# Question
Title: What would you suggest I play vs. the Ruy Lopez, if I already play the Two Knights Defense vs. 3. Bc4?
I play the Two Knighs Defense as Black vs. 1. e4 e5 2. Nf3 Nc6 3. Bc4, in the spirit of counterattack. What would you suggest I play as Black vs. the Ruy Lopez?

# Answer
There's a simple reason for which 3...a6 and 3...Nf6 are by far the most common replies to the Ruy Lopez: they're the most solid for black. It's very hard to force white into playing something dynamic without comprimising your own position. Of course, you can try something like the Schliemann Defence with 3...f5, though objectively this is dubious for black. However, assuming you aren't playing against titled players, it can still be worth trying if you have good preparation and if you trust that your tactical ability is better than your opponent's. Another option instead of the Schliemann is the so-called "Siesta variation", which features a similar f5 pawn break, though black scores better here than in the Schliemann.

```
[FEN ""]
1. e4 e5
2. Nf3 Nc6
3. Bb5 a6
4. Ba4 d6
5. c3 f5

```

This leads to very dynamic play. GM Laurent Fressinet used this in 3 different games at the World Blitz Championship 2017 against other GMs, and won all 3 of them. GM Valeri Yanderimov also has many games in this variation, with mixed results.

Alternatively, if you want something different, you can always try the Cozio defense, both the standard and the deferred variations. This is more solid, though players at lower levels are less likely to be prepared in this opening, and the resulting positions can be surprisingly dynamic with potential pawn storms and black having a strong bishop on g7. The answer to this question provides good insight into the differences between the direct and deferred versions. Of course, the dynamic character of the Cozio depends largely on what white decides to play, and thus you still have to be ready for more quiet or more drawish positions.
> 2 votes

---
Tags: ruy-lopez, two-knights, open-games
---


# Question
Title: Why white retreats the knight at the beginning of the game?
This is one variation from Bird's Opening:

1. f4 e5 2. e4 exf4 3. Nf3 d6 4. d4 g5 5. h4 g4

```

  [FEN "rnbqkbnr/ppp2p1p/3p4/8/3PPppP/5N2/PPP3P1/RNBQKB1R w KQkq - 0 6"]

```
The most popular move is Ng1 instead of Ng5. Am wondering why retreating the knight is a good idea. Doesn't this move violate some opening principles in developing your pieces? After white retreats the knight, he has only three pawns developed while black can continue with Bh6, developing the bishop whilst supporting the f4 pawn.

# Answer
> 4 votes
The opening is called King's Gambit and is usually reached with a slightly different move order after 1.e4 e5 2.f4....

It used to be popular a long time ago (100+ years) for its potential of wild games, but is probably slightly incorrect and not a good choice if your opponent knows what to do.

Arguing with general opening principals is not really meaningful here, because the opening is very concrete/tactical.

After your suggested Ng5 for instance you'd have to be prepared for f6 after which the knight is attacked and will be lost due to lack of retreating squares. White would get 2 pawns for the knight, but that won't be enough.

Retreating the knight, while not ideal, is a better option.

# Answer
> 2 votes
Ng5 loses a piece. Nh2 is awful after h5. Nd2 blocks your bishop and it has nowhere to go on the k side to defend.

So pretty much Ng1 looks like the best move here.

---
Tags: opening, kings-gambit, birds-opening
---


title: How to define a countergambit?

text:
# Question
Title: How to define a countergambit?
Am wondering if there is a definition of a countergambit. My understanding is, a countergambit happens when one side plays a gambit, instead of capturing the pawn, the other side also sacrifices a pawn.

Is my description accurate? Is the following line considered as a counter gambit?

1. f4 e5 2. e4

The move e5 is called From's gambit. Instead of capturing the pawn, white develops his king pawn, offering his f4 pawn. Is this considered as a countergambit? (Under a different move order 1. e4 e5 2. f4 it is called king's gambit.)

# Answer
You're right: a counter-gambit is an opening in which one side plays a gambit, and the other side rejects the gambit with another gambit (i.e. "gambits" the gambit). A popular counter-gambit is the Albin Countergambit:

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

1. d4 d5 2. c4 e5

```

> Under a different move order 1.e4 e5 2.f4 it is called King's gambit.

This is also a King's gambit but due to the order it is also cosidered a countergambit

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

1. f4 e5 2. e4

```
> 2 votes

---
Tags: gambits, kings-gambit, birds-opening
---


# Question
Title: Can I resign if my opponent only has his King?
Well, obviously if my opponent has only a King, I cannot lose...either a win or a draw. Suppose I also have a Queen(Forced win).

However suppose I want to lose (maybe I am winning and want to grant some points to my opponent or whatever), so can I resign under such a circumstance ?

(I understand that my opponent would have resigned before reaching such a position, but anyways is it legal to resign if opponent has only king? )

# Answer
Consider the following scenario:

The round is scheduled to start at 6:30pm and normally I would expect my game to finish comfortable before 11pm when I need to leave to catch the last bus home at 11:05pm. There is no zero tolerance. Instead players have one hour to arrive before they are defaulted. Normally I start my opponent's clock at 6:30pm on the dot if he hasn't arrived so that I have no problem with the last bus.

At 6:25pm the arbiter announces that he has had news of an accident on the motorway which is delaying some of the players. Consequently he rules that we may not start a player's clock until 7pm if they are not in the club. The default time of 7:30 is unchanged.

I complain bitterly to the arbiter but he is unmoved and won't change his decision.

My opponent eventually arrives with the other late players at 7:05pm. I started his clock on the dot of 7:00pm. The game drags on and on. Eventually at 11pm I queen my last pawn against my opponent's bare king. I offer a draw but he refuses. I knock my king over in disgust and head for the door and the last bus.

The next week the arbiter tells me that knocking my king over constitutes resigning. He also tells me that if I had walked out without resigning I would have "lost on time" but been awarded a draw because my opponent didn't have mating material.

This is perfectly legitimate. I have resigned against a bare king and this is legal. The only sanction I am likely to suffer is for not shaking hands after the game.

EDIT: This subject actually came up at the recent FIDE meeting in early September! Alex Holowczak (amongst others) was representing England at these meetings and his report appears here - http://www.englishchess.org.uk/wp-content/uploads/2015/10/C23.9.5.1-FIDE-Delegate-report.pdf .

Note, in particular this excerpt from Alex's report from the meeting of the Rules Commission:

> A proposal noted that you could run out of time but not lose if your opponent had a bare King, and asked why you should lose if you resign but your opponent had a bare King. I commented that this situation was so unlikely/unreasonable that it shouldn’t be legislated for.
> 7 votes

# Answer
The FIDE laws of chess contain two parts: Basic rules of play (Sections 1-5) and Competition rules (Sections 6-12).

The first part is what defines how the pieces move, when the game ends, and so on. These rules indeed allow players to resign at any point before the end of the game, so you can resign right before you would give a checkmate, but not after you have released the piece after the final move. The second part explains things such as the chess clock, scoresheets, the role of the arbiter etc. Curiously this part seems to have nothing to say about deliberately losing.

So technically, one could say that resigning in a won position on purpose **"is allowed" by the *rules of chess***.

However, the FIDE tournament rules, which are used in international tournaments, say that

> 8.(f) Where it is clear games have been pre-arranged, the CA shall impose suitable penalties.

I don't have a good credible source, but I think that deliberately losing games (which has happened) are usually considered in a similar way. In addition, deliberately losing games is generally considered unacceptable behaviour in sports <sup>*\[citation needed\]*</sup>. So in my opinion, it is clear that deliberately losing a game **is against the *rules of a tournament*** (unless explicitly specified if the tournament organizers want to allow such tactical manoeuvres). You can always ask the tournament organizer if you want confirmation.
> 8 votes

# Answer
If you do that in a tournament, it could be construed as a conspiracy to help your opponents position in the standings, and you both would be disqualified.
> 2 votes

# Answer
You can resign if you have enough material to checkmate. If you do not have enough material left to checkmate, you cannot resign because the game has already ended in a draw.
> -3 votes

---
Tags: rules, resigning
---


# Question
Title: Tablebases for variant where stalemate is a win?
Since time immemorial, some people have suggested that stalemate be declared a loss for the player who is unable to move. This proposal is sometimes called "abolishing the stalemate rule" although I prefer calling it "abolishing the checkmate rule" (the idea is to declare that the game ends when the king is captured, and that it is legal to move into check—although this way of phrasing the rule change means that a "true" stalemate, where a player has no legal moves even if moving into check is legal, remains a draw).

This rule change has some obvious effects on endgame theory. What I'm wondering is whether anyone has created tablebases for this variant of chess, to investigate more thoroughly how much endgame theory would be changed. For example, does the overall draw rate of KRP vs KR, or KQP vs KQ, change noticeably?

# Answer
> 3 votes
> What I'm wondering is whether anyone has created tablebases for this variant of chess,

Interesting proposal, but nobody has done the works to my knowledge. If you would like to participate, you may modify source code of https://github.com/syzygy1/tb.

---
Tags: rules, tablebases, stalemate
---


title: Stockfish blunders away a piece

text:
# Question
Title: Stockfish blunders away a piece
Using stockfish\_8\_x64 with Arena 3.5.1, I see a weird pick by Stockfish. Start here:

White, Stockfish, to move. It plays bb6-g1,losing the bishop and the win.

Also strange: the same engine does not make this weird move in the Tarrasch program. Playing with KBN against K, I've seen Stockfish often blunder away the advantage in these endgame setups.

Any clue how this could be happening, or why it would happen only with Arena?

EDIT: SmallChess answer is correct. The problem was a residual, non-zero value in the position "number of half-moves" setting. See my reply to his posting for more information.

# Answer
This is **not** a blunder, expected behaviour from the engine. Everything worked as intended. Try to copy the FEN string out, and you'll know.

Although the position looked winning, White didn't have enough moves to force checkmate before the 50 moves rule. Stockfish, knowing the position was a dead draw immediately asked for simplification.

The position you had is 100% equal, there was **no way** to win it. It's a draw. What Stockfish did was not wrong.

If the Tarrasch program didn't send out the 50 moves counter to Stockfish, you'd never get the problem on Tarrasch. If that was the case, it was an error in Tarrasch because the 50 move counter is part of the game.

**Solution?**

Setup a new board with the same position but reset the 50 moves counter.
> 29 votes

# Answer
There must be an issue with your copy of Arena 3.5.1 because Stockfish found a mate in 20. I'm using Scid for my GUI. I have attached the moves.
> 2 votes

---
Tags: endgame, stockfish, blunder
---


title: Scid vs PC, how to get ECO data ?

text:
# Question
Title: Scid vs PC, how to get ECO data ?
Installed SCID vs PC. Can this give a count or frequency distribution of the ECO codes of the games ? So far unable to do this.
Under the **Tools** tab there is a selection "Opening Report".
This gives a lot of data, most of limited value, such as oldest games, most frequent players, shortest wins. Finally there is 5. Theory Table.
This is a table of moves in 8 columns and 20 double rows. How to interpret this is obscure and certainly not intuitive. There is a Help Index. "Theory table" is absent from Help.

