn't move anymore which is a stalemate (= draw). If the king moves away the rook will continue to give checks.
Can you stop the rambling rook and find a way for white to win the game anyway?


It depends on what exactly the tutorial is trying to teach you.

If it is an opening tutorial, say about the Italian game, then obviously after 1.e4 black has any number of responses and you'll have to find a tutorial for each and every one of them.

If the tutorial teaches you about certain strategic situations, then only the sensible responses will be examined, and what is sensible is something you'll learn by being exposed to many different positions and moves. See: How do players "see" several moves ahead?

If the tutorial touches upon a tactical position, for example a mating attack, then it makes a lot of sense for you to try to find the right way to continue if the opponent had made a different move. It'll probably have some easy refutation and you'll learn a lot by trying to find it by yourself.


Why do players play this move (bishop to b6) in bullet chess?

Actually, ..Bb6 is a sound move not just in Blitz. The Italian and Scotch game are filled with it. There are plenty of reasons why you would make it:

After 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Bc5 5.Be3 White is threatening to win a piece, so Black can retreat to b6 and prevent his bishop from hanging.
Let's assume a central formation like e4+d3 vs e5+d6, with a Black bishop on c5 and a White bishop on e3. It is good for Black to retreat to b6 (even if ...Bxe3 or even just leaving it on c5 could sometimes be considered) in order to trade them on that square and open the "a" file. In your post you give a lot of importance to the fact that this doubles pawns and very little to the opening of the file. But I would say that, specially in Blitz, the file is way more important! White will have to worry about the a8 rook for the entire game.
Finally, Black could have retreated to b6 (or a7) to prevent a trade and keep a powerful bishop on the a7-g1 diagonal.


The following suggestions will work for players in the 1600-2000 elo range. If you are above 2000, you probably already have better techniques than these. And if you are 1600 or below, tactics is arguably a lot more useful to learn.

Here's an assortment of things I used to try when I wanted to learn a opening. Note: I had access to Fritz and Chessbase and that helped.

Get a book (or a chess video) on the major ideas in the opening or variation that you are interested in.
This is fundamental. Watch it, or read it multiple times to absorb the themes.
Get hold of a bunch of games with your opening of interest. (Chessbase or Fritz makes this really easy). Sort them in different ways into smaller databases for your own reference.
Play through the games in various speeds. Click the steps fast, every few seconds, or very slow to absorb what's going on.
(Ideally, you want to focus on the games where your color of choice wins. That way you'll know the winning themes.)
I often learned by playing through games of players who were a 100-200 points above me, rather than from GM's. The reason was that my opponents would deviate from theory very early on, and I could see how players of strength comparable to me handled the positions.
Pay attention to the minor pieces and see which squares they usually occupy. Chessbase has a cool feature that plots the probability of a piece occupying each square in your opening of choice. I found that very useful.
Play through the games paying attention mainly to the pawn structure.
For me, it was usually enough to learn the first 10-12 moves and then the ideas. If you play the same opening enough, you can increase that to a few more moves.
I learned this technique from Silman's book. I'd print out a position (from the opening I was trying to get familiar with) and then stare at it and try to write down a very detailed evaluation of it. This was surprisingly difficult for me. I could come with a few basic points, and then I 'd go over someone's annotations and see that they could look much much deeper into the position. Doing this often can be quite beneficial.
I'd run my games through Fritz's analysis and watch in horror at the things both me and my opponent had missed. But I also learned not to miss those things the next time.
Keeping your own annotations is extremely useful. I'd write notes and keep adding to it as I learned more. Reading my own notes was often more helpful than reading the IM's and GM's who had much deeper knowledge.

Hope that helps.


How could I have improved my attack in this game?

Nf5 would win the queen one way or another because of the threat Qg4+, Qg7++. For instance 16. Nf5 Qe6 17. Qg4+ Qg6 18. Ne7+

Other than that, when you are attacking and the opponent's pieces are undeveloped or discoordinated you really want to open files and not create a closed position. Therefore 17. exd6 e.p. or even better 18. exf6 e.p. seems natural. Then white will bring a rook to e7 and black should be lost soon.


What's the difference between "White is winning" and "White is better"?

In the late stages of the game, an advantage can be easily recognized to be enough to win or not. In the earlier stages (the end of the opening, typically), it's a lot harder to tell.

If White is better, and if he manages to obtain something sizeable out of this avantage, then he will win. If Black fights well, he'll still manage to draw, or turn the tables and win.


What is the reason for using gambits on defence?

The fact that an opening has the word "Defense" in the name usually signifies nothing more than the fact that it is a move by Black that leads into that opening. For instance, if White plays 1.c4 it is simply called the English Opening. But if, after 1.e4, Black plays 1...c5, then we reach Sicilian Defense positions; or if Black plays 1...e6 instead it is a French Defense. But the only reason the latter two are called "defenses" is because it is Black who chooses to enter each one, and the first-move advantage for White means that in the early stages of the game, Black is "defending" to some degree. This is the same reason why, for instance, when Black plays a certain setup it is called the King's Indian Defense, but when White does the same it is called the King's Indian Attack. The word "defense" in the name of an opening generally means no more than that Black has the choice to enter into it.

But Black's motives when playing one "defense" instead of another vary as widely as chess players do, and many times Black is striving to take the initiative away from White immediately. The Sicilian Defense and the King's Indian Defense, for example, both have rather aggressive reputations. Given the above explanation regarding the word "defense" in the names of openings, your question as stated boils down to, "what reasons does Black have for gambit play?" And to that, I would just say that gambit play has the same pluses and minuses for either color.


What are Complication and Simplification in Chess?

I don't think its easy to answer your question since both of these concepts can have multiple definitions depending on who you ask, but I'll give it a shot.

Generally, in the case where one side is winning, your conceptual understanding is correct.

When the position is equal, creating complications or simplifications are a matter of player preference.  For example, if Player A is rated lower than Player B, then Player A may be more apt to trade down (simplification) in order to get a drawish position.  In that case it is assumed that Player A would be content with a draw. Thus, reinforcing the statement that complications and simplifications are a matter of player preference.


