Why is 1. Nf3 not nearly as popular as 1.e4 and 1.d4?

It is funny since 1.Nf3 scores better than any other opening move per Mega 2020 at 55.5% winning percentage for white, compared to only 52.8% for 1.e4, 54.3% for 1.d4, and 54.4% for 1.c4.

I think a lot of it is psychological regarding the types of positions that can arise. 1.Nf3 is the most fluid of all the moves I mentioned, and I think that players simply like more concrete play than not. It also reduces what you need to memorize, or understand, if you go straight into a specific pawn formation with d4, e4, or c4.

I also think that at the lower levels, that fluidity can lead to positions that players, both players, but since it is white's choice, that he/she specifically is not as comfortable with since he/she can end up on his/her own in a hurry. You need to know A LOT more about transpositions into other openings, which is a major undertaking. The play is also more complicated, which drives weaker players away more.

At the upper levels, meaning 2700s, I do not believe that they are afraid of getting lost in the opening as easily, but there still may be an underlying desire to play
"their" openings, so they play more concretely.

One thing I do not believe is that after 1.Nf3 that 1...e5 is a valid response. White, having played 1.Nf3 probably likes d4/c4 openings, so is not likely to go into a double-king-pawn opening, but still has a great response:

 [FEN ""]

 1. Nf3 e5? 2. Nxe5!

Thanks for the gumball, Mickey! (from an old U.S. commercial for a Mickey Mouse gumball machine)

Based on my discussion with Phonon below, I am adding this chart that shows the flexibility of each main opening move that aims for the closed openings (d4/c4/Nf3). At the higher levels, this is a main reason, but at lower levels, I still believe that it is more about psychology, and believing that immediate occupation of the center is crucial. At lower levels this also can often put your opponent on unfamiliar grounds,


You should start with the section of the FIDE web site which describes the Swiss Rules. This has sections giving detailed descriptions of the different systems for making the pairings along with much other useful information.

It is also worth looking at the FIDE Tournament Rules which includes tables for round robin tournaments and descriptions of tie break methods which it is good to also have in a pairing program.


How to display figures instead of letters in position analysis notation in ChessBase?

Nevermind, figured it out.

File > options > Clocks+Notations > Figurines radio button


There actually is an ambitiously worked out answer out there:

http://web.ist.utl.pt/diogo.ferreira/papers/ferreira13impact.pdf

On page 77 you get the relevant table:

depth: elo:

20    2894

19    2828

18    2761

17    2695

16    2629

15    2563

…

So my comment was slightly off, depth 20 is already very strong. Still the point remains, that it is hard to compare search depth between different engines, because it is never brute force and selectively they go much deeper than the given depth. (In the paper they used Houdini 1.5, maybe some engine expert can relate Houdini-search depth to Stockfish search depth.)


Why does the engine dislike white in this position despite the material advantage of a pawn and other positional factors?

Interestingly, even without looking ahead and just evaluating the immediate position, Stockfish thinks Black is ahead by nearly half a pawn despite agreeing that White is ahead in raw material. Looking at the sub-scores, the "Imbalance" category is where most of Black's score is coming from.
"Imbalance" looks at which pieces are on the board and makes assumptions about how well they coordinate together. For example, each rook gets a bonus for each friendly knight and bishop but a penalty for other friendly pieces, and a penalty for enemy bishops and queens but a bonus for enemy knights and pawns.
In this position, Black is getting a bonus for having the bishop pair. White seems to be getting a penalty for having two rooks and a queen (the algorithm apparently thinks rooks don't work well with friendly rooks or queens) while Black's queen gets a bonus because the extra enemy rook and pawns are considered as potential targets just for existing. Overall the synergies between the various pieces actually give Black more of a score boost than the bishop pair itself does, and in total it's enough for Stockfish to think it outweighs the material deficit.


I found an easy way to save pgns in CBReader. File->Publish to WEB->One-click publication-> the browser will open with your game and 'Download PGN' option. Really fast and easy.


How can I load a position without kings into an engine?

For most such questions perhaps a chess problem engine like Popeye can easily solve it.
However, the kind of goals your question is indicating like extinction of opponent pieces can also be set in configurable chess variant engines, e.g., Fairy-Stockfish or Sjaak II. I would assume that in most cases this will be the easier and faster solution, assuming that the problem is within the scope of the possible rule configurations.


Do the rules of blitz chess allow a draw to be claimed if the position is dead drawn?

No. There is a rule like that for standard time controls (rule 10.2 under FIDE rules), however under blitz rules 10.2 doesn't apply. Appendix B, rule B.3.b:

b. Article 10.2 and Appendix A.4.c do not apply.

In blitz, the clock is just as much a part of the game as the board is. If you have a position like that with seconds left and your opponent has more, you are lost.


How should I proceed?

You should get on with your life.

It was a minor incident which you brought to the attention of the arbiter. You disagreed with his decision but did not lodge an appeal with the appeals committee and you did not escalate to the national federation. Instead you went straight to FIDE. They are clearly not wasting time on this and nor should you.


This is sort of the holy grail of chess training sofware ... something that substitutes for a human Master/GM level coach instructing and critiquing you whenever you needed it.

Till date, I believe nothing comes close to the quality of instruction/critique of a good human coach, though software that tries to offer some kind of interactive feedback-based training include:

Ubisoft's ChessMaster.

Very rudimentary feedback + post-mortem move analysis. The cheapest of the three ... the move-by-move feedback is usually mostly suited for tactical errors. Good for people just starting out using computers to train with.

Chessbase's Fritz

Probably the best bang for your buck of the three, given the quality of feedback and lots of bells and whistles. A fairly annoying/helpful "coach" who will flag any error you make (though doesn't clearly explain why it was a mistake). Features such as explaining (or more or less summarizing)  the benefits of each move in a given position, a hotness indicator for how critical or "on the edge of a cliff" a position becomes.

Chess.com's Chess Mentor

The most "human" like feedback but these are pre-programmed scenarios based on instructional positions you have to play through, rather than your own games.

Once again, these all fall short of explaining nuances in a way that you are guaranteed to understand (a human coach can figure out precisely what doesn't make sense to you and focus on that mental roadblock!) , though if you are not really intermediate-strength level yet, software such as the kind listed above might be of some help.


Weird early f4 suggested by engine (English Opening: Reversed Sicilian)

It is either f4 or f3 to defend the threat on f2.  Intuitively I prefer the tempo that f2-f3 gets, but the idea of f2-f4 with e2-e4-e5 is probably what the computer likes.


If you're looking for the puzzle with the longest forced sequence, it would be this position ,which contains a win for white in 549 moves.
[FEN "1n1k4/6Q1/5KP1/8/7b/1r6/8/8 w - - 0 1"]

It was found by computers from the generation of 7-man endgame tablebases, and there are several similar positions with the same distance to mate.
If that seems a little extreme, then the longest mate puzzle made by a human was Otto Blathy's 'monster', which is a mate in 292 moves but contains an illegal starting position (i.e. it could never occur in a real game).
If you won't accept that, then here are the current record-holders for the longest puzzles created by a person from legal positions - A mate in 271 with 'obtrusive units' (legal, but must have come about through piece promotion, such as having two dark-squared bishops) and a mate in 267 without those. And, surprisingly, both of those were created by the same person.
As for the "most variations that don't work" as you stated, it's probably also the mate in 549 listed above, with the number of moves that would let the other player slip out or otherwise prolong the sequence even more.


I think you are on to something, and statistically, there is a very good reason to play the Scotch over the Ruy Lopez, but that might not be all there is to it.

I think that the main reason is that we are taught that the Ruy Lopez is THE most classical opening, and is the best. I have seen that mindset in SO many books written by the top players over the years, in particular, Karpov. Also, I was watching "Method in Chess" videos recently, and GM Dorfman said that white is statically better because white has more space, and black is confined to three ranks, and white can play on the kingside, center, or queenside, and thus, black must always be on the lookout. I think that is just what classical Soviet players were taught, and that mindset has not been broken among the elite, especially since so many of them became trainers in other countries after the breakup of the Soviet Union.

Statistically, you are right on the money.

All the top players I looked at had similar results to Kasparov, meaning an overwhelming plus score with it. I left out Anand, Aronian, So, MLV, and Grischuk from the following list since they played it so few times (less than 6 each), it was clear that their reason was simply surprise.

Carlsen 11-1-6 (wins-losses-draws) 78%
Caruana 5-0-6 72%
Nepomniachtchi 34-6-29 70%
Nakamura 13-6-7 63%

These are against all players, and the problem is that in Carlsen's case, in particular, is most of the games were from when he was not the Carlsen we know today, and I could have left him out. Caruana's games were virtually all against elite competition!

Then I decided to search only for all games in the Mega 2020 database with players both above 2700, and then the stats fell dramatically down to a typical winning percentage for white, 58% even (53-25-97, 175 games total).

When I then did the same thing for 2700 players playing the Ruy Lopez, there were 2366 games with a breakdown of 580-373-1412, or only 54%.

That is still a healthy plus for the Scotch, but maybe the Soviets still were right, and that the only reason the stats for the Scotch are so good is that the opponent was not expecting it as much. Also, I did not attempt to look at hundreds of games to identify where the games where lost. It might have just been due to other circumstances.


Reason why Kasparov resigned in the "Enrage the Beast" game

White's position is just bad overall. The main reasons:

The passed c-pawn is a huge asset. It's likely it will eventually cost White a piece, but in the meantime it cramps White's forces.
All Black's pieces are far more active than their White counterparts, with the sole exception of the rooks (which are roughly equal in activity).
Knowing Kasparov, he was probably disgusted with his play at this point and fed up with the game. White's position is already objectively resignable in any case due to the two points above.


Think of it this way:
Check mate is where nothing the opponent can do will save them from having you take their king on the next turn, so even if by putting their king in checkmate, you expose your own king, they can take your king before you can take theirs.
There is NO circumstance in which your actions put your own king into check without an opponent making a move.


Giving moves as odds, what's the least number of moves by White which forces checkmate by the time it's Black's turn?

Interesting puzzle.

I came up with this.

[FEN ""]

1. d4 null 2. Qd2 null 3. Qf4 null 4. a4 null 5. Ra3 null 6. Re3 null 7. Nf3 null 8. h4 null 9. Nh2 null 10. Ng4 null 11. Rhh3 null 12. Rhf3 null 13. Nc3 null 14. Ne4 null 15. g3

After Black makes any move, it is a forced checkmate according Houdini. The best move is ’15... f6.’ It allows for mate in 10 moves.


What are the differences between the major online chess sites that allow to play?