Under Options there is a selection "Load ECO file". Found .eco in data subdirectory of bin. Loaded it. Seems to get me nothing.

# Answer
> 1 votes
You can get a count of how many of a particular ECO code (or a particular range of codes) is in the database.

In the Game List, select Change Filter (magnifying glass icon), then Search by Header (binoculars icon). In the dialog box that pops up, there are two fields for ECO code, allowing you to choose a start and end. For example, enter B00 and B99 if you want to count all the B codes. Then click the Search button. The Game List will now show the count of games in the database that match the filter.

---
Tags: software, scid
---


# Question
Title: Is there a Open Source or Shareware Legal Move Checker Executable?
**Background:** I wrote and use a custom macro in the NoteTab Pro text editor to convert PGN position analysis to XML. The resulting XML is used on my website to display chess puzzles. I need to check for legal moves in some cases. For example, a PGN move might say Rd6 in a position where two rooks can move to d6, but only one of them can legally move to d6 because the other is pinned to its King. I am disinclined to write a macro legal move checker due to the apparent complexity of the task. I do not want to reinvent the wheel.

Ideally, I am looking for an executable that can be called with FEN and next-move parameters, and return a positive or negative result based on the move's legality.

# Answer
> 2 votes
Simple problem. `python-chess` is a useful Python package that can do it for you easily. You will need to get a FEN, check if your move is a legal move.

> https://pypi.org/project/python-chess/

has everything you want.

---
Tags: software
---


title: How is MultiPV enabled in general?

text:
# Question
Title: How is MultiPV enabled in general?
I looked at the "Description of the universal chess interface (UCI)" dated April 2006, and did not find a command or option that seemed to address how a GUI might enable MultiPV (I assume that PV stands for Position Value). How does a GUI display MultiPV?

Background: I hope there is a simple UCI command that enables MultiPV, so that I can issue the command on my BabasChess GUI.

# Answer
> 1 votes
"MultiPV" is the UCI option you are looking for.

> setoption name MultiPV value 10

---
Tags: engines, software
---


# Question
Title: Do top chess grandmasters have significant drawing chances against top engines?
the likes of stockfish and komodo are much stronger than humans. The 3300 plus ratings of these engines suggests that even the top humans would find it impossible to draw even 1 game, but is this really true? Also, are these high ratings meaningful?

# Answer
Today's engines running on suitably powerful computers will most likely beat any top grandmaster.

Ratings are essentially numbers assigned to players such that a player is expected to beat some other player (a draw being counted as a half-win) some fraction of the time, based on their difference in rating. An important point is that the absolute ratings are irrelevant: if every player in the world got a 1000-point boost to their rating, nothing fundamental would change.

The mathematical details imply that according to the rating model, no matter how big the difference in rating, the weaker player will still win some fraction of the time. In the case of Elo, we assume that even the lowest-rated player in the world has a 9% chance of beating Magnus Carlsen. This is clearly a flawed assumption, but it's the kind that almost every rating system makes; and it's not too bad anyway, it works well for the most part (i.e. when rating differences aren't too big), and even at the extreme ends, the best human players can still blunder.

However, today's engines beat humans 100% of the time in a fair game (I wouldn't say there's explicit proof, but the fact that they don't even bother to hold such matches anymore says a lot, so let's just say this is true); thus it's completely meaningless to assign a FIDE rating to these silicon monsters: there is absolutely no difference whether a 2800 player meets a 3300-rated engine or a 4300-rated engine, as far as the Elo rating system is concerned. Even for an engine running on a desktop, if we assume that a top grandmaster could score some 5%, we'd still be looking at what statisticians call a tail event; rating systems (and statistics in general) are really bad at these.

So top computer engines have their own rating lists, no humans involved. But they still run on the Elo system, albeit apparently with a different 'base'. You can meaningfully compare engines here; a 100-point rating difference will probably correspond to a sensible winning percentage.

On the other hand, the difference between the FIDE rating list and computer chess rating lists (CCRLs) are completely meaningless. While CCRL base ratings were probably chosen to be higher because most computers are simply better than the best humans, this base rating is just arbitrary (at least as far as I know); we could subtract 2000 points from every rating in the CCRL and add 2000 to every rating in FIDE, and both lists will continue to function the way they have.

It seems that the modern way to compare humans to computers today is to look at scores from matches where players are given a handicap. If I recall correctly, this is reminiscent of the pre-Elo days, when players' strengths were gauged by how they fared against the best players under a handicap!

Long story short: the high ratings are meaningful when compared with other engines in the same list. On the other hand, they are absolutely worthless for comparison against humans.
> 3 votes

# Answer
For the first part, see my answer to a related question. Humans have no chance - they'd be lucky to even draw a game.

About the second part, engine elo isn't directly translatable to human elo. The way elo works, it depends on the anchor. The bottom of the elo ladder is 0 elo. What does 0 elo mean to you? If you rate a complete human novice as 0 elo, there're still players who can be worse than you (e.g. an engine that selects moves at random). So no, you cannot say that an engine that is 2800-rated on engine elo lists would be expected to draw a match with 2800-rated Carlsen.
> 0 votes

# Answer
Statistics state that for a 400 point rating difference, the higher rated player should win 99.9% of the time. The slight chance for the lower rated player is due to the player's increased knowledge and human error. Since at the grandmaster level, there is no huge increase of knowledge, and the computer will never tire, the human has, if effect, zero chance of even getting a draw.
> -3 votes

---
Tags: engines, computer-chess
---


title: Blitz games managment

text:
# Question
Title: Blitz games managment
Here is the problem : when I have the time, i usually find the right move.
Meaning, in a longer time frame games (more than 10min) I'm doing better.
I feel like struggling with 5 min. games and I don't know how to improve. I review my games usually using the computer but I haven't seen a big improvement, just a very small one. To me it feels like I'm missing something that would elevate my level. Any suggestions will be welcomed. Thank you.

# Answer
Tactics play the most important part of winning blitz games. The tactical player has a better chance of winning a blitz game rather than a quiet, positional player (it is the other way round for classical chess). Next is intuition. To succeed as a blitz player, you must be able to figure out the next move without going into deep calculations (i.e. 'feel' the next move). For example, here is a game from your Chess.com account I analysed with a computer:

```
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
[Event "Live Chess"]
[Site "Chess.com"]
[Date "2018.12.09"]
[Round "-"]
[White "quizhead (1238)"]
[Black "redhatkillers (1208)"]
[Result "0-1"]
[WhiteElo "?"]
[BlackElo "?"]
[Variant "Standard"]
[TimeControl "-"]
[ECO "A02"]
[Opening "Bird Opening"]

1. f4 g6 2. Nf3 Bg7 3. e4 e6 4. Be2 a6 5. d4 b5 6. O-O Ne7 7. c3 f5 8. e5 Bb7 9. Be3 Bh6 10. Nbd2 Nd5 11. Bf2 Bxf4 12. Bh4 Qc8 13. Bf2 Be3 14. Kh1 Bxf2 15. Rxf2 Qd8 16. Qc2 g5 17. Raf1 g4 18. Ne1 Ne3 19. Qd3 Nxf1 20. Bxf1 Qh4 21. Qe3 Nc6 22. Nd3 Na5 23. Nf4 Rg8 24. b4 Nc4 25. Nxc4 bxc4 26. Qg3 Qxg3 27. hxg3 h6 28. Bxc4 c6 29. Bb3 a5 30. a3 axb4 31. axb4 Ba6 32. c4 Ke7 33. Rf1 Rg5 34. Rd1 Rh8 35. d5 h5 36. dxc6 dxc6 37. Nd3 h4 38. Nc5 hxg3+ 39. Kg1 Bc8 40. b5 cxb5 41. cxb5 Rgh5 { Black wins. } 0-1

```

**10. Nbd2** is a normal move in an opening, but unfortunately not here. Your opponent has the massive d5 square for their knight. You should have paid attention to Nd5. It forks the bishop and the pawn, and you are forced to give up the pawn. 10. g3 would've saved the pawn, though that knight is still annoying.

**17. Raf1** allows a fork too. From the d5 square the knight is a serious threat. Usually when a knight is about to enter your territory, you must give it adequate attention.

**25. Nxc4** looks like it wins a pawm worsens your position. Your opponent didn't notice that 25... g3 wins your rook, and fortunately you had a chance to correct that by playing Qg3.

These are just some remarks. There is still much to learn, by playing more and more games and highlighting the positions where you blunder such tactics. It happens to us all. As it is said, the player to make the next to last mistake usually wins. We all do fall for such tactics, but one needs to minimize this to have a good chance at blitz.
> 2 votes

---
Tags: blitz
---


# Question
Title: What is the maximum number of en passants possible?
Out of curiosity, how many en passants can theoretically be done by both sides, and what is the fastest way to achieve that result?

# Answer
Every pawn has to take a pawn in an en passant capture, and each pawn taking another pawn will leave the 5th rank. Hence, the total possible number of en passant captures in a game is simply the number of pawns halved, i.e. 8. It can be achieved in the following sequence of moves:

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

1. h4 a5 2. h5 g5 3. hxg6/ep a4 4. b4 axb3/ep 5. a4 h5 6. a5 b5 7. axb6/ep h4 8. g4 hxg3/ep 9. c4 f5 10. c5 d5 11. cxd6/ep f4 12. e4 fxe3/ep 13. f4 c5 14. f5 e5 15. fxe6/ep c4 16. d4 cxd3/ep

```

This is the minimum number of moves required for 8 en passant captures, and this is due to:

* All moves being pawn moves
* Every pawn advancing 2 squares at its first move
> 8 votes

---
Tags: theory, problems, records, en-passant
---


title: The games AlphaZero lost

text:
# Question
Title: The games AlphaZero lost
AlphaZero lost 6 games to Stockfish in a 1000-game match from the starting position, at least one of which was with the white pieces: A game A0 lost with white. For some reason, these games haven't received much media attention. Does this mean AlphaZero hasn't solved the game of chess yet? So, there is still scope for improvement? The media's report that AlphaZero is the perfect chess-playing machine is false.

# Answer
> 12 votes
AlphaZero hasn't solved chess, and it won't until it can find a strategy that results in the same outcome of the game given perfect play from both sides. According to Wikipedia:

> A solved game is a game whose outcome (win, lose or draw) can be correctly predicted from any position, assuming that both players play perfectly.

Since AlphaZero has lost games to Stockfish with **both** colours, we can assure it didn't solve the game. AlphaZero plays itself in training games. Had it solved the game, all these AlphaZero vs AlphaZero games will end up in one same result: either a win for white, a win for black or a draw.

# Answer
> 2 votes
There is no such thing as perfect playing machine in chess. Google never claimed their engine was able to solve the game.

# Answer
> 1 votes
AlphaZero hasn't solved chess - to do so you'd need to know from the starting position which side wins (or if the game is a draw). This is in principle doable with a 32-piece tablebase, but in practice it's impossible.

> “Yes,” replied God, “I have done the 32-piece endgame.”
>
> “Ahh,” said Garry, “Of course that is trivially easy for you.”
>
> “No, no,” said God, “it was really tough. More than 10^35 legal positions — it took the matter from a good-sized planet to store. But let us play. You can have white.”

10^35 is a fantastically large number. If it takes one byte to store one position, one gigabyte is still only 10^9 positions, 26 orders of magnitude off the required number. So no, AlphaZero has not solved chess, and there's no way to do so in the foreseeable future.

Naturally this means there is still scope for improvement. If AlphaZero were a conventional engine its developers would be looking at the openings which it lost to Stockfish, because those indicate that there's something Stockfish understands better than AlphaZero. AlphaZero is a neural network engine however, which makes how to improve it less obvious. I am not an expert on neural networks, but you can follow the development of Leela (which is a reproduction of AlphaZero, based on the paper) on its developer blog.

---
Tags: engines, alphazero
---


# Question
Title: Who said "One bad move nullifies forty good ones"?
This quote is attributed both to Bernhard Horwitz and I.A. Horowitz, and I'd like to know which one said it.

One thing that helps is they don't have overlapping lifespans. Bernhard Horwitz died in 1885 and I.A. Horowitz was born in 1907. We can probably safely assume that, if I.A. Horowitz said it, he had to have been at least 20 years old, so an attribution to Bernhard Horwitz from before 1927 should be considered reliable. Likewise, if no references to this quote before 1927 can be found, then it's probably I.A. Horowitz.

Alternatively, we might find a source that gives a more detailed attribution, such as "Bernhard Horwitz uttered this at such-and-such tournament" or "I.A. Horowitz wrote this in the January 1935 issue of Chess Review".

My hunch is it was I.A. Horowitz because he wrote for *The New York Times* and *Chess Review*, so he was a prolific author, so he had many chances to say something notable. Still, Bernhard Horwitz did write at least one book, and it does seem more likely for a quote by Horwitz to be misattributed to the better known Horowitz than vice versa.

# Answer
> 4 votes
According to chesshistory.com, in October 1959, Al Horowitz wrote:

> It is axiomatic in chess that it is easier to achieve a winning game than to win it. *One bad move nullifies 40 good ones*, and precision technique is of the essence even when the game is well in hand.

The same can be found in his book, “All About Chess”, written in 1971.

However, in the Chess Review magazine (November 1961), Al Horowitz calls this quote an “adage”. Given this, I think that Al Horowitz is not the author of the quote, but thanks to him we know about it.

As for Bernhard Horwitz, I have not found reliable sources indicating that he is the author of the quote. At least, it is strange to me that it is not mentioned in his books.

---
Tags: quotations
---


# Question
Title: In a tournament game, what should a player do if he find that his opponent's position is impossible, which was caused by an earlier illegal move?
For example, if a player realises that his opponent has two bishops of the same colour after a certain legal move (and assuming that it is clearly not caused by any pawn promotion), which implies that his opponent has made at least one illegal move earlier (but it was recognised until much later in the game), what should this player do?

1. If there is a record, can he trace back the illegal move and declare that he wins the game because an illegal move was made earlier?
2. Even without a record, can he still win the game because he can theoretically prove the existence of at least one illegal move made by his opponent?
3. Or should the game continue as it is now, even though the position is impossible?

# Answer
> 5 votes
Section 7.5.1 of the FIDE Laws of Chess has the answer:

> **7.5.1** An illegal move is completed once the player has pressed his clock. If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined, the game shall continue from the last identifiable position prior to the irregularity. Articles 4.3 and 4.7 apply to the move replacing the illegal move. The game shall then continue from this reinstated position.

The player found guilty is not penalised for the illegal move, provided their opponent has intended to play a move:

> **4.7.1** A player forfeits his right to claim against his opponent’s violation of Articles 4.1 – 4.7 once the player touches a piece with the intention of moving or capturing it.

# Answer
> 1 votes
> If there is a record, can he trace back the illegal move and declare that he wins the game because an illegal move was made earlier?

No. The penalty for a first illegal move is an addition of 2 minutes to the other player's clock. Only a second illegal move loses the game.

According to FIDE Laws of Chess article 7.5.5 -

> **7.5.5** After the action taken under Article 7.5.1, 7.5.2, 7.5.3 or 7.5.4 for the first completed illegal move by a player, the arbiter shall give two minutes extra time to his opponent; for the second completed illegal move by the same player the arbiter shall declare the game lost by this player. However, the game is drawn if the position is such that the opponent cannot checkmate the player’s king by any possible series of legal moves

.

> Even without a record, can he still win the game because he can theoretically prove the existence of at least one illegal move made by his opponent?

No. If no record is being kept of the game then it must normally be blitz or rapid. In that case the illegal move stands and the game continues. According to article A.4.2 of the FIDE Laws of chess -

> **A.4.2** If the arbiter observes an action taken under Article 7.5.1, 7.5.2, 7.5.3 or 7.5.4, he shall act according to Article 7.5.5, provided the opponent has not made his next move. If the arbiter does not intervene, the opponent is entitled to claim, provided the opponent has not made his next move. If the opponent does not claim and the arbiter does not intervene, the illegal move shall stand and the game shall continue. Once the opponent has made his next move, an illegal move cannot be corrected unless this is agreed by the players without intervention of the arbiter

The illegal move has to be seen immediately (before another move is made or piece touched) and a claim made by player or arbiter.

---
Tags: rules, illegal-move
---


title: Why did this game end with a draw?

text:
# Question
Title: Why did this game end with a draw?
This game starts with

1. f4 e5
2. g4

IMO, black has a winning position here. How did it end with a draw?

# Answer
Either the game score is incorrectly recorded or this was a pre-arranged draw, because in that final position everyone beyond basic club level would realize that Black wins with Qh4# (a basic Fool's mate pattern).
> 6 votes

---
Tags: draw, birds-opening
---


# Question
Title: Was the value of thorn pawns fully appreciated in decades past?
Many videos on YouTube channel "Kingscrusher" which discuss the play of new neural-net engines like Leela Chess Zero focus considerable attention upon the development of "thorn pawns" which are pawns that have reached the sixth rank and are blocked by a pawn in front but do not have pawns ahead of them to either side. In my limited study of the game in decades past, I've seen great significance given to passed pawns, but never any special attention given to thorn pawns. Do such pawns have a significance that has only been fully brought out as a result of AI-assisted research, or have they always been understood but simply not in things I'd read? Or is Kingscrusher giving them more significance than they deserve?

A typical thorn-pawn situation would occur when Black has pawns at f7, g7, and h7, white moves h5, Black g6, and white pushes h6. If Black has castled kingside, that pawn at h6 can be very hard to capture, and its presence kills the escape square at g7 and the possibility of easily establishing one at h7. Was that a common pattern in years past, and if so what was it called?

# Answer
I had never heard the term, but such pawns are very important for their contribution to certain mating patterns, the most famous of which would be *Damiano's mate*, which was included in Damiano's 1512 book *Questo libro e da imparare giocare a scachi et de li partiti*. Here's an archetypal example:

```
[FEN "5rk1/6pQ/6P1/8/8/8/8/8 w - - 1 1"]

```
> 12 votes

---
Tags: pawns, terminology
---


# Question
Title: What is the Elo rating of Stockfish version that played AlphaZero?
AlphaZero has defeated Stockfish with all novelties and brilliant strategic sacrifices. But some people were disputing its win, because Stockfish was running on weak hardware (1 GB RAM), not access to opening book, not having free time control, maybe not have endgame table base, etc.

This setting by DeepMind is understandable from a scientific perspective though. It is to test intuitive/strategic play by deep learning technique vs. counting/tactical play by brute force search. However, this leaves chess lovers with many questions like what is the true strength of AlphaZero? What is the true advantage of strategic/positional sacrifice play? Were Morphy, Tal, and others correct and Stockfish wrong? Or full version Stockfish is still the best?

One work around is to replicate the Stockfish version that played AlphaZero, to see how strong it is compared to the full version and other engine and human. Thus we could infer the Elo rating of AlphaZero and answer most questions.

So, did anyone test it? Is anyone interested in testing it? Maybe Stockfish developers, because Stockfish's pride is at stake? Or is there other way to approach the problem?

Thanks

Edit:

* Note that Stockfish had good 64 threads CPU and could evaluate 70 million positions/second.
* The Stockfish Elo rating provided in the paper is the full version, thus this replication is needed.
* The paper.

# Answer
> 4 votes
The Stockfish version that played agaist AlphaZero was significantly compromised in several different aspects:

1. There was no opening book available
2. Time control was 1 minute/move, which throws out of the window various optimizations re: using more time thinking about difficult moves
3. Stockfish had `threads=64` set, but the actual hardware had only 8 CPU cores, that effectively slowed things down quite a lot
4. The hardware was quite different -- an average $1k PC (Stockfish) against a bunch of specialized hardware that might cost millions and is not accessible to anyone
5. There are more, but these are main points.

Answering your question, there's no way to measure how much rating Stockfish had in a very handicapped conditions it had to run.

Nonetheless, winning over Stockfish is quite an achievement, no matter how handicapped it was and how much was the difference in hardware cost.

---

UPDATE: in the recent article "AlphaZero: Shedding new light on the grand games of chess, shogi and Go" the rating for Stockfish was drawn as a line at **3500**. Besides that, the article provides the new games played with a reasonable time control for SF as well as opening books.

# Answer
> 3 votes
AlphaZero vs. Stockfish 8, 1000-game match as in the latest paper (with Stockfish operating at full power) yielded a score of +155 -6 =839. Using this calculator gives an elo difference of 52.

Stockfish 8's elo rating on computer chess rating lists is about 3378, giving AlphaZero a rating of about 3430.

Disclaimer: these rating lists are generated with hundreds of thousands of games between all the engines. With only 1000 games against a single engine, this 3430 rating is unlikely to be accurate. AlphaZero is certainly one of the stronger engines out there, but it's not clear exactly how strong.

# Answer
> 2 votes
"Stockfish was running on weak hardware (1 GB RAM)...This setting by DeepMind is understandable from a scientific perspective..."

I'm a master scientist and this is NOT understandable scientifically. You have introduced an unneeded and unwanted variable by running Stockfish on weak hardware. Poor experimental design. Poor science.

---
Tags: engines, strategy, stockfish, alphazero, hardware
---


# Question
Title: Morozevich variant in the Tarrasch french
I am confused with the Morozevich variant. I've seen quite a few funny games where they played ...g5, which gives very interesting moves, but I'm surprissed at not having seen any game in which white plays 4.e5, which seems a natural move, blocking the classical square f6 for the king-side knight. Here, What is the main idea of the Morozevich variation in the French vs. the Tarrasch?, Nh6 was proposed in a comment, but I think after Bd3,c5,Ndf3, the black knight is quite weak. How would you play against 4.e5?

# Answer
I don't think Black is in a hurry to develop the knight. 4...c5 is the main move. If White plays Qg4 the bishop goes back to f8. As a matter of fact the bishop sometimes goes back to f8 even if White doesn't play Qg4.

Of course Nh6 is fine and the knight will then go to f5 where it is happy.

Note: 1. There are other lines where the Bishop returns to f8, like 1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.e5 b6 5.Qg4 Bf8. 2. In non-Nf6 lines it is common for the knight to head to f5 via e7 or h6
> 2 votes

---
Tags: opening, french-defense
---


# Question
Title: Why play 7... Nxd5 instead of 7... exd5 in the QGD?
I'm currently following the rapid game Caruana-Nakamura in the London Chess Classic, and I have a basic question about the opening moves.

Why play 7... Nxd5 instead of 7... exd5? Is the idea to trade pieces since black has less space and that would free up his position? Do black's two knights kind of step on each other's toes, making a trade of one knight desirable?

Here's the game: https://www.chessbomb.com/arena/2018-london-chess-classic/04-Caruana\_Fabiano-Nakamura\_Hikaru.

# Answer
Both moves are played with exd5 being the more popular choice. After 8.Nxd5 exd5 is twice as popular as Qxd5 as played by Nakamura. It is likely Nakamura is trying some ideas in these sidelines in the hopes to catch his opponent unawares.
> 1 votes

# Answer
The white knight on c3 is better and potentially Nb5 could be annoying. Also black was planning to possibly bring the other knight to f6.

Also recapturing with the pawn gives you hanging pawns/an isolated pawn if you decide to break through with c5.
> 0 votes

---
Tags: opening, queens-gambit-declined
---


# Question
Title: Is any tool which allow analyse EPD file and add evaluation score per I want specify depth/multi PVL?
I tested some tools which allow analysis EPD files but they not work like I want:

1. I can use Arena but it will not annotate back EPD - it create protocol file.
2. I can use SCID vs PC but it will not allow to set depth for EPD file.

I found some Python script but it also not support depth and multi PV.

I can write such tool by I do not want duplicate known software. Do you know any tool which allow analysis EPD files.

# Answer
> 1 votes
With GradualTest, you can use it to control an engine to analyze a set of positions. The only version available through web.archive is 2.4 (a compiled version and program source) but exists version 2.6. The author is Gunnar Malin, available in GitHub.

Its syntax is: GradualTest \[switches\]

\** switches:

```
/a -    Init time in second, default=2.
/c -    Command to reset hash. Defaults to 'new'.
/e -    Method to set up the board. Values: edit, cbedit or setboard.
        Default=setboard. (cbedit is used if the engine have implemented
        Chessbase's method of edit.)
/i -    Input file to be tested.
/o -    Output file.
/s -    Init string for the engine. Defaults to
  'xboard\nhard\neasy\nnew\nlevel 1 1440 0\npost\n'.
/t -    Time to use at each position.
/w -    File to write positions with move not found.
/g -    File to write positions with only good moves
/u -    Use the UCI protocol.

```

It write also the following epd fields:

```
acd - Depth of the search for the pv line.
acn - Number of node serched for the pv line.
acs - Seconds searched for the pv line.
ce  - Centipawn evaluation of the pv line.
pm  - The best move from the engine.
pv  - The last pv line (pv=Predicted Variation).

```

With crafty (a winboard engine) I configured it in 'crafty.rc', sd=21 for instance, but with enough time to reach a depth of 21 ply. When the time to reach this depth was inferior than the time provided with GradualTest, the program somehow knows that position analyze has finished and proceded with the following position.

---
Tags: analysis, stockfish
---


title: Advancing the c6 pawn in the Caro-Kann

text:
# Question
Title: Advancing the c6 pawn in the Caro-Kann
I am having trouble understanding when Black should move c5 in The Advanced Variation of the Caro-Kann. I have posted two games of mine below:

In this first game, after the seventh move of White, the computer has no quarrel with the pawn advance c5 (though I played Ne7). However, here:

Which is a really similar position, if I play c5 (on the 8th move),Stockfish tells me it is not the right thing to do, but rather I should have played Ne7 which is a move also acceptable in the former position.

My question is: does anyone know when is the advance c5 appropiate? I cannot see any reason why these positions should be differently evaluated at all.

I mean in the second position I find no particular reason why playing c5 which in case of being captured allows the direct development of my kingside bishop can be a bad thing at all.

# Answer
The knight on c3 is the difference. In the second position, White can exploit superior development by quickly opening the centre with c4. It's not easy for Black to arrange castling.
> 14 votes

---
Tags: caro-kann
---


# Question
Title: Are a pair of bishops of the same color usually worth less than a pair of bishops of different colors?
People have been discussing about the value of a pair of two bishops. I am wondering if two bishops are of the same color, are they generally worth less than a pair of bishops of different colors?

Here are some thoughts:

* A pair of two bishops of the same color cannot checkmate the king.
* A pair of two bishops of the same color can stand in some same diagonal protecting each other. Is it a solid way to defend in some endgames?
* In some cases, both bishops can be "bad" and worth less.

# Answer
Two same-colored bishops can, as you note, protect each other. And unlike two knights, they can keep protecting each other indefinitely, even if one has to move. But that doesn't overcome their drawbacks.

The power of the two bishops is often because one can reach the squares the other cannot. With a mostly empty board, one of the two bishops can often control *any* square on the chessboard in one move. But if the two bishops are the same color, they lose this property. The two same-colored bishops can't do much that one bishop couldn't do, and really can't do much that a bishop plus another minor piece couldn't do.

As you noted, the two same-colored bishops cannot checkmate the opponent's king. There are other situations which also become draws if one side has two bishops of the same color instead of two different bishops. Bare king vs. two same colored-bishops and a rook pawn where the queening square is the wrong color is a draw. Two same-colored bishops and a pawn vs an opposite colored bishop is also an easy draw (there's no way to prevent the bishop from simply exchanging itself for the pawn.)

If you have a situation where you have two bishops vs bishop and knight (with some pawns on the board), then if you can arrange for a particular bishop to exchange itself for the knight, you can control whether or not the endgame will be a drawish opposite-colored bishops endgame. But if the two bishops are the same color, that option is not available; the bishops either are or aren't the same color as the opponent's.
> 4 votes

# Answer
A look at this position should make it clear that two bishops on the same color are usually worth less than a pair of bishops on opposite colors.

```
B6k/1B5P/2B5/3B4/4B3/5B2/6BK/7B w - - 0 1

```

This position is drawn because of the wrong rook pawn, even though White is comfortably ahead in material. If one of those Bishops were on a dark square, White wins easily.
> 4 votes

---
Tags: bishops, point-value, bad-bishop
---


# Question
Title: What is the least number of knights needed to cover the entire board?
I’ve seen the solutions to the lowest amount of queens, bishops, and rooks are needed to cover an entire board, as in they can attack all squares and are the only type of piece on the board. What is the solution for this with knights?

# Answer
> 25 votes
Depending on whether occupied squares need to be covered as well, the number is:

---

```
[Title " 12 knights, Without Covering Occupied Squares"]
[FEN "8/5N2/1NN1NN2/2N5/5N2/2NN1NN1/2N5/8 w - - 0 1"]

```

---

```
[Title " 14 knights, With Covering Occupied Squares"]
[FEN "8/2N1NN2/2N1N3/2N3N1/2N1N3/1NN1NNN1/8/8 w - - 0 1"]

```

---

Problems like this are called *domination problems* and solutions for knights and other pieces as well as a reference are given on the wikipedia page on mathematical chess problems

---
Tags: theory, problems, knights
---


# Question
Title: Is my representation of the Pirc Defense correct?
I tried to represents all the main lines of the Pirc Defense to play at a 2000 ELO level. Am I right with the following tree? What I mean by right is I wonder if I do not miss any popular line or choose a bad move at some level.

# Answer
If you are aiming to use this tree for practical use at 2000 level, you should start in the Pirc tabiya position after 1.e4 d6 2.d4 Nf6 3.Nc3 g6. That's where it all starts, with main choices being 4.f4, 4.Be2, 4.Be3, 4.Nf3, 4.f3. (*edit: Also 4.Bg5, 4.Bc4 and even 4.Bf4 as pointed in comments. And also 4.g3 and 4.h3*)

That way, you will not be confused by games without ...g6 at all, like the Philidor 3...e5 or some moderns with 3...c6, 4...Qa5.

I don't think the 1.e4 d6 2.d4 e6?! branch will ever be useful to you. With Black, you won't ever want to play this. With White, if you face it you can tackle it by following general rules, and in any case a tree is not useful there. Also, I wonder how this very obscure sideline appeared in your tree. If you use popularity to select lines, have you consider how far 2...e6 lies behind 2...Nf6 ? Have you restricted your base to tournament play, if possible above a certain level (say, 1800) ?

If need be, you can build a separate tree for early deviations, like 2.Nf3, 2.Nc3 or 2.f4 - keeping in mind that they will often transpose later in your main tree in case of d2-d4. But if you have practical purposes, you want to get rid of parasitic information. That will also allow you to go deeper that move 5 - which is mandatory at 2000 level !
> 1 votes

# Answer
After ...g6, playing Be2 and h4 with white is a popular option which is missing in your tree
> 0 votes

---
Tags: opening, pirc-defense
---


# Question
Title: Why doesn't white play Bd2 after this ...Qa5+?
I was looking at an analysis which shows this position ( from Bacrot - McShane 2018). At this point Black just played `...Qa5+`, and the only moves that are analyzed for white are `Kf2`, `c3` and `Qd2`.

This is not the first time I see such a position, and I never understood why `Bd2` is not even considered. As a black french player, I often discard moves like `...Qa5+` because it looks superficial to me after `Bd2`. But by looking at these games, it clearly looks like I'm missing something important here.

Any pointers ?