Why was 49...Rb4+ played in this puzzle?

Moving the king once like that is a priming move in order for Black to be properly aligned at a crucial point in a few moves.

Without the priming move this happens which allows White to win

8/7p/1pBP2pk/pP6/K6P/6P1/1rp5/4R3 b - - 1 49

1... Rb1 2. d7 Rxe1 3. d8=Q c1=Q 4. Qf8 Kh5 5. Bf3++

So it is desirable to get a check in when promoting in order to win the game:

8/7p/1pBP2pk/pP6/K6P/6P1/1rp5/4R3 b - - 1 49

1... Rb4 2. Ka3 Rb1 3. d7 Rxe1 4. d8=Q c1=Q+ 5. Kb3 Re3+ 6. Qd3 Rxd3+ 7. Ka2 Ra3++

I decided to show a simple mate ending. It is possible for white to prolong the inevitable . This would be done with 3. Be4 . Although it is possible for white to slightly delay, Black still wins with Rb1.


Black could castle, but that doesn't make the king any safer! White could follow with f5 0-0 Qd2, threatening both f6 and Bh6.
Anyway even if Black could castle that doesn't make f5 a bad move (the only downside being the e5 square becoming a bit weak)


How to play computer from a particular position on chess.com app

You can also do this on chess.com.

Go to the "Learn" Tab
Click on "Analysis"
Setup your position via FEN or just by placing pieces
Click "Finish vs Computer"


Does it change anything to play blindfold chess for a "good" chess player?

GM Alexandra Kosteniuk on a stream today mentioned how her father would encourage her to solve studies and puzzles by visualising the solutions and then say, setting it up on a board and then solving it blindfolded.
So if you're already at a stage where you can look at a puzzle on a screen and work out the solution without moving any pieces, the next step is to solve puzzles taking a glance at the board and then doing it blind.
This will help you in learning to retain the board in your mind, and having a guide like knowing it is a mate in 3 for example, will be a crutch so you can build up performing more complex calculations.
After you have managed this blindfold problem solving, you can then try playing blindfold chess. There are programs that help to train for this - off the top of my head, I know Lucas Chess offers a feature like this.
Even if you never play a blindfolded game against a real opponent, practicing it the right way can help your visualization and memory, thus helping your overall performance in any game.


On how old hardware can modern engines be run, and how strong are they?

could modern Stockfish theoretically, with the hardware at the time,
  be entered into the 1974 World Computer Chess Championship?

No. Modern Stockfish is not compatible with 1974 computer architecture.

Modern engines which can run on 64-bit Linux should be able to run on an early 90's Digital Equipment Corporation 64 bit Alpha PC running Unix with a suitable recompile and perhaps tweak of the code.


Why is it a mistake to capture the forked rook?

The key point is that taking the rook reduces your positional advantage.

Your knight is active but the rook is passive;
With your knight on d4 the squares the rook can move to are extremely limited. After 8. ... Nxc2+ 9. Kf1 h6, only f3 and g3 are better squares for the rook. However, with the advancement of pawns on the king side, the queen will be chased away and the development of Nf6 will trap the rook. This will gain both the material advantage and the increasing positional advantage.

This is reflected in the Stockfish evaluation as Nxb3 yields -2.3, with the -2 coming from the material whereas Nxc2+ yields -3.8.


How can I identify Zugzwang opportunities?

Zugzwang positions happen naturally as you work to improve your own position by taking good moves away from your opponent.  Eventually, when every move is bad (or useless), your opponent will be in Zugzwang.  You'll probably find these positions more often in closed games.  Tigran Petrosian was a master at balling his opponents up so they'd run out of moves.

Here's a recent thread where IMO Black is in zugzwang:  Why did Black resign this game?


For the record (adapted from my comment above): as with other such interfaces, if you move the King to its target square, the corresponding Rook will automagically land on the right square to complete the Castling.  (A move like Ke1-g1 or Ke8-c8 can only mean Castling.  Usually the computer will refuse the move if Castling is illegal for some reason.)


If there was perfect play from both sides, will it be draw or win for one?

Most Grandmasters will argue that chess is a draw with perfect play from both sides. However, in practice it is shown that white has higher win rates than black, but this is due to the first-move advantage. This is because white technically gains a small advantage from having the first move, and black will equalize with their move.

It is possible that a first-move could cause a disadvantage with perfect play, because despite having perfect information, the black player could potentially be able to counter any strategy white attempts to play. It is more likely however that if one side were to have a forced win, it would be for white.

The answer to this question will not be known for a long time because only in 2012 were endgame tablebases able to solve any position with 7 pieces perfectly (including the 2 kings). For comparison of how impressive this feat is, 6 pieces was only solved in 2005. Obviously, this problem is exponential because with more and more pieces, the complexity increases further and further, until eventually the game is solved for 32 pieces. One could argue that the starting position is static so we don't have to consider every combination of 32 pieces on the 64 squares, but the number of possibilities is still enormous and will take a long time to know for certain.


Calculating the precise number of combinations of possible moves from a given position

Your estimate is a bit high. In particular you overestimate the number of king moves. At most a king has 8 moves (not including castling which does not apply here), however here, both the black and the white king have a lot less legal moves than your estimated 10. The white king because it is on the edge of the board and the black king because it is not allowed to run into check. A more realistic number for the possible king moves would be 4. The number of legal moves for all four white pieces here is somewhere between 30 and 40. With these estimates you should have around 1 million variations which is confirmed by the data below.
I wrote a simple (should be done with recursion), not-elegant loop in python-chess to count all the legal variations until the 3rd white move and ended up with 347 863 variations. If I go one ply further (i.e. like in your example) until the 3rd black move I get: 1 403 476 variations.
The program loops through all variations and adds the number of legal moves for the 5th ply (3rd move by white). Example program below is until the 3rd white move. Simply add a loop if you want to go until the 3rd black move.
import chess

board = chess.Board("8/8/8/8/4k3/8/8/2BQKB2 w - - 0 1")

counter = 0

for move1w in board.legal_moves:
    board.push(move1w)
    for move1b in board.legal_moves:
        board.push(move1b)
        for move2w in board.legal_moves:
            board.push(move2w)
            for move2b in board.legal_moves:
                board.push(move2b)
                counter += board.legal_moves.count()
                board.pop()
            board.pop()
        board.pop()
    board.pop()

print('The number of variations is:')
print(counter)


From my experience (small to medium central European Opens), offering a handshake without words is a commonly accepted form of resignation.

