# Question
Title: What was the point of Shirov's 47...Bh3?
One of the most famous moves ever is Shirov's 47...Bh3!! in Topalov - Shirov, 1998.

```
[FEN "8/8/4kpp1/3p1b2/p6P/2B5/6P1/6K1 b - - 0 47"]
[Event "Linares"]
[Date "1998"]
[White "Veselin Topalov"]
[Black "Alexey Shirov"]

```

I've always taken that for granted and never really thought about it. Can anybody give an explanation of why it is the best move?

# Answer
I interpret the question as follows

> How can a player arrive at ...Bh3?

This is tightly connected to the point behind ...Bh3. With a material advantage, black is clearly looking for a win. Yet, it is well known that opposite colored bishops give the defending side a strong chance to draw. Thus, precise play is required.

Black's plan is

1. Get the king to e4 by Ke6-f5-e4
2. Do d5-d4 to limit the enemy bishop
3. Push a4-a3-a2
4. Queen one of the pawns

White's plan is

1. Get the king to d4 by Kg1-f2-e3-d4
2. Prevent the enemy king from reaching e4
3. Prevent the enemy from pushing d5-d4
4. Prevent the enemy king from supporting the black a-pawn

Next, black has to answer the question

> What is the most direct way to make the plan work?

The key point is that black's bishop doesn't really help much in promoting the pawns. It is the king that plays the key role. Thus, sacrificing the bishop to win a tempo makes total sense! In addition, after gxh3, white can no longer create a passed pawn on the kingside! Thus, the bishop sacrifice wins a tempo and ruins white's counter-play. For example

```
[FEN "8/8/4kpp1/3p1b2/p6P/2B5/6P1/6K1 b - - 0 47"]

1...Bh3! 2.gxh3 Kf5 3.Kf2 Ke4 4.Bxf6 d4 5.Be7 Kd3 6.Bc5 Kc4! 7.Bd6 Kc3 8.Ke2 Kc2 9.Bb4 d3+ 10.Ke3 a3 0-1

```
> 14 votes

# Answer
What a great endgame to analyze!

Where should I start with???

> What was the point of Shirov's 47…Bh3?

We know that 3 healthy pawns win against a bishop in endgame.

Tablebases show the following endgame as won for Black , **if it is his turn to move**, by playing `Kf5` ( **the only winning move!**) :

```
[StartFlipped "0"]
[fen "8/8/4kp2/3p4/p7/2B5/8/6K1 b - - 0 1"]

```

Black will simply stretch White's pieces and win-it is a standard motif and I believe that any strong FIDE master ( or higher of course ) can win this endgame with **ease**.

Looking at the position after `...Bh3!!` we can see that either side's king side pawns play no significant role in the game, so we have the above endgame, **with "spectators" on the king side**.

Since we know that the endgame is won for Black **with inactive king side pawns** it is not hard for us to find `...Bh3!!`, as Black will implement the same winning plan like in the above endgame.

Still, I doubt Shirov knew the above endgame "by heart", so he had to calculate a lot to confirm that the "pawns vs bishop" endgame is won, thus "a tip of the hat" from me.

I personally would never even think of playing such a move, to be honest.

> Can anybody give an explanation of why it is the best move?

Since both sides king side pawns are spectators, it is really the above mentioned "pawns vs bishop" endgame. With 3 passed pawns Black **easily overloads White's pieces**, and forces a fast win.

I personally thought to play `...Be4`, but since I have 2 passed pawns, and my King is somewhat blocked, I had to work harder to force a win.

I played the below game against engine. Each time I finish playing one variation, I would set another and play it. Also I have added my own analysis of the moves computer refused to play. That way all the relevant moves would be covered. The key was for Black king going to the queen side, overloading White king and bishop by creating protected `a2` and `d3` pawns, after which Black reroutes king to the king side and grabs the pawns with decisive advantage. It is clear why this is longer and harder way of playing, then more straightforward way Shirov picked. Here are the lines:

```
[StartFlipped "0"]
[FEN "8/8/4kpp1/3p1b2/p6P/2B5/6P1/6K1 b - - 0 0"]

1... Be4 2.Kf2 (2. g4 Bf3 3.g5 fxg5 4.hxg5 Kf5 5.Kf2 Bh5 6.Bf6 Ke4 7.Ke1 Kd3 8.Be7 d4 9.Bc5 Kc4 10.Be7 Kc3 11.Ba3 d3 12.Bc1 Kc2-+) (2.g3 f5 3.Kf2 Kd6 4.Bd4 Kc6 5.Ke3 Kb5 6.Kd2 Kc4 7.Bb2 Kb3 8.Kc1 a3 9.Ba1 Kc4 10.Kd2 d4 11.Ke2 Bg2 12.Kd2 Kd5 13.Ke2 Ke4 14.Kd2 Bf1 15.Kc2 Bc4 16.Kd2 Kf3 17.Bxd4 Kxg3 18.Ke3 f4+ 19.Kd2 a2 20.Be5 a1=Q 21.Bxa1 Kxh4-+) 2...f5 3.g3 Kd6 4.Bb4+ Kc6 5.Ke1 Kb5 6.Bf8 Kc4 7.Kd1 d4 8.Kc1 d3 9.Kd1 Kb3 10.Bg7 a3 11.Bd4 a2 12.Kd2 Kc4 13.Ba1 Bc6 14.Bb2 Bb5 15.Bc3 Kd5 16.Ke3 Bc4 17.Ba1 Ke6 18.Kd2 Kf7 19.Kc1 Kg8 20.Bd4 Kh7 21.Kd2 (21.Kb2 Kh6 22.Be3+ Kh5 23.Ka1 Kg4 24.Bf4 Kf3 25.Kb2 Ke2-+) 21...Kh6 22. Ba1 Kh5 23.Ke3 Kg4 24.Be5 Bb5 25.Kd2 Kf3 26.Bc3 (26.Kd1 Ke3-+) (26.Kc1 Ke2-+) 26...Kxg3-+

```

It took me a lot of moves to win this endgame, and the pitfalls where you can squander your advantage are numerous-White indeed can offer some resistance.

Since king side pawns are irrelevant, we can roughly conclude that Shirov's way wins in 26 moves, according to tablebase, **without** giving White **any chance** to offer any resistance.

Hopefully this answer helped. If you have further questions leave a comment.

Best regards.
> 10 votes

# Answer
Topalov's 47. .. Bh3!? is not a novel concept, but the assumed 48. gxh3? gives up the game.

Proper play doesn't give Black the third and overwhelming passed pawn. The thematic-in-opposite-color-bishops draw is held with 48. g3 followed by bringing the king out to prevent the Black's king from invaded holds the draw.
> 1 votes

---
Tags: analysis, endgame, bishop-endgame, famous-moves
---


# Question
Title: Should I calculate on my opponent's time or on my time?
I play regularly 45+45 games with a duration between 2-4h. During my opponent's time I normally try to guess their moves or try to understand the position better. Regularly I have the problem that I reach the endgame too tired to calculate deeply and correctly.

On chess.com I read about the idea "think on their time, check on your own".The reason for this: "If you calculate on their time, you have a much bigger tree to calculate through - they prune it for you by making their chosen candidate move" (same link).

Are there more concepts about time management especially during your opponent's time to find a balance between time efficiency and exhaustion? Thanks!

# Answer
Of course there are times when it is correct to calculate on your opponent's time and times when it is not. What you need is some guidelines because sometimes it is even correct not to calculate on your own time!

* Don't calculate while you are in your opening prep
* Don't calculate when your move is completely forced. Be aware that recaptures are not forced. It is worthwhile spending at least a little time looking for a zwischenzug which could turn the game in your favour.
* If you can make a good guess as to what your opponent's next move is going to be then it is worthwhile to calculate on opponent's time
* If your opponent has several good alternatives and the position is complex then skip calculating on opponent's time, go and get a coffee, go to the bathroom if needed, or just walk around looking at other games / stretch your legs. You will save energy and feel the benefit when it is your turn.
* Recheck your calculations once but note that rechecking over and over again is counterproductive and tiring.
* If the game is relatively calm then use your opponent's time to think of plans for your opponent and work out how you will stop these plans before they can get going. This is a lot less tiring than calculating. Try and put yourself in their position and ask what you would try and do in their position. This is a key component of the way stronger players play.
> 25 votes

# Answer
Don't change the way you think based on which side is on move. You should always be thinking about your pieces, pawns, king safety, worries about the position, optimal squares, plans to improve your position or specific pieces, possible tactics, opponent's goals, comparing your pieces to the equivalent opponent pieces, etc. It's a mistake to separate thinking from calculating, they flow naturally together. From your thinking you will naturally start to wonder whether certain lines could work or not, in relation to the above considerations, and explore those further. Whose move it is is quite secondary.

The thinking is constant. You're just making moves when you're content enough with your analysis of that position, or when there seems little to gain from further analysis, and sometimes adjusting as your opponent plays specific moves as well.
> 0 votes

---
Tags: time-control, time-management
---


# Question
Title: Have any tournaments considered a draw to be a loss for both sides?
In most tournaments, a win is 1 point and a draw is 0.5 points for both sides. I'm aware of "armagadden matches" where a draw is 0 points for white, and 1 point for black.

Have there been any tournaments where a draw is 0 points for both sides?

This would seem to be another possible solution to the problem of too many draws, by removing any incentive to draw from both sides. (It might have a negative consequence of leading both players to play out draws for the full 50 moves hoping for the tiny off-chance of a blunder.)

# Answer
> 5 votes
> Have there been any tournaments where a draw is 0 points for both sides?

The answer is "Yes" and surprisingly enough the tournaments where this was the case were the very top world tournament, the world championships!

After Fischer won the title in 1972 by the score of 12½–8½ in a traditional best-of-24 competition with draws counting, he demanded for the next match that this be changed to one where draws didn't count (i.e. scored zero), the first player to win 10 games won the match unless he reached 9 wins first. FIDE rejected his unfair "draw-odds-with-no-draws" proposal but accepted his proposal that draws not count.

The number of wins to win the title was dropped from 10 to 6 and Karpov then won the 1978 title match with +6–5=21. In 1981 he won again with 6–2=10 but when the 1984 title match was terminated by FIDE president, Campomanes, after 48 games with the score on +5 −3 =40 in Karpov's favour the system was changed back to best of 24 games with draws counting for the rematch in 1985.

# Answer
> 5 votes
Never heard of. A few thoughts:

* As we all know :-), chess is a draw.
* win 3/draw 1/loss 0 tournaments do exist (same rule idea, less drastic).
* In Swiss tournaments, I say this would be an invitation to even more "Swiss gambit" (although evidently you can't overtake in the last round, as all scores are integer)
* It's also pointless for an 1:1 match, thus it probably could be tried only in a round robin.
* Just for fun, I applied your proposal to a random GM round-robin: Candidate 2020. The ranking did not change much. (But that is obviously no argument, since they would have played differently.)
* Evidently, you need even more fine scoring (and could use the standard one, naturally...)
* The proposal would suit hazard play: Why not throw in a possibly incorrect sacrifice? You don't lose much if it doesn't work.
* Coda: Might be worth an experiment.

---
Tags: tournament, draw
---


# Question
Title: Is PGN split utility available anywhere?
A couple of places on the web mention a free utility called pgnsplit, that does the following: "A commandline tool to convert pgn-files including games with variation into pgn-files where each variation get its own game."

Sadly, all links to it seem dead. Does anyone know if it is possible to download it anywhere, or to find similar functionality in any other common chess database software?