```
r1b1kb1r/3n1ppp/p1n1p3/qpppP3/3P1P2/4BNP1/PPP1N2P/R2QKB1R w KQkq - 1 10

```

# Answer
> 6 votes
The point here is that Bd2 blocks your queen's mobility and also leaves the defense of the d4 square. So after say Qb6 you pretty much have to go back with Be3, which will move closer to a draw by threefold repetition if blacks continues again with Qa5+.

Also if after Qb6 you play c3 instead of going back with the bishop, now your bishop is not well placed, and black's Queen on the other hand is very good on b6. So its safe to say that you kind of lost some piece coordination in the process.

One of ideas behind Kf2 is that you are pretty close to castling by hand with only two moves, such as Bg2 and Re1, and on the other hand black's Queen is misplaced on a5 and will most likely reroute later on to other squares.

All this being said, its still important to note that Bd2 is not a bad move. When i let Stockfish run for one or two minutes i see a diference of 0.1 for both moves. It gives 0.4 for Kf2 and 0.3 for Bd2, so its just an ok move.

# Answer
> 3 votes
Perhaps Black hopes to gain an advantage with the following sequence: --Qa5+, Bd2 Qb6, Be3. Now Black has the next move. If Black plays Qb6 in the first place, then White has the next move.

---
Tags: analysis, french-defense
---


title: What types of pawns are there?

text:
# Question
Title: What types of pawns are there?
I have heard of a few types of of pawns, such as passed pawns, thorn/fawn pawns, promoted pawns, and en passant pawns. But that is all I can remember. What other types of pawns are there?

# Answer
**Backward pawn**: a pawn that is behind its colleagues on a pawn chain. It cannot safely advance because it will be captured. These pawns are often a liability because they can be attacked. Example:

```
8/8/8/3p4/3P1P2/4P3/8/8 w - - 0 1

```

The pawn on e3 is backward. If Black e.g. places rooks on the e-file, White will have to guard the pawn with pieces, which is passive. Black also has a "captured square" on e4 where he can station his pieces and they cannot be pushed away by White's pawns.

**Central pawn**: a pawn on the two central files (d- and e-files). Compare "flank pawn".

**Connected passed pawns**: see passed pawn. Being connected means there are two passed pawns of the same color on two adjacent files. This is almost always a very strong trump.

**Doubled pawns**: two pawns on the same file. This is sometimes bad because they are inflexible. They can, however, guard key squares in the middlegame. Compare "tripled pawns".

**Flank pawn**: a pawn on the sides of the board (the a-c files and the f-h files). During the middlegame they usually less valuable than a central pawn because central control is an important tenet of chess strategy. Compare "central pawn".

**Hanging pawns**: two adjacent pawns side-by-side, with no other pawns on the adjacent files. They guard squares and mark out space. Example:

```
8/8/8/2pp4/8/8/8/8 w - - 0 1

```

Black's two pawns (note no pawns on b- and e- files) are hanging pawns. Black will try to keep them in place since they control squares, while White will try to force one of them to advance. If White succeeds, then the Black pawns leave behind a hole, e.g. if Black is forced to play ...d4, then the c4-square becomes a weak square White can occupy.

**Isolated pawns**: a pawn without a friendly pawn on its adjacent files. These are usually a liability because if they are attacked, they have to be defended by pieces, not pawns.

**Outside passed pawn**: see also "passed pawn". This refers to a passed pawn that is far away from the action. For example, if there's an ongoing Kingside attack, then any passed pawn on the queenside would be extra valuable, because the defender needs to balance between using its pieces on the kingside and using them to restrain the pawn.

**Passed pawn**: a pawn that has no enemy pawns that are in front of it on its same file as well as on files to its left and right. These are generally trumps because the opponent needs to use pieces to stop them from queening.

**Thorn (fawn) pawns**: as far as I know, this terminology only exists in the computer chess community. They refer to protected pawns on the 6th rank that are blocked by another pawn. Example:

```
6k1/5p2/4pPp1/4P3/8/8/8/8 w - - 0 1

```

The White pawn on f6 is a "fawn". It attacks an important square around Black's king, and also makes e7 (usually an important square for Black's pieces to maneuver) inhospitable. Black would love to be rid of it, but it's protected by the pawn on e5. That makes it a "thorn" in Black's position. As far as I know, "fawn" came about as a mispronunciation of "thorn".

**Tripled pawns**: three pawns on the same file. This is almost always bad because they can be easily attacked and none of the pawns can defend each other. Compare "doubled pawns".
> 9 votes

# Answer
passed pawns: When there is no enemy pawn on the adjacent file(s), it's called a passed pawn.

> https://en.wikipedia.org/wiki/Passed\_pawn

Promoted Pawn is when one player's pawn goes to the end of the enemy camp and you can choose a piece (Queen, bishop, rook, knight) you wish (except the king or a pawn itself)

en passant: Better to show with an example

> https://en.wikipedia.org/wiki/En\_passant

Isolated pawn: When you don't have any pawns in the adjacent file but there are enemy pawns either on the same file or on the adjacent ones.

> https://en.wikipedia.org/wiki/Isolated\_pawn

There are more pawn types i.e. Isolated queen pawn, hanging pawns but for a beginner it's hard to explain and it's not too relevant if you play chess for fun.
> 2 votes

---
Tags: pawns, terminology
---


# Question
Title: Any online site with limited number of games per day like chess.com or chess24
I have a problem that when I start to play I cannot stop, and I am looking for some good online chess web site that have limited number of rated games per day for, lets say non premium user, or something like that. Like thay have for tactis.

# Answer
> 2 votes
I have heard others make the same complaint and a friend decided to use the Makua software which will limit your computer time. There is probably other software that does the same, mostly for parents to limit their kids but you can use it on yourself.

---
Tags: online-chess
---


# Question
Title: In King's gambit, is Fisher's conclusion that "3...P-KN4 ... is inexact" inexact?
I was reading A Bust to the King's Gambit by Bobby Fischer. The game starts with

1 P-K4 P-K4 2 P-KB4 PxP 3 N-KB3

```

  [FEN "rnbqkbnr/pppp1ppp/8/8/4Pp2/5N2/PPPP2PP/RNBQKB1R b KQkq - 0 3"]

```

Bobby Fisher commented that

> "the move I played 3...P-KN4 against Spassky, but this is inexact because it gives White drawing chances in the ensuing ending: e.g., 4 P-KR4 P-N5 5 N-K5 N-KB3 6 P-Q4 P-Q3 7 N-Q3 NxP 8 BxP B-N2 and now 9 P-B3! (replacing Spassky ’s 9 N-B3) 9...Q-K2 10 Q-K2 B-B4 11 N-Q2 leads to an ending where Black’s extra Pawn is neutralized by White’s stranglehold on the dark squares, especially KB4."

It seems that the move 3...P-KN4 is still played frequently even today (even more popular than Fisher's recommended move P-Q3). So does this mean that Fisher's conclusion that "3...P-KN4 ... is inexact" inexact?

# Answer
> 1 votes
Apparently instead of 5...Nf6 in the line Fischer gave, 5...d6 6.Nxg4 Be7 is superior for Black.

You might look to Shirov for what is best in the King's Gambit. He gave 1.e4 e5 2.f4? in his book and said "Prove me wrong". In the past I saw him play a 3-minute game against 3000 rated computer on ICC in the King's Gambit and he crushed it.

---
Tags: opening, kings-gambit, fischer
---


# Question
Title: Why different openings are used by computer players?
If few best computer players would be playing against themselves, chances of white winning would depend on the opening used. That way after simulating thousands of games the best opening would be found that is strictly better than the others. Is there a flaw in this procedure? Has this ever been done before?

# Answer
> 2 votes
You may underestimate the number of games you need to determine the "best" opening by simulation. The differences between different openings are very small and to get a solid statistical judgment a few thousand games for each opening may be insufficient.

Then comes the question of the best response: There is an opponent, after all, and to build an opening book you must test for the strongest responses.

Still, this is all statistical and we know that it is not possible to solve chess computationally at the time being. A deep analysis may find a flaw in the "best" opening that is out of sight for current chess engines.

To your last question: For the chess variant "Schoolbook" (a variant of the Carrera-Capablanca type with rook-knight and bishop-knight compounds) its author Sam Trenholme has started to build an opening book using the method you propose, see http://www.chessvariants.org/index/msdisplay.php?itemid=MSschoolbook (comment at the bottom of the page).

# Answer
> 1 votes
Such a process would only find out which opening works best against the current version of itself. Nobody cares how well a computer plays against itself.

For some computer vs computer events (like TCEC), it is common practice to pick some opening position after 8 moves or so, and then play without opening book.

For *customers*, people who buy engines to play games against it, it is most important that it plays a wide variety of openings (variety is more fun), and that it is very up to date with current theory, for practice reasons.

So the main people interested in really great opening books for computer vs computer play are the kind of people who run their engines 24/7 on sites like Playchess to play against other computers, trying to improve their computers' ratings. They basically do this process manually, by watching the results and updating the opening books by hand where needed.

And on top of all that, remember that chess is most likely a draw. All the very theoretical, forced, deep lines that computers are great at analyzing out (like the Najdorf Poisoned Pawn, say) tend to lead to forced draws in all lines. Once everybody knows too much, they have to switch to something less well known.

# Answer
> 0 votes
If the question is asking why computer engines don't use much narrower opening books that could theoretically be analyzed deeper (and thus be objectively 'better'), the answer is simply that it actually makes the engine weaker because the chance of leaving the book becomes greater with a deep-but-narrow book (as suggested) instead of a shallow-but-broad one.

You could come up with an incredibly detailed book for one specific mainline opening (and some people have tried this, a notable example being for the Halloween Gambit), but there are several problems:

* If the opening your engine will play is known because there's really only one line used, it's easier to research that and include a refuation in a competing engine's book.
* If your engine only has a very narrow book, then it's relatively easy to generate an opening book that is broader and using a small amount of randomness in the engine would provide a fair chance of deviating and staying in book long after your engine is thinking for itself (which is generally a bad idea for an engine in the opening).
* If your engine knows a certain opening up to move 50, then it's not difficult for a competitor to take that book and expand that one opening up to move 55, thereby having a decent advantage. It's a real problem when your book contains thousands of different lines, though.

As a result of these, having a broader book is a benefit both offensively (you might be in book longer) and defensively (less likely to be brought out of book quickly), and requires only a small sacrifice in depth.

# Answer
> 0 votes
Time, availability of faster computers, and progress in Artificial Intelligence have invalidated my previous answer.

With Alpha Zero and Leela Zero we now have programs learning Chess strategy and openings from intensive self-play and giving winning percentages for moves and positions.

It is possible **now** (i.e., in 2018).

EDIT: However, even the above-mentioned engines have not yet solved Chess. They also produce quite a variety of opening lines and do not slavishly play one and the same line every time.

# Answer
> 0 votes
Yes, there's a flaw, and it's that the opponent also has a move. At best, you can only choose your first move (and only then if you are White). After the first move, because the opponent is also trying to maximize his chances of winning, he's not going to pick an opening which you win more often than not. Therefore you can't just find the opening that gives you the best result when you play against yourself, and play only that opening - the opponent will not allow it.

At best, you might be able to say "with 1. e4 I maximize my chances of winning", but that's already done by all computers.

---
Tags: opening, engines
---


# Question
Title: PGN-Extract output each game to a separate file with name like opponentA-opponentB.pgn
How can I use PGN-Extract to split a multi-game pgn into separate files with just one game per file. With the pgn being named for the opponents? Like opponentA-opponentB.pgn

# Answer
To a limited extent, you can do something like this already using the -Tp argument which selects games by a particular player. So:

pgn-extract -TpLeko --output Leko.pgn games.pgn

but there is not currently (2018.12.19) a way to have the file names generated automatically from the contents of the source file. Without a way to bound the number of players of interest this would require a lot of file opening and closing for a large input file. Some thought would also need to be given to how player names are mapped to file names.
> 1 votes

---
Tags: pgn
---


# Question
Title: Is the result in mini-chess known with perfect play?
I do not know, if "mini-chess" is the official name of the game I am talking about.

In mini-chess, the players only start with the pawns (In particular, there are no kings!)

* The players play the moves alternate, as in the usual chess.
* If a player manages to get a pawn to the opponent's back rank, he immediately wins.
* If a player cannot move, he loses.
* En passant is like in the usual chess.

Is it known which player wins with perfect play ?

# Answer
> 10 votes
The game is also known under the name pawns-only chess. There is a variation of this game called breakthrough that has more strategical depth by allowing the pawns to also move diagonally.

Since I had already implemented breakthrough, it was very straightforward to add an implementation of pawns-only chess to my Stockfish fork for fairy chess variants (actually I only had to define the rules in a simple structure, see the commit). I have run a single-threaded search for ~10 hours using 2GB of RAM, which yielded a mate score for all first moves, so the results should be reliable, although they are no strict mathematical proof, because Stockfish does forward pruning in its tree search.

The results of Stockfish's search state that the moves **1.b4, 1.c4, 1.f4, and 1.g4 are winning for white, whereas all other first moves are a win for black** with perfect play. See the input and output below for details. Since the search was single-threaded and depth-limited, the results should be reproducible.

While writing this answer, I found that someone else independently had obtained the same results, see his chess stackexchange answer and github repository.

input:

```
setoption name hash value 2048
setoption name multipv value 16
setoption name UCI_Variant value pawnsonly
position startpos
go depth 40

```

output (truncated):

```
info depth 40 seldepth 38 multipv 1 score mate 18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv b2b4 g7g5 c2c4 f7f5 d2d4 g5g4 e2e3 g4g3 f2g3 e7e6 g3g4 f5g4 e3e4 d7d6 d4d5 e6d5 e4d5 h7h6 a2a4 g4g3 h2g3 h6h5 b4b5 b7b6 g3g4 h5h4 g4g5 h4h3 g2h3 a7a5 b5a6 c7c6 a6a7 c6d5 a7a8
info depth 40 seldepth 36 multipv 2 score mate 18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv g2g4 b7b5 f2f4 b5b4 e2e4 c7c5 d2d3 h7h6 a2a4 b4a3 b2a3 g7g6 h2h4 f7f6 f4f5 g6g5 h4h5 a7a6 c2c3 e7e5 f5e6 d7e6 d3d4 c5d4 c3d4 f6f5 e4f5 e6f5 g4f5 g5g4 f5f6 a6a5 f6f7 g4g3 f7f8
info depth 40 seldepth 40 multipv 3 score mate 20 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv f2f4 c7c5 e2e4 h7h5 c2c4 d7d6 g2g3 g7g6 f4f5 a7a6 a2a3 b7b5 b2b3 g6f5 e4f5 e7e6 c4b5 a6b5 f5e6 f7e6 h2h3 d6d5 g3g4 c5c4 b3c4 h5g4 h3g4 b5b4 a3b4 d5c4 g4g5 c4c3 d2c3 e6e5 g5g6 e5e4 g6g7 e4e3 g7g8
info depth 40 seldepth 40 multipv 4 score mate 20 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv c2c4 f7f5 d2d4 a7a5 f2f4 e7e6 b2b3 b7b6 c4c5 b6c5 d4c5 h7h6 h2h3 g7g5 g2g3 d7d6 c5d6 c7d6 f4g5 h6g5 a2a3 e6e5 b3b4 a5b4 a3b4 f5f4 g3f4 g5g4 h3g4 e5f4 b4b5 f4f3 e2f3 d6d5 b5b6 d5d4 b6b7 d4d3 b7b8
info depth 40 seldepth 39 multipv 5 score mate -19 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv b2b3 c7c5 c2c4 g7g5 a2a3 f7f5 b3b4 d7d6 h2h3 f5f4 g2g4 f4g3 f2g3 h7h5 g3g4 h5g4 h3g4 e7e6 e2e4 c5b4 a3b4 e6e5 d2d3 a7a6 c4c5 d6c5 b4c5 a6a5 c5c6 b7c6 d3d4 e5d4 e4e5 d4d3 e5e6 d3d2 e6e7 d2d1
info depth 40 seldepth 37 multipv 6 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv e2e3 b7b5 g2g4 e7e5 f2f4 e5f4 e3f4 c7c5 f4f5 d7d6 a2a3 d6d5 b2b3 h7h6 a3a4 b5b4 a4a5 a7a6 h2h3 g7g6 f5g6 f7g6 h3h4 c5c4 g4g5 h6h5 b3c4 d5c4 d2d3 c4d3 c2d3 b4b3 d3d4 b3b2 d4d5 b2b1
info depth 40 seldepth 37 multipv 7 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv a2a4 g7g5 f2f3 c7c5 a4a5 d7d5 e2e4 d5d4 e4e5 h7h5 g2g3 g5g4 f3f4 e7e6 f4f5 e6f5 d2d3 b7b5 a5b6 a7b6 c2c4 d4c3 b2c3 b6b5 d3d4 c5d4 c3d4 b5b4 e5e6 f7e6 d4d5 b4b3 d5e6 b3b2 h2h3 b2b1
info depth 40 seldepth 37 multipv 8 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv d2d3 g7g5 d3d4 b7b5 d4d5 a7a5 e2e3 h7h5 f2f4 g5f4 e3f4 h5h4 c2c3 a5a4 b2b3 a4b3 a2b3 e7e6 c3c4 b5b4 g2g4 h4g3 h2g3 f7f5 c4c5 e6d5 g3g4 f5g4 c5c6 d7c6 f4f5 g4g3 f5f6 g3g2 f6f7 g2g1
info depth 40 seldepth 37 multipv 9 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv h2h4 b7b5 g2g4 c7c5 c2c3 e7e5 f2f3 d7d6 d2d3 d6d5 e2e3 c5c4 d3d4 e5d4 e3d4 f7f5 g4f5 h7h5 f3f4 a7a6 b2b4 c4b3 a2b3 a6a5 f5f6 g7f6 c3c4 d5c4 b3c4 b5c4 f4f5 c4c3 d4d5 c3c2 d5d6 c2c1
info depth 40 seldepth 37 multipv 10 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv f2f3 g7g5 c2c4 f7f5 e2e3 e7e5 b2b4 f5f4 e3f4 e5f4 c4c5 d7d6 d2d4 d6c5 d4c5 c7c6 a2a3 a7a6 a3a4 h7h6 g2g4 f4g3 h2g3 h6h5 b4b5 h5h4 g3h4 g5h4 b5a6 b7a6 f3f4 h4h3 f4f5 h3h2 a4a5 h2h1
info depth 40 seldepth 37 multipv 11 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv g2g3 g7g5 g3g4 c7c5 a2a4 d7d5 a4a5 e7e6 b2b3 e6e5 c2c3 e5e4 d2d3 e4d3 e2d3 d5d4 c3d4 c5d4 b3b4 a7a6 h2h3 f7f6 f2f3 h7h6 b4b5 a6b5 h3h4 g5h4 a5a6 b7a6 f3f4 h4h3 f4f5 h3h2 g4g5 h6g5
info depth 40 seldepth 39 multipv 12 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv h2h3 b7b5 h3h4 f7f5 a2a3 c7c5 b2b3 d7d5 c2c3 c5c4 b3c4 d5c4 h4h5 e7e5 d2d3 c4d3 e2d3 a7a5 g2g3 a5a4 f2f3 h7h6 g3g4 f5f4 g4g5 h6g5 h5h6 g7h6 d3d4 e5e4 f3e4 f4f3 d4d5 f3f2 e4e5 f2f1
info depth 40 seldepth 37 multipv 13 score mate -18 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv d2d4 b7b5 h2h3 g7g5 e2e3 h7h5 e3e4 f7f6 d4d5 a7a5 c2c3 h5h4 b2b3 b5b4 c3c4 c7c6 d5c6 d7c6 c4c5 e7e6 g2g4 h4g3 f2g3 f6f5 e4f5 e6f5 h3h4 g5h4 g3h4 f5f4 h4h5 f4f3 h5h6 f3f2 a2a4 f2f1
info depth 40 seldepth 35 multipv 14 score mate -17 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv e2e4 g7g5 d2d4 b7b5 f2f3 h7h5 c2c3 f7f6 b2b3 e7e6 d4d5 e6d5 e4d5 f6f5 g2g3 g5g4 f3f4 a7a5 a2a3 a5a4 d5d6 c7d6 b3a4 b5a4 c3c4 d6d5 c4c5 d5d4 c5c6 d7c6 h2h3 g4h3 g3g4 h5g4
info depth 40 seldepth 35 multipv 15 score mate -17 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv c2c3 b7b5 e2e4 g7g5 d2d4 a7a5 f2f3 c7c6 g2g3 d7d6 d4d5 c6d5 e4d5 e7e6 h2h4 g5h4 d5e6 f7e6 g3h4 h7h5 b2b3 b5b4 c3b4 a5b4 f3f4 d6d5 f4f5 e6f5 a2a3 b4a3 b3b4 a3a2 b4b5 a2a1
info depth 40 seldepth 35 multipv 16 score mate -17 nodes 52290435219 nps 1359031 hashfull 1000 tbhits 0 time 38476253 pv a2a3 b7b5 e2e4 g7g5 d2d3 a7a5 d3d4 h7h5 f2f3 f7f6 e4e5 f6e5 d4e5 a5a4 g2g3 e7e6 h2h3 h5h4 g3h4 g5h4 b2b4 a4b3 c2b3 c7c5 a3a4 b5a4 b3a4 c5c4 a4a5 c4c3 a5a6 c3c2 f3f4 c2c1

```

# Answer
> 2 votes
The game you describe reminds me of Dawson's chess where the pawns are just one step apart and no en passant is allowed.

This game is instensively analysed and the winner depends in a non-trivial way on the length of the pawn chain!

# Answer
> 1 votes
I suspect that Black should win.

A strategy for Black is to repeat moves and keep symmetry. Since W has no breakthrough idea, W's best bet is to keep sacrificing pawns. Black could grab the first W pawn and then when W sacs a second one, offer B's fifth rank pawn as a counter-sac - using the idea that this pawn can reach W's back-rank faster. B recaptures W's second pawn only when W captures this pawn. After W sacs enough pawns, B can queen first.

---
Tags: chess-variants, solving
---


# Question
Title: Good follow up to 1.d4 Nf6 2. e3 for black
I play the nimzo Indian defence, and so in response to 1.d4 I play Nf6, planning on playing e6 and Bb4. However, if they follow up with any other moves, I am at a bit of a loss as to what to play. I tend to just play d5 and develop my pieces, but I was wondering if there was any other good opening I could use in response to that.

# Answer
> The Nimzo-Indian can be closely paired with The Queen's-Indian, or The Bogo-Indian, or much less closely paired with the Benoni.

Lets forget about the Benoni for now and focus on the other two options.

In the Bogo and Nimzo you see Black's Bishop going to b4. The general idea is to fight for the e4 square, but in some cases Black will trade the Bishop off and then put his own pawns on dark squares (d7-d6 and e6-e5). When you play an early d5 as Black you kill this secondary plan -- which is totally fine but something to keep in mind.

In the Queen's Indian you target e4 with Bb7 and the other Bishop usually goes to e7. Here you are also fighting for e4 and because you aren't taking out Whites Queen's-knight who usually will attack the e4 square, you need help of a pawn and d7-d5 is often played.

> So, what's with the Benoni?

If White is avoiding c4 and Nc3 then they are playing slowly and it is not critical. If they play c4 but avoid Nc3, say 1.d4 Nf6 2.c4 e6 3.Nf3 then many players like to play 3...c5! Since White has put their Knight on f3 a lot of aggressive lines with f2-f4 are avoided.

Nick De Firmian paired the Nimzo with the Benoni. Karpov paired the Nimzo with the Queen's Indian. Fischer sometimes played a hybrid of the Queen's Indian and the Nimzo Indian.

The smallest amount of theory to know would pair the Nimzo with the Bogo-Indian.
> 1 votes

---
Tags: opening, nimzo-indian
---


# Question
Title: Do someone found if there exists a ever winning side?
Have chess science advanced enough to determine if there is a a chess side that always win if both sides are given unlimited time to think for the next move?

Note the question Is not dumb as might seem. We have been speaking of consequences of that all the evening and we wanted to share this idea to the community. Even algorithms that do the next computation knowing the best possible game but given limited moves to try to force the opponent out of the known best possible game.

# Answer
> Have chess science advanced enough to determine if there is a a chess side that always win if both sides are given unlimited time to think for the next move?

Chess engines are imperfect (for now at least), we've seen it a lot of times with terrible blunders, such as Leela blundering its queen against Andrew Tang, Stockfish getting crushed by AlphaZero making it look like a joke and so on. So no, there isn't a technology that allows us to know if there is a *winning side*. What we know though is that white does have the advantage because of the first move, but that's only temporary.

Also time doesn't really matter, what matters are the moves played, if black played the absolute best moves, we currently know that it would end in a draw. But again, we can't know if that would be the case with a perfect game.
> 0 votes

# Answer
A) Absolute best moves are synonim of perfect game. B) Absolute Black best moves are nulling the temporary White advantage. C) A clear advantage is mostly not sufficient to win a game because chess rules. A+B+C = perfect game is always draw. At now it is only a conjecture, but the demonstration is not so far.
> 0 votes

---
Tags: theory, computer-chess, game-complexity
---


# Question
Title: Why don't the ratings of Carlsen and Caruana change after 4 games in the WCC 2018?
By now there were 4 games and all were drawn. Should it not mean that Caruana should get points?

# Answer
The exact workings of FIDE rating calculations can be found in the official rules. As you can see in Table 8.1b, a rating difference of 3 points (as is the case with Carlsen-Caruana) means that both players have the same expected score: 0.5. The value of ΔR, which is the expected score minus the result (in the case of a draw, 0.5) is therefore 0.5-0.5=0, i.e. no change in rating.

If instead their difference were 4 points rather than 3 (meaning that Carlsen's expected score would be 0.51 instead of 0.5), a draw would mean that his ΔR would be -0.01. With a K value of 10 (as he has a rating above 2400), his gain/loss would therefore be -0.01\*10. In other words, a draw with a rating difference of 4 would mean that he would lose 0.1 rating point (whereas Caruana would gain 0.1 point).
> 9 votes

# Answer
FIDE apply a monthly update of rating but, during matches or tournaments, the ratings of participants it remains unchanged until the event is completed.
> 1 votes

---
Tags: rating, world-championship
---


# Question
Title: Is 80 points FIDE equivalent to twice as good a player?
I read somewhere that if you're around 80 points better than another player, statistically you should get around twice as many points against the same opposition. This impressed me because it's not how we generally think about ratings. I worked out that Magnus Carlsen is about 64 times the player I am, which sounds about right.

My question is, can anyone verify this using the mathematics of the Elo system?

# Answer
> 12 votes
Given the equation that models the expected score (already posted by Glorfindel), it is mathematically impossible for player **A**, rated *X*+80 to score twice as much as player **B** (rated *X*) against the same opposition (rated *Y*). The closest you can get is if *Y* is very high, in which case the odds of winning are vanishingly small but **A** has 58% higher chances than **B**.

If you change the rating difference to 120 points, then the assertion can be true, again given that *Y* is much higher. For example, if *X*=1000 and *Y*=2000, player **A** is expected to score 0.006 and player **B** 0.003. Also if **A** plays against **B**, the expected scores are 0.67 to 0.33, so in that sense you can say that a 120-point rating difference makes a player "twice as good". If we consider a less extreme value for *Y*, say 1400, then the expected scores are 0.166 for **A** and 0.091 for **B**, where **A** scores almost but not quite twice as much as **B**.

# Answer
> 13 votes
This can't be true. I (rated ~1900) expect to score 100% against a 1000 player. I don't think a 1980 rated user is able to score 200% against the same opposition.

In table 8.1b in the FIDE rating regulations, you'll find the expected scores corresponding to a rating difference. A rating difference of 80 corresponds to an expected score of 0.61, which is much lower than twice the 0.5 expected score for equally rated players.

The only point in the table where a rating difference of 80 corresponds to a doubled expected score is at the very end. Against opposition rated 500 points *higher* than you, your expected score is 0.04; against opposition rated 580 points higher it's only 0.02. The expected score formula is explained on Wikipedia:

> If Player A has a rating of RA and Player B a rating of RB, the exact formula (using the logistic curve) for the expected score of Player A is
>
> EA = 1 / (1 + 10 (RB \- RA) / 400)

# Answer
> 1 votes
It depends on the FIDE ratings of the players. If Person A is rated 1300 and Person B is 1220, A is not twice as good as B. Conversly, Carlsen is rated 2843 FIDE, and I would argue he is at least twice as good as a 2763 player (if they played 10 matches, each match 10 games long, Carlsen would almost definitely win 9/10 to 10/10 matches).

The reason for this is that it becomes harder to keep increasing as you get a higher rating. 99% of chess players are below 2200, even though there's an extra 600 points above. The trend on a graph of rating vs #players is not linear; it is closer to an exponential decay function. There are vast number of players under 1400, but only an extremely select few over 2800 at a time (usually 5 players max).

Chess is a game where most people can go to roughly 1800ish with hard and dedicated work. However, only people with true talent can continue past that point. Then, once hitting 2000, an even smaller number of people can continue forward. This phenomena becomes stronger as you climb up the rating latter, which explains why such a small percent can ever make it to GM level.

As a result, if Person A and Person B are in a high rating bracket, Person A being 80 points higher indicates he truly has an additional "special something". Meanwhile, if A and B were in a low rating bracket, A being 80 points higher could be attributed to something like playing in a few more tournaments.

EDIT - Carlsen example fixed.

# Answer
> 1 votes
120 points of rating difference, are expected to produce 67% of game points for the stronger player. This apply for all ratings, so is true for a game of a 2800 vs 2680, as for a game of a 1600 vs 1480. Anyway, expected game points are useful to calculate rating variation, not directly the players comparision. If this really means "strong twice" or not, it is a subjective point of view.

---
Tags: rating
---


# Question
Title: Plans for black when White castles short in the Sicilian dragon
What are the plans for Black when White castles short in the Sicilian dragon? Very broadly speaking I am thinking of two plans.

1. Go for a King's Indian like kingside attack with e5 played at a suitable time.
2. Do a6-b5 and generate queenside pressure.

Is one more sound than the other? Or is it just a question of style? What should I be aware of before deciding which one to adopt?

# Answer
Pretty much any open Sicilian when both sides have castled King-side Black can seek counter-play against the center by undermining the Knight on c3 with b5-b4 ideas or if allowed Rxc3 exchange sacs.

Also thematic is trying to play d5. Bent Larsen said something to the effect that the Sicilian was a positional trick where you trade a wing-pawn for a center pawn, then with 2 center pawns vs one you will be able to eventually take over the center.

I haven't seen games where Black has prospects of a king-side attack in a Dragon where White castled King-side. Usually White is trying to attack there with f2-f4 etc.