The handshake is not part of any official rules. However, there is some reasoning behind it:

You shake hands after the game ended (just as you do before it starts). So you only start extending your hand once that end is "set in stone".

If you extend your hand without a concrete reason on the board for an end of the game (checkmate, stalemate, 3-fold repetition etc.), you silently imply the other possible reason: That you just resigned, which is possible unilaterally. The "silently" part is the reason why this is done this way: It's less disturbing for neighbouring boards than saying "I resign" or laying down your king (in many piece sets, you can't make sure that it doesn't start rolling around).

If you instead wanted to only offer a draw, the game would not have ended (yet), as your opponent still has to accept. Thus, extending your hand makes no sense yet. But conversely, if you (properly by words) offer a draw, now your opponent may offer a silent handshake! Because once they (silently) agree to your draw offer, the game is over, and they can indicate this by stretching out their hand.

Of course, this "implied" way of ending games, even if it is more polite to other ongoing games, has the drawback that lead to the question here: It requires that both players are on the same page of what is actually implied. Even more problematic than the question are for example cases where one side saw a 3-fold repetition and implied "draw", but the other didn't see the repetition and assumed "resignation". Probably not the case here, it sounded like neither mentioned anything else but resignation or free draw offer.

Edit: Because the question came up why the players would act this way, there are some thinkable scenarios:

Black was dishonest. He deliberately acted ambiguously to trick White (in the hope that the arbiter would be convinced of his story that he only wanted to offer a draw). (correct result: 1-0)
Black was very inexperienced. Sometimes, weaker and especially younger players have the habit of always offering a draw before they resign (sometimes no matter how lost their position is), in the vague hope that the opponent is nice or doesn't see how winning they are. The handshake genuinely was intended to be a draw offer that White misinterpreted. (correct result: 1-0 with a degree of uncertainty. In my opinion, White should not be punished for acting in good faith, while Black with certainty did not offer a draw the correct way and thus has the weaker case).
It was actually White who was dishonest. We don't know the position. Maybe it wasn't actually all that winning and White exploited Black's naivete of not explicitly offering a draw by words. (correct result: 1/2-1/2)

All these cases are mostly applicable to amateur tournaments. Top (and even advanced) players know that they just look like fools if they offer draws in lost positions or try to cheat that way.

To know which of these cases applies, we need more information (for example, what was each player's rough evaluation of the final position, how reasonable can we expect both players treat handshakes as resignations/draw offers? etc.).


Good question, and to understand the differences, we have to first discuss "reversed" openings.

The most common example of a reversed opening is the King's Indian Attack (1. Nf3 2. g3 3. Bg2 4. O-O 5. d3).  Compare that to the King's Indian Defense (1... Nf6 2... g6 3... Bg7 4... O-O 5... d6).  The only major difference between the following two positions is which "side" has the move:

King's Indian Defense

[title "White to move"]
[fen "rnbq1rk1/ppp1ppbp/3p1np1/8/2PPP3/2N2N2/PP3PPP/R1BQKB1R w - - 0 1"]

King's Indian Attack:

[title "White to move"]
[fen "r1bqkb1r/pp3ppp/2n2n2/2ppp3/8/3P1NP1/PPP1PPBP/RNBQ1RK1 w - - 0 1"]

In the second diagram, white has a full extra tempo over black in the first diagram.  However, this extra tempo is not so useful.  Depending on what white does, black will adopt various formations to nullify white's extra move.  In the first diagram, black can wait to see how white develops before committing.

In fact, Bobby Fischer said (somewhat tongue in cheek) that in the following symmetrical position, black has the edge:

[title "White to move"]
[fen "rnbq1rk1/ppp1ppbp/3p1np1/8/8/3P1NP1/PPP1PPBP/RNBQ1RK1 w - - 0 1"]

1. ( 1. c4 e5) e4  c5

If white plays 6. e4, then black will respond with 6... c5, but if white plays 6. c4, then black will play 6... e5, in both cases leading to a fighting game.

So with that lengthy introduction, now we can look at the Bird.  To begin, after 1. f4, black can immediately strike with From's Gambit: 1... e5! when black scores incredibly well (49.5% from the link in EdDean's answer).  White's best might be to transpose to a King's Gambit with 2. e4.

Furthermore, black will again have an edge that white usually does not have in the Dutch - the ability to see how white develops and then react accordingly.  White can certainly play a quiet system like 1. f4 2. Nf3 3. e3 4. d4 5. c3 and play with that color complex, but if white does that, he is squandering his first move advantage and can claim only equality.

If white tries an enterprising system like the Leningrad Dutch (1. f4 2. g3 3. Nf3 4. Bg2 5. O-O 6. d3 with the plan to play e4), then black will have the opportunity to strike back with h7-h5-h4 when white will have to defend against a fairly vicious attack.  In the Dutch there are various ways to avoid this plan from white although they are beyond the scope of this question.

Hopefully this gives you a bit of an introduction to not only the differences between the Bird and the Dutch, but also how to evaluate reversed openings.


Should you always try your best (play as if your opponent is a grandmaster)?

Is it a good strategy to always play like a grandmaster?

Obviously yes, but unfortunately 99% of chess players are unable to do this even if they wanted to. ;)

Is it a good strategy to knowingly play moves that you know (or strongly suspect) to be mistakes?

No.