Nowadays there is really a abundance of good chess servers. And they are all relatively similar. I think you need a site where you can:

Play blitz chess
Play correspondence chess
Do tactics training
Learn via articles and/or videos

If you want everything on one site, www.chess.com is probably your best bet. As far as I know ICC, chess24, playchess and FICS don't have correspondence games. For beginners it is often hard to play blitz, and even later you might learn more from longer games.

The downside of chess.com is that the players are relatively weak. But if you are just starting out, this is not going to bug you for a few years.


Most different openings by transpositions?

Another well-known example is the following:

[fen ""]
1. f4 {Bird's Opening} 1... e5 {From Gambit} 2. e4 {King's Gambit} 2... d5 {Falkbeer Counter Gambit} 3. exd5 exf4 {King's Gambit Accepted}

A total of 5 distinct names.
Bird's Opening
From Gambit
King's Gambit
Falkbeer Counter Gambit
King's Gambit Accepted


Kasparov in My Great Predecessors, Part 4:

  Generally speaking, Larsen's contribution to the development of opening theory is not very great, since usually he aimed to lure his opponents into little-studied variations and mainly relied on his skill in the middlegame. Nevertheless, he played a key role in the development of what is currently one of the most popular lines in the Semi-Slav Defence, the so-called improved Meran Variation: 1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc4 e6 5 e3 Nbd7 6. Bd3 Bb7!?

One of Larsen's ideas was to allow a check on b5 and give up castling rights. In return he got a strong knight on d5. He first used this idea in the Candidate match Ivkov-Larsen 1965, see game below. Read more about it here.

Sample games:

  [FEN ""]
  [Event "Larsen-Ivkov Candidates Quarterfinal Match"]
  [Site "Bled YUG"]
  [Date "1965.07.05"]
  [EventDate "1965.06.27"]
  [Round "6"]
  [Result "1/2-1/2"]
  [White "Borislav Ivkov"]
  [Black "Bent Larsen"]

  1.c4 Nf6 2.Nc3 e6 3.Nf3 d5 4.d4 c6 5.e3 Nbd7 6.Bd3 dxc4 7.Bxc4
  b5 8.Bd3 Bb7 9.e4 b4 10.Na4 c5 11.e5 Nd5 12.Nxc5 Bxc5 13.dxc5
  Nxc5 14.Bb5+ Kf8 15.Qd4 Qb6 16.Be2 h6 17.O-O g6 18.Bd2 Kg7
  19.Rac1 Rac8 20.Qh4 g5 21.Qg4 Ne4 22.Rxc8 Rxc8 23.Qxe4 Nf4
  24.Qe3 Qxe3 25.fxe3 Nxe2+ 26.Kf2 g4 27.Ng1 Nxg1 28.Rc1 Rxc1
  29.Bxc1 Bxg2 30.Kxg1 Bd5 31.Bd2 Bxa2 32.Bxb4 Kg6 33.Kf2 Kf5
  34.Bc3 h5 35.Kg3 Kg5 36.h4+ Kf5 37.Bd4 a5 38.Bc3 a4 39.Bd4 Ke4
  40.Kf2 1/2-1/2

.

  [FEN ""]
  [Event "1/4"]
  [Site "Cm  Las Palmas (06)"]
  [Date "1971.??.??"]
  [Round "6"]
  [Result "0-1"]
  [White "Wolfgang Uhlmann"]
  [Black "Bent Larsen"]
  [ECO "D47"]

  1.c4 Nf6 2.Nc3 e6 3.Nf3 d5 4.d4 c6 5.e3 Nbd7 6.Bd3 dxc4 7.Bxc4
  b5 8.Bd3 Bb7 9.e4 b4 10.Na4 c5 11.e5 Nd5 12.Nxc5 Nxc5 13.dxc5
  Bxc5 14.Bb5+ Ke7 15.O-O Qb6 16.Bd3 h6 17.Qe2 Rhd8 18.Bd2 Kf8
  19.Rac1 Rac8 20.Rc2 a5 21.Rfc1 Kg8 22.h3 Ne7 23.Ne1 Bd4
  24.Rxc8 Rxc8 25.Rxc8+ Nxc8 26.b3 Ne7 27.Nf3 Bc5 28.Be1 Nf5
  29.Kf1 Qc6 30.Bb5 Qc7 31.Bd3 Nd4 32.Nxd4 Bxd4 33.f4 Qc1 34.Qd2
  Qa1 35.Qc2 Bc3 36.Qb1 Ba6 0-1


Find an opening based on the position of one player only

Using my free, open source pgn-extract program you can specify a grep-like FEN pattern to be searched for in a PGN file of games. The program comes with a file of opening lines (eco.pgn) so a search such as:
pgn-extract --fenpattern "*/*/*/*/3PP3/2P2P2/PP4PP/RNBQKBNR" eco.pgn

would output any matches along with the associated ECO information in the tags. I didn't find anything for this particular pattern.


As @Glorfindel pointed out, this is a knight's tour.
One sequence is Nc3-a2-c1-b3-a1-c2-a3-b1-d2-f3-h2-f1-e3-g2-e1-d3-b2-d1-f2-h3-g1-e2-g3-h1.
[FEN "8/8/8/8/8/pNnbPPpN/RBppPbrP/pkKPrqQR b - - 0 1"]

1... Nxa2 2. null Nxc1 3. null Nxb3 4. null Nxa1 5. null Nxc2 6. null Nxa3 7. null Nxb1 8. null Nxd2 9. null Nxf3 10. null Nxh2 11. null Nxf1 12. null Nxe3 13. null Nxg2 14. null Nxe1 15. null Nxd3 16. null Nxb2 17. null Nxd1 18. null Nxf2 19. null Nxh3 20. null Nxg1 21. null Nxe2 22. null Nxg3 23. null Nxh1

How did I create the sequence? I used Warnsdorff’s Rule:

Always move to an adjacent, unvisited square with minimal degree.

Where the degree is:

the number of unvisited squares that are adjacent to a given square

In the case of ties, I calculated ahead and made sure that the knight didn't get stuck.


I don't think SCID supports Mac OSX officially. The files you have are raw sources, which you'll need to compile with TCL. Why not try a newer (and better) SCID alternative?

Download SCID vs PC

http://scidvspc.sourceforge.net


I had the same problem which (to some extent) I've managed to overcome.

I didn't ever get enough chances to practice OTB games so I could never get used to it. My solution was to play online games with a real board in front of me. I made myself play out the moves on the board and used my computer only to get my opponents move and to enter mine. As long as time constraints aren't too much of an issue it's not much hassle. After a while playing with actual boards was just as easy as without.


Exchange sacrifice to dominate black squares in Najdorf

I found it! It was Lazaro Bruzon vs Vassily Ivanchuk, 11/2005. Here's the link to the game (totally recommended!):
http://www.chessgames.com/perl/chessgame?gid=1366555

Thank you for the help!


How do I determine the bye player in a Swiss tournament?

Note:   Independently from the route followed, the assignment of the
  pairing-allocated bye (see C.2) is part of the pairing of the last
  bracket.

https://www.fide.com/component/handbook/?id=170&view=article

In simple terms, this means that the bye normally goes to one of the players currently tied for last place, but there may be complications if this conflicts with other rules (for example, if every player in the last bracket already got a bye).

It is not stated, but I think that it makes sense to give the bye to someone in the last bracket because that way the bye is least likely to influence who wins the tournament.


What locations in the USA have FIDE approved tournaments frequently?

All FIDE rated tournaments have to be registered in advance with FIDE. Once registered with FIDE they appear on the FIDE website. The page for the USA is here.

As you can see the US is very poorly served for FIDE rated tournaments. The main centers are New York, San Francisco, LA and St Louis.


in silman's book, question about open files and global exchange

It seems to me that after e5 and exchanges on e6 and g7 the d6-pawn is hanging ...

 [FEN "r1qr2k1/p2bppbp/3p2p1/1p1P4/3B1P2/1B3Q1P/PPP3P1/3RR1K1 b - - 0 17"]

 1... Re8 2. c3 e5 3.dxe6 Bxe6 4.Bxg7 Kxg7 5.Bxe6 Rxe6 6.Rxe6 fxe6 7.Rxd6


How to use nodestime option in Stockfish 10?

https://github.com/official-stockfish/Stockfish/commit/926f215061311392bc26c7bc4bde5b719dbab4e5

has everything you need. Essentially, it's an option for chess engine testing, not for production use. The option ensures the engine plays perfectly equally during development.

As a user, you shouldn't bother with this option because number of nodes per ms is not something easy to give a value.


Leaving the score aside, what are the criteria allowing Stockfish to choose its "best move"?

The first three lines:

info depth 31 seldepth 47 multipv 1 score cp -771 lowerbound nodes 86977322 nps 1898570 hashfull 990 tbhits 0 time 45812 pv f1f3
info depth 31 seldepth 47 multipv 1 score cp -761 lowerbound nodes 87198087 nps 1898499 hashfull 990 tbhits 0 time 45930 pv f1f3
info depth 31 seldepth 47 multipv 1 score cp -790 upperbound nodes 99439222 nps 1905696 hashfull 992 tbhits 0 time 52180 pv f1f3 b7f3

Are not actually complete searches. The lowerbound and upperbound following score cp ... indicates that the value is not the actual value of the move. Instead, the value is a bound that was obtained when stockfish failed outside of its aspiration window.

When this happens, Stockfish needs to perform a search at the same depth again, with a wider aspiration window. This is why you have 4 lines at depth 31: stockfish searched the position a total of 4 times at depth 31 because it failed outside of its aspiration window 3 times in a row. The first three scores are not exact, and hence only the score from the 4th search (which is exact) is used to determine the best move.

So the criterion used to determine the best move is the internal score of the deepest search which did not fail outside of its aspiration window.

The internal score differs from the cp score in that stockfish evaluates positions with a granularity of 1/256 of a pawn, rather than 1/100 of a pawn. So two positions may have the same cp score, but stockfish may still be able to rank them internally.

The answer changes again when stockfish uses multiple threads. In this case, a voting system is used, where each thread has a different voting weight based on its score and max depth reached.


there are different books that cover this topic,
for example Neishtadt book on tactic " Improve Your Chess Tactics: 700 Practical Lessons & Exercises" has a chapter dedicated to miracle saves, which is stalemate and perpetual.
On John Speelman tactic book as well there si chapter on that,
I'd say many chess tactic books have a chapter on this topic generally.


En Passant - Usage after one or more move(s)

No. You can take a pawn en passant only on the next move.

See 3.7d, here.

  A pawn attacking a square crossed by an opponent’s pawn which has
  advanced two squares in one move from its original square may capture
  this opponent’s pawn as though the latter had been moved only one
  square. This capture is only legal on the move following this advance
  and is called an "en passant" capture.


