# Question
Title: Is there any correlation between average rating and the time of the day?
Crosspost to Stats.SE.

I play online bullet, mostly lichess, sometimes chess.com. Once I noticed that my average performance varies depending on the time of the day: e.g. at the morning I can lose 50 rating after a dozen of games, but I will easily regain it at the evening. One possible explanation is that my brain may work worse at the morning because of sleepyness or something. But can the reason be not me but my opponents?

Imagine two countries, A and B, in different time zones. Players from A and from B tend to play chess at the evening; let it be 00:00 UTC and 12:00 UTC respectively. And, for some reason, players from A are generally stronger than players from B. In the extreme example players from different countries never meet each other, so their ratings establish independently. So even if two players have similar strength, the player from B will have higher rating (because he is stronger among his population).

In this setting, if I play at 00:00 UTC I will meet opponents from A, and if I play at 12:00 UTC I will meet opponents from B. Players of my rating will have different absolute strength in these cases.

Another (imaginary) example about days of the week: it could be possible that on average stronger players tend to play on weekdays and weaker players on weekend, which leads to the similar effect.

Have anyone ever analyzed this kind of statistics and is the phenomenon in question possible, or it is believed that ratings are homogeneous in this sense?

# Answer
I tried to calculate the day/night score rate on a couple of GMs with lichess account. Data is from the lichess bullet games. I use the UTCDate and UTCTime tag in the game header to classify day/night time.

It does not consider opponent's day/night, this is just a simple stats about the perf of the given player.

Here is the result.

```
The day is from 6am to 6pm in their respective local time given utc offset.
The rest of the hours are covered for the night. Game type is bullet.

            id  utc cty  dsrate  nsrate  dgames  ngames                              profile
      GMJOEY93    8  PH 0.74531 0.75417    2880    4674       https://lichess.org/@/GMJOEY93
     AnishGiri    1  NL 0.69815 0.70350     593    1199      https://lichess.org/@/AnishGiri
 DrNykterstein    1  NO 0.74074 0.71805    1404    7583  https://lichess.org/@/DrNykterstein
gmwesleyso1993   -6  US 0.83078 0.86842     523      19 https://lichess.org/@/gmwesleyso1993
   alireza2003    1  FR 0.72139 0.60589     402    4802    https://lichess.org/@/alireza2003
  Azerichessss    4  AZ 0.62517 0.63803    1430    2543   https://lichess.org/@/Azerichessss

dgames = day games
ngames = night games
dsrate = day_score/day_games
nsrate = night_score/night_games
DrNykterstein = Magnus

```
> 3 votes

---
Tags: rating, online-chess
---


# Question
Title: For fixed-depth search, how much is the efficiency different between odd and even moves?
If a chess engine calculates in even depth, in the final position, it has to move again, whereas if it calculates at the odd depth, then the opponent has to move at the end of calculation (ignoring quiescence search here = no wild exchanges take place).

In these cases, does the expected strength of engine drastically differ? Meaning, would we get completely different "elo" formulas if we considered even and odd search depth separately?

It obviously makes no sense to compare engine of depth 5 with engine of depth 6, but I believe there would be a different gap from going even -\> odd than odd -\> even.

# Answer
In even depth search in the final position, the first player does not move again, but internally it has the side to move. At depth 0 it will normally call qsearch().

For odd depth search in the final position the second player has the side to move internally but it will not make a move.

All of these searches do need another condition that is on `search depth extensions` like check, pawn\_push\_to\_7th\_rank and others.

I took stockfish code and disable qsearch() and extensions. Instead of calling qsearch() I just return evaluate(). Here are the results for depth 4 vs depth 3 and depth 5 vs depth 4 in 1k games.

#### D4 vs D3

```
Score of Stockfish 070122 d4 vs Stockfish 070122 d3: 715 - 247 - 38  [0.734] 1000
...      Stockfish 070122 d4 playing White: 357 - 120 - 23  [0.737] 500
...      Stockfish 070122 d4 playing Black: 358 - 127 - 15  [0.731] 500
...      White vs Black: 484 - 478 - 38  [0.503] 1000
Elo difference: 176.3 +/- 23.8, LOS: 100.0 %, DrawRatio: 3.8 %

```

#### D5 vs D4

```
Score of Stockfish 070122 d5 vs Stockfish 070122 d4: 665 - 279 - 56  [0.693] 1000
...      Stockfish 070122 d5 playing White: 357 - 118 - 25  [0.739] 500
...      Stockfish 070122 d5 playing Black: 308 - 161 - 31  [0.647] 500
...      White vs Black: 518 - 426 - 56  [0.546] 1000
Elo difference: 141.4 +/- 22.6, LOS: 100.0 %, DrawRatio: 5.6 %

```
> 2 votes

# Answer
Assuming there's no horizon effect, there should be no significant difference between a position with only the who to move being changed, although the initiative does have some difference in the evaluation, it's hard to program in a static position. (Since a move can both have a positive and negative effect, this can be ignored.)
> 1 votes

# Answer
What you describe is called the Odd-Even Effect, see https://www.chessprogramming.org/Odd-Even\_Effect There are some observations one can make here. One is that in a plain alpha-beta implementation, going from an even to an odd ply will take a longer amount of time than going from an odd to an even ply.