"Mistake" in the sense that there is an answer that screws you if your opponent finds it.
Because either they find it (short term downside) or it works out and you just reinforced a flawed pattern in your brain (long term downside). Blundering your pieces left and right is not a sound strategy, not even against "noobs" (after all, you still need to have some material left to actually mate).

Is it a good strategy to knowingly play moves that you know (or strongly suspect) to not be best (but still okay)?

Sometimes.

In many situations, there are multiple candidate moves and it may have some benefit to play the move you judge second or third instead of the "best" one.

Sometimes it's better to settle for a small but safe strategical advantage (that you are confident to transform into a win against a "noob" anyways) instead of a potentially big advantage that needs a lot of precise tactical play to hold (with the additional risk that you miscalculated somewhere).

Keeping the game less complicated when ahead gives the better player some meta advantage (he's less likely to blunder, and as long as he doesn't, he will eventually win), which might make an otherwise suboptimal move the most advantageous.

Or vice versa, sometimes it may be worth it to go for a move that gives your opponent some advantage in one aspect of the game, while you only get a smaller one in some other aspect. Most gambits come to mind, for example. What matters is that you still should not play clear mistakes, only slightly "worse" moves where you do get some compensation. Sacrificing a pawn for initiative that's probably worth less than a pawn, or even sacrificing a piece for a mate attack is fine. Sacrificing initiative by moving out the queen too early for some hit-or-miss chance to apply the Scholar's mate is not a good strategy, because if they find a good answer, you end up with no compensation at all; and if they don't, they are so inexperienced that any healthy opening would probably have won easily (and quickly!) as well without using a strategy that is useless against better players (again: either short or long term disadvantage).

Making the game more complicated when things are even gives the better player some meta advantage (he's more likely to find a better way through the jungle), which might make an otherwise suboptimal move the most advantageous.

However, these kinds of strategies are used by grandmasters as well, so ironically you are still playing like them.

Is it a good strategy to knowingly play moves that you are not sure about (they may be good, they may be bad)?

No.

Often, this cannot be avoided, of course (your skill sets limits to calculation depth and positional judgment). Thus everyone has to do it to some degree. It's not a "good" strategy though. Ideally you should always try your best to evaluate a given position.


Looks like I am late to the party. Anyway:

Free PGNs of many top players are available here. Almost all 2700+ players are there. As for women, only a few from very top are there. These PGN files have anywhere from few hundred to couple thousand games available for each player. Although this does not fully comply with OPs request, it seems like an improvement over the current only answer. If you have some better/more PGNs available, you can post a download link in a comment or run them through this script and suggest an edit to this answer.

The results

EDIT

Bonus - world champions.

Also of interest - Morphy and Anderssen have amazing draw rates of 0.085 and 0.1, respectively.


Can a player resign after checkmating their opponent?

No, this is not possible.

for example move the piece, don't press the clock and then resign?

In particular, that loophole is explicitly covered by the rules:

6.2.1 During the game each player, having made his move on the chessboard, shall stop his own clock and start his opponent’s clock (that is to say, he shall press his clock). This “completes” the move. A move is also completed if:
6.2.1.1 the move ends the game (see Articles 5.1.1, 5.2.1, 5.2.2, 9.6.1 and 9.6.2)

and 5.1.1 is 5.1 in the version of the rules you quoted, so checkmate ends the game before the clock is pressed.
I guess both players could pretend the checkmating move wasn't made (or pretend they don't see it's checkmate), but this is considered cheating, and when discovered may result in both players losing the game and even being expelled from the tournament.


How does his 3 step plan by Petrosian works?

when he proceeds with stage 2 by bringing the rook to a file, isn't he
removing one attacker of the e pawn? Now black's pieces will not be
tied to the e pawn anymore. So, how is this plan any effective?

Currently black controls the a file with the rook on a8. The whole point of step 1. "tie down black pieces defending e pawn" is to force the a8 rook to give up the a file to defend the e pawn with Re8. Only when that is accomplished can white take over the a file with Ra1. The whole point of having a multi step is achieving the last step. The earlier steps are only necessary because without them the last step cannot be forced.


What were Fischer's 179 demands for a World Championship rematch?

If it was only about the 1975 match, It could have been a mistake by the video editor. As far as many sources from the web, there were only 3.

Not counting the draws, first to win 10 games wins the Championship.
If the result is 9-9, then the title goes to Fischer but the prize money is split equally.
There will be an unlimited number of games.

The first one was accepted and the other two were rejected by FIDE delegates. Hence the match was forfeited and the champion title was given to Anatoly Karpov, his challenger.

As far as Fischer being concerned who was very demanding in character and liked to impose his own rules, the number 179 could have been total demands throughout his career.

Some other sources mention that he only asked for two rules. You can read the digital version of the newspaper article here: NYTimes

And there is one another source that mentions as per the video. It is the Independent article. I feel that the video editor got the directions from here. Because 179 demands seem very unlikely. If it were true, it is not a World Championship match but some sort of dictatorship.


Generate Simple Mate In 1 From Tablebases (for kids)

It's possible to generate mates in 1,2,3 etc with tablebase, but that's probably not what you want. You should understand:

You will need good programming knowledge
You will need a week generating 6-men tablebase mates
You will generate too many mates than you can possibly study

If you are confident in programming, you can do this:

Modify the Gaviota tablebase generator (ask the author for source code). Find where it calculates distance-to-mate, if it's one (or two or three), print the position out.
Modify the Syzygy tablebase generator. Syzygy reports distance-to-zero, so you may need to use online probing (e.g. Nalimov) or an engine.
Use the public API in https://syzygy-tables.info. Start from a randomised position. Use the API result to move your position to mate-in-one.

If you don't have any idea what I'm talking about, generating mate positions with tableabse is not for you. You should:

Buy a book with mate-in-one positions. There is an Android app that can read a chess diagram and convert it to PGN.

EDIT: You shouldn't generate total random FENs. You should try to generate FENs that either side has an extra rook, queen etc.