Did Stockfish regress from October to December 2020? If so, why?

It is of course always possible that Stockfish did regress. The way changes are tested for Stockfish, or most engines for that matter, always allows for regressions to pass some of the time. (you simply can't play long enough test matches in reasonable time to be very sure that you don't regress) This is not much of an issue since most of the time you will detect which changes brought improvement and which did not. However you can "run unlucky" and hit a couple not so good changes in a row. In fact I do recall an instant when Stockfish was reverted a number of commits since such a regression was measured.
However, in this case if the tests were run against Stockfish 7. I think a more likely explanation may simply be that the newer Stockfish did slightly worse against that specific opponent. Strength is not absolute, you can be better against some opponents and worse against others. The interesting thing then of course is to be on average stronger than the older version however that can still allow an engine to be weaker against certain opponents. Especially, if like the case here, the opponent is several hundred points weaker. At that point it is less about playing the absolute best move and more about beating up the much weaker opponent more efficiently. And especially since the supposed regression is only 10 rating points, I wouldn't interpret too much into it.


Why are doubled pawns in this case particularly devastating?

I first need to note that there is a fairly large difference between the structure in your first diagram and the one reached in the Nimzo-Indian line: in the first diagram, white has not yet played d4. This gives him the option of playing c4 and c3, which is actually quite a strong structure as the d4 square, which would normally be weak with pawns on c4, d3 and e4, is defended by the c3-pawn.

That being said, I don't agree with the assessment that this is an uncommonly bad case of doubled pawns for white. While doubled pawns are, in general, unfavorable for the side that has them, their existence is usually not enough to significantly change the evaluation of a position. In fact, the second line gives us an approximation of how much opening theory thinks that white's structure has been crippled: about the difference between a bishop and a knight.

I wrote the above and then realized that I may have misinterpreted your question. You may be wondering why white's structure in the first diagram is worse than black's.

The doubled-pawn structure is a slight disadvantage and has both plusses and minuses which may be exploited in a given piece configuration by either side. One plus would be the possibility which I mentioned in the first paragraph. Your idea of putting a rook on b1 is another option, although that may be mitigated by black playing b6. White pushing d4 is also an idea, although it may not be so favorable here because a capture on e5 would leave the c-pawns isolated.

Black's structure is better, though, because each of his pawns on the queenside has the potential to be defended by another pawn rather than a piece. White, by contrast, will always have two pawns not defended by pawns: the a-pawn and at least one c-pawn. The attention that white's pieces will have to use defending the pawns on average will outweigh the other considerations.


Do you get an extra turn when you promote your pawn?

Once you have promoted your pawn do you get a second move to move it out
  of danger?

No.

  Or do you still only get the promotion as your move and it becomes
  the opponents move?

Yes.

From the FIDE Laws of Chess:

  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.

There is no discussion of extra turns.


Who is the youngest player to defeat a reigning World Chess Champion in a classical chess game?

I'll start an answer just to get going as kmartin suggested.
I'm sure it'll be superseded by other findings.

Carlsen beat Anand in Linares 2009 when he was 18 years and 3 month old.

(Other games that came to mind but narrowly miss out: Carlsen beating Topalov, 2007, Radjabov beating Kasparov, 2003)


What are the possible terms for interference in the bishop endgame?

Dvoretsky in Endgame Manual just calls this technique interferring.

Building a bridge in RPvR endgames is slightly different as it is about sheltering your king from checks from the enemy rook, not about preventing the rook from sacrificing itself for the last remaining pawn.


Why do many people think that top grand masters can always reach a draw?

The basic dynamic in modern top-level chess is that White wants to find a way to get some edge, often quite small, out of the opening. Black wants to find a way to equalize or otherwise draw. This means that a lot of what has been rejected by White are lines that lead to equality. So, I would agree that a top-10 player wanting a draw with White will basically never lose because he will simply select one of those ways that has drawn in the past. With Black, though, I disagree because making a draw is the essence of the challenge and often eludes even Carlsen.


In most early-stage Pircs, black is slightly worse, so of course, the computer will prefer any move that equalizes, or in this case, gives you a slight advantage.

White is not well-placed in the center due to the pin on the Nf3, and the Bd3 interferes with the Qd1's protection of the center (d4) too. Black can effectively "blow-up" the center here, which leaves him at least equal.

It comes down to specific tactics here, and d5 works. If you wait, white may play d5, and your opportunity would be lost.

One more note: I do not play e4, so I don't think about this much, but in many e4 openings, black wants to get in the equalizing d5, thus you don't usually see the bishop on d3 since it makes d5 easier to achieve. It is usually on e2, c4, or b5, so Bd3 was probably not best. In d4 openings, which I play, Bd3 is common, but black already has d5 in, so it is fine.

  [FEN ""]

  1. e4 d6 2. d4 Nf6 3. Bd3 e5 4. c3 Bg4 5. Nf3 Nc6 6. Be3 d5 7. Nbd2 (7. exd5 Qxd5 {The black queen is now well-placed, and threatens e4.}) 7... dxe4 8. Nxe4 exd4 9. cxd4 Nxe4 10. Bxe4 Bb4+ 11. Kf1 $15


Traps and alternate variations in the Spanish Game

I don't play the Lopez, so I can't answer the part relating to experimental variations, but I can list some of the common traps:

Tarrasch Trap in the Open Variation

After 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. 0-0 Nxe4 6. d4 b5 7. Bb3 d5 8. dxe5 Be6 9. c3 Be7 10. Re1 0-0 11. Nd4 Qd7?, White wins a piece:

[FEN "r4rk1/2pqbppp/p1n1b3/1p1pP3/3Nn3/1BP5/PP3PPP/RNBQR1K1 w - - 0 12"]

   12. Nxe6 Qxe6 (or fxe6) 13. Rxe4

Tarrasch Trap in the Steinitz Variation

After 1. e4 e5 2. Nf3 Nc6 3. Bb5 d6 4. d4 Bd7 5. Nc3 Nf6 6. 0-0 Be7 7. Re1 O-O, White wins a pawn:

[FEN "r2q1rk1/pppbbppp/2np1n2/1B2p3/3PP3/2N2N2/PPP2PPP/R1BQR1K1 w - - 0 8"]

   8. Bxc6 Bxc6 9. dxe5 dxe5 10. Qxd8 Raxd8 11. Nxe5

Mortimer trap

After 1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. d3 Ne7 5. Nxe5?, Black wins a piece for 2 pawns:

[FEN "r1bqkb1r/ppppnppp/5n2/1B2N3/4P3/3P4/PPP2PPP/RNBQK2R b KQkq - 0 5"]

   5...c6 6. Nc4 d6 7. Ba4 b5 8. Bxb5 cxb5

Noah's Ark Trap

After 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 d6 5. d4 b5 6. Bb3 Nxd4 7. Nxd4 exd4 8. Qxd4?, Black wins a piece:

[FEN "r1bqkbnr/2p2ppp/p2p4/1p6/3QP3/1B6/PPP2PPP/RNB1K2R b KQkq - 0 8"]

   8... c5 9. Qd5 Be6 10. Qc6+ Bd7 11. Qd5 c4

Mate in the Exchange Variation

After 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6 dxc6 5. O-O Bg4 6. h3 h5 7. hxg4?, Black has good mating chances:

[FEN "r2qkbnr/1pp2pp1/p1p5/4p2p/4P1P1/5N2/PPPP1PP1/RNBQ1RK1 b kq - 0 7"]

   7... hxg4 8. Nxe5 Qh4 9. f3 g3 lead to mate

Mate in the mainline

After 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. Nc3 Bc5 6. Nxe5 Nxe5 7. d4 Bb4 8. dxe5 Nxe4 9. Qd4 Nxc3 10. bxc3 Ba5?, White has a mating attack:

[FEN "r1bqk2r/1ppp1ppp/p7/b3P3/B2Q4/2P5/P1P2PPP/R1B1K2R w KQkq - 0 11"]

   11. Ba3 b6 12. e6! Qf6 13. Bxd7+ Kd8 14. Bc6+! Qxd4 15. e7#

Suggestion for the community: should we turn this answer into a community wiki? I realise I've listed only a handful of traps.


What is the easiest possible way to start teaching children how to play chess?

The easiest way depends on age.

If they are really young, just start simple with how a plain board and introduce the pieces one by one (where they go on the board and how they move). Then put all the pieces on the board and show how the pieces move together.

If they are a little older, I would play show them short games with tactical ideas and mating patterns.  No need to dwell too much on the opening yet or the endgame.  Stick to the fundamentals first and make sure they have a firm grasp on that.

You probably will also find some tips on http://www.chesskid.com and http://www.chesskids.com


Assume the image was taken from Black's side (otherwise the queen is not protected).

No. The Black queen is protected by the black pawn, and thus can't be taken by the White king. The only possible move is to move the king to the other direction one square.


Why do some players consider it rude not to accept a rematch in online blitz?

They may have made a fatal mistake and think that in another game they can win.

It happens sometimes. You could make a mistake, or miss a mating pattern, and suddenly you've lost the game although you thought you were in the lead. In this case, many people may ask for a rematch because they think that they should have won and want to redeem themselves. If you decline this request, they may see it as claiming a "cheap win".

They may also get offended by you declining their request because they might see it as "running away" from them, a more able player. This is almost insulting because they may see it as acknowledging that they "should have won", but running away with the victory regardless.

They could be Rating Farming.

If your opponent beat you by a large margin, they may ask for a rematch in order to secure a couple of easy wins against you, especially if you have a higher rating than them. Declining this rematch is denying that possible rating boost and could be taken the wrong way.

Both of the above reasons depict your opponents in a rather negative way, however I think that anyone who blocks another user on the basis that they won't accept a rematch request may not be the best sportsman. The thing is, if they are asking for a rematch because they like your playing style, or want to learn from you, they aren't going to block you if you decline, are they?

Perhaps it's me, perhaps not, but I think that anyone who blocks others for not accepting a rematch is either trying to get easy wins for rating or annoyed / in a bad mood about their own play.

Being frustrated about making mistakes, if allowed to affect your play, will lead to more mistakes and more frustration. Frustrated players make rash decisions and are more likely to take out their anger on their opponent.

I don't think you are breaking any unspoken code of online chess, I just think that some of the chess players out there lack a certain amount of maturity. Take them to a real tournament where you are face to face with your opponent and perhaps they'll learn some tips.


White is an exchange up with a much safer king and more active / developed pieces. There are many ways to win. The most straightforward here is to exchange pieces where and queen a pawn.