This has to do with how the algorithm operates. I'll explain with a toy example, consider a depth 0 search. That is just an evaluation so 1 node. A depth one search will take 20 nodes, you will have to look at each move. However, look at the depth two search. If you search the best move first (which thanks to good move ordering heuristics you might well do), let's say 1.e4, then you will need to look at 20 replies, that's 21 nodes so far. For each other worse starting move, there exists a "refutation", i.e. a response move proving that this other starting move is no better than e4. So for each of those 19 moves you only need one response each, that would make it 38 nodes, a total of 59. As you can see here, from the even depth 0 to odd depth 1 the search amount increased by a factor of 20, from the odd depth 1 to even depth 2, only by a factor of 3. This pattern continues to higher depths.

And this is what you will actually observe with weak engines that just implement a plain alpha-beta search. With strong engines that does not really happen anymore though, since those don't have a uniform search depth in the first place. So if Stockfish searches depth 10 that does not mean it searches 10 ply variations in all parts of the tree, in important parts it might search 15 or 20 plies while in irrelevant parts of the tree it might reduce heavily and only search 5 plies deep, for instance when calculating a line that gives away the Queen. Naturally with this imbalanced a tree, the effect will be very small.

Now what about playing strength? Here is where my answer becomes a bit more vague and anecdotal. When you search an odd number of plies, you will be the last one to move. E.g. for depth 1 you make one move and the search ends. This means, a naive evaluation will give higher evaluations for you there and lower evaluations for even depths. This again is what you find in weak engines, depth 0 would be evaluated 0.00, depth 1 would be evaluated e.g. +0.20 after 1.e4 and then depth 2 would be evaluated 0.00 again, after e.g. 1.e4 e5. You can work around this with a tempo bonus as has been suggested in other answers. However, this still has an effect: Loosely speaking, on odd search depths the player to move thanks to the extra tempo can play more actively, since the opponent won't be able to respond on the last ply. With weak engines this can have minor beneficial effects, since playing actively generally speaking is a good thing in chess. So you will at times see engines playing stronger on odd depths than on even depths.

However, once again, if your engine is strong, not only will it naturally have good heuristics and evaluation functions that automatically make it play this actively, they also once again don't have a pronounced Odd-Even effect due to search extensions, reductions and all sorts of other search optimizations. So I would expect whatever effect there is in Stockfish, if any, to be much smaller than it would be in a much weaker engine.

One last thought, are even or odd ply searches more "efficient" in time to playing strength, in weak engines? Based on the above thoughts I would say, it is not clear. Odd depth searches take longer but also possibly produce slightly better quality moves. How this tradeoff evaluates likely differs from engine to engine, but that is entirely speculation.
> 1 votes

# Answer
You are correct that using the same position evaluation function would make a difference at odd depth compared to even depth. Indeed, in many (turn-based) abstract games including chess, the average board position favours the player who has the turn. The fact that there are exceptions to the average (called zugzwang) does not change the fact that **tempo is beneficial on statistical average** over all positions relevant to good play. This is precisely why Stockfish include a tempo bonus. You can see that it is small but positive (≈ 0.2 times the material value for a pawn at the start of the game), indicating that the designers of Stockfish found that SF does better than if the bonus was zero or too big.

Thus the expected strength of a good chess AI based on alpha-beta search should not differ much whether you cut off the evaluation at odd or even depth, **precisely because** its position evaluation function ought to already (statistically) correct for the difference in tempo.
> 0 votes

---
Tags: engines, depth
---


title: Why is this rook move a mistake?

text:
# Question
Title: Why is this rook move a mistake?
Recently I was playing a game on chess.com (300 rating) and after the game the engine showed that this move was a mistake, losing two points of material.

```
[FEN ""]

1. e4 a5 2. d4 h5 3. f3 f6 4. c3 c6 5. Nh3 b6 6. Bc4 e6 7. O-O d6 8. Na3 b5 9.
Nxb5 Ba6 10. Qb3 cxb5 11. Bxb5+ Nd7 12. Bxa6 Rxa6 13. Nf4 Rb6 14. Qc2 g5 15.
Nxe6 Qe7 16. Nxf8 Kxf8 17. b3 Rc6 18. Ba3 Nb6 19. Rfd1

```

Is there a reason I should play f4 instead? It seems like a dangerous move that has no merit.

# Answer
You're not actually losing two points of material by playing Rfd1, but rather you're not gaining the advantage.

You currently have 3 pawns for a knight, which is roughly even, however black is somewhat cramped for space, their knight is undeveloped, their king is under x-ray attack from both the bishop on a3 and rook on f1, and they have two isolated pawns.

By pushing e5 or f4, you are threatening to open direct lines to the black king, eventually turning your positional advantage into a material advantage.