> 3 votes

# Answer
> What are the plans for Black when White castles short in the Sicilian dragon

Good news. Black's position is fine; a useful half-open c-file without risks being blow off on the king side. White's short castling is a weaker plan to fight for advantage.

Black has decent chances to take over the board:

* Move your rooks to the c-file
* Prepare for thematic d5 push
* Unblock the g7 dragon bishop

Black has stronger queenside chances while White is not significant better at kingside. I'd be happy to play as Black.
> 2 votes

---
Tags: castling, kings-indian, sicilian-dragon
---


# Question
Title: What would be the Elo rating of a computer which plays all optimal moves?
What would be the Elo rating of a computer which plays all optimal moves?
By playing all optimal moves, I mean that it always wins if possible, or else draws if that is the best result possible.

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

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

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

---

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

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

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

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

---

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

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

---

1 I haven't done all the calculations myself by hand. I just plugged the appropriate numbers into this calculator. It's entirely possible that the formula used there differs from the current FIDE rules, but the basic premise is the same even if the numbers are inexact.
> 19 votes

# Answer
This is extremely hard to say, because the initial position is probably a draw. Besides playing perfectly, the computer also has to *set problems* for the opponent.

If the position is a draw, then there may be fifteen different moves that don't lose. The computer will have no reason to prefer one over another, so perhaps it'll just decide to drop a pawn or so knowing it can hold all the endgames. Why not?

This is already very obvious when trying to use tablebases to learn how to draw worse endgames. In, say, Rook + Bishop vs Rook, the computer (playing the stronger side) will sometimes just give away the rook or bishop!

"Perfect chess" is hard to define.

I suspect that current engines, that aim for a good position, would very often get superior positions against perfect engines. They would just never manage to actually win them, of course. Against human grandmasters with some experience playing the perfect table-based engines, I suspect that perfect engines would have a lower TPR than current engines.
> 7 votes

# Answer
The max rating of a system is going to depend on the details of the system and who the participants are. There's not just one "Elo" formula, and the details can be important.

Under FIDE ratings regulation 8.54, "A difference in rating of more than 400 points shall be counted for rating purposes as though it were a difference of 400 points." This allows a rating to become arbitrarily high, regardless of the strength of the opponents - you can always get at least one rating point by winning.

Under the USCF correspondence chess ratings system, "Rating differences that exceed 350 points are figured as 350 points." So, similar to the FIDE system, points could continue to be gained even with a large ratings difference, allowing a rating to become arbitrarily high.

However, under the USCF rating system for OTB play, ratings are stored as floating points instead of integers, and there isn't a maximum allowable difference listed, allowing someone to gain a fraction of a point for a win against someone far below them.

The question then becomes: how often could the human get a point off the computer? If the human could, on average, get one point every 10,001 games (either a win or two draws), the computer's rating would stabilize at 1600 points above the human. If the human could get a point every 1,001 games, the computer's rating would stabilize at 1200 points above.

And if this ever moved out of the theoretical, then once it became clear that this computer is perfect, GMs would begin to copy its moves, especially in the opening but probably going into what would ordinarily be the middlegame. I think we'd start seeing draws much more often once this happens - it's much easier to draw if you're essentially playing it against itself for the first 20 moves, and you *know* the line to that point isn't losing.
> 1 votes

# Answer
5200 ELO or greater, based on this:
> -1 votes

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Tags: rating, elo
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# Question
Title: What's next after first 5 months and 700 points?
I started playing chess in July. I was at a 600 rating on Chess.com for a month. I started playing seriously in August and have played regularly (at least a few blitz and rapid games everyday). Currently, I am rated 1300 on Chess.com after 800 games(10 minutes). I seem to have moved past my blundering days (although still blunder every now and then). I also play shorter games on lichess (rated 1400 on blitz).

I haven't really read any literature yet. I started reading Logical chess by Chernev. I play the games out on the board and they are fascinating but I don't see how I can improve with them. Also, I do puzzles on lichess frequently. I haven't seen any significant changes in my thinking process recently when I play games. What's the next thing I should do?

My goal really is to be able to create and execute longer plans in the game while being able to read the opponents plan and defend. I was told this corresponds to the ~1900 rating range, so that would be my target (rating wise) by the end of 2019.

# Answer
> 4 votes
This is an open-end question. My recommendation is join serious face-to-face tournaments where you play games at the classical time control. Playing blitz is fun, but not a good idea for learning chess.

# Answer
> 1 votes
Unless you're Magnus Carlsen, you pretty much never move past the blundering stage. They just tend to be smaller blunders.

In addition to the advice in this answer, I highly recommend analyzing your own games. Those are two of the things that helped me jump from around a 1400 USCF rating, to eventually breaking 1700, before dropping back down to my current rating of ~1600. That still took me a few years, though, mostly because I was usually one of the two lowest rated players in the small local tournaments I played.

If you can get a coach, or even a stronger friend to train with in person, that is very helpful as well. They can more accurately pinpoint exactly what you need to work on to improve.

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Tags: learning, beginner, study, planning
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# Question
Title: Have there really been more books published on chess than any other sport?
> In the history of sport — and publishing — it’s not even close: one sport has had more books (and for that matter, magazines, tracts, pamphlets and handbills) published about it far more than any other: Chess.

Source: publishingperspectives.com

I often hear, but have never seen justification for, the claim that there are more books published on chess than any other sport.

My questions are:

1. Is this true?
2. What are the origins of the claim?

# Answer
## Is the claim true?

**No**. Using the Google Books Library Project, there are:

## Where does the claim come from?

From Wikipedia, the claim likely originated from H. J. R. Murray in 1913:

> In 1913, preeminent chess historian H. J. R. Murray wrote in his 900-page magnum opus A History of Chess that, "The game possesses a literature which in contents probably exceeds that of all other games combined."
> 2 votes

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

It stands to reason that there will be a large number of newspaper and magazine accounts about football.
> 6 votes

# Answer
I believe that there are many more books written on fishing than on chess, but chess has many books in print from days gone by.
> -2 votes

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Tags: history, books, statistics
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# Question
Title: Can't understand a sentence from Nimzowitsch's Chess Praxis
In the chapter "Centralization" of his Chess Praxis, Nimzowitsch writes

> The mechanics of centralization can be seen in the way that, after the necessary restraint of a possibly mobile opposing pawn center, we draw the noose tighter and tighter around the central squares...But if we manage to make this long-range action effective and establish some of our pieces in the center, then we should be really pleased with the success of our policy of centralization.

What does he mean by "*drawing the noose tighter*"? So far, I have come to conclusion that "*drawing the noose tighter*" means the "*long-range action*" mentioned in the next sentence and therefore some sort of pressure on the center exerted by long-range pieces.

# Answer
> 3 votes
After re-reading the chapter Centralization I think that Nimzowitsch meant the following:

* First you restrict the opponent's pawns
* Then you start impacting the opponent's center *from the distance* using long-range pieces (the so-called "*long-range action*")
* Then you start closer-range actions against the opponent's center (i.e. "*you draw the noose tighter*"), e.g. by occupying some central square

# Answer
> 2 votes
To understand his writing it is good to look examples. Let's take a line of the Nimzo Indian: 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 **Black restrains e2-e4**

4.Nf3 b6 5.e3 Bb7 6.Bd3 0-0 7.0-0 Bxc3 8.bxc3 Ne4 **Black centralizes his Knight**

9.Qc2 f5 **Black draws the noose tighter**

10.Nd2 Qh4 11.g3 Ng5 12.gxh4 Nh3 mate **Black is really pleased**

\[Event "?"\] \[Site "?"\] \[Date "????.??.??"\] \[Round "?"\] \[White "?"\] \[Black "?"\] \[Result "\*"\] \[WhiteELO "?"\] \[BlackELO "?"\]

1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 b6 5. e3 Bb7 6. Bd3 O-O 7. O-O Bxc3 8. bxc3 Ne4 9. Qc2 f5 10. Nd2 Qh4 11. g3 Ng5 12. gxh4 Nh3#

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Tags: terminology, aaron-nimzowitsch
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title: What are unsolved problems in chess?

text:
# Question
Title: What are unsolved problems in chess?
Are there any problems in chess that remain unsolved?

# Answer
You can try finding the perfect Babson: compose a problem with four main lines. They consist of a defensive promotion of a black pawn to a queen, rook, bishop or knight, which forces White to promote to the same piece type in each case.

Examples already exist, but they involve duals, which make them imperfect.
> 5 votes

# Answer
Is there a forced win for White?
> 7 votes

# Answer
Is it good or not for chess and the players if the World Championship match could be eventually decided by rapid, blitz, and armageddon?
> 2 votes

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Tags: theory, problems, mathematics
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title: Node Cap for Stockfish

text:
# Question
Title: Node Cap for Stockfish
I discovered something quite unusual when working with stockfish 10 chess engine in arena. The discovery leads me to ask: Why does Stockfish\_10\_x64 have a Node Cap when searching moves based upon amount of Nodes used?

# Answer
> 1 votes
To play a position, an engine is usually given a search depth. Arena always does this. Probably in your case the search depth was set to a limited number of nodes. You can check this by keying in CTRL+L. The adjust level box pops in. There, you can see how the depth was specified, whether a time limit, a nodes limit, a search depth limit or an infinite depth.

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Tags: engines
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title: Why queen traps happen so frequently?

text:
# Question
Title: Why queen traps happen so frequently?
I am aware that in most chess games the king is the one to be checkmated. Yet when playing many online chess games I have found the queen is the the one being checkmated. Is this simply another variation of chess?

# Answer
> 5 votes
The short answer: because it is the most valuable piece after the king.

The long answer: For a piece to be trapped two things must happen: you need to threaten to capture it, and you need to make this in a way it can't **escape** or be **protected** without loss of material or a positional drawback suck as mate.

1. For a piece to be protected effectively, the piece attacking it must be more valuable than the piece being attacked, so **any** piece can attack the queen and if there is a trade the attacker will gain a material advantage. **So other pieces can be protected in more ways than the queen.**
2. For a piece to be able to escape, it must be **able to move**, and it needs a **safe square**. The queen is the most mobile piece, but moving in straight lines, it can be easily blocked by another piece, and **any** piece can do this, since a trade would mean material loss for the defending side. **So the queen can be blocked in more ways than most pieces.** For a square to be safe for the queen, it needs to be free from attacks (except from the opposing queen), again, since any trades that happen after the queen moves to that square will result in material loss. Other pieces can move to squares attacked by stronger pieces, if the defender has another piece protecting that square. **So the queen has less safe squares available than most pieces.**

That sums it up, but there are MANY exceptions when you take into account the actual position, since a square can be safe if moving to that square uncovers a discovered attack with a mate threat, or many other situations.

# Answer
> 4 votes
Blundering away the most powerful chess piece is a common mistake. Many players would simply resign for a new game.

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Tags: rules, tactics, checkmate
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title: Sicilian dragon classic games

text:
# Question
Title: Sicilian dragon classic games
I am trying to collect a list of Sicilian Dragon classic games, which every dragon player must be aware. I would really appreciate if you could share some classics and also highlight the most important move/part in the game.

I am okay with either color winning. The two games where the dragon kills the Yugoslav that immediately spring to mind are Kasparov's dragon vs Viswananthan Anand in 1995 WC

http://www.chessgames.com/perl/chessgame?gid=1018626

http://www.chessgames.com/perl/chessgame?gid=1018628

# Answer
> 3 votes
Fischer - Larsen, Portoroz 1958 also known as "Slaying the Dragon" in his book, 60 Memorable games is recommended **required** reading.

The opening moves for the dragon, accelerated and hyperaccelerated dragon may be found in Parimarjan Negi's *e4 vs. the Sicilian: Vol 2*.

# Answer
> 2 votes
Karpov-Kortchnoi from the 1974 Candidates Final which turned out to decide the World Champion is a famous and appealing dragon game and part of chess history.

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Tags: sicilian-dragon
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title: Ideas for the English opening

text:
# Question
Title: Ideas for the English opening
I'm playing recently the English opening. specifically this line in the two knights variations