Looking for a comfortable DTC endgame database

After some extensive Googling, it appears to me that the the DTC tablebase named jaet that you linked is the only one that is online currently. As such, there may not exist "click and drag" DTC tablebases out there.

However, if you are still adamant about using a "drag" feature, you're best bet is to use the Lichess board editor to create your position, and then copy paste the FEN into jaet.

I'll demonstrate this easy process using some pictures for the benefit of any who do not understand how to do the above mentioned process. Some people are visual learners, so you never know.

Go the Lichess board editor.

Use the "drag" feature to create your position.

Copy the FEN.

Paste the FEN into the right bar at the jaet site

Click the "Lookup FEN" button that's next to the FEN bar and check the results.


Comprehensive list of ECO codes together with the list of moves


What are good sources to learn the Torre Attack?

One of the books of the "Move By Move" series is about the Torre Attack. It's written by IM Palliser and published in 2012, so it's still relatively recent.

Digging up old games is definitely a good idea when studying an opening, but you can also find interesting material from recent games. This year, Kramnik played the Torre Attack against the King's Indian a couple of times: in blitz (Kramnik - Vachier-Lagrave) and rapid (Kramnik - Nepomniachtchi), but also in classical time control (Kramnik - Radjabov).


I think answers to this question fall into 2 categories : problem composition and computer-driven few-pieced endgames' thorough analysis. The second one — to which your discovery belongs — being a tad bit more efficient than the first, that's probably all there is to say about it, if you're about sheer numbers. Art still has a long way to go on this road.

Regarding computer-driven endgames, the longest known so far is 549 moves long.

[FEN "1n1k4/6Q1/5KP1/8/7b/1r6/8/8 w - - 0 1"]


Chess engine with danger (mate) warnings for beginners?

Showing only the worst moves for a position is not something you'll find. Computer engines are not appropriate for warning against risk of blunders. My suggestions:

Take back a move against computer if you make a bad move
Review your game

You're asking the question because you're afraid of losing. There's no shame to lose against a computer. You learn more by going back your game (or takeback) then explicitly being warned.


Calculate the first N unknown moves of a chess game

Well, this should be semi-simple for a computer, at least. We know with absolute certainty that there are only 20 possible moves for both black and white (pawns and knights) on the first turn. After that, the only possible moves are moving the piece moved again, moving another pawn or knight, or moving a piece freed by the first move.

Knowing this, we can calculate the number of possible board positions after two turns. Luckily this has already been done here:

  There are 400 possible chess positions after two ply moves (first ply move for White followed by first ply move for Black).
  There are 5,362 possible positions (White’s second ply move) or 8,902 total positions after two ply moves each. There are 71,852 possible positions or 197,742 total positions after four moves.

This is a LOT, but it is possible to at least guess which one was used in the game.

The method I propose is to go though all of the movements of the game after the first four, but starting with the default chessboard as if the game had only just started. If a move occurs which is impossible, this indicates that this move has been made by a piece moved in the first two turns.

Despite this, there could be cases where a pawn moved on white's first turn and a pawn moved on white's third turn can take the same piece. If white takes with the pawn moved on the first turn, there would be no way to spot this, since you would assume the pawn moved on the third turn was used.

Sorry that this is only a half-answer; I will try to find more information to improve this.


Why are three chess sets needed for Kriegspiel and dark chess?

I've never actually played Kriegspiel, but I've read a bit about it, and after what I understand it would be like this:

At a very minimum, two boards and one set of pieces are required. As the players only have access to the pieces of their own color, both players can share one set of pieces. However, they need a board each.

However, unless the referee is a very good player, he will probably have trouble detecting everything if he has to look back and forth between the two boards. Therefore, it's better he has his own with all the pieces on it. That adds up to three boards and two sets of pieces.

I can't see any reason to introduce a third set of pieces.


Yes, Ne6 staves off mate, but it does not stave off the loss for long, but more importantly, it does not demonstrate the main point of the tactic, which is why they continue with the "worse" gxf6 in the solution.

Technically speaking, the computer thinks that after 1.Qxf6, that 1...Qc7 is the "best" move, in which case, black should just resign anyway after 2.Qxf8+ Rxf8 3.Bxc7.

There was an error in your analysis that lengthens the game also. 3. Bxg8 allows black to take the queen, and win back some of the material, but does not change the outcome.

P.S. This is a common phenomenon, but sometimes in reverse too. You will see site do this, which I believe is correct since you are trying to teach the main point of a tactic; but I have also seen sites use the computer moves as the main line, and thus, miss the point of the tactic from a human perspective.

  [FEN "3rrn1k/pp4pb/2pQ1n1p/q3B3/3P3P/1BP3N1/PP3P2/R3R1K1 w - - 0 1"]

  1. Qxf6 Ne6 2. Bxe6 Rg8 3. Qf7 {But you are up two pieces, and the attack continues with Nh5 next.} (3. Bxg8 $4 gxf6 4. Bxf6+ Kxg8 5. Bxd8)


it still seems to me that White wins more material playing Qb1 instead
of what appeared to be the solution

No, if you compare the two final positions the only difference is that in the Nc4 line white has an extra knight and black has an extra bishop, so no difference if you are counting points.

Why did White play Nc4, not Qb1? What am I missing?

Good question!
Both final positions are completely lost for white. The only practical difference is that in the Nc4 line the extra piece for either side creates more possibilities for white to try and create something. Black has more work to do to get the full point. In particular the knight can land on d6 where it is a very good piece.
Another significant point is that in the Qb1 line in the final position Qxb5 comes with check and tempo whereas in the Nc4 line Qxb5 is not check.
Small points perhaps but noting them helps you build your ability to fight on in lost positions.


How many moves ahead does Anand calculate in his mind?

first of all see here. here is a quote

  Asked how many moves ahead he can think, Kasparov replied that it
  depended on the positions of the pieces. "Normally, I would calculate
  three to five moves," he said. "You don't need more.... But I can go
  much deeper if it is required." For example, in a position involving
  forced moves, it's possible to look ahead as many as 12 or 14 moves,
  he noted.

for a supercomputer it obviously depends on how well-written it is, there is a concept called alpha-beta, which is used to limit thinking into unnecessary moves, like the computer usually wont consider the opponents (white) c3,b5,d6,f7, combo, on the first move. however after c3, b5 it should consider d6, and have a reply ready. from a page called Creating a chess engine from scratch on chess.com:

  A computer can easily evaluate a few million positions per second, a
  human probably 1-2 positions per second!! Usually speed is measured in
  MNodes/sekund which means million positions (Nodes in computer science
  jargon) per second. Fritz running on my old laptop does about 2.5
  MNodes while Deep Blue did about 200 MNodes per second. Raw power is
  not all - the evaluation function is also very important. Pretty much
  all engines use the same algorithm for searching through the search
  tree of possible moves to find the next move. This algorithm is known
  as alfa-beta search or it is some variant of this.

an important difference is that a computer has to consider things a human takes for granted, such as the concepts behind a known opening, even though a good program can remember which combos work (and rate them, then play based on  its ratings), its extremely difficult for it to recognize concepts, such as a fork independent of the result, this can be a advantage because a human may fork, and not see another better future move.

hope that helps!


Nf5 ...Qh7, Nd6+ (discovered attack) wins the queen. Note that any other attempts to save the queen fails:

Nb4 or Nce7 or Nge7 or Nf6 with the idea to attack the white queen fail because Nxg7+ is check
Qg6 has the same problem as Qh7, i.e. loses the queen after Nd6+
Qxe5 Rae1 (or Rfe1) pins the queen. Unpinning the queen with Nge7 (or Nce7) and an attack on the white queen does not help since after Rxe5 the knight on e7 is pinned and cannot capture the white queen.


What openings are good for the repertoire of a tactical player?

TL;DR

Good repertoire for fighting chess for white.  As black, you can play 1...c5 against 1.Nf3, and against 1.d4 I would recommend looking at the following openings and picking your favorite:

Grunfeld
King's Indian Defense
Slav
Dutch

This is going to be a long answer, so bear with me...

Your white opening looks acceptable.  I won't really get into the merits of any of your specific choices other than to say be careful with the Advance Caro and Advance French - those don't always let you play a tactical game against strong opposition.  You could look into the French Tarrasch (surprising, I know, but even the closed main line gives white kingside attacking chances) and the Panov-Botvinnik Attack against the Caro.

Against 1.d4, almost all players have difficulty right now.  From the very best GM's down to the average club players, the last 5-10 years have shown that white has excellent chances for an advantage with queen pawn openings.  There are two openings that are currently "in vogue" at the top level - the Grunfeld and the Slav.  These two openings are by no means the only options, but current theory holds that black can maintain equality with best play, and additionally, black has chances to win with both openings.  I'll also mention the Dutch, the King's Indian Defense, the Nimzo/QID, and the classical QGD in this answer.

Grunfeld

The Grunfeld is one of the best openings for black against 1.d4 right now.  Black does not occupy the center, but instead attacks it from afar with moves like Bg7, c5, Nc6, and sometimes e5 and Rd8.  White has not been able to find a clear advantage against black's best play, and most Grunfeld endgames favor black due to the queenside pawn structure.  I would recommend the Grunfeld for players who are not afraid to study theory - sometimes a LOT of theory.  Furthermore, Grunfeld players should be willing to take on certain disadvantages in exchange for counterplay.  Black will frequently have a large space disadvantage early in the game and it takes experience to push back white to get to an advantageous endgame.  That said, the Grunfeld offers EXCELLENT winning chances against lower rated players, especially in endgames that look equal at first.

Slav

The Slav is another very common opening right now.  If you want a crash course on the Slav, you can look at Anand's games in the last few matches that he has played.  The Slav is another opening that can require a lot of theory, especially when you get into the Botvinnik System and the Moscow/Anti-Moscow variations.  The biggest drawback to the Slav is that white can force a symmetrical game by playing an early cxd5.  The Exchange Slav is very boring, but if you are a higher rated player, it is still possible to grind your way to victory in the Exchange Slav.

Dutch

The Dutch is quite possibly the best opening for a tactical game, but black is really playing with fire.  It is very easy to slip into a lost position if you are not playing every move accurately.  Within the Dutch, there are a few systems that are all playable - the Stonewall, the Leningrad, and the Classical.  The biggest advantage to playing the Dutch is that white players that have memorized 25 moves in the Catalan won't be able to play by memory and will have to figure out what to do at the board.  Furthermore, black frequently will get a kingside attack going with the Leningrad Dutch.

King's Indian Defense

The KID is another opening where black can be positionally lost without many mistakes.  For example, if you play the Queen's Gambit Declined as black, you can make 3 or 4 subpar moves without really getting a bad position.  The Dutch and the KID are another story - one misstep and black might already be losing.  If you are willing to take that chance, or you are confident in your ability to deal with tactics, then the KID is a good choice.  It offers black a kingside attack (usually) and chances for the full point.