One possible continuation is:

```
[FEN ""]
[StartPly "36"]

1. e4 a5 2. d4 h5 3. f3 f6 4. c3 c6 5. Nh3 b6 6. Bc4 e6 7. O-O d6
8. Na3 b5 9. Nxb5 Ba6 10. Qb3 cxb5 11. Bxb5+ Nd7 12. Bxa6 Rxa6
13. Nf4 Rb6 14. Qc2 g5 15. Nxe6 Qe7 16. Nxf8 Kxf8 17. b3 Rc6 18. Ba3 Nb6
19. e5 Qd7 20. c4 Nd5 21. Qd2 Nb4 22. f4 g4 23. d5 Rc8 24. Rae1 h4 25.
Bb2 h3 26. g3 Qf5 27. Bc3 Rh7 28. a3 Na6 29. Bxa5 *

```

White has picked up another pawn, and now has two outside passed pawns. Black will have to give up more material to stop them and still has to contend with the pressure from the e5 pawn.
> 4 votes

# Answer
In addition to what Herb said,

1. your rook on `f1` is already perfectly placed; it lines up on the black king.
2. Further, `Rfd1` doesn't force any action. Thus Black has time to solidify his kingside. Indeed, in Stockfish's analysis, White returns that rook to `f1` two moves later.

And you are correct, `f4` is a move that requires careful consideration. Good on you. However, it is hard to see how Black can exploit that open diagonal (`a7-g1`), having no black-squared bishop and a precariously placed queen.

Regarding `f4`, Stockfish rates the position at about +4:

```

    [FEN "5knr/4q3/1nrp1p2/p5pp/3PP3/BPP2P2/P1Q3PP/R4RK1 w - - 0 20"]

    1.f4 gxf4 2.e5 Kg7 3.Rae1 Qd7 4.Bxd6 Rxd6 5.exd6 Qxd6 6.Qf2 Ne7 7.c4 Nbc8 8.Qxf4 Qxf4 9.Rxf4 Kf7 10.Ref1 f5 11.d5 Rh6 12.Rd4 Rd6 13.Re4 Kf6 14.Re2 Rd7 15.Re6+ Kg5 16.Ra6 Nxd5 17.cxd5 Rxd5 18.a3 Nd6 19.Ra8 Ne4 20.Rh8 Kg6

```

You can see by about the 6th move how ugly Black's position is getting. He's giving up material to take the pressure off.

On `Rfd1`, Stockfish drops the score to +1.72:

```

    [FEN "5knr/4q3/1nrp1p2/p5pp/3PP3/BPP2P2/P1Q3PP/R4RK1 w - - 0 20"]

    1. Rfd1 Kf7 2.Rf1 Qb7 3.f4 gxf4 4.Rxf4 Nd7 5.c4 Ne7 6.Raf1 Ra6 7.R4f2 Ke8 8.Qd2 Qc7 9.Qe2 Qa7 10.Bb2 Kd8 11.Kh1 Nc6 12.Rd1 Kc8 13.Bc3 Kb8 14.Rf5 Kc8 15.Rb5 Qc7 16.a3 Rb6 17.d5 Rxb5 18.cxb5 Nb4 19.Bb2

```

Comparing the variations, you can see how the 2nd variation is much less dynamic and Black is in less danger.
> 2 votes

---
Tags: beginner, pawns, rooks
---


title: Can black make a draw offer?

text:
# Question
Title: Can black make a draw offer?
I am playing a chess game and my opponent is black and he asked me if I would accept a draw since I have a King and a Knight while he has a King and a Bishop. I told him that he can make an offer and he mentioned it's against etiquette when black makes an offer. Can you please lead me to locate the source? The game is on GameKnot.com.

# Answer
> 7 votes
There is no such rule.

It would be against etiquette for one side to offer a draw repeatedly, or to offer one in a position which is a certain loss. FIDE rule 11.5 lists "unreasonable offers of a draw" as one thing that can constitute distracting or annoying an opponent, which is prohibited.

In an official over-the-board game, the proper time to request a draw is after you've made your move but before you hit the clock (FIDE rule 9.1.2.1.) That seems to be impossible in an online game, so I would say that it would be best to make the offer right before you move, so that the offer notification doesn't come during your opponent's thinking time.

---
Tags: etiquette
---


# Question
Title: Dataset: Chess Positions and evaluation value
Is there anybody out there who knows about a very good dataset of chess **positions** (e.g. FEN notation or 64 fields with pieces in it) combined with a Stockfish-like evaluation score?

I did find something on Kaggle, but the number of games was quite small so it wasn't good for Machine Learning purposes.

# Answer
> 6 votes
This is what I use for my training purposes for this project.

Source

---
Tags: computer-chess, database, human-versus-machine
---


# Question
Title: Why is it a blunder to capture this pawn even if its defender is pinned?
```
[FEN "1r1q1rk1/p4pp1/3p1b1p/2pQ4/4P3/P1P2P2/1P2B1PP/1K1R3R b - - 0 20"]
[Title "The Position"]

1... Bxc3??

```

In this position, I believed that the best move for Black is **Bxc3**. It’s a free pawn, creates a threat on b2, and exposes the white king.