# Answer
Here is the author's page courtesy of archive.org. The zip file on that page includes the readme.

Direct download of the zip file
> 10 votes

# Answer
As of 2017.04.01, pgn-extract (version 17-38) does provide variation splitting functionality via its --splitvariants flag. So, if you want this in a Windows/Linux/Mac OS environment it is available. Disclosure: I am the author of pgn-extract.
> 12 votes

# Answer
The only one I've found that will probably do what you want is PGN Extract. It's a command line tool, so hopefully you're comfortable with that. It has a Windows binary, but if you need it for Linux or Mac I hope you're comfortable with compiling from source.

---

**Update**

It appears PGN Extract will only separate unique games in a single PGN into multiple PGNs, not branches. Sadly PGN Split was one of a kind, and there doesn't appear to be a replacement. One of few programs that managed to disappear *completely* from the internet.
> 3 votes

# Answer
This will do it.

https://www.cs.kent.ac.uk/people/staff/djb/pgn-extract/

I built it on mac--works great.
> 2 votes

# Answer
I don't understand what you meant by pgn split, but I once purchased a chess pgn book and it has all the games (312) in one pgn file. Now I need to split it into each chapter with exactly 12 games each. I searched over the internet and didn't manage to find anything helpful. So I wrote a python program to divide it into separate files.

```
import os

name = 'Your pgn file here'
units = 12
test_sub = "[E"
path = 'F:/Chess/pgns/'
file = ''

with open(path+name+'.txt', encoding="utf8") as f:
    test_str = f.read()

# using list comprehension + startswith()
# All occurrences of substring in string
res = [i for i in range(len(test_str)) if test_str.startswith(test_sub, i)]

print('No of games in each pgn =',units)
print('Total games found =',len(res))
print('Splitting',len(res),'games into',len(res)//units,'pgns.....')

os.mkdir(path+name)

for i in range(len(res)//units):

    file = path+name+'/'+name+'- Unit-'+str(i+1)+'.pgn'

    if i==len(res)//units-1:
        with open(file, 'w', encoding="utf8") as file:
            file.write(test_str[res[i*units]:len(test_str)])
    else:
        with open(file, 'w', encoding="utf8") as file:
            file.write(test_str[res[i*units]:res[(i+1)*units]-1])

print('Success!!')

```

Note: This divides the given pgn into equal number of files mentioned as `units` in the program, it doesn't divide a pgn into separate pgn's based on variations.
> 2 votes

---
Tags: software, pgn
---


# Question
Title: How can I load a position without kings into an engine?
I would like to be able to do load a position into a whatever possible (advanced) engine without kings. For example, the goal of the game would be to annihilate all the possible pieces instead of checkmating the king, and/or the king isn't even on the board. I sometimes test that. One example is when I want to see if a rook can stop two pawns at the 6th rank (it can't, I figured that out). Is there, maybe, an engine for that?

# Answer
For most such questions perhaps a chess problem engine like Popeye can easily solve it.

However, the kind of goals your question is indicating like extinction of opponent pieces can also be set in configurable chess variant engines, e.g., Fairy-Stockfish or Sjaak II. I would assume that in most cases this will be the easier and faster solution, assuming that the problem is within the scope of the possible rule configurations.
> 5 votes

# Answer
one simple solution would be on chessbase,

when you set up a position, you can ignore the king, you will get a warning that it is illegal, if you ignore that, then you can have it,

PS: i think the keyboard shortcut is s, and then clear the board,
> 0 votes

---
Tags: engines, analysis, stockfish, chess-variants
---


# Question
Title: Can White avoid a loss in this endgame study by Lazar?
This is the position with White to move. This was created by Lazar in 1935 according to Susan Polgar in a Chess Daily News article from 5/27/2008.

```
[FEN "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

```

**Can White draw this?**

> The obvious starting move is promotion of the d pawn. Promoting to a knight or a bishop loses to Bxh2.

> Promoting to a Queen leads to Bf4. Checkmate can only be avoided by Qd2+. But Kf3 and Qxf4 should also lose as Black is in time to take the h pawn and that probably wins.

> Promoting to a Rook is probably the only choice but I don't understand how the position will be drawn.

# Answer
The first half of white's move is forced - d8. Then white has a choice of knight, bishop, rook or queen. Black has two threats which white must parry to get a draw. The first is to play Bf4 and then move the king out of the way to deliver checkmate. The second is to take the white h pawn and then queen the black h pawn.

Let's look at what happens if white chooses a queen.

```
[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=Q Bf4 {threatening mate} 2. Qd2 Kf3+ 3. Qxf4 Kxf4 4.Kd2 Kf3 5. Kc1 {the white king has to stop the c pawn queening} Kg2 6. Kd2 Kxh2 {and the h pawn is going to queen}

```

Can white draw by choosing a knight?

```
[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=N Bf4 {threatening mate} 2. Ne6 Bxh2 {now going to threaten to queen the h pawn} 3. Ng5 Ke2 {threatening mate again} 4. Nxh3 {taking the deadly h pawn and stopping the mate!} Ke1 {putting white into zugzwang} 5. Ng1 Bf4#

```

The problem was the knight couldn't lose a move whereas the bishop could. How about if white chooses a bishop?

```
[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=B Bxh2 2. Bb6+ Ke2 3. Bc7 {inviting stalemate by BxB} Bg1 4. Bb6 {asking for stalemate again} h2 5. Bf2 h1=Q 6. Bg3 Be3#

```

That just leaves the rook. The advantage the rook has over the queen and bishop is that it can parry Bf4 mate threats by Rd2. Then when the king moves out of the way white is stalemated because the rook can't take the bishop. Furthermore if white can play Rd3 then that threatens the black b3 pawn which frees the white king to take on c2. Let's see how that could go.

```
[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=R Bf4 {threatening mate} 2. Rd2 {blocking the threat} Be5 (2...Kf3= {stalemate}) 3. Rd3+ Kf2 (3...Kxd3= {stalemate again}) 4. Rxb3 Kg2 5. Kxc2 Kxh2 6. Rb7 Kg2 7. Rh7 h2 8. b4 h1=Q 9. Rxh1 Kxh1

```

So, those two ideas for white are enough to guarantee the draw.
> 26 votes

---
Tags: problems, stalemate
---


title: Can a zugzwang be a bad move?

text:
# Question
Title: Can a zugzwang be a bad move?
There's this related Helpful Zugzwang? but it's not quite what I am asking. I mean a double (or further) zugzwang.
So a player puts another player in zugzwang, and the other player makes a move. However, after that move, the first player doesn't have good moves either and it's a reverse zugzwang, or a self-zugzwang. Is it possible?

# Answer
> 18 votes
> So a player puts another player in zugzwang, and the other player makes a move. However, after that move, the first player doesn't have good moves either and it's a reverse zugzwang, or a self-zugzwang. Is it possible?

No. What you describe is incompatible with the definition of zugzwang. By definition if you place your opponent in zugzwang then any move they can make is a bad one which gives you the advantage. If they have a good move which puts you in zugzwang then, by definition, your previous move was not a good move which put your opponent in zugzwang.

# Answer
> 8 votes
You may be thinking of what is known as "reciprocal zugzwang" which are positions where either side would stand worse for having the move. They are very common in endgames, and feature prominently in the fundamental strategies of King and pawn play. Here is a simple example.

```
[FEN "8/8/1p2k3/p3Pp2/P4K2/1P6/8/8 w - - 0 1"]

```

Here is a more complex example.

```
[FEN "6k1/8/8/5PPP/ppp5/8/8/1K6 w - - 0 1"]

```

# Answer
> 4 votes
If we had enough computing power, every board state could be assigned a score recursively according to these rules:

1. A win is 1 for the winning player and 0 for the losing player.
2. A draw is 0.5 for both players.
3. The score for the player whose move it is is the maximum of their scores among all their possible moves, and the other player's score is the minimum among those scores.

I'll rewrite your question so the players and moves are labeled:

> So in move N, White puts Black in zugzwang, and Black makes a move. However, after that move (that is, at move N+1), White doesn't have good moves either and it's a reverse zugzwang, or a self-zugzwang. Is it possible?

If, at move N.5 (that is, the half-move after move N), Black has a move that puts White in a losing position, then Black's score for that move is 1. And since Black's score in a position where it's their turn to move is the maximum of their score among all their moves, and one of their moves has a score of 1, it follows that their score in that position is 1. But a (full) zugzwang, by definition, is a position where the player whose turn it is has a score of 0. So Black was not in zugzwang.

# Answer
> 3 votes
Actually, what the poster describes is possible and not at all incompatible with the definition of zugzwang!

To avoid all references to concrete positions, let us define:

* Full point zugzwang: If Black could pass this move, the position is won for Black. But any move loses for Black.
* Half point zugzwang 1: If Black could pass this move, the position is drawn for Black. Any move loses for Black.
* Half point zugzwang 2: If Black could pass this move, the position is won for Black. Any move draws for Black.
* White zugzwang: Just reverse colors.

OK, now we just assume that White has one tempo move that puts Black into HPZ2, but lacks a second tempo move to turn HPZ2 to HPZ1. Thus the White tempo move avoids a loss, Black is in HPZ2, makes a move, White is in HPZ2 too since pass moves lack either, and game will be drawn. In that position, White also could have a move that actually wins, and thus putting Black in Zugzwang is a bad move. Observe:

```
[FEN "8/8/p7/P2p1k1p/3P3P/5K2/P7/8 w KQkq - 0 1"]

```

1.a4 HPZ1 for Black (passing wins), 1...Ke6! 2.Kf4 Kf6 HPZ1 for White (passing wins), drawn. Incidentally 1.a3! HPZ2, also puts Black in zugzwang and wins, as White has another tempo move. So in this case it was merely a "wrong" choice of zugzwang. It is easy to think of a position where White wins with PxP, but I'm too lazy to come up with one since I now have my first OTB game in years and must go :-)

---
Tags: zugzwang
---


title: Looking for polyglot opening books

text:
# Question
Title: Looking for polyglot opening books
I understand the Polyglot opening format is open source, but I can't find available opening books for polyglot. I'm looking to use a book to automatically identify (and exclude) opening moves from a program to analyze large numbers of PGN files.
Is there a reliable place existing (open-source) polyglot books are available?

# Answer
> 3 votes
I found two sources for Polyglot opening books:

1. Richard Pijl has released his opening book alongside *The Baron 3.43*, which he says is almost identical to the version that played in the 2018 WCCC. Read more about these here.
2. Sourceforge claims to have a polyglot book collection for download here. The main page is here.

EDIT: Found two more here.

> **The openings book "Human.bin".**
> This "polyglot book" is a part of Deep Saros and play very aggressive and fun line of openings, like: Grob Attack, Blackmar-Dietmer Gambit, Englund Gambit, Greco Gambit, Albin Counter Gambit, Goering Gambit, Borg Defence, Polish Defence, Damiano Defence, From Gambit, Amar/Paris Opening, Fred Defence, Barnes Opening, etc...

and

> **The openings book "Titans.bin".**
> This "polyglot book" was prepared by Flavio Martin, an Italian chess player and has been very strong. Is an excellent tool for analysis, preparation and training, and a viable alternative to other openings books. It's certainly being testing!

---
Tags: opening, computer-chess, pgn, polyglot
---


# Question
Title: Where can I find chess tournaments near me for kids or teens?
Where can I find chess tournaments near me for kids or teens? I am 13 and in the U.S.

# Answer
> 8 votes
Junior tournaments in the US doesn't narrow it down very much. As a chess player living in the US your first stop should always be the US Chess Federation website.

If you are looking for tournaments then the USCF has a webpage which allows you to search for "Upcoming Tournaments". You can apply filters for the dates, type of events (Junior Grand Prix is the closest to "Junior") and proximity.

However this will not list minor internal club competitions which might not be rated. You would do well to also contact your nearest chess club to find out what they have to offer. Again, the USCF can help you. They have a web page where you can search for chess clubs in your area.