Other Openings

Just to touch on alternatives - the QGD is always a solid choice, but black can have a very hard time finishing development.  The bishop on c8 sometimes cannot be developed until move 20 or even later.  If you are not comfortable playing a cramped position, stay away from the QGD.

The Indian Systems (Nimzo and QID) are good choices, but per your question, I didn't mention them very much.  At the GM level, these defenses are still played, but white has found ways to get a good game against both the Nimzo (look into 4.Qc2) and the QID.  Furthermore, since the Catalan is so popular, you will frequently not get the chance to play a true Indian Defense.

Final Thoughts

You might notice that I did not recommend any gambits like the Albin Countergambit or the Budapest.  With good play, white gets a great position against both of those choices.  With quiet play, white still gets an equal position and black's initiative dries up quite quickly (for example g3 against the Budapest).  Additionally, the Benoni and the Benko Gambit are not mentioned because black has to solve quite a few problems according to modern theory.

Ultimately, you will have to try out all of these openings and decide which one you like the best.  Personally, I play the KID, the Grunfeld, and the Dutch mostly.  The main point is that if you want a super sharp game, don't allow symmetrical positions (for example, your choice to play the Sicilian as black against 1.e4).


Tatyana Sergeeva (Татьяна Сергеева) and Lyazzat Tazhieva (Ляззат Тажиева) are representatives of Soviet/Kazakhstan school of chess.

According to this article from sports.kz, GM Bolat Asanov says:

  В 1996 году в мировом рейтинге женская сборная Казахстана занимала 8-9-е места. К сожалению, победная цепь разорвалась. Резервы «не поспели» и не смогли заполнить образовавшиеся пустоты: ушли из жизни Татьяна Сергеева, Ляззат Тажиева. ...

My translation:

  In 1996, in the world rating, Kazakhstan women national team was around the 8-9th place. Unfortunately, the winning streak was broken. The young blood was not ready fast enough and they were not able to fill the emerging gaps: Tatiana Sergeeva and Lyazzat Tazhieva passed away. ...

Therefore, sadly, these high-rated FIDE players of the 90s are not alive, unless there is some error in the report of "PROSPORT Kazakhstan" Talap Koybagarov or information given by Bolat Asanov.

Lyazzat Tazhieva:

July 2013, Shymkent Chess Tournament in memory of Lyazzat Tazhieva
In Shymkent, there seems to be a sports school named after Lyazzat

Tatyana Sergeeva (this is harder, as the last name is so much more common):

Wiki page in Kazakh lists Tatyana Sergeeva (Zhivaeva) to pass away in 2000. Also, it mentions her participating in the final of World Chess Olympiad in 1996 and 1998.:

  Татьяна Ильиничина Сергеева (Живаева) (1.01.1957 - 15.09.2000 Алм. қ-сы.), ХДСШ-і (1981). Респ-ның 4 дүркін (1977, 1980, 1991, 1996) ч-ны. 2 Рет КСРО ч-тының (1977-т.б., 1981- Алм.) финалында ойнады, Бүкілдүниежүзілік ш-т олимпиадасына (1996 - Ереван, 1998 - Элиста) қатысты.

  Қазақстан - спортшылар елі. Энциклопедиялық анықтамалық. - Алматы: "Сөздік-Словарь". ISBN 9965-822-57-3

with an apparent source of "Kazakhstan — Sportsmen Country. Encyclopedia."


A chess engine's depth used to denote how many half moves it calculates ahead (roughly speaking), however this has long not been true anymore. Traditionally you would search one depth at a time, so first 1 ply deep, then 2 plies deep, then 3 and so on, each iteration increasing the depth by one ply. Modern engines however have various search heuristics which lets them search deeper in relevant positions and less deep in less important positions. Because of that, the iteration counter that is still called depth there, is hardly representative of the actual depth of the main line. (also of course the depth of the different calculated lines can be very different)
One thing that (AFAIK) still counts for something is the "seldepth" number, which denotes the deepest line looked at. However that number too is not too relevant, one line being calculated very deeply doesn't necessarily tell much about the other lines.


Take a look at Wikipedia's time control article:

Fischer delay (or time increment), invented by Bobby Fischer. When it becomes a player's turn to move, the delay (or increment) is added to the player's remaining time. For example, if the delay is five seconds and the player has ten minutes remaining on his clock when his clock is activated, he now has ten minutes and five seconds remaining.

And in the usage of chess servers:

On chess servers (like Internet Chess Club and Free Internet Chess Server) the time control is usually expressed with a formula: time+increment. Where time is a fixed amount of time (in minutes) assigned at move 0 for the entire game, and increment (in seconds) is the amount added after each move.
When the increment is 0 the time control turns into a sudden death: so a 5+0 game is a game with sudden death at 5 minutes.
When the increment is bigger than 0 the time control is a Fischer delay: e.g. a 2+12 is a game with Fischer delay with 2 minutes + 12 seconds each move.
A game can even have a time set to 0: the clock is set to 0 and started after the first move with the increment only on both sides, and each move each player is granted only the increment: a 0+10 is a game where after the first move each player has 10 seconds to move.

To sum it up:
Time increment gets added to your current time to compensate for a probable delay (for humans is the reaction time and for servers may compensate for latency etc.). If you are fast enough to play your move before the increment ends, the extra time gets added to your current time thus augmenting your remaining time.


On what basis were players chosen to compete in the Magnus Carlsen Invitational 2020?

Magnus Carlsen had the major saying in the selection. There was no "objective" qualification of any kind, besides the hope to create an interesting line-up.

Firouzja was included because he beat Carlsen in the Banter Blitz Cup, so a "rematch" would attract many viewers.

Disclosure: I work for chess24. I wasn't involved in the decision process, and I can't publish everything I know about this.


Grandmaster Larry Christiansen recommends studying 200 recent games per week from games that relate to your opening repertiore.  TWIC is ideally suited for doing that.


How do you know when a FEN position is legal?

Here is a well organized list that should validate 99.99%+ of common positions:
Board:

There are exactly 8 ranks (rows).
The sum of the empty squares and pieces add to 8 for each rank (row).
There are no consecutive numbers for empty squares.

Kings:

See if there is exactly one w_king and one b_king.
Make sure kings are separated 1 square apart.

Checks:

Non-active color is not in check.
Active color is checked less than 3 times (triple check is impossible); in case of 2 that it is never pawn+(pawn, bishop, knight), bishop+bishop, knight+knight.

Pawns:

There are no more than 8 pawns from each color.
There aren't any pawns in first or last rank (row) since they're either in a wrong start position or they should have promoted.
In case of en passant square; see if it was legally created (e.g it must be on the x3 or x6 rank, there must be a pawn (from the correct color) in front of it, and the en passant square and the one behind it are empty).
Prevent having more promoted pieces than missing pawns (e.g extra_pieces = Math.max(0, num_queens-1) + Math.max(0, num_rooks-2) + Math.max(0, num_knights-2) + Math.max(0, num_bishops-2) and then extra_pieces <= (8-num_pawns)). A bit more processing-intensive is to count the light squared bishops and dark squared bishops separately, then do Math.max(0, num_lightsquared_bishops-1) and Math.max(0, num_darksquared_bishops-1). Another thing worth mentioning is that, whenever the extra_pieces is not 0, the other side must have less than 16 pieces because for a pawn to promote it needs to walk past another pawn in front and that can only happen if the pawn goes missing (taken or playing with a handicap) or the pawn shifts its file (column), in both cases decreasing the total of 16 pieces for the other side.
The pawn formation is possible to reach (e.g in case of multiple pawns in a single col, there must be enough enemy pieces missing to make that formation), here are some useful rules:

it is impossible to have more than 6 pawns in a single file (column) (because pawns can't exist in the first and last ranks).
the minimum number of enemy missing pieces to reach a multiple pawn in a single col B to G 2=1, 3=2, 4=4, 5=6, 6=9 ___ A and H 2=1, 3=3, 4=6, 5=10, 6=15, for example, if you see 5 pawns in A or H, the other player must be missing at least 10 pieces from his 15 captureable pieces.
if there are white pawns in a2 and a3, there can't legally be one in b2, and this idea can be further expanded to cover more possibilities.

Castling:

If the king or rooks are not in their starting position; the castling ability for that side is lost (in the case of king, both are lost).

Bishops:

Look for bishops in the first and last ranks (rows) trapped by pawns that haven't moved, for example:

a bishop (any color) trapped behind 3 pawns.
a bishop trapped behind 2 non-enemy pawns (not by enemy pawns because we can reach that position by underpromoting pawns, however if we check the number of pawns and extra_pieces we could determine if this case is possible or not).

Non-jumpers:

(Avoid this if you want to validate Fisher's Chess960) If there are non-jumpers enemy pieces in between the king and rook and there are still some pawns without moving; check if these enemy pieces could have legally gotten in there. Also, ask yourself: was the king or rook needed to move to generate that position? (if yes, we need to make sure the castling abilities reflect this).
If all 8 pawns are still in the starting position, all the non-jumpers must not have left their initial rank (also non-jumpers enemy pieces can't possibly have entered legally), there are other similar ideas, like if the white h-pawn moved once, the rooks should still be trapped inside the pawn formation, etc.

Half/Full move Clocks:

In case of an en passant square, the half move clock must equal to 0.
HalfMoves <= ((FullMoves-1)*2)+(if BlackToMove 1 else 0), the +1 or +0 depends on the side to move.
The HalfMoves must be x >= 0 and the FullMoves x >= 1.
If the HalfMove clock indicates that some reversible moves were played and you can't find any combination of reversible moves that could have produced this amount of Halfmoves (taking castling rights into account, forced moves, etc), example: a side with many pawns and a king with castling rights and a rook (the HalfMove clock should not have been able to increase for this side).

Other:

Make sure the FEN contains all the parts that are needed (e.g active color, castling ability, en passant square, etc).

Note: there is no need to make the 'players should not have more than 16 pieces' check because the points 'no more than 8 pawns' + 'prevent extra promoted pieces' + the 'exactly one king' should already cover this point.
Note2: these rules are intended to validate positions arising from the starting position of normal chess, some of the rules will invalidate some positions from Chess960 (exception if started from arrangement Nº518) and generated puzzles so avoid them to get a functional validator.


How can I convert a possible pieces' moves to an actual move in a bitboard?

There are actually two questions in your post

How to convert Attacks in Bitboards to a list of moves?

How to represent those moves?

How to represent those moves?