Does a draw on the board need to be declared before the time flag is reached?

This was undoubtedly a draw. FIDE rules, emphasis mine:

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.

So the game was over, and it was a draw. No player needs to claim or acknowledge or anything. That the clock was still ticking and everything else was irrelevant as far as the rules were concerned.
(there is also another rule that would apply, a flag fall is only a win for the opponent if he has a series of legal moves that lead to checkmate, and here he clearly didn't -- but it's moot because if you don't notice the stalemate, you don't notice this either)
Now, the problem is that no player noticed the stalemate, so they didn't realize what the actual result of their game was. So of course they didn't ask an arbiter either.
What you, as a spectator can do is always very hard to say. As far as the rules are concerned, you hardly exist, and if you do the rules only want you to stop interfering.
But in this case, the game was over. There was no danger that you would distract the players, nor was there any way for you to influence the result anymore. In my personal opinion, it was fine for you to walk up to them and point out the stalemate, to prevent the wrong result from being reported. Or alert an arbiter. But maybe others disagree.
One thing that is not the answer is "accept the fact that white effectively surrendered by shaking hands and accepted the defeat". That happened after the game already finished, so shouldn't influence the result.


What do the engine annotations 0.53/24 mean?

The score 0.53/21 means the chess engine evaluates the position after 6... Ng8-f6 at 0.53 pawns (or 53 centipawns) in White's favour after completing a search depth of 21 ply (or half-moves). It means White has a slight advantage.
Similarly -0.25/24 means the engine evaluates the position after 6... e7-e6 as 0.25 pawns (or 25 centipawns) in Black's favour after a search depth of 24 half-moves.


Around 00-01 Fide had a great online arena. What happened to that?

Actually FIDE publish a new chess platform named FIDE Online Area (http://arena.myfide.net/) . Furthermore there are several tournaments to encourage chess players to use this arena such as ;

The 1st FIDE World Online Amateur Blitz Championship 2015
The 1st FIDE World Online Junior Blitz Championship 2015
The 1st FIDE World Online Women Blitz Championship 2015.

Instead, ICC(Internet Chess Club) is the most visited online chess area among professional chess players. (http://www.chessclub.com/)


How to deal with Stonewall Attack 'counter'?

No opening approach is equally well suited to all responses.  The Stonewall does often allow for an active king bishop, an active knight on e5, an open f-file, and the promise of a g-pawn advance against a castled King.  On the other hand, it means a diminished role for the queen bishop and (if things don't work out according to plan) the queen knight, and it gives White a backward e-pawn and some central holes.  White's center can easily become weak without a lot of piece protection there.  You'll want to be mindful of these tradeoffs when using this "telegraphed" opening.

I first learned about the Stonewall from a book by prolific author Fred Reinfeld called How to Think Ahead in Chess.  He devoted almost half of this small book to this opening, basically endorsing it wholeheartedly for the beginning player and failing to discuss its drawbacks.  He even encouraged the reader to stick as closely as possible to a specific  move order and a predetermined set of opening- and middle-game objectives.  An extraordinarily bad set of advice, on later reflection.

EDIT: You asked for advice about adapting to a Black king move to the queenside.  You might want to try to make the most of your f-file strength, going after the f-pawn and penetrating the Black position on f7.  If black creates good counterplay with a c-advance and good hits against your center, you may be able to avoid serious problems by exchanging pieces and setting up a chance to liquidate your e-pawn before it becomes an endgame liability.


Games of Mikhail Tal under the influence of alcohol

I [William Hartson] remember him vying for first place with another Soviet grandmaster in a tournament in Holland. On the night before the final round they began buying each other drinks and lining up the empties on the table. When I left them at around 2am, Tal had the remains of 11 drained brandies, his rival had 11 empty rum-and-cokes. They continued for another two hours. At 8.30 in the morning, Tal trotted downstairs to start the last round looking fresh and relaxed. He won easily to take first prize, while his drinking companion was happy with a quick draw.

Source: The Independent

I'm going to search for this game when I get home this evening.


Why are there no more exhibition games between top players and computers?

There are a combination of answers to this question. I will answer in what is, in my opinion, descending importance.

It's just boring now. Initially this was a case of human pride. A few decades ago it was a commonly held belief that no computer could ever perform at the master level or beat a grand master. It quickly became apparent that this was not the case. Due to the exponentially increasing power of computer hardware and sophistication of engine development grand master after grand master fell as systems went from needing to run on specialized hardware to beat a world class player to being able to run on a modern $1500 USD laptop. Notice that the rise of the Intel Core processor seems to fit with your time frame for lack of interest.
In the developed world we have become accustomed to the fact that computers can out-perform humans in nearly any field and I think most people just accept the fact that narrow AI will eventually have a place in every field - even if most don't have the vocabulary to express the idea in that way. Narrow (or Weak) AI is artificial intelligence that has expert, human level ability in only a single thing, such as chess. Strong AI is the boogieman of the Terminator movies and the Matrix.
Because of number 1 and number 2 there is no money in it. IBM put a lot of money into the Deep Thought/Deep Blue matches for PR reasons. Now it's Watson and language. And if there is no money, who's going to agree to play?

AI has moved on to driving cars and diagnosing cancer and heart disease. Chess was only ever just a stepping stone to more important things that can make money.


Could you show me the code(s) of one or more simple chess program(s) written in C#?

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


Unless you have a good reason, why would you block your own queen bishop and release tension on the important d5 square?

The idea of the gambit is to intensify pressure on the d5 square. Volunteering yourself away by Nd2 is unusual.


Good openings for a beginner (for white)

The Scotch Game is definitively an opening for beginners (playing as White).

It's opened game that permits to player having two bishops free easily (see behind). Moreover, theory is simple and this opening is not countered easily by weak players because few weak players know it.

Here's a diagram:

[fen ""]

1. e4 e5 2. Nf3 Nc6 3. d4


Why isn't the active color allowed to be in check in a FEN legal position?