# Answer
> 5 votes
I've never played chess in the US but if I were you I'd call some of the chess clubs nearby and ask for information. While you can definitely find some events online, the people who are dedicated to this stuff will give you better advice themselves.

Anyway don't hesitate to show up to an adults tournament. Even if that's not what you're looking for, you may end up knowing someone who can help you (a coach, an organizer or even a bunch of fellow kids/teens)

---
Tags: tournament, children
---


# Question
Title: What is the point of c3 in the Sicilian Alapin?
In the Alapin variation of the Sicilian, the game goes 1. e4 c5 2. c3. However, this sequence just blocks the b1 knight from its best square, and it doesn't develop anything. Both squares attacked by the pawn are already being attacked by black's other pawn.

What is the point of the move 2. c3? I do understand that it can be used to avoid a mainline Sicilian, but at least develop some other good piece.

# Answer
> 5 votes
You are asking a good question, because the answer gets to the root of good opening play. The object of the opening is not just to get the pieces out. If it were, then after 1.e4 c5, 2.Bc4 would be a popular move. The reason why it is not is that c4 is not yet clearly a good square because 2..e6 neutralizes the Bishop, and an eventual ..d5 will take advantage of it. The real object is to get the pieces onto effective squares, and which squares are effective depends on the Pawns.

The Pawns have three tasks. One is to move out of the way and give freedom to the pieces. Another is to create safe and stable locations for the pieces after they are developed. A third is to deny effective squares to the opponent. If it were simple to achieve all three objectives then the opening phase would be easy, but it is part of ones playing style to make personal choices about the importance of each objective. This adds to the fascination of the game.

I am not trying here to explain to you everything that might be said about 2.c3, but rather to help you understand the subtlety that any explanation would need to address.

# Answer
> 7 votes
The move c3 prepares d4; if Black proceeds blindly by playing, for example, 2. ...Nc6, 3. d4 gives White full control of the centre and a strong advantage.

To prevent White dominating the centre, Black tends to counterattack with 2. ...d5 or ...Nf6, which often leads to French-like structures that can throw off a player with the black pieces who is familiar with Sicilian main lines but not with others.

# Answer
> 3 votes
I think there was good points and explanation so far, I will just add few.

I recently also started to play Alapin, and there are two points two that:

1- make your opponent uncomfortable! as mentioned before the structure and form of the play is not what black players are looking for, and it make it uncomfortable to face it.

2- Also, white is trying to avoid open sicilian which gives black two central pawn and very unbalanced and dynamic game, here you will generally end up in an IQP position, and play is more dynamic from white and requires static play and patience from black,

so, you change the nature, you make black uncomfortable with minimum risk, it could be a viable option.

# Answer
> 3 votes
The idea is that c3 supports d4 and if black plays cxd4 then white recaptures with the c-pawn leaving white with the better center. If white is able to carry out that plan then he will have a clear opening advantage. However, in actual play, the idea is a little slow. After 2...d5 white really doesn't have a good answer. 3. e5 just gives black an improved version of the French while 3. exd5 will likely lead to an IQP position. Plus, it allows black to bring the queen to the center of the board without allowing the typical Nc3 with a gain of time. I'll point out that 2...Nf6 is very good for black for similar reasons.

White's idea of 2.c3 is fundamentally sound. All mainstream openings deal with the central pawn structure in the first 2-3 moves in one way or another. It's just that the actual position on the board makes it impossible for white to get the structure he's trying to get if black plays correctly. Even so, after 2...d5 white is still a little better. The d-pawn will likely become isolated but white still has more space in the center and the open lines will give white a lot of piece activity. If you doubt me, try playing the black side against a strong engine.

Keep in mind, Larsen said the open Sicilian (with Nf3 and d4) was a positional mistake. I'm not sure I completely agree but he does have a point that white is losing something in trading the central d-pawn for black's less valuable c-pawn. The Alapin attempts to solve that by replacing white's d-pawn after it's captured. It doesn't completely succeed but white is able to convert the first move advantage into something (central space and an active position) which gives at least a small positional advantage.

# Answer
> 2 votes
Actually g1 knights best square is f3 and is not blocked - but the point is pretty obvious to take on d4 with pawn and have firm control over central squares. And b1 knight that lost ability to go to c3 either will go to c3 after cxd4 recapture or will be routed into play via a3 or d2.

---
Tags: opening, analysis, sicilian-defense
---


# Question
Title: In online correspondence chess, are the ratings adjustments based on the pre- or post-game ratings?
When playing rated online correspondence chess, it's quite possible that the players' ratings change during the game. When the game is over, which rating will be used for rating adjustments? The ratings they had before the game began, or the rating at the end of the game?

# Answer
Every site that I have seen uses the rating at the end of the game.
> 1 votes

# Answer
Online sites use the rating at the beginning of the game. You can tell that because that's the rating they display even if it's changed.
> 1 votes

---
Tags: rating, elo, correspondence-chess
---


# Question
Title: How to create your own opening book for your own chess engine?
I am currently working on a chess engine in Java. I am using the minimax algorithm with alpha-beta pruning to select the best move. However, it is inefficient to use the algorithm for selecting opening moves.

So here is my question for people who have experience with making their own engines:

How do you make your own opening book? Do you create your own database to store different openings and their successive variations? Or is their a general database that one can connect to and extract moves?

I would gladly appreciate any help from anyone who has experience or knowledge on this.

# Answer
> 7 votes
It may depend a little on what your code can access, but either way you should read Ed Schröder's pages on this topic. Schröder was the author of the Rebel Chess software until his retirement about a decade ago. In the '90s Rebel was the strongest consumer/commercial chess software and the first such to beat a GM (Anand). Since retiring he turned Rebel into ProDeo and released it for free on his website.

Start with this introduction, though you should already know all that, then have a look at this more in depth explanation. Then check this page for details on adding Rebel/ProDeo books to any engine (will require compiling C code for each platform you want your engine to be able to work). You should be able to add to the books from PGN records before compiling them.

EDIT: Not quite sure why this was voted down, but probably the mention of C when the OP states Java. I should mention that *most* chess processing software is in C or C++ because it provides better processing capabilities; it compiles to assembly language or machine code, unlike Java, which requires the JVM to run and that makes Java less efficient. Yes, it is possible to compile Java into machine code, but hardly anyone ever does it because then it is no longer platform independent (such as it is). So the OP will be running into the C hurdle no matter what.

Beyond that, these sites on the chess programming wiki on opening books and opening suites may be of use. You'll find a bunch of Ed Scröder's stuff there because he is one of the pioneers who made the shift from hardware electronic chess systems (e.g. Mephisto) to personal computing software. With the added bonus that now he's giving his software and, more importantly, his knowledge away to whoever wants it. If that's really not enough to immerse one's self in the subject then nothing is.

# Answer
> 4 votes
Back in 2013 Steve Maughan posted an excellent YouTube video Create a Polglot Chess Opening Book in which he takes you through the steps to extract high quality games from a large pgn database, clean the files and create a Polyglot database bin file. Although almost 8 years old it is still very useful.

He uses the following free software:

Scid, which can be downloaded from Sourceforge. Alternatively Scid vs PC also works.
Polyglot, which can be downloaded from Ed Schröder's Rebel13 site.
pgn-extract, written by our very own David J Barnes (@kentdjb), which can be downloaded from his site.

Steve Maughan starts by downloading a large games database. He uses Ed Schröder's 2.2 million database from 2013. You can source your own such. Or if you want to follow in Maughan's footsteps then a 2.5 million database from 2015 is available for download on Ed Schröder's site. Download file here.

Next he extracts "high quality" white wins and black wins into two separate pgn files. He defines "high quality" to mean 2400+ winner and reasonable strength opponent. He does this using Scid's filter option to select the files and then saves the two resulting search sets. If you use the more modern Scid vs PC (as I do) then you want the "General" option in the Search menu instead of the "Header" option but it works in a similar way. Save the file under the Tools menu "Save all filter games" option.

Then he cleans his two high quality extract files using pgn-extract using the command line:

```
pgn-extract -s -C -N -V -tstartpos.txt -oclean_white2400.pgn white2400.pgn

```

and same again for black2400.pgn

Note that startpos.txt just has the starting fen position, i.e. fen and then "rnbq...NR w KQkq - 0 1". Polyglot, which is coming up next only handles games which start from the start position so this filter is also required.

Next use polyglot to "clean" the files. We want it to run silently and remove comments and variations and annotations.

First we want a file of short variations (max 16 ply) where there are at least 50 matching games in the database. So, mainline, more or less.

```
polyglot make-book -only-white -pgn clean_white2400.pgn -bin w1.bin -max-ply 16 -min-game 50

```

Second we want a file of more obscure (minimum of 5 matching games) opening variations in greater depth (up to 60 ply)

```
polyglot make-book -only-white -pgn clean_white2400.pgn -bin w2.bin -max-ply 60 -min-game 5

```

Then we merge the two white books:

```
polyglot merge-book -in1 w1.bin -in2 w2.bin -out w12.bin

```

Do the same for black and then merge the white and black books into one high quality book so:

```
polyglot merge-book -in1 w12.bin -in2 b12.bin -out HighQuality.bin

```

Obviously you can tune the criteria according to your views and requirements, but overall a very powerful set of tools.

---
Tags: opening, engines, database, programming
---


# Question
Title: How many times can the same pawn move be made in a game?
How many times in a game can "the same pawn move" be made? By "the same pawn move", I mean, a move made by a pawn that would be notated the same way.

For instance, after 1.e4 e5 2.d4 exd5 3.e5, black and white have each played e5 once: so twice so far.

How many times can a single pawn move be played?

\[the second part of this question has been split out here\]

# Answer
> 16 votes
Eight is the maximum due to the geometry of the board. Only five of one side and three of the other can converge on the same single square.

Addendum: o@Red\_Floyd2 on reddit found a faster way in 18.0 moves on e4.

```
[FEN ""]

1. e4 d6 2. e5 dxe5 3. Bc4 e4 4. Be6 e3 5. dxe3 fxe6 6. Qd6 cxd6 7. e4 Qb6 8. e5 dxe5 9. Bg5 e4 10. Bf6 e3 11. fxe3 gxf6 12. e4 Nc6 13. e5 fxe5 14. Nc3 e4 15. Nxe4 e5 16. Ng5 e4 17. Nxe4 e5 18. Ng5 e4

```

The fastest it can be done, from my testing so far, is 19.0 moves for c4.

```
[FEN ""]

1. c4 b6 2. c5 bxc5 3. Qb3 c4 4. Qb6 c3 5. bxc3 axb6 6. c4 d6 7. c5 dxc5 8. Ba3 c4 9. Bc5 c3 10. dxc3 Qd5 11. c4 bxc5 12. cxd5 c4 13. d6 exd6 14. Nd2 c5 15. Nb3 c3 16. Rb1 c4 17. Nc5 dxc5 18. Rb3 cxb3 19. Kd1 c4

```

19.0 again for e4.

```
[FEN ""]

1. e4 d6 2. e5 dxe5 3. Qf3 e4 4. Qf6 e3 5. dxe3 gxf6 6. e4 Qd5 7. exd5 e5 8. Bf4 e4 9. Be5 fxe5 10. Bd3 exd3 11. Nd2 e4 12. Nc4 f6 13. Ne5 fxe5 14. d6 cxd6 15. cxd3 exd3 16. Nf3 e4 17. Ne5 dxe5 18. f3 exf3 19. O-O e4

```

Just for fun, as far as unique proof games go, here is one that has three White pawns cross e5. This was sourced from the Die Schwlabe Chess Problem Database.

```
[Title "Olli Heimo, Suomen Tehtäväniekat 2001, Dedciated to Joose Norri 1st Prize, Unique Proof Game In 25.5 Moves"]
[FEN ""]

1. e4 b5 2. e5 Bb7 3. e6 Bf3 4. gxf3 Nf6 5. Bg2 Ne4 6. fxe4 a5 7. e5 Ra6 8. Ba8 b4 9. Nf3 b3 10. Rg1 bxc2 11. Rg6 cxb1=B 12. Rh6 Be4 13. d3 a4 14. dxe4 a3 15. Qd6 axb2 16. a4 bxc1=B 17. a5 Be3 18. fxe3 exd6 19. O-O-O Be7 20. Rf1 O-O 21. Ne1 Re8 22. Rff6 Bf8 23. e7 Nc6 24. e6 Na7 25. e5 c6 26. e4

```

# Answer
> 6 votes
If you just ask for *white* moves, then of course queening all pawns on e8 is impossible since you need 16 captures. 7 (12 captures) is trivial. Including Black, I assume that the maximum is bringing five white pawns to e4 and three black to e6 (6 white, 2 black captures, even more trivial), and the answer is thus 8x "e5". (This is actually "half an answer", I make way for an additional answer with a strict proof and a proof game.