This question has been discussed here and here thoroughly. But to provide some context to the readers of this post, a very simple way to do this can be to use a class / struct to represent a move

From ( where the moving piece was )
To   ( where the moving piece will be )
Special Move Flag  ( whether the move was a special move, i.e enpassant, casting, promotion)
Promoted Piece ( if the move was a promotion move, what piece did it promote to )

You can also have extra attributes such as captured piece, type of castle etc. But that information can also be deduced using the From and To squares.
So considering the above, we can represent the move as follows
struct Move {
    char from;
    char to;
    char spMoveFlag;
    char promotedPiece;
};

However, a lot of chess engines, including mine use another method that can compress the move into just 16 bits. Read more about that here.
Once we know what a move is, we can answer the next question

How to convert Attacks in Bitboards to a list of moves?

Let's consider that we have a knight on the square d4. We also have a function that returns the attacks of a knight given the square.
. . . . . . . .
. . . . . . . .
. . 1 . 1 . . .
. 1 . . . 1 . .
. . . n . . . .   =  knightattacks(SQ_D4)
. 1 . . . 1 . .
. . 1 . 1 . . .
. . . . . . . .

So let's store this inside a variable knightAttacks
uint64_t knightAttacks = getKnightAttacksBB(SQ_D4);

If you notice carefully we already have 1 of the 4 attributes we need to represent the move, which is the From square - D4. Now all we need to do is somehow get the To square to complete this since a knight cannot perform any kind of special moves.
A very common method is to pop the least significant bit until your knightAttacks is left with nothing i.e 0.
0000011100001000
            ^
            Least significant bit (lsb)

You can follow the link I provided to know how you can perform this, or there is a chance that your compiler might already provide you with it.
You simply need to create a function that clears the lsb of a bitboard and returns its index. Let's call it poplsb().
Altogether, your code can look like this
int from = SQ_D4;
uint16_t knightAttacks = getknightAttacks(from);

while (knightAttacks)  {
     int to = poplsb(knightAttacks);
     MyMoveList.Add( NewMove(from, to, 0, 0) ); // The last two 0's denote that there is no special move
}

This works because each time you pop the lsb, a bit gets cleared until the number is == 0. That's when the loop stops and you have a perfectly good list of moves. The same idea applies to any kind of moves you have created using Bitboards.


@Arka Mukherjee, I find most players under 2100 weak tactically, so at 1200, you are certainly weaker than you understand you are. I do not say that to be mean, but just as a very logical person, who has been a reasonably strong player for over 30 years.

At your level, memorizing theory is mostly a waste of time. In 40 years of playing, I cannot tell you how many weaker players I have seen that carry around an arm full of opening books, but they never progress. You do not need to memorize openings when your opponent is not going to play them because he has not memorized them. You need to understand opening pawn structures. Chess Opening Essentials: The Complete Series (Volumes 1 - 4) is a very basic way to start this.

This is, of course, on a different level, but I recently read something about Kramnik training young prodigies, and one of them played an opening he saw a higher-rated GM play, and he imitated the play by rote, but soon went astray. He did not understand, at least on the much higher level he was at. Understanding is the key.

Beyond that, tactics are the most important thing you can do. Most chess games between weak players are decided by who drops the last piece, and these books would help you win more material, and thus, win more games.

I recommend starting with "1001 Brilliant Ways to Checkmate", and then "1001 Winning Chess Sacrifices and Combinations" (21st Century Editions) by Reinfeld.

I recommend doing 50 per day, spending no more than two minutes per move on each problem. In pencil, write down next to the problem how easy you found it on a scale of 1-5 because you will do these books multiple times. That immersion method has worked very well for me. I took a friend, who was about 38 at the time, from 1000 to 1850 on ICC in three months following this method.


How do I find players to play in person?

Almost every city has a local chess club. You can always join your local club and find other events or activities through your club.


I have an old book in my house, 500 King's Gambit Miniatures, and in the first pages the games, at the least, didn't pass 30 moves. I think it is a very good definition.


According to XBoard's manual [ref. 1]:

  "...XBoard 4.2.7 and earlier... The internal move legality tester
  [had problems with] castling or en passant-capture rights."

If you're running 4.2.7 (or earlier), then a newer release should solve this problem.

Caution:  Although this is not relevant to the specifics of the question, I feel that if you are running this version, then it would be remiss of me were I not to mention that there is also a reported security risk (mid-grade: stack overflow) inherent to XBoard 4.2.7 [ref. 2, 3].

References:

https://www.gnu.org/software/xboard/manual/xboard.html#Limitations
https://www.cvedetails.com/vulnerability-list/vendor_id-2551/product_id-4447/version_id-19153/Tim-Mann-Xboard-4.2.7.html
http://seclists.org/fulldisclosure/2004/Mar/40


Why does 6.Bc4 prevent 6...e5 in the Sicilian Najdorf?

e5 is bad against the Fischer-sozin variation, because of 7. Nf5, which puts pressure on the d6 weakness.

Now granted, you could play Nf5 whenever black plays e5, whether you're playing Be2 (the classical system), or Be3 (the english attack).

So the real question is, what's the difference between:
e5 in the Sozin variation, and
e5 in the classical variation, f4 variation, english attack, etc. anything but Bc4 and Bg5.

The difference is, after white plays Nf5 in the classical variation, black has this amazing resource which is 7...d5.

If black plays e5 against the Sozin variation, 7. Nf5, d5 doesn't work because the pawn is capturable.

If black plays e5 against the Bg5 variation, 7. Nf5, d5 doesn't work because the knight on f6 is pinned, therefore the pawn on d5 is safe to capture.

The remaining question is: Why is d5 a necessary resource?

Well, d6 is going to fall and black will no longer play for a win because of the attack on the d file. He/she will have to worry and protect the d6 pawn while white goes for some kingside attack or whatever. After d5, black has no problems. Literally no weaknesses, none, and finally black can play for a win.

Also, in the classical system, after d5, 8. Bg5 is the best move in which black gets in d4. Doesn't that just look crushing for black? And, which side would you rather pick? Black!


In general, in a bughouse game, one of the players in the team attacks while the other team member defends. Thus, when the defender gets attacked, the attacker sacrifices a lot of material. This material goes to the other team member (attacker), who can the use the material to fuel their attack. Thus, the defender loses (or saves) the match. Defensive strategies are therefore very important indeed.

The key square is usually the f2-square for white (f7 for black). Let's focus on black defending, since that is usually the case. Thus, the f7-square is critical. White will sac a bishop on f7, drop a knight on g5 and something diagonal on f7, leading to a quick win. The basic idea is to defend with e7-e6, blocking the a2-g8 diagonal. Yet, white can drop a pawn on f5 or sac a knight on f7 and drop a second knight on g5.

The main problem is that white can drop a pawn on h6 and open up the g7 and f6 squares for attack. If black plays h7-h6, then white drops a pawn on g6, attacking on f7. If you have to castle, then usually kingside is preferred, since queenside is vulnerable to a heavy piece dropped on a8 followed by a knight getting to a7. Also, a white pawn getting to a7 with a black king on c8 is a killer. Kingside castling makes the pawn drop on h6 perhaps even more deadly. Also, h7 starts becoming an issue.

So, here are a few tips how to survive as black against white attacking:

Drop an extra pawn on h6, so you get an f7, g7, h7, h6 pawn structure.
Play e7-e6
Drop a bishop on g8 to support f7
Always have a pawn, bishop or knight on f7 (never the king)
Drop a pawn on f6 (after getting a pawn on h6) getting more control over g5 and e5 (where white tries to place a knight)
Be ready to sac a queen on a white knight on g5 to buy time
Never move the c-pawn or f-pawn. In general, avoid any pawn moves, unless you are sure about what you are doing. After the c-pawn moves, c7 and d6 become weak, which is simply lethal.
Exchange your bishops for the opponent's knights by pinning them to the enemy queen or king (check with your team mate if knights are good). In general, keep those enemy knights pinned. E.g. drop a bishop on h5 to protect on f7 and pin the Nf3 to Qd1.


OK I just realized that I upgraded Winboard at the same time and it's actually Winboard that is now adding the ! and ?.  The meaning seems to be given on this page:

  A question mark as the last character in the pv field should be used to indicate the reported score is from a fail low, and thus represents an upper bound only. Similarly, an exclamation point should be used to indicate a fail high / lower bound.


One suggestion I have seen for how to improve learning when studying openings and tactics is to involve the other senses. This involves not just using sight, looking at the position on a computer, but also setting up the position on the board and playing through it (touch) and (for openings) saying the moves out loud (hearing) as you play them.

I was a bit sceptical when I read this but your experience backs this up. The obvious way to address this problem is to follow the advice and set up tactics problems on a real board so you practice "over the board".


Chapter "Final Reflections on Education in Chess"

page 373 in this pdf file:Lasker's Manual of Chess


Please Critique my game played by my engine

Nice efforts, you've made a working chess engine, your journey has started. But you have more works to do:

(respond to your comment) 3...e4 must be a bug because your engine just gave up a pawn for nothing in the next move. Searching for d=3 should be able to see it. Also see the next comment.
Your engine seems to like attacking the most valuable piece (queen), your 3...e4 may have been caused by this blindness. I'm guessing (you'll need to check it yourself) you put too much weight in attack threats.
The engine moves the queen out too early. You will need to check your PST table and make sure your PST evaluation beats the temptation of moving the queen out. A common mistake in early chess engines is that they put too much weight into the number of squares that the queen can control in the opening.
Please check your PST again why your engine would prefer moving 1.e3. You must instruct the engine to move into the centre.
Don't use the default position for testing. It's still too early for your engine to handle it. Set yourself some simple positions where there is a direct way to win, for example: back-rank mate in two, pushing the pawn for promotion etc. Your engine blunders too much, even at depth 3 and no understanding of tactical threats. Make sure you can play those easy positions.
I'm guessing you set yourself at d=3 because it's too slow for you to go further. Consider to implement the easy extensions, such as null move and hashing. In particular, your engine won't go anywhere without hashing.


When should I trade into opposite colored bishops?

Opposite-colored bishop endgames aren't always drawn; it depends on the pawns. The drawish aspect comes from the fact that either bishop can halt a passed pawn in its tracks, and the opposite bishop can't help overcome the barricade.

If you have a positional or material advantage, avoid going into such an OCB ending if you can. If you can't, then start action on both sides of the board, creating a passed pawn on each. Sac a pawn to accomplish this, if necessary. This will force your opponent to dedicate his bishop to one side and his king to the other.

Leave your bishop to guard one wing, preferably the wing where the opponent's pawns are less of a threat, and/or yours are easier for the bishop to defend. Then, send your king over to help push the passed pawn (or create one). He can chase the opponent's bishop away, or force it to give itself up for the passed pawn your king, but your bishop can't. So, king on offense, bishop on defense.