However, Stockfish labels it a blunder. The advantage goes from around `−2.5` to `−0.5`.

After Black plays **Bxc3**, Stockfish suggests the move **b3** for White. I do not see how this justifies labeling the bishop move a blunder.

# Answer
> 7 votes
Because you have opposite-colored bishops and it's nearly impossible to win in the endgame. You can, however, take advantage of the weak white king.

After 20... Bxc3 the game will most likely continue:

```
[FEN "1r1q1rk1/p4pp1/3p1b1p/2pQ4/4P3/P1P2P2/1P2B1PP/1K1R3R b - - 0 20"]

1... Bxc3 2. b3 Bd4

```

This will you protect your pawn on d6. You've lost your chance to win now.

20... Qa5 or, even better, 20... Qb6 begins the attack. Here's a possible (and interesting) continuation:

```
[FEN "1r1q1rk1/p4pp1/3p1b1p/2pQ4/4P3/P1P2P2/1P2B1PP/1K1R3R b - - 0 20"]

1... Qb6 2. Qd2 Qb3 3. Ka1 Bg5 4. f4 Bxf4 5. Bc4 Bxd2
6. Bxb3 Bxc3 7. Bxf7+ Rxf7 8. bxc3 Rf2

```

The bishops are gone and your opponent's pawns are split. You also threaten to move your other rook on the second rank.

# Answer
> 6 votes
Positions with opposite color bishops and heavy pieces are known to be very complicated and double-edged. The tension between two sides can last for a long time because of continuous maneouvering of rooks and queens.

Consequently, evaluation of the position depends mostly on the dynamical resources and weaknesses in pawn structure and not on just pawns counting (but of course it counts too). After **1. ... Bxc3 2. b3** and subsequent **Bc4**, **Ka2** White hampered black's attack along the b-file. And it's not clear for black how to proceed.

At the same time white has a clear plan of advancing king's side pawns evolving the attack. f7 pawn is pinned and it would be a long-term target for white's pieces on light-squared diagonal a2-g8.

I think, that exchanging off queens will bring white's edge in the endgame.

To see more deeply we can make intermezzo move **1. ... Qb6** threatening mate. Now b3 can not be played. And white needs to play **2. Qd2** to protect c3 and b2. Then black's idea to put all his heavy pieces along b-file and continue attack. White is in trouble because his bishop can not take part in defense, for example:

```
[FEN "1r1q1rk1/p4pp1/3p1b1p/2pQ4/4P3/P1P2P2/1P2B1PP/1K1R3R b - - 0 20"]

1...Qb6 (1...Bc3? 2. b3 Qb6 3. Bc4=) 2. Qd2 Qb3 3. Ka1 Bg5! (3...Rb6 {with idea of Rb8. With edge for black.}) (3. Qc2? Bxc3 4. Qb3 Rb3 5. Kc2 Rxb2 6. Kxc3 Re2) (2... Rb7 3. Bc4 Rfb8 4. b3 Qa5 {targeting a3 and c3. Also good for black strategically.}) 4. f4 Bf4 5. Bc4 {only move} Bd2 6. Bb3 Bc3 7. Bf7 Rf7 8. bxc3 Rf2 {with very good chances in the endgame for black}

```

Main line of my variations is from previous answer by double-beep.

# Answer
> 1 votes
The pawn is actually a goner in any case after 1...Qa5 or 1...Qb6 - White can't play 2.c4 since Black can play Rxb2+, breaking the pin with 2. Kc2?? or 2. Kh2?? leads to 2...Rxb2+ 3. Kxb2 Qxc3+ and checkmate, and the pawn is attacked more times than it can be defended.

The real difference is that if you take the pawn immediately, White can play 2. b3 followed by 3. Ka2, which leads to a solid defensive set up against which you don't have immediate attacking ideas. This is why Stockfish wants to play 1...Qa5 or 1...Qb6, preventing this defense, before taking the pawn.

Note that although 1...Bxc3 wins a pawn, you still aren't actually ahead in material because in the current position you are a pawn down, and White has positional trumps as well - in particular your d6-pawn is weak and it's hard to eject the Queen from d5.

# Answer
> 1 votes
It's not so much that Bxc3 is a blunder, as that **not** doing Qd6 is a blunder. Stockfish gives +4.5 to this position with White to move, and -0.4 after Bxc3, so Bxc3 compared to nothing at all improves your position by 4.1. It's just that Qd6 improves your position even more. Even if a move doesn't give up material, keep in mind that every move costs a tempo. Opportunity cost is just as important as direct cost, and an opponent's weakness left unexploited is just as much a blunder as giving yourself a weakness. "When you see a good move, look for a better one."