---
Tags: problems, pawns, records, notation, mathematics
---


# Question
Title: Why do chess engines cause immediate draws rather than giving the opponent the opportunity to blunder or run out of time?
Consider a chess position like this one:

```
[FEN "K7/4k1p1/8/8/3B4/8/8/8 w - - 0 1"]

1. Ka7 (1. Bxg7) 1... g5 2. Ka6 Kd6 3. Ka5 Kd5 4. Ba7 Kc4 5. Bb6 Kc3 6. Bc5 Kb2 7. Ka4 Ka1 8. Kb3 g4 9. Kc2 g3 10. Bb4 g2 11. Bc5 g1=N (11... g1=Q 12. Bxg1) 12. Bb4 Ne2 13. Bc5 Nc1 14. Ba3 Na2 15. Bb2#

```

No forced mate is possible there. But a helpmate is possible, so if Black runs out of time, or just plays exceptionally terribly, then White will win. Given that, why does Stockfish pick Bxg7 there, which immediately ends the game in a draw, rather than picking basically any other move (except for the losing Bf6+) to at least have some hope of winning?

# Answer
> 14 votes
Unlike playing with people, an engine will make the best move it can find, assuming perfect play on the part of the opponent. Engines don't play "hope chess" - they don't assume (or hope) that the opponent will make a mistake.

# Answer
> 9 votes
Engines are usually coded with the assumption that their opponent will play the best moves that they can imagine, as pointed out by Pat Barron above. This is called a minimax decision rule.

Just to explain why this rule is used - it is a simplifying assumption. If you code or train the engine any other way, you will need two models - one for the opponent, and one for the engine. Using minimax, you only need one model - the engine effectively assumes it is playing itself and acts accordingly.

The idea of exploiting opponents based on a reading of their ability is a very interesting one, but it would be a wholly different challenge to just learning to play chess as well as you can. The problem with an engine that assumes its opponent is weak, is that (for example) you can hustle it by pretending to be weak, and springing a trap. AI algorithms tend to be extremely fragile to exploitative attacks like this, and have limited ability to learn between games to prevent it happening over and over again.

# Answer
> 1 votes
The situation above is that if white makes any move other than Bxg7.

Then black goes g1=Q and has the advantage with the possibility of a win if black can take the bishop.

The table has a list of draws, they all assume that white plays a lot better than ignoring taking a pawn that is about to be promoted.

---
Tags: engines, draw
---


# Question
Title: Is it normal for a chess engine to blunder material if its evaluation is only based on naive material evaluation?
For the past couple of weeks, I've been making a chess engine, and right now I'm working on creating its search and evaluation phases.

To start off with, I made the evaluation phase a simple count of material so I could focus on the search phase, and then I would come back to create a more nuanced evaluation function. So right now, I have negamax, with alpha-beta pruning, iterative deepening, and quiescence searching implemented, which I'm pretty happy about.

But the problem is sometimes my engine still decides to willing blunder away pieces. Here's an example from a recent game, where the computer is black and it's black to move. For some reason, my engine decided that Ng4xf2 was the best move here. And then once it lost the knight for a pawn, it just went on as if it had made an equal trade.

Can this kind of blundering by a chess engine be explained away by a very naive evaluation phase, like my engine currently has? If it can be then, then of course the solution would be to create a much stronger evaluation function, which I'll do. But if it can't - and I must admit I don't see how it could - then I'm afraid there's a problem with the search phase, which would be a disappointing, but not impossible, setback.

I found this question, which seems to give an answer, but the reason why I still don't see how the evaluation function could be the culprit is that at the very least, in my mind, an evaluation phase based purely on material gain shouldn't make basic blunders where it loses material literally on the next move (especially with quiescence searching!)

Can anyone with experience in this area of AI programming offer any insight here? Also, let know if you need to see any code and I'll be more than happy to provide it.

# Answer
It's always a question at what depth you stop. Eg.g, with 5 plys, your engine might be happy with

1. ... Nxf2 **one pawn ahead**
2. Bxf2 Bxf2 **still one pawn ahead**
3. Kxf2 Qxf3+ **still one pawn ahead and even check!**

and not see 4. Kxf3. Something like this chould be prevented e.g. by selectively expanding until no capture / no check is made. Even then, the evaluation might stop with the last move leaving your queen attacked.
> 7 votes

# Answer
This exact bot has already been created. On lichess, it is simpleEval. You could potentially use it to debug a lot of your issues by seeing what this engine does against you in a given position.

Having played this bot several times, no that move Nxf2 would probably be incorrect. This seems like a bug on your end. Assuming you have enough depth in the bot's calculation, that type of a blunder would be the last possible way it blunders. Specifically, your bot should make incredibly terrible moves from a positional standpoint as long as it doesn't see any tactics that win material in the upcoming moves. I've seen "+10" positions where technically the bot is up material. This is much more likely to be the bot's response to a specific situation than sacrificing anything unless it finds a forced win of material back in the near term.

Sorry that you might have to revisit some code you thought was already working.
> 13 votes

---
Tags: engines, programming, computer-chess, minimax
---


# Question
Title: Can there be a checkmate with maximum points of material (103) while covering 64 squares?
Is it possible to compose a game where these three conditions are simultaneously satisfied?

1. No White piece is gone but every Black piece except the king is.
2. All the white pawns are promoted to a queen.
3. On the last move, every square on the board is covered by the White pieces.

Bonus: The last promotion (preferably the h pawn) delivers checkmate.

# Answer
As per Hauke's invitation, here is an optimal proof game for such a position. This is optimal because a queen must move to give the Black king a square and forty pawns moves must take place. White's h pawn *does* give checkmate in the end.

```
[FEN ""]

1. a4 b5 2. axb5 a5 3. b4 Na6 4. bxa5 Rb8 5. c4 Rb6 6. axb6 c5 7. bxa6 d5 8. d4 e5 9. e4 f5 10. f4 g5 11. g4 h5 12. h4 Qc7 13. cxd5 Qc6 14. dxc5 Bd6 15. dxc6 Be6 16. cxd6 Bd5 17. a7 Kf7 18. fxe5 Ke6 19. a8=Q Bc4 20. b7 Bd3 21. exf5+ Kd5 22. c7 Ke4 23. hxg5 Ba6 24. gxh5 Ne7 25. f6 Kf5 26. e6 Ng6 27. hxg6 Bc4 28. e7 Be6 29. e8=Q Bd7 30. g7 Be6 31. g8=Q Rh6 32. d7 Rh7 33. g6 Rh6 34. g7 Rh8 35. d8=Q Bd7 36. Qexd7+ Kg6 37. f7 Rh6 38. f8=Q Rh4 39. c8=Q Rh7 40. b8=Q Rh8 41. gxh8=Q#

```

Another proof is that, even with the Black king on b6 or g6, it is impossible to capture all Black pieces in time with only pawn moves.

```
[FEN ""]

1. e4 e5 2. f4 f5 3. exf5 Qf6 4. fxe5 d5 5. exf6 Be6 6. a4 Kf7 7. b4 c5 8. fxe6+ Kg6 9. b5 Nd7 10. a5 Ne5 11. a6 Re8 12. b6 Nf7 13. axb7 Bd6 14. bxa7 Re7 15. fxe7 Bf4 16. exf7 Bg5 17. c4 Nf6 18. d4 Rd8 19. cxd5 Kf5 20. dxc5 Rd6 21. h4 Ng8 22. hxg5 Rf6 23. gxf6 h5 24. g4+ Kg6 25. gxh5+ Kf5 26. h6 Kg6 27. h7 Nh6 28. h8=Q Ng8 29. f8=Q Nh6 30. f7 Ng8 31. e8=Q Nh6 32. c6 Ng8 33. a8=Q Nh6 34. c7 Ng8 35. b8=Q Nh6 36. c8=Q Ng8 37. d6 Kf6 38. d7 Kf5 39. d8=Q+ Kg6 40. fxg8=Q#

```
> 13 votes

# Answer
```
[FEN "3k4/6QP/8/4Q3/8/2Q5/QQ4QQ/RNBKQBNR w KQkq - 0 1"]

1. h8=Q#

```

This is trivial, as already five queens can threaten the whole board. The only thing you must pay attention to is giving Black a last move. Here it is Kd7-d8.

Bonus question for Rewan: An answer with the shortest proof game :-)
> 10 votes

---
Tags: problems, checkmate, records, pieces, point-value
---


# Question
Title: Looking for tactical Sicilian lines besides the Dragon and Najdorf
I am looking for a tactical Sicilian. But I don't want a really popular line like the Najdorf or Dragon that has been analyzed to death.

# Answer
You should take a look at the Kveinis variation. I play it, and it is a good and surprising variation, with a lot of tactical traps.
> 2 votes

---
Tags: opening, tactics, sicilian-defense
---


# Question
Title: Why not immediately force a draw when losing is possible but winning isn't?
In my last question, I asked why engines sometimes force a draw when they can still win. Now, I'm asking about the opposite situation:

```
[FEN "5K2/5n2/8/3n2k1/8/8/8/8 w - - 0 1"]

1. Ke8? (1. Kxf7) 1... Nd6+ 2. Kf8 Kh6 3. Kg8 Ne7+ 4. Kh8?? Nf7#

```

It's completely impossible for White to win here, but Black winning is still possible, if White blunders into the corner or runs out of time. Isn't the obvious move then for White to play Kxf7, to secure the draw immediately? Why does Stockfish instead suggest Ke8, which keeps the game going and leaves open the possibility of a loss?

# Answer
Chess engines just don't work that way. They don't have a "risk" or a "just in case" module. They just try to maximize their eval function. (They value stuff like king safety, but that's something different).

Typical case: on a given position white has an easy to calculate simplification that takes to a trivially winning K+P vs K endgame. Say this is a mate in 30. On the other hand, in the same position, white has a very hard to find (for humans) mate in 15. No human would risk to miscalculate the brilliant mate in 15 when you can get into a prosaic won endgame, but to the engine mate in 15 is just better than mate in 30, so there it'll go.

Another reason for engines not to behave these ways; it just doesn't add Elo points to their strength.
> 3 votes

---
Tags: engines, draw
---


title: Knight Moves Around the Board

text:
# Question
Title: Knight Moves Around the Board
It is well known that a lone knight can move all around the board covering each square once and only once. Is this possible when the lone knight starts only on certain squares ? How many unique solutions does this problem have now that powerful engines exist?

# Answer
> 2 votes
> Is this possible when the lone knight starts only on certain squares ?

If you stop and think about this for a second you will realize that the answer is obviously "Yes". If you have a "Knight's Tour" (that's what it is called) starting on square X then by definition it also goes through square Y (for all squares Y on the chessboard). Hence the exact same moves, just starting on Y, will also be a Knight's Tour.