The active color (i.e. the color which has the next move) is allowed to be in check, and as ajax points out, at most twice.

But perhaps you meant the inactive color not being allowed to be in check.  Why is that?  The answer is: if the inactive color is in check, it would mean that at least the last move by the inactive color was illegal, allowing its own King to remain in or be exposed to check.


The thin line between winning and losing at the top level?

Note: I'm an average player, who learnt chess about 2 years ago, maybe I'm not the right guy to answer such question but I will try.

I wanted to ask a similar question, maybe I will today or tomorrow. As for your question.

Top level players do make mistakes, maybe they underestimate the opponent, maybe under time pressure, maybe they just don't see the moves, or maybe they are focusing on the attack.

To prove my point I'll show you 2 games and I"ll talk about the mistakes, you can click on the links to watch the videos

Levon Aronian vs Boris Gelfand Round 2 Candidates Tournament 2013

[FEN ""]
[White "Levon Aronian"]
[Black "Boris Gelfand"]
[Event "2013 Candidates Tournament"]
1. Nf3 c5 2. c4 Nc6 3. Nc3 g6 4. e3 Nf6 5. d4 cxd4 6. exd4 d5 7. cxd5 Nxd5 8. Qb3 Nxc3 9. Bc4 Nd5 10. Bxd5 e6 11. Bxc6 bxc6 12. O-O Be7 13. Be3 Qd5 14. Rfc1 Qxb3 15. axb3 Bb7 16. Ne5 O-O 17. Ra4 Rfd8 18. Nc4 Bf6 19. Na5 Rd7 20. Rb4 Ba6 21. Nxc6 Rb7 22. h3 Kg7 23. Rxb7 Bxb7 24. Ne5 Bd8 25. b4 Rc8 26. Bh6 Kg8 27. Rxc8 Bxc8 28. Nc6 Bf6 29. b5 Bd7 30. g4 g5 31. h4 gxh4 32. g5 Bxc6 33. bxc6 Bd8 34. Kg2 Bc7 35. Kh3

If you want a full analysis on that game you can watch the video, I"ll talk about 2 moves that changed the game.

16. Ne5 getting the knight involved, the more brilliant move is 18. Nc4 and 19. Na5 I didn't see that coming! putting pressure on the pawn, basically that knight destroyed black in my opinion.

Did Boris see it coming? Maybe he did, maybe he just ignored the knight, we all do ignore our opponent's moves, in the end of the middle game, especially if the opponent is attacking, we have to counter-attack, and we don't defend anymore, keep in mind that in this particular tournament, you get 2 hours for the first 40 moves, no time pressure, the game ended in 35 moves.

The next move is 26. Bh6 which finished Boris off. If the king takes, then eventually the knight will fork the black bishop. Didn't he see it? He should see that. The first thing I look at is the major minor pieces of my opponent. If black focused a bit he could've seen it, (Boris is a GM) so white has a knight, a rook and a bishop, it's obvious, has no where to go, if he didn't check the king, so Boris should have thought about what happens if the bishop attacks his king.

Bobby Fischer vs James Sherwin 1957 US Chess Championship

[FEN ""]
[White "Bobby Fischer"]
[Black "James Sherwin"]
[Event "1957 US Chess Championship"]
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bc4 e6 7. O-O b5 8. Bb3 b4 9. Nb1 Bd7 10. Be3 Nc6 11. f3 Be7 12. c3 bxc3 13. Nxc6 Bxc6 14. Nxc3 O-O 15. Rc1 Qb8 16. Nd5 exd5 17. Rxc6 dxe4 18. fxe4 Qb5 19. Rb6 Qe5 20. Bd4 Qg5 21. Qf3 Nd7 22. Rb7 Ne5 23. Qe2 Bf6 24. Kh1 a5 25. Bd5 Rac8 26. Bc3 a4 27. Ra7 Ng4 28. Rxa4 Bxc3 29. bxc3 Rxc3 30. Rxf7 Rc1 31. Qf1 h5 32. Qxc1 Qh4 33. Rxf8 Kh7 34. h3 Qg3 35. hxg4 h4 36. Be6

Let's focus on 30. Rxf7 Rc1 31. Qf1. Black didn't see Rxf7 and of course he didn't see Qf1. That's how you outsmart your opponent! I had to show a game played by Fischer. It answers your question perfectly. Let's say if

Rxf1+Rxf1+
Qxd5Rxf8+
Kxf8exd5

And white has a passed pawn.

All I want to say is that GMs do make mistakes, they do underestimate the opponent, ignore a move, or maybe they just don't see the game so well. But sometimes they are just outsmarted!


What are the shogi equivalents of Fool's and Scholar's mate?

A very fast checkmate (6 moves) is described here:

1. P-7f P-8d 2. P-5f P-5d 3. R-5h S-4b 4. P-5e Px5e 5. Bx5e P-8e 6. Bx7c+ mate

apologies in advance for everyone who feels insulted because of the use of figurines instead of real Shogi pieces - I couldn't find another analysis board


Why play 7... Nxd5 instead of 7... exd5 in the QGD?

Both moves are played with exd5 being the more popular choice.  After 8.Nxd5 exd5 is twice as popular as Qxd5 as played by Nakamura.  It is likely Nakamura is trying some ideas in these sidelines in the hopes to catch his opponent unawares.


You need to connect to your server with ssh -X command to enable X forwarding. The details of how this needs to be configured can be found in this answer on
Unix and Linux Stack Exchange.


Should a beginner try to learn 1 specific opening in depth or is not the best use of time?

What is your level?

For an absolute beginner learning general opening principles (fight for the centre, develop minor pieces, castle for king safety...), tactic training and paying attention not to blunder pieces in one move, will be much more useful than learning an opening.

Also if you play mostly low rated opponents there is not much point studying a specific line in the Sicilian to move 30 if all your opponents know is the first 4 moves of the Italian game.