---
Tags: analysis, beginner, blunder, pins
---


# Question
Title: Using pgn-extract to output FEN + evaluation
I'm using `pgn-extract` to convert a PGN database into FEN + evaluations. My goal is something like this:

```
1. e4 e6 2. d4 b6 3. a3 Bb7

```

Into this:

```
rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1 { 1.20 }
rnbqkbnr/pppp1ppp/4p3/8/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2 { 0.00 }
rnbqkbnr/pppp1ppp/4p3/8/3PP3/8/PPP2PPP/RNBQKBNR b KQkq d3 0 2 { 0.90 }
rnbqkbnr/p1pp1ppp/1p2p3/8/3PP3/8/PPP2PPP/RNBQKBNR w KQkq - 0 3 { 0.70 }

```

So far, I've only been able to use: `pgn-extract --quiet --evaluation -C --fencomments 1.pgn` to get something like this (with both fen and evaluation following the SAN):

```
1. e4 { 1.20 } { rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0
1 } 1... e6 { 0.00 } { rnbqkbnr/pppp1ppp/4p3/8/4P3/8/PPPP1PPP/RNBQKBNR w
KQkq - 0 2 } 2. d4 { 0.90 } {
rnbqkbnr/pppp1ppp/4p3/8/3PP3/8/PPP2PPP/RNBQKBNR b KQkq d3 0 2 } 2... b6 {
0.70 } { rnbqkbnr/p1pp1ppp/1p2p3/8/3PP3/8/PPP2PPP/RNBQKBNR w KQkq - 0 3 }
3. a3 { 0.60 } { rnbqkbnr/p1pp1ppp/1p2p3/8/3PP3/P7/1PP2PPP/RNBQKBNR b KQkq
- 0 3 }

```

Is there a way to go directly to what I want?

# Answer
One way is by using the python chess library.

* Install python
* Install python chess with `pip install chess`

### p.py

```
import chess.pgn

fn = 's.pgn'

with open(fn, encoding='utf-8') as h:
    while True:
        game = chess.pgn.read_game(h)
        if game is None:
            break

        for node in game.mainline():
            comment = node.comment
            com = comment.split('\n')
            fen = com[1]
            val = com[0]
            print(f'{fen} {{ {val} }}')