> How many unique solutions does this problem have

According to Wikipedia:

> On an 8 × 8 board, there are exactly 26,534,728,821,064 directed closed tours (i.e. two tours along the same path that travel in opposite directions are counted separately, as are rotations and reflections). The number of undirected closed tours is half this number, since every tour can be traced in reverse.

---
Tags: knights, mathematics, solving
---


# Question
Title: Why is there association between a queenless position and the endgame?
Why does there seem to be some idea that trading queens is the start of the endgame? What does trading queens have to do with the endgame? Why are queenless positions often considered to be endgame positions?

I have also heard repeatedly people saying "trading queens doesn't mean it's the endgame guys" so it seems like an "urban myth" kind of thing. How everyone loves debunking common knowledge. That actually shouldn't count as common knowledge anymore because everyone debunks it.

There is definitely some association between having no queens, and the endgame. How did this association begin and why does it exist?

# Answer
> 7 votes
Some say the endgame begins when the kings can come out and join the fight. Usually it's not safe for them to do so until queens are off the board.

# Answer
> 4 votes
To assume that the game has reached the endgame just because the Queens have been exchanged is a bad conceptual mistake that can lead to disaster.

A classic example is a game Verlinski-Alekhine where Queens are traded very early in the game and white plays the early middlegame "as if" it was an endgame already with the result of getting run over by the young future world champion.

The game is #2 in the collected Alekhine's games written by himself.

---

(Added) In the classic book of Romanovski, a cornerstone of the soviet school of chess, the endgame is defined as the phase of the game when the Kings take an active role.

# Answer
> 4 votes
Some positions are clearly not end games and some others clearly are. Unfortunately there are some positions in between that seem to defy classification. Why is that? Wikipedia The start of the endgame does an excellent job on surveying opinions of highly knowledgable players. Note the quote from the fourth World Chess Champion

> Alexander Alekhine: "We cannot define when the middle game ends and the end-game starts."

Hence sometimes we should take the borderline cases out of the defintion of the general concept, to make it more abstract, simpler and more elastic. For the offending cases, fundamental strategic questions like king safety, importance of material, have to be decided on a case by case basis.

---
Tags: endgame, queens
---


title: Where does the money come from?

text:
# Question
Title: Where does the money come from?
I prefer watching top players' games. Recently, the Silver Lake Open has ended and now Serbia Open Masters is going on. So my question is, who pays for the travelling and accommodation costs of players? Is it the organiser, the players themselves or their country's government who covers these costs?

# Answer
For invitationals generally the organizers will pay (or the invited players won't accept the invitation). For open tournaments it's a different matter, and the players themselves pay.

An event like "Serbia open masters" might be funded by Serbia's chess organization, though (I have not checked).
> 7 votes

# Answer
All three.

For top players, it's the organizer who foots the bill just to get the name value. For some countries, they'll pay for their players to travel to a well-known tournament to show the "greatness" of their country. The less famous tournaments couldn't afford a top 20 GM, but have been known to "bribe" lower GMs, hoping other GMs will join at their own expense.

I don't have the knowledge, but I assume that title tournaments, eg. World Championship, that FIDE pays the expenses as it keeps all the profits.
> 6 votes

---
Tags: tournament, tournament-directors
---


title: What is a pawn hook?

text:
# Question
Title: What is a pawn hook?
On my question (Why is 11. .. h6 such a bad move?) someone commented that I should read about the concepts of hooks. One definition that I found was:

> A hook is an advanced pawn which can be exploited by the opponent to open lines. (https://chessbookreviews.wordpress.com/2018/07/03/one-small-step/)

I found more examples on the internet that did not explain the concept clearly to me. Do you have further explanations and examples for this concept?

# Answer
> 17 votes
Here's a position from one of my games. I'm playing White versus a master:

```
[FEN "r2qk1nr/pp2bp2/2p1p2p/3pPnp1/1P6/P1N2N2/2P2PPP/R1BQR1K1 b kq - 0 11"]
[White "D M"]

1... g4

```

This position isn't great for me, but his pawn storm really isn't all that strong. But imagine if I had a pawn on h3 instead of h2.

```
[FEN "r2qk1nr/pp2bp2/2p1p2p/3pPnp1/1P6/P1N2N1P/2P2PP1/R1BQR1K1 b kq - 0 1"]
[White "D M"]

1... h5 2. Nd2 g4 *

```

Now I've got the choice of playing hxg4 or letting him play gxh3. Either way, my king is going to be significantly more exposed than it was in the actual game. But because I *didn't* have that hook for him to grab, the pawn storm came to nothing and the game was eventually drawn.

# Answer
> 3 votes
Your troubles might stem from the fact that all pawns are hookable, loosely speaking.

I thus define strictly operational: A pawn hook is a pawn in a position that allows the opponent to advance an own pawn, and open a file for its rooks by a capture.

Now consider D.M.'s two positions and the h hook exploited by storming with the g pawn. As soon as the hook "grabs", the opponent has three options:

* Capture
* Be captured
* Advance

The first two lead to the desired line opening. Thus, Black might first advance its own h-pawn to h4 so that White can't play h3-h4 (even if this is a pawn sacrifice here, which might be the lesser evil). Compare to the position with Ph2: Advancing to h3 is answered with g3 (uh-oh, g2 stinks, but again, maybe lesser evil), advancing to g3 without reserves leads to the opening of the g line but the rooks stare at a protected pawn, and even if it is annihilated by again playing Ph4, its comrade on g2 still protects the king. Or maybe it typically ends like this: 1...g3 2.fxg3 hxg3 3.h3 and a piece sacrifice on h3 is needed.

Moral: Both positions offer hooks for a pawn storm! Strictly speaking, h3 doesn't create a hook, it moves the hook to an easily exploited position! It's just that the unadulterated f2-g2-h2 position is far more stable against pawn storms.

# Answer
> 2 votes
We can ask how effectively the castled King is guarded by the pawns in front of it. For simplicity of notation consider only short castling, with White on the attack, but all the ideas apply to long castling and Black attackers as well.

At the beginner level, the advice is often given to leave the f7,g7 and h7 pawns where they are. The logic is that this leaves the attacker with few avenues of approach. They can play Qh5 and Ng5 for example but often this can be met simply by Nf6. Successful attacks usually involve bringing more attackers into play than there are defenders. This often requires opening lines for Rooks and Bishops. For example if Black has played h6, then g5 can open the g-file (in case of gxh) or the h-file (in case of ...hxg), or the c1h6 or b1h7 diagonals This will not work if Black is able to play ..h5, so White will often try to control that square first. Similarly, if Black has played ..g6, the line opener will be f5 or h5. The Pawn on h6 or g6 is sometimes referred to as a "hook". The prelude to attacking play often centers around creating a hook. If ..Nf6 is not available then Qh5 and Ng5 may force ..h6. Black may play to prevent these manoeuvres or to create stronger counterthreats elsewhere

---
Tags: learning, strategy, terminology, middlegame, pawn-structure
---


# Question
Title: Term for sacrifice that causes opponent to block an escape square?
A decoy or deflection typically lure an opponent's piece *away* from a square. What is it called when you sacrifice in order to lure/force an opponent ***to*** a certain square in order to prevent another piece escaping?

Here is a bad example that I've made that shows the idea. The reason it's bad is because the lure isn't actually needed since d8 is already attacked by the black rook.

```
[FEN "3r1rk1/ppp2ppp/8/2b5/4P1RP/5q2/PPQ5/RN2KN2 b - - 0 1"]

1... Rd1+ 2. Qxd1 Qf2#

```

# Answer
What you are looking for is called "attraction". That is, you attract a piece to a specific square. One of the most famous types of attraction is seen in this example:

```
 [FEN "r1b2rk1/pp2pp1p/1qp3p1/4Q3/1n1N4/1P6/PBP2PPP/R4RK1 w - - 0 1"]

 1. Qg7+ Kxg7 2. Nf5+ Kg8 3. Nh6#

```

Here is a nice link with another example.

This is also exactly a deflection since you deflected the queen away from f2. By the way, 1...Bf2 2. Qxf2 Rd1 also the same.

Here are two examples of what Rewan Demontay described as "self-blocking" below. In the first, a study by Nimzovich, it is what I believe the OP is asking for. The other is another type of self-blocking move, but it is not the opponent that forces it. This is more common in some endgame tactics to draw where one side walls the king in so it will be a stalemate.

```
 [FEN "5rn1/2N1npk1/R7/4P3/8/4P3/Q7/K6R w - - 0 1"]

 1. Rg6+ $3 fxg6 (1... Nxg6 2. Qxf7+ Rxf7 (2... Kxf7 3. Rh7#) 3. Ne6#) 2. Qf7+ $3 Rxf7 (2... Kxf7 3. Rh7#) 3. Ne6#

```

Here is the other self-block, but for another reason.

```
 [FEN "8/r6k/3r3p/5p1K/5P2/p6P/Q7/8 w - - 0 0"]

 1. h4 Rd1 2. Qf7+ Rxf7 {Stalemate}

```
> 11 votes

# Answer
As far as I know, the term for a sacrifice that causes a player to block an escape square called a “selfblock,” altough it is a type of selfblock.

For a composed example, here is one that shows the idea. White sacrifices a pawn on d4 and a rook on e4 and this causes Black to move their pieces to those squares, thus taking away escape squares from the Black king.

```
[Title "Julio César Infantozzi, Mate In 16 Moves"]
[FEN "R1n2N2/4pk1B/2Q1r2B/2K2b2/Rr1n2P1/1q1P1PP1/4N2b/8 w - - 0 1"]

1. Qe8+ Kxe8 2. Rxc8+ Kf7 3. Bg8+ Kxg8 4. Ng6+ Kh7 5. Rh8+ Kxg6 6. Nf4+ Kf6 7. Rf8+ Ke5 8. Bg7+ Rf6 9. Bxf6+ exf6 10. Re8+ Ne6+ 11. Rxe6+ Qxe6 12. Ng6+ Bxg6  13. f4+ Rxf4 14. gxf4+ Bxf4 15. Re4+ Bxe4 16. d4

```

You can find more such chess problems here, and there is even a ChessBase article on the subject.

I found a game where this actually occurs, pulled from this chessgames collection.

```
[Title "Tigran Levonovich Petrosian-Ara Minasian, 66th Armenian Championship, Yerevan Armenia, 3/19/2006"]
[FEN ""]
[startply "56"]

1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Nxe4 5. Qe2 Ng5 6. Nxg5 Qxg5 7. d4 Qe7 8. dxe5 Nd4 9. Qd3 Qxe5 10. Bd2 Ne6 11. Re1 Qd6 12. Qh3 Be7 13. Bd3 c6 14. Nc3 Qc7 15. f4 g6 16. g4 O-O 17. f5 Ng5 18. Qe3 Bf6 19. Rf1 d5 20. fxg6 d4 21. gxh7+ Kg7 22. Qe1 dxc3 23. Bxc3 Qb6+ 24. Kh1 Bd4 25. Qh4 Ne6 26. Qf6+ Bxf6 27. Bxf6+ Kh6 28. Rf5 Ng7 29. Rh5+ Nxh5 30. g5#

```

White “sacrifices” their rook to h5 with a check, which in turn causes Black to move their knight there, depriving the king of an escape square, aka a selfblock.
> 5 votes

# Answer
In PDB the keyword "Lenkung" in German ("steering" in English) is used for the tactic of White forcing Black to move a unit to a specific square where White wants it to be. "Steering" has wider usage than what the OP seeks. For one thing, this square might or might not be a black king-flight. For another, in some cases the steered unit is Black's king. To narrow a search down to what the OP wants, you could also use PDB's keyword "Remote selfblock".