If you study an opening make sure to not only study the move but also the typical plans which can be for instance typical pawn breaks, exchanging bad bishops and keeping the good one, typical regrouping manoeuvres, etc

Opening theory can be very complex. For a beginner I recommend to start with the main line and not too deep (how deep will depend on the opening). As you encounter side lines in your games or feel that you lose because you are on your own after your main line theory ends, you can always learn more.

Getting away with one opening will not be possible as with black you will have to prepare for at least d4 and e4. And if you are white and start with e4 you need to be prepared for at least e5, c5, e6, c6...
As above I recommend to start studying what you encounter most often first and play the other opening s on general principles until you learn them.


When you move one rook to the center, the other rook, obviously, cannot cross it. If you play Rfd1, you cannot then play Rae1. And if you play Rad1, you cannot then play Rfc1. So, part of this decision is planning ahead and thinking about which other file you are likely to want a rook on.

Relatedly, if you play a move like Rae1, you are trapping your f-rook, often making it vulnerable to an attack from the bishop. Be careful before playing a move like that.

If the opponent has a bishop on g7, it is sometimes a good idea to get the rook off of the a1 square, especially if the center is not closed. This allows you to more easily play b3 or b4 without putting your rook in danger from the bishop.


Why wasn’t Rashid Nezhmetdinov a grandmaster?

Rashid Nezhmetdinov, aka “Super Nezh”, was clearly GM strength, having a plus score in the 20 games he played against World Champions, including a plus score against his friend, Tal. He was also a five-time Russian champion (this title predates the Soviet Union, and is not the same as champion of the Soviet Union).

I was a Russian linguist in the Air Force during the cold war (1980-1988), and all of my Russian teachers were “off the boat” as they say, meaning they were natives of the Soviet Union, so we heard many stories about life there, and Nezhmetdinov’s story is not uncommon: Lack of favor.

During his peak years, Nezhmetdinov only managed to play outside of the Soviet Union one time, and he finished second to Korchnoi at Bucharest 1954, which again showed that he was strong enough to be a GM. Unfortunately, strength is not the only factor in getting a title. FIDE has long had in place title rules that were designed to make sure that federations could not manipulate titles, thus you have to play x-number of other titled players, and x-number of players from other countries. So, back then, it was harder to get titles because there were not as many titled players as there are today.

Typically, in the Soviet Union, there were also “favorites”, and they were people, who were Communist Party members, or related to those, who were. If you were not a favorite, you could not travel abroad freely as you can today, and they lived behind what was called “The Iron Curtain”. The Party also worried a lot about players defecting, so in essence, your whole country was a prison of sorts. There were exceptions, who were not Party members, but who were so talented that they could bring the Party great favor and prestige, especially when it made the West look bad. Nevertheless, I read somewhere that Nezhmetdinov was a low-level party member, but he was also not a prodigy as were the Tals and Spasskys of the time.  As great as Rashid Nezhmetdinov was, he had huge flaws in his game, and thus, he would probably never become World Champion, and the top chess players knew it, and thus, the Party did not favor him. If you were not given the opportunity, you cannot succeed. He was also an ethnic minority, a Tatar, which also surely played a role in this.

Personally, I would love it if FIDE would posthumously award Nezhmetdinov the Grandmaster title. He is easily the best player ever not to get the title, during the era of titles. I have since written an email to FIDE President, Arkady Dvorkovich, regarding the possibility of posthumously awarding Rashid Nezhmetdinov the GM title.

For anyone, who does not know of Super Nezh, I suggest you search for some of his games. He has what might be the greatest queen sacrifice ever.

I was asked in comments why black resigned after 33. Ke2, so I added a sample line just showing where to put the white pieces, and how that will eventually lead to an easy win, and Chernikov knew it.

 [Event "Rostov on Don"]
 [Site "Rostov on Don"]
 [Date "1962.??.??"]
 [Round "?"]
 [White "Nezhmetdinov, Rashid"]
 [Black "Chernikov, Oleg L"]
 [Result "1-0"]
 [ECO "B35"]
 [PlyCount "65"]
 [EventDate "1962.??.??"]
 [EventType "game"]
 [EventRounds "1"]
 [EventCountry "URS"]
 [FEN ""]

 1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 g6 5. Nc3 Bg7 6. Be3 Nf6 7. Bc4 O-O 8. Bb3 Ng4 9. Qxg4 Nxd4 10. Qh4 Qa5 11. O-O Bf6 12. Qxf6 Ne2+ 13. Nxe2 exf6 14. Nc3 Re8 15. Nd5 Re6 16. Bd4 Kg7 17. Rad1 d6 18. Rd3 Bd7 19. Rf3 Bb5 20. Bc3 Qd8 21. Nxf6 Be2 22. Nxh7+ Kg8 23. Rh3 Re5 24. f4 Bxf1 25. Kxf1 Rc8 26. Bd4 b5 27. Ng5 Rc7 28. Bxf7+ Rxf7 29. Rh8+ Kxh8 30. Nxf7+ Kh7 31. Nxd8 Rxe4 32. Nc6 Rxf4+ 33. Ke2 (33. Ke2 a6 34. c3 Rf7 35. Nb4 a5 36. Nc6 a4 37. a3 Kg8 38. Be3 Kf8 39. Nd4 Rb7 40. h4 Ke7 41. Bf4 d5 42. g3 Kf6 43. Kd3 Rb6 44. Bg5+ Ke5 45. Nf3+ Ke6 46. Kd4 Rb8 47. Ne5 Rg8 48. Bf4+- {and Kc5 next wins}) 1-0


Where can I find Pauls' 1874 article on the n-queens problem?

The only old documents I find available online from the Deutsche Schachzeitung periodical are from Volumes 20, 21, 44, 45, 56, 57, which are available at the Internet Archive. So if you really are after Pauls' exact article for historical reasons, you might have to track down a hard copy of Volume 29 at a library.