```

### s.pgn

multiple game is supported.

```
[Event "Magnus Carlsen Inv KO"]
[Site "chess24.com INT"]
[Date "2021.03.17"]
[Round "1.22"]
[White "Carlsen,M"]
[Black "Aronian,L"]
[Result "1/2-1/2"]
[WhiteElo "2847"]
[BlackElo "2781"]
[ECO "C47"]

1. e4 { 1.20 } { rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1 } 1... e5 { -0.20 } { rnbqkbnr/pppp1ppp/8/4p3/4P3/8/PPPP1PPP/RNBQKBNR w KQkq e6 0 2 } 2. Nf3 { -0.20 } { rnbqkbnr/pppp1ppp/8/4p3/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2 } 2... Nc6 { -0.40 } { r1bqkbnr/pppp1ppp/2n5/4p3/4P3/5N2/PPPP1PPP/RNBQKB1R w KQkq - 2 3 } 3. Nc3 { -0.20 } { r1bqkbnr/pppp1ppp/2n5/4p3/4P3/2N2N2/PPPP1PPP/R1BQKB1R b KQkq - 3 3 } 3... Nf6 { 0.00 } { r1bqkb1r/pppp1ppp/2n2n2/4p3/4P3/2N2N2/PPPP1PPP/R1BQKB1R w KQkq - 4 4 } 4. d4 { 0.80 } { r1bqkb1r/pppp1ppp/2n2n2/4p3/3PP3/2N2N2/PPP2PPP/R1BQKB1R b KQkq d3 0 4 } 4... exd4 { -0.30 } { r1bqkb1r/pppp1ppp/2n2n2/8/3pP3/2N2N2/PPP2PPP/R1BQKB1R w KQkq - 0 5 } 5. Nxd4 { 1.30 } { r1bqkb1r/pppp1ppp/2n2n2/8/3NP3/2N5/PPP2PPP/R1BQKB1R b KQkq - 0 5 } 5... Bb4 { 0.30 } { r1bqk2r/pppp1ppp/2n2n2/8/1b1NP3/2N5/PPP2PPP/R1BQKB1R w KQkq - 1 6 } 6. Nxc6 { 4.20 } { r1bqk2r/pppp1ppp/2N2n2/8/1b2P3/2N5/PPP2PPP/R1BQKB1R b KQkq - 0 6 } 6... bxc6 { 0.40 } { r1bqk2r/p1pp1ppp/2p2n2/8/1b2P3/2N5/PPP2PPP/R1BQKB1R w KQkq - 0 7 } 7. Bd3 { 0.20 } { r1bqk2r/p1pp1ppp/2p2n2/8/1b2P3/2NB4/PPP2PPP/R1BQK2R b KQkq - 1 7 } 7... d5 { -0.60 } { r1bqk2r/p1p2ppp/2p2n2/3p4/1b2P3/2NB4/PPP2PPP/R1BQK2R w KQkq d6 0 8 } 8. exd5 { 0.80 } { r1bqk2r/p1p2ppp/2p2n2/3P4/1b6/2NB4/PPP2PPP/R1BQK2R b KQkq - 0 8 } 8... cxd5 { -0.30 } { r1bqk2r/p1p2ppp/5n2/3p4/1b6/2NB4/PPP2PPP/R1BQK2R w KQkq - 0 9 } 9. O-O { -0.10 } { r1bqk2r/p1p2ppp/5n2/3p4/1b6/2NB4/PPP2PPP/R1BQ1RK1 b kq - 1 9 } 9... O-O { 0.30 } { r1bq1rk1/p1p2ppp/5n2/3p4/1b6/2NB4/PPP2PPP/R1BQ1RK1 w - - 2 10 } 10. Bg5 { 0.90 } { r1bq1rk1/p1p2ppp/5n2/3p2B1/1b6/2NB4/PPP2PPP/R2Q1RK1 b - - 3 10 } 10... Be6 { 0.80 } { r2q1rk1/p1p2ppp/4bn2/3p2B1/1b6/2NB4/PPP2PPP/R2Q1RK1 w - - 4 11 } 11. Nb5 { 0.60 } { r2q1rk1/p1p2ppp/4bn2/1N1p2B1/1b6/3B4/PPP2PPP/R2Q1RK1 b - - 5 11 } 11... c5 { 0.70 } { r2q1rk1/p4ppp/4bn2/1Npp2B1/1b6/3B4/PPP2PPP/R2Q1RK1 w - c6 0 12 } 12. a3 { 0.70 } { r2q1rk1/p4ppp/4bn2/1Npp2B1/1b6/P2B4/1PP2PPP/R2Q1RK1 b - - 0 12 } 12... Ba5 { 0.80 } { r2q1rk1/p4ppp/4bn2/bNpp2B1/8/P2B4/1PP2PPP/R2Q1RK1 w - - 1 13 } 13. b4 { 1.10 } { r2q1rk1/p4ppp/4bn2/bNpp2B1/1P6/P2B4/2P2PPP/R2Q1RK1 b - b3 0 13 } 13... Bb6 { 1.00 } { r2q1rk1/p4ppp/1b2bn2/1Npp2B1/1P6/P2B4/2P2PPP/R2Q1RK1 w - - 1 14 } 14. bxc5 { 2.20 } { r2q1rk1/p4ppp/1b2bn2/1NPp2B1/8/P2B4/2P2PPP/R2Q1RK1 b - - 0 14 } 14... Bxc5 { 0.10 } { r2q1rk1/p4ppp/4bn2/1Nbp2B1/8/P2B4/2P2PPP/R2Q1RK1 w - - 0 15 } 15. c3 { 0.40 } { r2q1rk1/p4ppp/4bn2/1Nbp2B1/8/P1PB4/5PPP/R2Q1RK1 b - - 0 15 } 15... h6 { 0.30 } { r2q1rk1/p4pp1/4bn1p/1Nbp2B1/8/P1PB4/5PPP/R2Q1RK1 w - - 0 16 } 16. Bh4 { -0.20 } { r2q1rk1/p4pp1/4bn1p/1Nbp4/7B/P1PB4/5PPP/R2Q1RK1 b - - 1 16 } 16... Rc8 { -0.10 } { 2rq1rk1/p4pp1/4bn1p/1Nbp4/7B/P1PB4/5PPP/R2Q1RK1 w - - 2 17 } 17. Nd4 { 1.00 } { 2rq1rk1/p4pp1/4bn1p/2bp4/3N3B/P1PB4/5PPP/R2Q1RK1 b - - 3 17 } 17... Bxd4 { -3.20 } { 2rq1rk1/p4pp1/4bn1p/3p4/3b3B/P1PB4/5PPP/R2Q1RK1 w - - 0 18 } 18. cxd4 { 0.20 } { 2rq1rk1/p4pp1/4bn1p/3p4/3P3B/P2B4/5PPP/R2Q1RK1 b - - 0 18 } 18... g5 { -0.10 } { 2rq1rk1/p4p2/4bn1p/3p2p1/3P3B/P2B4/5PPP/R2Q1RK1 