Here's a case where White does force Black to self-block:

```
[Title "Manfred Schmidt. Freie Presse (Chemnitz), 15 Jan 1988, no. 2873. Mate in 4"]
[fen "8/p1K4B/k1N5/8/1R6/8/2b5/8 w - - 0 1"]
[StartFlipped "0"]

1. Bg8 Bb3 2. Bc4+ Bxc4 3. Ra4+ Kb5 4. Ra5#

```

FEN 8/p1K4B/k1N5/8/1R6/8/2b5/8

PDB link

1. Ra4+ Kb5 2. Ra5 would work, except that Black's bishop guards a4, and Black's king can escape via c4. So White first steers that bishop to c4 where it will block a king-flight.
> 2 votes

---
Tags: terminology, sacrifice
---


# Question
Title: FIDE Laws: what exactly does 'colours reversed' in 7.3 mean?
Article 7.3 of the FIDE Laws reads:

> If a game has started with colours reversed then, if less than 10 moves have been made by both players, it shall be discontinued and a new game played with the correct colours. After 10 moves or more, the game shall continue.

I'm not sure what 'colours reversed' means in this rule. It doesn't seem to mean that the colors of the board itself are reversed, because that's fully covered by Article 7.2.2

The two big possibilities I can think of:

1. The board and pieces were set up correctly, but Black moves first instead of White. \[Would this ever actually happen? Everyone suddenly forgetting that White goes first?\]
2. White moves first, but the King and Queen of both players start off in switched positions, so that White has an essentially 'Black' starting setup, and Black has an essentially 'White' starting setup.

If it's possibility #2, then what's the point of Article 7.2.1? It reads:

> If during a game it is found that the initial position of the pieces was incorrect, the game shall be cancelled and a new game shall be played.

I imagine that the King and Queen being switched probably accounts for 95% or more of the cases where "the initial position of the pieces was incorrect." Why have 7.2.1 as a rule if it's nearly always overridden by 7.3?

Or maybe there's another interpretation of 7.3 that I've missed entirely. I don't know.

# Answer
> I'm not sure what 'colours reversed' means in this rule.

It is really very simple. Suppose you and I are playing in a Swiss tournament. The draw shows that you are to play white against me in the next round. By accident we sit at the board with the black pieces in front of you and the white pieces in front of me and we start our game.

We are playing the correct opponent but the wrong colours. We are playing with ***colours reversed***.

Why does this matter? Because the rules for Swiss pairing decide what colours players can have. If our error is discovered within 10 moves then this can be fixed by abandoning the current game and starting a new one with the correct colours.

If this doesn't happen and we end up completing our reversed colours game then the arbiter needs to go back and manually change the draw to show the actual colours we played. That lets the pairing software know our true colour history and prevent either one of us playing three consecutive games with the same colour which the pairing rules don't allow.
> 28 votes

---
Tags: rules, fide, pieces
---


# Question
Title: Is three knights versus knight really winning?
Take a look at the following position, reached in the #40974 Tactics Problem on chess.com

```
[fen "4N1K1/5P2/6k1/8/6n1/8/N7/8 w - - 0 1"]

```

The engine gives +6.22 for white in this position. I already understand that any move other than **f8=N+** draws. *(For example, promoting to a queen allows perpetual Nh6+ and Nf7+ unless white gives up the queen which would also draw)*

My question is: **Is white really winning after promoting the pawn to a knight with check?**

How does one proceed to checkmate in this position, with three knights against a knight? And worse, **in less than 50 moves?** (otherwise it's a draw, of course)

I know that three knights versus lone king is possible (although quite hard!), but it seems to me that three knights versus knight is extremely unlikely to be winning upon perfect play...

# Answer
> 22 votes
It is winning for white. You can enter all positions of six pieces into a tablebase, like this online one.

It's mate in at most 39 moves, for example:

```
[FEN "4N1K1/5P2/6k1/8/6n1/8/N7/8 w - - 0 1"]

1.f8=N+ Kf5 2.Kg7 Ke4 3.Nb4 Kd4 4.Kf7 Kc5 5.Na6 Kd4 6.Nac7 Ne5 7.Kf6 Nc4 8.Ke6 Na5 9.Nd6 Nc4 10.Nf5 Kd3 11.Nd5 Na5 12.Nf6 Nc4 13.N8d7 Kd2 14.Nd5 Ke2 15.Kf6 Kd2 16.Nc5 Kc2 17.Nd4 Kd2 18.Kg5 Na5 19.Kf5 Nc4 20.Ke4 Kd1 21.Kd3 Ne5 22.Kc3 Ke1 23.Ne4 Ng6 24.Kc2 Ne5 25.Nf4 Nc4 26.Kc3 Ne5 27.Nf5 Kf1 28.Kc2 Nc4 29.Nfg3 Kg1 30.Kd3 Na5 31.Ke2 Nc6 32.Nf5 Ne5 33.Nd2 Kh1 34.Kf2 Ng4 35.Kg3 Nh6 36.Nxh6 Kg1 37.Ng4 Kh1 38.Nf2 Kg1 39.Ne2#.

```

There were many other choices along the way for both sides that would lead to the same amount of moves.

Edit: I think this is probably a quite modern study, where the composer used tablebases in the process of composing the study, but I might be wrong.

# Answer
> 8 votes
The tablebase says that it is mate in 38 moves after f8N+. That is for perfect play of both sides. If black does not play perfectly it might be shorter (same for white).

Since it is a chess problem/study, it does not really matter how easy it is to win, though I would not expect it to be too difficult (against a human player).

# Answer
> 4 votes
As long ago as 1895 KNNNvKN was treated as winning:

```
[Title "Moritz Lewitt; Deutsches Wochenschach 14 Jul 1895"]
[fen "3K2NN/8/8/8/8/8/1P6/n2k4 w - - 0 1"]
[StartFlipped "0"]

1.b4 Nc2 2. b5 Na3 3. b6 Nc4 4. b7 Na5 5. b8=N!

```

FEN: 3K2NN/8/8/8/8/8/1P6/n2k4

This is in PDB with no further moves given, even though the bK is out of play and mate is 34 moves off. Clearly it was thought that showing White safely promoting was enough to prove White wins.

Solution below:

> 1.b4 Nc2 2. b5 Na3 3. b6 Nc4 4. b7. Now 4 ... Na5 threatens 5 ... Nxb7 and 5 ... Nc6+, so White must push the pawn, and must promote to knight to counter the threatened fork.

According to the Syzygy tablebase White (with 3 knights) wins in 72.4% of positions, and 27.6% are drawn. The winning process is indeed hard in the worst cases: according to Kirill Kryukov, White wins in the following position, though Black can make the win last 90 moves:

```
[Title "KNNNvKN longest win. White to move."]
[fen "7N/N7/1k6/8/8/8/2K1n3/1N6 w - - 0 1"]
[StartFlipped "0"]

1.Nc8+! Kc7 2.Ne7! Kd7 3.Neg6! Ke6 4.Kd3! Ng3 5.Nd2! Kf6 6.Nf3! Nf5 7.Nf4! Ng3 8.Nd4 Nf5 9.Nde6 Nh4 10.Nd8! Nf3 11.Nd5! Ke5 12.Nc3 Kf6 13.Ne4+ Kf5 14.Ke3 Ng5 15.Ng3+! Kf6 16.Nh5! Kf5 17.Nf4 Kf6 18.Kf2 Kg7 19.Nfg6! Ne4+ {Nh7} 20.Kf3 Nc5 21.Kg3 {Ke3}

```

FEN: 7N/N7/1k6/8/8/8/2K1n3/1N6

---
Tags: endgame, tactics, checkmate, knight-endgame
---


# Question
Title: Why are side pawns better than center pawns in this position?
So center pawns are usually regarded as more powerful than side pawns, which is why I have a question about this position.

After `1. d4 d5 2. Bf4 c5` the engine and theory recommend playing `3. e3` to defend the pawn on d4, but if black exchanges for the pawn on d4, doesn't black end up with two center pawns and white end up with one because they exchanged the side c-pawn for the center d-pawn?

```
 [FEN " "]
 [StartPly "5"]
 1. d4 d5 2. Bf4 c5 3. e3

```

Wouldn't it be better to play `3. c3` so you can keep the center pawns?

```
 [FEN " "]
 [StartPly "5"]
 1. d4 d5 2. Bf4 c5 3. c3

```

# Answer
Chess strategy is complex and has several ingredients mingling at the same time. It is true that 3 c3 helps white mantaining two center pawns *if black decides for a c:d4 pawn exchange*. But black isn't forced to that and the move c3 has some incovenients. To list just two:

* blocks the c3 square which is the natural place for developing the Q-side knight;
* gives up the idea of attacking black's center with the move c4.

The move 3 e3 on the other hand helps white development since it opens the way out for the K-side bishop.

Moreover, the loss of one centre pawn is balanced by the fact that after white will castle K-side the absence of the e pawn will make the e-file a natural place for a white rook which will play an important role in the fight over the e5 square.
> 17 votes

# Answer
Move 3 is a bit early for such positional evaluations, but some food for thoughts:

* after 3...cd 4.ed, e7-e6 will be played, rather sooner than later but then the pawn structure in the center is fixed, which makes it hard for Black to "exploit" his extra central pawn. Any expansion with ...f6 and ...e5 is out of question for at least the next 20 moves because of White control over e5 (Pd4, Nf3, Bf4, Re1...); even if it somehow becomes possible, it is not sure to be desirable at all.
* For the sake of controlling the center, White's c-pawn is not much worse than Black's e-pawn. Indeed, while Black cannot hope for ...e5, White may change the pawn structure with c2-c4 at some point, heading for an isolani.
* Beside pawns, the center is also useful for pieces. White chances of occupying the e5-vanguard position with a knight are much better than Black's chances of occupying e4 because of the semi-open e-file.
* Since she has a tiny advance is development, White often tries to select non-symmetrical pawn structures, so the exchange Caro-Kann structure with 3.e3 cd 4.ed might be more attractive for most players than the exchange Slav structure with 3.c3 cd 4.cd.

All that being said, 3.c3 is a decent move that some players would prefer over 3.e3. And in both cases, Black is not at all forced to release the tension by 3...cd.

And by the way, 3.e4 is a whole different story.
> 5 votes

# Answer
I am really not an expert of this opening, but maybe 3.c3 is better in a sense.

After 1.d4 d5 2.Bf4 c5 3.e3, according to you, black should "refute" this inaccuracy by taking immediately on d4 3..cxd4 4.exd4 and now we have the Caro-Kann Exchange Variaton, with white having played the suboptimal Bf4 (1. e4 c6 2.d4 d5 3.exd5 cxd5 4.Bf4). After 4...Nc6 5.c3 Bf5(!) black has solved the problem of how to develop its white squared bishop and should have no further problems. Of course it is nothing for black in the winning sense.

```
 [FEN " "]
 [StartPly "5"]

 1.e4 c6 2.d4 d5 3.exd5 cxd5 4.Bf4 Nc6 5.c3 Bf5

```

In the line 1.d4 d5 2.Bf4 c5 3.c3 black can also take on d4: 3...cxd4 4.cxd4, but then we have reached the Slav Exchange Variation (1.d4 d5 2.c4 c6 3.cxd5 cxd5 4.Bf4) and here 4.Bf4 is found among the top moves. Furthermore the Slav Exchange Variation poses black more problems to consider, than the Caro-Kann Exchange Variaton.

```
 [FEN " "]
 [StartPly "4"]
 1.d4 d5 2.c4 c6 3.cxd5 cxd5 4.Bf4

```

Considering values of pawns alone has led us to a good idea in this case. Of course it should go without saying that in general there are more factors to consider in a chess postion, *Space*, *Material* and *Activity* among the top candidates. Only a good engine and a lot of experience can help us out here.