Also, try to keep your king in front of the pawns, so he can cover their advance squares.

Note: The OCB ending is an exception to the endgame rule of having your pawns on squares of the opposite color to your bishop. The exception applies only to the defender. If you follow that rule, your opponent's bishop will pick them off, and your bishop won't be able to defend them. So, if you're defending an OCB ending, put your pawns on the same color squares as your bishop.

If you're the attacker, put your pawns on squares of the opposite color to your bishop. That way, they cooperate with the bishop to keep the opponent's king away or drive him off.

If you're defending an OCB ending, keep your king on the same wing as, and in front of, the opponent's pawn majority, and defend your (possibly weak) pawns on the other wing with your bishop. Blockade your opponent's passed pawn with your king. Put your king on a square of your bishop's color, so your opponent's bishop can't dislodge it.

If you can, try to leave the base pawns of your pawn chains where your bishop can reach all of them quickly. If you can arrange two chains, one on each wing, with the bases near the center, then your bishop may be able to defend both from just one square.  If your opponent's king comes over to try to drive your bishop off Defense Junction, then he can't reach the pawns. No way to make progress.

If you can't arrange this, then try to stagger the chains a bit so that your bishop and king can navigate across the board, and keep an eye on the pawns at the bases of the chains. Leaving a few gap squares is important for the king's mobility, because if you don't stagger the chains and your king has to use the opposite colored squares to cross the board, your opponent's bishop can usually just attack the squares around the pawns when your king tries to get through, and block it.

Move a pawn only when absolutely necessary.  If he can't make progress, you'll get your draw.

Almost every endgame book treats this topic; I recommend a couple, such as Howell's Essential Chess Endings, Glenn Flear's Starting Out: Minor Piece Endgames, or Bruce Pandolfini's Endgame Course. Andrew Soltis' GM Secrets: Endings has an especially understandable and thorough discussion of "Bees of Opps".

So, the short answer is: Trade into an Opposite-Colored Bishops ending if you're likely to lose otherwise, and use its special characteristics to save the draw. This can sometimes work even if the opponent has 3 connected passed pawns, and you have none!


For an opening to be good in bughouse, it needs to incorporate both boards.  Timing, material trades, attack/defend all have a huge influence.  On top is predictability. If you know what the ops will try, then you may come up with a counter.

For example, 3 ... KxN is playable by black if there are limited material and a huge flood does not come on board. If the other board can control the flow of pieces then this sac will fail.  Yes, KxN could get hammered if several drops come into play.
But look what the other side gets. A drop knight vs a drop pawn. No immediate easy path to getting more pieces. Most likely a time bulge.  (Typically one player waits for pard to get them stuff to drop on the exposed king.)  With enough of a time lead, the off board can wait and force you to play a few moves without extra stuff.

As part of team opening, the knight sac can be useful, but need to first gain enough drops to make it a threat.  To do this, will need play on other board to be faster, and get 3 or more drops in hand.


For white's next move, should it be recorded as Nge2 or Ne2 as there is only one knight which can legally move to e2?

It doesn't matter. The purpose of algebraic notation is to produce an unambiguous record of the game, not a canonical representation that you could compare character by character.

This is not spelled out on the official rules, but I believe it is the inescapable conclusion considering that some parts of the notation are explicitly optional (here I'm talking about the FIDE Laws of Chess); for example:

  [...] each player is free to use the name which is commonly used in his country [...]

  A longer form containing the square of departure is acceptable.

  [...] an x may be inserted [...]

  [...] ‘e.p.’ may be appended.

  [...] The last four [capture, check, checkmate, and en passant] are optional.

That said, the rules are clear that disambiguation is only needed when two identical pieces can move to the same square, so the "correct" notation would be Ne2.


How can I improve my knowledge of pawn structure theory?

The old classical book by Hans Kmoch, Pawn Power in Chess is almost entiely devoted to this subject.

It is often used as a reference because of its numerous useful examples, but also mocked for the author's tendency to over-theorize every principle and forge neologisms that have not made their way, half a century later, into common chess vocabulary.

But as long as you don't mind skipping some sophisticated words like 'leucopenia' or 'melanoarchia', it remains an excellent ressource for studying pawn structures.


If you are new to chess, you should not be concerned with openings at all.

Several reasons for this:

As a beginner player you are much more likely to lose a game because you blunder a piece or because of some other simple tactics than because of lack of opening knowledge.
It is essential to have a decent understanding of chess before you start studying openings. This will allow you to learn an opening together with its typical plans (and not just learning moves by heart.) If you do this, you will know how to punish an incorrect move of your opponent and also how to continue the game in the middle game (when you are on your own). Contrary, if you just learn moves by heart you will not know what to do if your opponent plays a move that is not in your memory.
You have not developed a style yet, so would not be sure which opening suites you best.

What should you be doing now?

Focus on tactics, i.e. solve tactics puzzles. First and foremost avoid blundering pieces in one move. When solving tactics puzzles make sure that you always recognize the pattern(s) that are used in the puzzle.

Get a feel for how the pieces move. I am sure you know how they move, but you need to be able to quickly assess a position, seeing what is attacked, where pieces can move, etc, without having to consciously think about each and every move. This is also sometimes called "board vision" and it will improve as you play or train chess.

Learn some basic general principles like "piece activity, king safety, central squares control, ...". Reading/watching annotated/commented games and recognizing these principles in the games of master players will help you a lot.

Studying basic endgames can be instructive as well.


Which approach is better to teach tactics?

I would use the second approach, almost entirely just because the problems are much easier, but also because those sorts of simple two-move tactics are more likely to come up in games between beginners and just spotting them at all will give her a big advantage at that level.

I would actually suggest a few other sources of tactics which might be even better:

Chess Tactics for Students by John Bain has quite simple puzzles and is grouped by theme.
The Manual of Chess Combinations, vols. 1a and 1b, also starts with very simple puzzles and is grouped as well, although it's by goal (e.g., "win a rook"), not by theme (e.g., "fork").
The online site Chess Tempo will feed you tactical problems from real games that are matched to your ability, so there's no worry about getting a book that is too easy or too hard.


There are a couple.  The most popular is likely Embed Chessboard.  The nice thing about it is that the tags are simply PGN references:

  [pgn parameter=value ...]
  ... chess games in PGN format ...
  [/pgn]

So if you're already familiar with PGN, put it into your Wordpress page and the plugin detects it..

Would you share your Wordpress site URL in comments once complete?


Do professional level chess players mainly stay consistent in their opening play?

No two people are alike, and no two chess players are alike either.

To begin with, world class grandmasters study chess all the time, and they can play just about every opening under the sun and score incredibly well.

However, in order to get the very best results possible, most grandmasters will study and memorize moves and plans for a handful of openings for each color and each 1. e4 and 1. d4.  By doing this, they gain a slight advantage over their opponent in terms of a better position, using less time, or sometimes just a psychological edge.

Since the top players spend so much time learning these openings, they tend to not switch openings all that frequently.  Changing one's repertoire would require redoing all the studying and memorization that had already been done.  Frequently though, as other players discover and show new ideas, the repertoires evolve.  A player might substitute one line for another or find an improvement in some opening line.  The advent of super-strong computers has definitely increased the speed with which opening lines change.  Nowadays players must constantly be looking for improvements and tweaking their lines in order to stay on top of things.  Another factor is the internet - minutes after completion, the game is available for anyone in the world to see.  Surprises can generally only be used once.

To discuss Fischer specifically, his entire career he mostly played 1. e4 and the King's Indian Defense and the Najdorf Sicilian as black.  His openings did evolve and change over time, but he was fairly consistent, especially with 1. e4.  For this reason, when he played 1. c4 against Spassky in the '72 World Championship, it was a huge surprise.  Spassky had spent his time figuring out how to meet 1. e4 and had to readjust to play the Queen's Gambit Declined.


When you check someone, do you have to say "check"?

In a tournament game, you are not supposed to speak at all other than to offer a draw or adjust a piece. This includes saying check. This tends to seep into casual games among more experienced players (I haven't said check in years).

For players that do not compete in tournaments at all, I don't think that there is any obligation to point it out.

When your opponent makes an illegal move, though, as it sounds like you did after missing the check, it has to be pointed out. You can't just follow it up with a mate immediately. In blitz, making an illegal move means a loss. In a longer game, a minor time adjustment.


Game analysis: What would motivate a human player to sacrifice White Knight at move 10 in this game?

I am quite certain that it is possible to find this move for a higher level chess player.

This has little to do with calculation depth actually. Yes, the engine is able to look 10 moves ahead and conclude that White is going to win his piece back in most or all positions resulting from the sacrifice. But for a human player, all that matters is if he can "see" (recognize) the right pattern. Concrete calculation only follows to make sure that this pattern is actually winning (and most of the work is done in the first 3 moves, instead of 10). Unfortunately, there is no easy heuristic blueprint (else we would all be GMs), most of this ability to "see" comes from experience. However, there are a few hints:

First of all, White has the more active position (he has castled already, his pieces are much better developed (to active squares), and he has some space advantage), so he should generally put himself in the mindset of the attacker, not the defender.
Looking at the developed pieces in particular, the knight on b5 is very strong and puts pressure on c7 and d6 - and from the latter could attack f7 as well - which also happens to be in the scope of his bishop on c4.
His queen and other bishop are ready to attack as well, but for now, there are pawns in the way. A friendly one blocks the file for the queen, and a hostile one defends f4 from the bishop. Nxe5 will help in both cases, but that alone does of course not justify a sacrifice.
Now the crucial part is to switch focus from attacking d6 to occupying d6. Important features that make this pawn advance really strong all by themselves (aside from the fact that passed pawns on the 6th rank are rarely a bad idea): Black's bishop on e7 will be attacked immediately, and Black has not castled yet, so d7+ is a very serious threat.
Additionally, all of White's pieces gain activity: The bishop on c4 gets freed, the queen gets additional scope along the d-file, the knight on b5 gets additional safety on c7 and without a black pawn on d6, the ones on c5 and e5 become very vulnerable to the other knight and bishop.

So, White's position would be overwhelmingly strong - if only the black pawn on d6 did not exist. A GM will probably see this immediately. For us normal folks, maybe that is the mental exercise you are looking for: If you "sense" that you have an advantageous position that possibly allows some tactics, check the important pieces and pawns (not the one on a6 obviously) of your opponent and judge the position with them missing. Once you have found a keystone, the actual calculation often is not that difficult. You just have to find a way to deflect the pawn/piece you identified as holding your opponent's position together, leading you to look out for moves like Nxe5.