On the other hand, if you are primarily interested in the mathematical content of Pauls' article, then a decent (though also partial) exposition is available from "A survey of known results and research areas for n-queens" by Jordan Bell and Brett Stevens, in Discrete Mathematics Volume 309, pp.1-31 (2009). For instance, they spell out Pauls' method of proof for the existence of solutions to the n-queens problem (which appears in the first part of the article for which you want the second part):

  Theorem (Pauls 1874). For all n>3, n non-attacking queens can be placed on the n x n standard chessboard.

The Bell--Stevens paper does point out that Pauls' part II gives a proof that the 92 solutions to the 8-queens problem given in 1850 by Nauck are exhaustive. But unfortunately,
Pauls' method of proof isn't given. (That said, Pauls' work here is mentioned alongside Gauss' earlier claim that a brute force computation could be used to prove that 92 is the total number, so perhaps that gives a hint at how Pauls proceeds.)

Edited to add: Bell and Stevens do point to two other old secondary sources which they say offer "excellent summaries" of prior work done on the 8-queens problem. These are:

E. Lucas, Récréations mathématiques. 2ième éd., nouveau tirage. Librairie Scientifique et Technique Albert Blanchard, Paris, 1973.
T.B. Sprague, On the eight queens problem, Proc. Edinburgh Math. Soc., 17 (1899), pp. 43–68.

The first is available online via Gallica (see the section on "Le problème des huit reines"), but it appears not to discuss the work of Pauls; rather, it focuses on the work of Günther (S. Günther, Zur mathematischen Theorie des Schachbretts, Arch. Math. Phys., 56 (3) (1874), pp. 281–292), which work also receives an English-language exposition in an 1874 Philosophical Magazine article by Glaisher.

The Sprague piece is also available online, via Google Books, but sadly it doesn't address Pauls either; instead, it again offers a look more at the Günther/Glaisher work, but this does at least mean explicitly addressing the matter of the 92 8-queens solutions on the standard chessboard, among other things.


Systematic ways to approach more difficult problems

for example this one below,don't even know where to begin.Earlier the
way I solved problems was finding all the checks,captures and threats
and the solution used to come within few seconds but now things are
not that easy

"Finding all the checks,captures and threats" looks like a great way to solve the puzzle you've posted. There are no immediate checks but there are some good candidate captures and threats.
[fen "r1b2r1k/p1p3pp/2pp1q2/8/N1Q2n2/1P1N4/P1P2PPP/3RR2K b - - 0 1"]

1... Nxd3 2. Qxd3 Qxf2? 3. Rf1! (1...Be6? 2. Qxf4! Qxf4 3. Nxf4 Rxf4 4. Rxe6)(1...Nxg2 2. Kxg2 Bh3+ 3. Kxh3 Qf3+ 4. Kh4 g5+ 5. Kxg5 Rf5+ 6. Kh6 Qh5++)

Nxd3 is a capture which looks like it might win the f pawn and create back rank mating threats but white looks to be fine after recapturing with the c pawn when the white queen is still threatening the c6 pawn. If white recaptures with the queen then the f pawn is poisoned! It is met by the embarrassing Rf1. So, that doesn't work
The white queen is a little bit short of moves, but the threat Be6 is met by Qxf4 and at the end of the exchanges the bishop on e6 is hanging, so that doesn't work either. Finally -
The capture Nxg2 is a really promising looking sacrifice which is well and truly poisoned. Kxg2 is met by Bh3 and then Qf3+ with mate to follow soon. If white doesn't move the e1 rook then black is just winning a pawn and exchange plus the white king is very exposed. If white does move the e1 rook then Qf3 with the threat of Bh3 is going to be devastating.

So, "checks, captures, threats" does work. You just have to keep the analysis going for more than 2 or 3 moves and find two piece sacrifices as you hunt the king. The fun part of tactics!


How Do Top Engines' Achieve Large Search Depth

I am not a specialist about programming chess engines, but the notions of depth is a little bit misinterpreted. "Depth" is somehow the maximal value reached by the engine during his search but the engine is absolutely not searching in every position with a depth of 20 moves. Modern engine uses heuristics to determine line of play and reducing the number of positions to analyse.

I don't precise way to do so but I can imagine that line of play with too much imbalance are not completely analysed by the engine, for example.

One point as well is about the evaluation function of your algorithm, if the function is too time-consuming then the algorithm would run longer as well.

One thing is about the transposition table (TT), you need to check if the TT is not becoming too large which would result into some memory issues.

I really believe that the number of positions to analyse at each step is strongly bound by the way of choosing which position to analyse or not.

I think you know the chessprogramming wiki, but there is a lot about improving searching on http://chessprogramming.wikispaces.com/Search.

I hope I've helped you :)


My bottle of water accidentally fell and dropped some pieces. Now what?

There are two articles in the FIDE Laws of Chess which cover this, 7.4 and 7.1.

7.4.1 If a player displaces one or more pieces, he shall re-establish the correct position in his own time.
7.4.2 If necessary, either the player or his opponent shall stop the chessclock and ask for the arbiter’s assistance.
7.4.3 The arbiter may penalise the player who displaced the pieces.

So, first of all you should expect some kind of time penalty for what you did. Note that it doesn't make much difference that it wasn't your fault in the sense that you may not have done it deliberately.
Playing in a tournament some years ago I saw something similar happen. One player stood up and his leg caught the tablecloth pulling it, displacing a glass of water and the board which also got soaked. The arbiter came running over and the first thing he did was add two minutes to the opponent's time because of the disturbance caused. This was at standard time controls so the moves were recorded but in any case both players were of a sufficient level to be able to recall the position exactly.

7.1   If an irregularity occurs and the pieces have to be restored to a previous position, the arbiter shall use his best judgement to determine the times to be shown on the chessclock. This includes the right not to change the clock times. He shall also, if necessary, adjust the clock’s move-counter.

So, if neither of you can recall the exact position immediately prior to your accident then you should try and agree on a previous position. Unless you are both complete beginners you are likely to at least remember the opening.


Two moves! And this has a name as well! It is called Fool's mate!

 [title "Fastest Mate"]
 [fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

 1. f3? e5 2. g4?? Qh4++