w - g6 0 19 } 19. Bg3 { 0.40 } { 2rq1rk1/p4p2/4bn1p/3p2p1/3P4/P2B2B1/5PPP/R2Q1RK1 b - - 1 19 } 19... Ne4 { -0.40 } { 2rq1rk1/p4p2/4b2p/3p2p1/3Pn3/P2B2B1/5PPP/R2Q1RK1 w - - 2 20 } 20. Qa4 { 0.10 } { 2rq1rk1/p4p2/4b2p/3p2p1/Q2Pn3/P2B2B1/5PPP/R4RK1 b - - 3 20 } 20... Nxg3 { -2.90 } { 2rq1rk1/p4p2/4b2p/3p2p1/Q2P4/P2B2n1/5PPP/R4RK1 w - - 0 21 } 21. hxg3 { 0.60 } { 2rq1rk1/p4p2/4b2p/3p2p1/Q2P4/P2B2P1/5PP1/R4RK1 b - - 0 21 } 21... Rc3 { 0.10 } { 3q1rk1/p4p2/4b2p/3p2p1/Q2P4/P1rB2P1/5PP1/R4RK1 w - - 1 22 } 22. Qd1 { -0.40 } { 3q1rk1/p4p2/4b2p/3p2p1/3P4/P1rB2P1/5PP1/R2Q1RK1 b - - 2 22 } 22... Qf6 { -0.60 } { 5rk1/p4p2/4bq1p/3p2p1/3P4/P1rB2P1/5PP1/R2Q1RK1 w - - 3 23 } 23. Qd2 { -0.10 } { 5rk1/p4p2/4bq1p/3p2p1/3P4/P1rB2P1/3Q1PP1/R4RK1 b - - 4 23 } 23... Rfc8 { -0.40 } { 2r3k1/p4p2/4bq1p/3p2p1/3P4/P1rB2P1/3Q1PP1/R4RK1 w - - 5 24 } 24. Rfe1 { 0.10 } { 2r3k1/p4p2/4bq1p/3p2p1/3P4/P1rB2P1/3Q1PP1/R3R1K1 b - - 6 24 } 24... Bf5 { -0.50 } { 2r3k1/p4p2/5q1p/3p1bp1/3P4/P1rB2P1/3Q1PP1/R3R1K1 w - - 7 25 } 25. Bxf5 { 3.30 } { 2r3k1/p4p2/5q1p/3p1Bp1/3P4/P1r3P1/3Q1PP1/R3R1K1 b - - 0 25 } 25... Qxf5 { -1.20 } { 2r3k1/p4p2/7p/3p1qp1/3P4/P1r3P1/3Q1PP1/R3R1K1 w - - 0 26 } 26. Re5 { -1.10 } { 2r3k1/p4p2/7p/3pRqp1/3P4/P1r3P1/3Q1PP1/R5K1 b - - 1 26 } 26... Qd3 { -0.90 } { 2r3k1/p4p2/7p/3pR1p1/3P4/P1rq2P1/3Q1PP1/R5K1 w - - 2 27 } 27. Qxd3 { 10.20 } { 2r3k1/p4p2/7p/3pR1p1/3P4/P1rQ2P1/5PP1/R5K1 b - - 0 27 } 27... Rxd3 { -0.80 } { 2r3k1/p4p2/7p/3pR1p1/3P4/P2r2P1/5PP1/R5K1 w - - 0 28 } 28. Rxd5 { 0.10 } { 2r3k1/p4p2/7p/3R2p1/3P4/P2r2P1/5PP1/R5K1 b - - 0 28 } 28... Rc2 { 0.10 } { 6k1/p4p2/7p/3R2p1/3P4/P2r2P1/2r2PP1/R5K1 w - - 1 29 } 29. Ra5 { 0.30 } { 6k1/p4p2/7p/R5p1/3P4/P2r2P1/2r2PP1/R5K1 b - - 2 29 } 29... Rxd4 { -1.30 } { 6k1/p4p2/7p/R5p1/3r4/P5P1/2r2PP1/R5K1 w - - 0 30 } 30. Rxa7 { -0.20 } { 6k1/R4p2/7p/6p1/3r4/P5P1/2r2PP1/R5K1 b - - 0 30 } 30... Rdd2 { 0.60 } { 6k1/R4p2/7p/6p1/8/P5P1/2rr1PP1/R5K1 w - - 1 31 } 31. Rf1 { 0.40 } { 6k1/R4p2/7p/6p1/8/P5P1/2rr1PP1/5RK1 b - - 2 31 } 31... Ra2 { 0.70 } { 6k1/R4p2/7p/6p1/8/P5P1/r2r1PP1/5RK1 w - - 3 32 } 32. a4 { 0.50 } { 6k1/R4p2/7p/6p1/P7/6P1/r2r1PP1/5RK1 b - - 0 32 } 32... Kg7 { 0.50 } { 8/R4pk1/7p/6p1/P7/6P1/r2r1PP1/5RK1 w - - 1 33 } 33. Ra5 { 0.30 } { 8/5pk1/7p/R5p1/P7/6P1/r2r1PP1/5RK1 b - - 2 33 } 33... Rd4 { -0.30 } { 8/5pk1/7p/R5p1/P2r4/6P1/r4PP1/5RK1 w - - 3 34 } 34. Re1 { 0.50 } { 8/5pk1/7p/R5p1/P2r4/6P1/r4PP1/4R1K1 b - - 4 34 } 34... Rdxa4 { 0.20 } { 8/5pk1/7p/R5p1/r7/6P1/r4PP1/4R1K1 w - - 0 35 } 35. Rxa4 { 6.30 } { 8/5pk1/7p/6p1/R7/6P1/r4PP1/4R1K1 b - - 0 35 } 35... Rxa4 { -0.60 } { 8/5pk1/7p/6p1/r7/6P1/5PP1/4R1K1 w - - 0 36 } 36. f3 { -0.60 } { 8/5pk1/7p/6p1/r7/5PP1/6P1/4R1K1 b - - 0 36 } 36... g4 { -0.40 } { 8/5pk1/7p/8/r5p1/5PP1/6P1/4R1K1 w - - 0 37 } 37. fxg4 { 0.50 } { 8/5pk1/7p/8/r5P1/6P1/6P1/4R1K1 b - - 0 37 } 37... Rxg4 { -0.30 } { 8/5pk1/7p/8/6r1/6P1/6P1/4R1K1 w - - 0 38 } 38. Kf2 { 0.00 } { 8/5pk1/7p/8/6r1/6P1/5KP1/4R3 b - - 1 38 } 38... Rg5 { 0.10 } { 8/5pk1/7p/6r1/8/6P1/5KP1/4R3 w - - 2 39 } 39. Re4 { 0.20 } { 8/5pk1/7p/6r1/4R3/6P1/5KP1/8 b - - 3 39 } 39... Kg6 { 0.40 } { 8/5p2/6kp/6r1/4R3/6P1/5KP1/8 w - - 4 40 } 40. g4 { 0.60 } { 8/5p2/6kp/6r1/4R1P1/8/5KP1/8 b - - 0 40 } 40... Ra5 { 0.00 } { 8/5p2/6kp/r7/4R1P1/8/5KP1/8 w - - 1 41 } 41. Kg3 { -0.20 } { 8/5p2/6kp/r7/4R1P1/6K1/6P1/8 b - - 2 41 } 1/2-1/2