One example to illustrate the idea: 1.e4 c5 2.Nf3 e6 3.d4! cxd4 White voluntarily allows black to exchange his c-pawn against a valuable center pawn. This *is* a positional problem, but feasable because white gets something in return, more space and more active pieces. White can simply take back (4.Nxd4) or play the sly 4.c3, the Morra Gambit. Now it is white posing the positional threat of promoting his c-pawn to a center pawn with 5.cxd4. Black can accept the challenge, after 4..dxc3 5.Nxc3 white has traded material for space and time, it is playable AFAIK. Black can also defend with 4..d3.

```
 [FEN " "]
 [StartPly "5"]
1.e4 c5 2.Nf3 e6 3.d4! cxd4 4.Nxd4 ( 4.c3 4...dxc3 ( 4...d3 ) 5.Nxc3)

```
> 5 votes

# Answer
The number of central pawns is one of the factor that matter in the evaluation of a position, but it's definitely not the only one.

While I think both **3.e3** and **3.c3** are playable, 3.e3 helps your development, while **3.c3** does not. If Black takes on d4, White gets an amazing outpost on the e5 square. In fact, Black would wish he could put his e6 pawn on the "c" file instead so that it could fight for the control of e5 and get a similar outpost on e4.
> 3 votes

# Answer
Just a small addendum: As a Bf4 player who never plays London but his own obscure systems (which are extremely dangerous for both sides - in the days before computer preparation, I clobbered a few GMs with them I only play e3. My own experience is that the most doubly-edged Black plan is pestering b2 with his queen. e3 (developing, also keeping the option Nc3, eat b2 and die!) is asking for it. After c3, you can wuss out by answering Qb6 with Qb3, but that is extremely drawish. Oh, and immediate cxd4 gives White a nice outpost on e5.
> 3 votes

---
Tags: opening, pawns, pawn-structure, 1.d4, london-system
---


title: A Swiss nightmare

text:
# Question
Title: A Swiss nightmare
Inspired by a recent question, here a fantasy:

The Superduperquantumcomputer "Deep Ponder" has cracked Chess. Assume a 9 round Swiss tournament with 2^9 players, White always wins. Will the pairing computer (definitely not super quantum) go berserk? I don't think so, one can always float and the problems will only occur for the topmost players.

Anyone like to do the experiment? (Would do it myself - I have enough time...but no Swiss program.)

# Answer
> 3 votes
> Assume a 9 round Swiss tournament with 2^9 players, White always wins. Will the pairing computer (definitely not super quantum) go berserk?

Thank you for clarifying the difference between NA (National Arbiter) exam you took in Germany and the full FA (FIDE Arbiter) exam. This kind of stuff is covered in the FA exam.

The program won't go berserk. Here is the explanation.

The pairing system used by Swiss Manager is the FIDE proprietary JaVaFo pairing engine. It implements the FIDE (Dutch) pairing system. This is one of four approved pairing systems:

Dutch
Dubov
Burstein
Lim

I guess you might think that the pairing program would go berserk because with only two results possible for each game there would only be 2, 3 or 4 score groups and as more players play each other and so are ineligible to play each other the program would "struggle" to find acceptable pairings which meet the rules.

Here is what article A.2 of C.04.3 FIDE (Dutch) System says:

> For pairings purposes only, the players are ranked in order of, respectively
>
> a: score
>
> b: pairing numbers assigned to the players accordingly to the initial ranking list and subsequent modifications depending on possible late entries or rating adjustments

In other words, in every score group there is ALWAYS an ordering.

There then follow more paragraphs of complicated rules which, in truth, were generated from the original algorithms used by the first FIDE pairing program. Here is what the official JaVaFo website has to say:

> **A bit of history**
> In its original presentation, the wording of the Dutch System was more similar to a software algorithm than a classical set of rules. There was a good reason behind that. In fact, the legend says that first came the Swiss Master program that was implementing the Dutch System, then the rules to be published by FIDE were modelled on the behaviour of such program.

So, there is a well defined algorithm which works in exactly the same way regardless of the scores and composition of players. There IS a problem which can arise with the Swiss system but it arises in the exact OPPOSITE way to what you describe. If the number of players is only slightly bigger than the number of rounds (say 2 or 3 bigger) then it can happen in the last round, penultimate round in rare circumstances, that it is impossible to generate a legal pairing (no two players playing each other if they have played each other previously).

Moving on to the subject of expirmental evidence.

2^9 = 512 and I so I don't think anybody who isn't being paid to run a tournament with roughly 500 players is going to enter 500 players into a tournament file.

Just to satisfy the curiosity of those (perhaps you included) who want to see what a tournament where white always won would look like I've constructed such a tournament with 2^6 (=64) players playing a 9 round Swiss. To make it directly comparable to a 512 player 9 round Swiss I should probably have stopped after 6 rounds, but continuing to 9 let's you see what would happen if more rounds were played.

I've uploaded it to Chess-results here.

---
Tags: rules, fide, swiss-pairing
---


# Question
Title: Why does Stockfish evaluate this position as equal?
After solving the puzzle while I was analyzing this endgame, I was just surprised to see stockfish evaluates this position as equal.

After Ke4, Ke6 (Opposition); Kf4, and f5 -- I can't find out any idea for white to stop black from queening (assuming that black didn't blunder).

Do I miss some tactics here?

# Answer
Since this position has less than 6 pieces, the full checkmating line can be produced with the Shredder's online 6 piece DTM tablespace. Here is the full checkmating line that I obtained by playing through it.

```
[FEN "8/5p2/5k2/8/3K2p1/6P1/8/8 w - - 0 1"]

1. Kd5 Kf5 2. Kd4 Ke6 3. Ke4 f5+ 4. Kf4 Kf6 5. Ke3 Ke5 6. Kd3 f4 7. Ke2 f3+ 8. Ke1 f2+ 9. Kxf2 Kd4 10. Ke2 Ke4 11. Kf2 Kd3 12. Kf1 Ke3 13. Kg2 Ke2 14. Kg1 Kf3 15. Kh2 Kf2 16. Kh1 Kxg3 17. Kg1 Kh3 18. Kf2 Kh2 19. Ke2 g3 20. Kd2 g2 21. Kd3 g1=Q 22. Kc4 Qe1 23. Kc5 Kg3 24. Kb5 Qc3 25. Kb6 Kf4 26. Ka6 Qb3 27. Ka5 Ke4 28. Ka6 Kd5 29. Ka5 Kc5 30. Ka6 Qb6#

```

One of Black's tactics that you missed is the move 3... f5+. According to the tablebase this is the only winning move for Black. As such, if you miss it you miss the entire win. Another factor is that Black's f pawn causes is able to force the White king away from their pawn. Blacks king is then able to triangulate with their extra space and squeeze White out. White cannot take the Black pawn or else it is simply a faster loss.

Although, I will note, Shredders seems to blip out on move four and mislabels Kf5 as Kf4. This must be some unknown bug.
> 4 votes

---
Tags: engines, analysis, endgame, stockfish
---


# Question
Title: Are there any online chess tournaments for beginners( or new players)?
I have been playing online chess for a long time on sites like lichess and chess.com. But I have never played in any FIDE or AICF organized tournament. In this pandemic are there any online tournaments for new players organized by FIDE or AICF?

# Answer
> 1 votes
There are online tournaments organized by FIDE (https://new.arena.myfide.net). They are more or less like lichess tournaments and you get a special online FIDE rating and you can receive special online titles (https://www.notion.so/FIDE-Online-Arena-Titles-045a5cbfb0994e0b9c04e05ee44c0491). To my best knowledge, there are no tournaments in which you can receive real FIDE points. I think because cheating is always a problem in online games.

---
Tags: tournament, fide, online-chess, beginner
---


title: All draw Round Robin

text:
# Question
Title: All draw Round Robin
Do you know a chess tournament (I wrote Round Robin, since it seems extremely improbable for Swiss) where all games ended drawn? Since of course even I can come up from personal experience with a four player tournament where this happened, let's assume at least 8 players. Calculating with a fairly valid drawing probability of 1/2, I get 1/2^(8\*7/2)~10^-9, so this would be a very rare event.

# Answer
> 5 votes
According to the Wikipedia page of chess world records, the record for draw percentage is 93.3 (that tournament had ten players), meaning no: there hasn't been a recorded tournament with 100% draws.

---
Tags: draw
---


title: Interesting knight vs bishop endgame

text:
# Question
Title: Interesting knight vs bishop endgame
The following endgame, from Almasi vs Sanikidze, is becoming a real riddle. The position, after the 43th move by Almasi, is the following:

```
[fen "8/1N4k1/7p/4ppbP/4P3/1PP5/1K6/8 b - - 0 1"]

```

White King on b2 Knight on b7 pawns on b3 c3 e4 h5. Black to move King on g7 Bishop on g5 pawns on e5 f5 h6. Black to move.

Even on lichess.com evaluation goes up and down as far as depth 43(!) without reaching a clear verdict. With perfect play, is a win for White or a draw?

# Answer
> 1 votes
I would say you gave yourself an answer. If a computer analysis with depth 43 does not find a clear solution, the game would end probably in a draw if both sides play perfectly. Nevertheless, this situation is extremely complicated to analyze for a human and therefore I would say that for both sides a win is possible.

If you would like to know how to advance in this position for one or both sides I would suggest changing the question.

---
Tags: endgame
---


# Question
Title: Examples where top engines in a tournament match don't agree in evaluation
I'd like to know about computer games of some recent tournaments where two top engines diverge in evaluation of a position, in the sense that both think are winning the game (or both losing). I saw a match in the last CCC where Stockfish as white had +3 in his evaluation and Leela -3, that was the maximum I've ever seen.

This is interesting because usually the two engines seem to agree all the time about which one is winning (or at least one thinks it is winning/losing and the other thinks it is a draw) even if there's a gap between the two evaluations.

Best by now I found :

https://www.chess.com/it/computer-chess-championship#event=ccc-rapid-2021-elite-round&game=508 : about +1 and -1

---

**EDIT:**

It seems I had an hallucination about the game between Stockfish and Leela

# Answer
> 4 votes
I finally found through a script several games where (not so big) divergence occurs!

I analized roughly 3000 games with time control 15+3 and just 10 show a notable divergence.

**It's interesting and intuitively correct that this happens a lot more when black wins!** Indeed in the list below there are 3 wins by white, 6 by black and 1 draw even if black wins much more rarely than white between engines.

---

**CCC main league 2021** :

Stockfish classic - Stooflees : +1.41 vs. -2.53

Komodo - Rubi : Long divergence with pick +1.22 vs. -1.35

**CCC elite round 2021** :

Stooflees - Ethereal : +0.84 vs. -1.75

Stockfish - Stooflees : +2.91 vs -0.27

SlowChess - Stoofvless : +2,76 vs. -1.04

Ethereal- Stoofvless : Long divergence with pick +1,07 vs. -0.97

**CCC final 2021 Stockfish - Lc0**:

Game 9 : Long divergence with pick +0.46 vs. -2.19

Game 409 : +0.37 vs -1.99

**CCC 2021 Leela vs Dragon round 2** :

Game 2 : Long divergence with pick +0.34 vs. -1.04

Game 68 : Long divergence with pick +0.89 vs -1.13. This game is strange, the two engines don't agree with drawing the game, 307 moves are played!

# Answer
> 1 votes
This happens, but it's rare and is getting rarer. Here's a very recent game between Stoofvlees and Komodo Dragon displaying such eval divergence. The discrepancy was only there for a few moves, too.

**Edit**: As I said this does not happen often and it's getting rarer. Examples of Stockfish-Leela games in the past where it happened are this game from Season 15 and this one from Season 18; both games are over a year old at this point and involve versions \>100 elo weaker than today's.