Now in this case, the real calculation would merely amount to:

Bh3 counter attack - easily defended by Qf3, even adding pressure on f7 at the same time
Bxd6 - you can simply retake, regaining your piece while maintaining a good attack
Black retreats his bishop (e.g Bd8) - you can continue with d7+, and after Bxd7, d6 is open for the knight. At this point, you may have to calculate 2-3 additional moves, but really, if you have arrived here, you have done most of the work already.
Additionally, Tony Ennis' idea around f4 is worth having a look at, too.
Last but not least, you always have to consider that Black can refuse the sacrifice. Well, then Nxe5 either just won a pawn (probably the safer choice by Black) or has opened another attack angle after ...Qxe4 - you can now play Re1 with pressure along the opened e-file on an uncastled king.

As a contrast, list of reasons why people tend to overlook opportunities like this:

They are too occupied with the last move of Black (Qg6) that threatens Qxe4 and focus solely on the defense of that threat. End of list.

In all honesty, I still belong to that group too. Hindsight is 20/20.


As someone who plays 4.Ng5 as White, I can tell you what I've found to be the hardest Black line against me: 4...d5 5.exd5 Na5 6.Bb5+ c6 7.dxc6 bxc6 8.Be2 h6 9.Nf3 e4 10.Ne5 Bc5!?

[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Na5 6. Bb5+ c6 7. dxc6 bxc6 8. Be2 (8. Qf3 Be7 9. Bxc6+ Nxc6 10. Qxc6+ Bd7 11. Qf3 O-O) h6 9. Nf3 e4 10. Ne5 Bc5!? (10...Bd6 11. f4 exf3 12. Nxf3) 11. c3 (11. O-O Qd4 12. Ng4 Bxg4 13. Bxg4 e3) O-O 12. b4 (12. O-O Qc7) Qd5!?

The theory move is 10...Bd6 hitting the knight, but as White I've found that 11.f4 exf3 12.Nxf3 gives White a comfortable enough game a pawn up.

10...Bc5!? takes f4 off the table because of king safety, and Black can attack the near-trapped knight with the queen instead. A main line might be 11.c3 (11.O-O Qd4) O-O 12.b4 (12.O-O Qc7) Qd5!?


At the lower right corner, the square's color should be White.  I have seen some glass chess boards and most of the times the frosted pieces/squares represent the Black side, and the clear pieces/squares the White side.


Preparing for an OTB tournament: I must do well!

First, from a pure chess standpoint, you are probably as close to prepared as you will be since there is only so much you can learn between now and Friday.

The most important things will be to get a good night's sleep, and the cardinal rule in a team tournament is "don't lose". I know that sounds funny, since it seem obvious, but if you have a four-board team, and you lose, then the remaining three players have to go 2.5/3 to win the match. What that means is that, in practice, you cannot play too wildly since wild play can put the team in a very bad position. Stay solid, and if you can win, great; but be satisfied with a draw if you really do not have anything more.

As far as the nerves are concerned, they are a problem; but you will find that the more you play, the more you will get used to tournament play, and the nerves will subside.

Lastly, at the board during the game except for obvious recaptures, and assuming you have the time, just BRIEFLY consider every reply your opponent has before you make your move. In other words, I am going to play Ng5, but for a second, I just scan every move my opponent can make. I am not analyzing, but subconsciously, if I left something hanging, I often notice it. This will hopefully cut down on the one-, or two-move, blunders


is there any good and free software available for setting up swiss
  tournaments? All of those I've tried have very few options and little
  functionality available.

Vega is a swiss pairing program which has been approved by FIDE. It is free if you install it on Linux and if you install it on Windows it is free up to 30 players in the tournament. It is a lot more user friendly than other programs you have to pay for and is excellent for amateur use.

The only drawbacks for professional use are the 30 player limit if used on Windows and the lack of a website for publishing the pairings and results. The program allows you to prepare HTML files for uploading to your own (or the tournament) website but it does not come with a standalone website like Chess-results.com which comes with Swiss Manager.


Books dealing with the g3 Queen's Indian

I will have to explore through some of the new (and older) literature on the Queen's Indian to give you better recommendations, but off the top of my head I recall at least 3:

Play the Queen's Indian by Andrew Greet: if I remember correctly the fianchetto variations are discussed somewhere at the end of his book. One plus about this book is that it's quite readable.
Starting Out: The Queen's Indian by John Emms: This is probably what you're looking for, there's an extensive study on the g3 variation (up to 70 pages almost). Also see his post here.
Queen's Indian Defence by Jacob Aagaard: I've heard good things about this one, but haven't read it myself, see chapter two. Apparently it contains numerous references to insightful games, for whatever variation that is covered in the book.

Finally, to browse through the known variations and played games, there are many websites that you can look through, but these two should get you started:

365chess
Queen's Indian (E15) page on chessgames


All that I have analysed from the above game are enlisted below. I don't know which side @Ian Bush was on, so I am making suggestions for both sides. Hope it helps. Here it goes:

FOR WHITE

White had a slight positional disadvantage in the game as early as move no.7 since by this time, Black had castled, king is in safety, king-side pieces well developed, but White had a centred exposed king, queen-side pieces developed before king-side pieces (against golden rule), center pawns e4,d4 not supported by any pawn.
White should have played 3. c4 which is more mainstream and allows White an early control of the centre which can add to his advantage in the middlegame.

o-o-o is not a good move because of the fianchetto bishop on g7 and also the centre is very dynamic. So white loses the opportunity to attack on the kingside early as Black has the option to blow up the center and rupture the attack.

Bf4 is dubious. Better is 16. Nf5 which attacks the g7 bishop and occupies much space on the king-side and if it is captured by the bishop, pawn recaptures and the kingside attack is easier for White now.

Bg4 is better and is followed with the idea of Rd5..h5..h6 which tries to mend the position.

f3 might have been replaced by 31. Qd6 followed by 31. .. Kg8 32. Bf3 going for a fightback.

Qh8# could have sealed the game however.

FOR BLACK

.. Ng4 seems premature. Developing Queenside pieces might have been better.

.. Qf6 would have been better, aiming for 31. .. Bg4 and 32. .. Rd8.

.. Kg7 is a blunder. 35. .. Rd8 is quite stable.

.. Nd4 was the best move.

Otherwise Black had a good game and the final position was almost equal , a little in favour of Black. However the game could go anyway because of White's passed pawns.


Caro-Kann advance variation w/ 3. c5 dxc5

OK, after reading your reply to my question above, I can more accurately answer.

First, contrary to Fuxia's comment, the move you played, 4...Nc6, is actually more popular now at higher levels than Botvinnik's 4...e6. To quote GM John Shaw's 2016 book:

  4...Nc6 is more popular these days and can be viewed as slightly more ambitious, as well as somewhat riskier. It can lead to exceptionally
  sharp play....

Thus, based on your answer above, I would not play 4...Nc6 since it simply does not suit your style. If you are going to play 3...c5, then I would play 4...e6 as it leads to more positional lines, that are easier to understand. Also, not that you are old, but if you are having problems with blundering, going into sharp lines with 4...Nc6 may be suicide.

Here is what I would recommend:

  [FEN ""]

  1. e4 c6 2. d4 d5 3. e5 c5 4. dxc5 e6 5. Nf3 (5. Be3 Nh6! {This is actually very positional since if white takes, most of the lines favor the black bishops.}) (5. a3!? {Shaw}) Bxc5 6. Bd3 Nc6 7. O-O Nge7 {with the idea Ng6, Qc7, and maybe f6 after O-O. Also, instead of Qc7, you can also play Bb6-c7 with the same type of pressure on e5.}

Now, in any case, that is barely touching the surface. If you want to play that line, you will need to look at more specific material. Here are some study materials.

"Opening Repertoire: The Caro-Kann" by IM Jovanka Houska (chapters 9-11)
"Playing 1.e4: Caro-Kann, 1...e5 & Minor Lines" by GM John Shaw (chapter 2).
"Practical Black Repertoire with d5, c6. Volume 2 The Caro-Kann and Other Defences" by GM Alexei Kornev (chapter 6+7)

All three books have advantages, and all are pretty new, having been published in 2015, 2016, and 2017 respectively.


What is an example of a very difficult one-move checkmate?

Very difficult is relative and given enough time players of most strength should be able to find a mate in one.

I don't have a concrete example, but in my view the following features would make it more difficult (some of these exclude each other):

a large number of possible moves (i.e. lots of pieces on the board and an open position)
the mating move is done by a piece moving to the back (towards the mating player)
it is a non-standard mate (not one you have seen before in your tactics excercise, but rather of a studies type)
the mating move is a move where the moving piece uncovers a piece that helps in the check mate (either by taking away squares from the king, or more tricky by pinning a possible defender)
lots of pins are involved that prevent defenders from defending
there are tempting moves that don't work for not-too-obvious reasons
the move is an en passant capture or an underpromotion or castling
(not sure this counts) the mate requires retrograde analysis to prove that en passant capture is allowed or that castling is allowed
large distances are involved, both in the move itself and in the attacking of the king (say moving a queen from h8 to a1 to check mate a king on a8 might not be that obvious)
the position is such that the pawns move unexpectedly in a direction you would not expect (down, left, right)
asking for a mate in one  for black (without specifying that it is black's move) This can be particularly tricky if it looks as if white could mate as well.


Has the 75 move draw rule ever been invoked in a FIDE rated standard game involving a GM?


Bishop's opening - avoiding positional lines as Black after 2...Nf6 3. d3

3...c6 is in my opinion by far the best move here. Usually white would continue with something like 4.Nf3 Be7 5.O-O (5.Nxe5 Qa5+) d6. 5...d6 is a more solid choice but 5...d5 is another option if you want to blast open the center quicker. For a nice game with 5...d6 played, take a careful look through Gelfand - Yusupov, Munich 1994.


Which engine is better at Chess960-Stockfish or Leela?

Currently, it's Stockfish: in the latest FRC exhibition (November 2020) Stockfish beat Leela +8 -0 =42.


Compare the position after 3...Bc5 to that after 4.b4 Bxb4 5.c3 Bc5 6.d4.

[fen ""]

1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4 Bxb4 5.c3 Bc5 6.d4`

It's true that the Black bishop has simply returned to c5 and can retreat safely again, but note that that is all Black has gotten to do while White got in the central c3/d4 push. In simplest terms, the point of the Evans Gambit is that gain of time, getting in those moves to expand in the center (and open lines for potential development/attack) without Black continuing her development in the meantime. Such things usually aren't free of course, and here it has cost White the b-pawn. White has traded in a bit of material in attempt to have greater dynamic potential and the initiative.