```
[FEN ""]
1.c4 e5 2.Nc3 Nf6 3.g3 Nc6 4.Bg2

```

But I find it difficult to see when it's advantageous to go queen side with `a3 b4` idea rather then play in the center with `e3` maybe `d4` later on.

Any thoughts ?

# Answer
This is a tough question and depends a lot on where the f8 Bishop is going (b4, c5, e7, or even g7), as well as where is the Knight g1 is going (e2 or f3).

In the position of the diagram the most common move among top players is 4...Bc5. Then after 5.e3 with the idea to place the Knight g1 in e2 and to control the square d5 with the Bishop in g2, Black can still react by temporarily sacrificing a pawn with 5...d5 6.cxd5 Nb4 and a wild game. If Black prefers a more positional battle with 4...Bc5 5.e3 a6, then White prefers to expand on the queen-side: 6.Cge2 a6 7.0-0 0-0 8.a3 Ba7 9.b4 with a very flexible play.

Check this nice game between Nakamura and Grandelius at Gibraltar in 2015 (even if the move order is more subtle)
> 3 votes

# Answer
I am not a chess master so take this with a grain of salt. However, I also play the English quite often. Without taking a look at any computer, what I often play is as you suggested e3 to prepare d4 but probably first play Nf3.

I think that playing those moves or preparing a queenside expansion pretty much depends on the position, but in this particular position I would not consider doing this (a3 b4) at least for now. Note also that in some position a3 (not necessarily followed by b4) might be convenient to avoid the jump of the Black knight to b4, however, now (with the absence of Black bishop from f5) that does not look particularly dangerous.
> 2 votes

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Tags: opening, english-opening
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