---
Tags: engines, tournament, evaluation
---


# Question
Title: How many unoriginal pawn moves can be made in a single game?
Consider an "unoriginal pawn move" to be a pawn move whose notation matches a move already played in the game. For instance, after 1.e4 e5 2.d4 exd4 3.e5, there is one unoriginal pawn move, the e5 played by white. If e5 is played again later, that would be another unoriginal pawn move.

(For clarity, "e5+" would be a different move than "e5").

How many unoriginal pawn moves can be played in a single game (assuming all standard rules, legal moves etc)?

\[originally asked as part of this question\]

# Answer
60 unoriginal pawn moves can be made in a game by quadrupling the pawns 4 times. One can use the same capture once in each column of 4. Then you can use the exact same move 1+3+3+3+3 times in each column. And finally in the black columns white can make a move (to row 3) and vice versa Total: 15\*4 =60

Here is an example game.

```
[FEN ""]

1. Nc3 Nc6 2. Ne4 Ne5 3. Nf6+ exf6 4. Nf3 Ne7 5. Nd4 Nd5 6. Nc6 Nf3+ 7. exf3 Nc3 8. dxc3 dxc6 9. Bd3 Bd6 10. Bg6 Bg3 11. hxg3 hxg6 12. Be3 Be6 13. Bb6 Bb3 14. axb3 axb6 15. Ra5 Rh4 16. Rc5 Rb4 17. cxb4 bxc5 18. b5 c4 19. c3 b6 20. Rh5 Ra4 21. Rc5 Rb4 22. cxb4 bxc5 23. b6 c3 24. b7 c4 25. b8=Q c5 26. b5 c2 27. b6 c6 28. b4 c1=Q 29. Qf4 c3 30. Qg5 fxg5 31. b7 g4 32. b8=Q c4 33. Qf4 c2 34. Qg5 Qf4 35. gxf4 c1=Q 36. f5 Qf4 37. g3 f6 38. gxf4 fxg5 39. b5 c3 40. b6 c2 41. b7 c1=Q 42. b8=Q Qc5 43. b3 Qd6 44. b4 c5 45. b5 c4 46. b6 c3 47. b7 c2 48. Qa7 c1=Q 49. b8=Q g3 50. f6 g2 51. f5 Qcc7 52. f4 Kd7 53. f7 g1=N 54. f6 g4 55. f8=Q g5 56. f7 g6 57. f5 g3 58. f6 g2 59. f3 g4 60. f4 g3 61. f5 g5 62. Qh8 g4 63. f8=Q Ne2 64. f7 g1=N 65. f6 g2 66. Qfh6 Nh3 67. f8=Q g1=N 68. Qfg8 g3 69. f7 g2 70. f8=Q Nc3 71. Qe2 Ngxe2 72. Qaa8 g1=N

```
> 6 votes

---
Tags: problems, pawns, records, notation, mathematics
---


title: Why is 11. .. h6 such a bad move?

text:
# Question
Title: Why is 11. .. h6 such a bad move?
```
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
[Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]

1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. Nc3 Nxc3 6. dxc3 Be7 7. Be3 O-O 8.
Qd2 Be6 9. h4 Nc6 10. Be2 Ne5 11. Ng5 h6 12. Nxe6 fxe6 *

```

I (black) like playing the Petroff and my opponent answered with a Nimzowitsch attack. I tought that my position would be quite decent. After 11. .. h6 the engine turned from +-0 to +2 without losing any material. I understand that the move was not perfect positionally but could somebody explain the huge change?

# Answer
> 18 votes
By playing `11...h6`, you created a weakness on `g6`, and you created a target on `h6`, now it is easier for white to open up a position around your king by pushing their g-pawn. White also has a potential bishop sacrifice on h6.

In general it is best to avoid pawn moves in front of your king, especially when facing a pawn storm.

# Answer
> 12 votes
To add to the existing answers, you just gave up your light squared bishop for no apparent reason, while creating many light square weaknesses around your king with the same move! Now white is the only player with a light squared bishop and you will have a tough defensive job if white plays correctly.

# Answer
> 4 votes
White has easy ideas like `1. Nxe6 fxe6 2. Bxh6 gxh6 3. Qxh6` with ideas of `Rh3` to `g3`.

# Answer
> 2 votes
If we see from black prospective its pieces don't have a clear plan.For me as a player from black side I will try to bring the other rook on the king side. So as to defend the position strongly because black knight and bishop are having very less squares on the other hand white will bring his other rook on the king side with castling.Pushing those king side pawns makes it look horrible for because even if white is able to create one open file on the king side like g and h file.I don't see any defense for black and after then white can even sacrifice his bishop to get his queen in the game.If you think of taking black king to the other side of the board to me it looks to be very difficult.

# Answer
> 2 votes
It sounds like you want a more concrete answer than "your light squares are now very weak", "white has the bishop pair", and "you've just created a hook for white to utilize by pushing the g-pawn to g5 \[and you likely won't have h5 as a response\]". Obviously your engine can give you the most concrete justifications, but I would argue that after 13.0-0-0, white will play f4 driving your knight back (f4 right away can be met by Bxh4+, so no need to rush it), followed by g4 and g5, busting open your kingside without even losing a pawn, I believe. The rook from d1 will join in. If you, as black, ever take hxg5, the h-file will open for white's h1 rook, and if not white will play f5 and then take on Bxh6, thereby having the bishop and queen also join in the attack.

# Answer
> 1 votes
The main reason that this move is weak is that you already have all major white figures targeting fields surrounding black king, and you are adding problems to it because the *only option* you have is to take the knight weakening the position even further by making g6 undefended. Notice that even if the white bishop would capture the pawn at h6, he would not be in as bad position as you could imagine, taking into accounts all the threats that you would have to control.

But what is the mistake you ask? The mistake is that you did not move the attacked bishop first. The best is to move it to f5 and then you are almost there. You could move to d7 but it seems a more defensive move than it should be. Notice that d7 both attacks and defends. And now after white castles 0-0-0, you can safely play h6. Simply put, you forgot a supporting move. You have other moves besides h6 but h6 is not that bad after 0-0-0.

You have to play safe, that is all. h6 is simply to quick and obvious choice. But, it is so weak choice at that moment that it must be considered a blunder. You are not in that bad position after all.

---
Tags: positional-play, evaluation, petroff-defense
---


# Question
Title: Why are these sequence of steps played to solve this puzzle?
```
[FEN "rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b KQkq - 0 1"]
[StartFlipped "0"]

1... Bxa3 2.Nxa3 Qa5+ 3.Kf1 Qxa3

```

FEN: rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b - - 0 1

I thought that the solution would be equivalent to 1... Qa5+ 2. Kf1 Bxa3 3. Nxa3 Qxa3. But apparently, my solution is wrong. What is the difference between these two sequences? Why should you take the White bishop first?

# Answer
The answer was given in a comment:

> After your Qa5+ how do you make White play Kf1? What do you do if he plays Qd2?

This is correct. There's really nothing you can do after Qa5+ Qd2 that gives Black a significant advantage.

> He can play Qd2 after Bxa3; Nxa3 Qa5; too right?

White can play that, but it doesn't help in that position. You can take the knight with your queen. (If you played Qa5+ first, then ...Qxa3 loses to Nxa3, and ...Bxa3 is obviously responded to with Qxa5.)

```
[FEN "rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b KQkq - 0 1"]
[startflipped ""]

1... Bxa3 (1... Qa5+ 2. Qd2 Qxa3? (2... Qxd2+ 3. Kxd2 Bxa3 4. Nxa3 {Material is even.}) (2... Bxa3 3. Qxa5 Bb2 4. Qb4 Bxa1 {Rook and bishop for the queen for now, although Black's bishop may get trapped. Certainly White has the advantage.}) 3. Nxa3 Bxa3 {Two pieces for the queen; White is clearly ahead.}) 2. Nxa3 Qa5+ 3. Qd2 Qxa3 {Black is up a knight.}

```
> 5 votes

---
Tags: analysis, puzzles
---


# Question
Title: What are these types of OTB events from the USCF?
Looking into OTB tournaments, I see that the USCF allows you to filter searches for the following types:

* Heritage Event
* American Classic
* Grand Prix
* Enhanced Grand Prix
* Junior Grand Prix
* National Championship Event
* State Championship Event
* Regionals

Some of these are self-evident, but what are "Heritage," "Classic," "Grand Prix," and "Enhanced" types?

# Answer
> 2 votes
According to the Saint Louis Chess Club:

* National Events. Co-sponsored by the USCF, these events offer official U.S. titles and most are open to bidding by USCF affiliates. *(Meaning that any affiliate - such as a club or organization holding USCF affiliation - may make a bid to host these tournaments.)*
* Grand Prix. Major events, usually open to all, listed in date order. See "USCF GRAND PRIX" for more information.
* American Classics. Events that are open to all and have attracted more than 400 players for three consecutive years.
* Heritage Events. Tournaments held for at least 25 years.

I could not find a "USCF GRAND PRIX" section on the Saint Louis Chess Club's website, but Wikipedia says:

> The USCF Grand Prix is a set of chess tournaments for prize money rated by the United States Chess Federation. In general, a tournament must have at least $300 in guaranteed prizes to award "Grand Prix" points.
>
> At the end of the year, prizes are awarded to players with the most points. The first prize is usually $10,000.
>
> These prizes provide incentives to grandmasters to play in small regional tournaments which they would otherwise avoid.

I could not find a specific definition of "Enhanced Grand Prix", but from context of things I did find, it appears that "Enhanced Grand Prix" refers to tournaments that offer a larger number of Grand Prix points due to having a larger guaranteed prize pool. It also appears (according to this news item) that holding an "Enhanced Grand Prix" event requires the organizer to make a mandatory contribution to the USCF Professional Players Health and Benefit Fund.

"Junior Grand Prix" is a separate Grand Prix competition for Junior players (under 21 years old).

{Added 10/23/2022} A complete description of US Chess Grand Prix is available at https://new.uschess.org/us-chess-grand-prix-program.

---
Tags: tournament, terminology, uscf, otb-chess
---


title: Tempting bad moves

text:
# Question
Title: Tempting bad moves
The following is, unfortunately, a very common experience'o'mine:

Chess book. Grandmaster game. Diagram.

I (after 1 microsecond): Play Nxe6, willya?

scrolldown, author: "Nxe6 was the decisive mistake." Oh bother.

Now, it is a very obvious explanation that mistakes made even by a GM must be very tempting mistakes for a FM patzer like me too, but "obvious" doesn't mean "proven" (and moreover, my style could be a critical factor here too). Thus this is clear science fodder: Collect 100 GM and 100 patzer blunders, give the positions to a GM and a patzer group, count how many of them get repeated. Has such an experiment (or, more general, a treatise on what makes a blunder tempting) ever been done? (Books specializing on blunders exist, for starters, but rather tend to research the reasons.)

# Answer
> 1 votes
A tempting bad move is the one that might have some idea behind it, yet your execution is more direct than it should have been. You play a move without preparatory steps to what you want to execute. That groups tempting moves into:

1. Those with a bad idea that have no substance in it and are a wishful thinking. These might be used only in blitz chess where the defensive move is not that obvious and needs some thinking. You play in order to confuse the opponent into thinking that there is something to it. Of course, most of the time you are just not aware that there is nothing to it, you just hope there is.
2. Those that have some idea but require a preparation which you might not have sufficient skills to execute. You play the move just to reveal another weakness that you forgot to protect first.

Your normal move is always tactical one that never lowers your chances which you have got so far, or you play a defensive move if your opponent attacks. To attack, you always have to prepare the terrain first, unless your opponent played such a blunder that a mate is obvious. Best dish is turkey served called or how that saying actually goes. :)

---
Tags: psychology, blunder
---