```

The move text must be in a single line, use `-w 10000` option in pgn-extract.

```
pgn-extract --quiet --evaluation -C --fencomments -w 10000 1.pgn

```

### Output

out.txt

```
rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1 { 1.20 }
rnbqkbnr/pppp1ppp/8/4p3/4P3/8/PPPP1PPP/RNBQKBNR w KQkq e6 0 2 { -0.20 }
rnbqkbnr/pppp1ppp/8/4p3/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2 { -0.20 }
r1bqkbnr/pppp1ppp/2n5/4p3/4P3/5N2/PPPP1PPP/RNBQKB1R w KQkq - 2 3 { -0.40 }
r1bqkbnr/pppp1ppp/2n5/4p3/4P3/2N2N2/PPPP1PPP/R1BQKB1R b KQkq - 3 3 { -0.20 }
r1bqkb1r/pppp1ppp/2n2n2/4p3/4P3/2N2N2/PPPP1PPP/R1BQKB1R w KQkq - 4 4 { 0.00 }
r1bqkb1r/pppp1ppp/2n2n2/4p3/3PP3/2N2N2/PPP2PPP/R1BQKB1R b KQkq d3 0 4 { 0.80 }
r1bqkb1r/pppp1ppp/2n2n2/8/3pP3/2N2N2/PPP2PPP/R1BQKB1R w KQkq - 0 5 { -0.30 }
r1bqkb1r/pppp1ppp/2n2n2/8/3NP3/2N5/PPP2PPP/R1BQKB1R b KQkq - 0 5 { 1.30 }
...

```

### Command line

```
python p.py >out.txt

```
> 3 votes

---
Tags: engines, evaluation, pgn
---


# Question
Title: What are the strategic ideas behind Bf4?
```
rnb2rk1/ppq2pbp/2pppnp1/8/2PPP3/2N2N1P/PP2BPP1/R1BQK2R w KQ - 0 9

1. Bf4 Nh5 2. Bh2 e5

```

In the game, I played **Be3**; but the engine seems to like the line above. Why is **Bf4** better (in a strategic way) than **Be3**? I mean the Bishop will be sent off to h2, and black will gain one time to play **e5** and develop his queenside pieces.

# Answer
Be3 is rather passive. It defends f2 and d4 but otherwise doesn't do a lot.

Bf4 is much more aggressive. It eyes up the black queen on c7 and pins the d5 pawn threatening an embarrassing c5. Black's response of putting the knight on the rim and pushing the e5 pawn is pretty much forced. Getting the pawn to e5 has taken black 2 moves whereas normally in these structures black would avhieve that in one move.

If white wants to start a quick pawn storm on the king side then the "dim" black knight on h5 gives white a quick start with g4 coming with tempo. Although white should probably worry about king safety before adopting that plan.
> 4 votes

# Answer
Since the first part of your question was already answered, I'll tell you why Bh2 is may be considered "useful".

Notice that white's c and e pawns have a strong hold on the d5 square, rendering a d6-d5 pawn push from black impossible. This in turn makes the d6 black pawn a backwards pawn (not protected by any other pawns) and notice that the Bh2 not only x-rays the queen but also puts a lot of pressure on that pawn. It also places pressure on the advanced e5 pawn which cannot move without exposing the weak d6 square to the bishop.
> 2 votes

# Answer
..e5 and ..c5 can both be strong moves if followed up consistently. Usually one of them is necessary to avoid a cramped position. In the given position Black has already played both ..e6 and .. c6, pretty much guaranteeing a lost tempo. Also it is not yet clear that the Black Queen belongs on c7.

In a Kings Indian formation Black hopes for one of six developments.

1. If ..e5 is answered by d5 he hopes for a pawn storm on the K-side with ..f5,..f4 and perhaps the g- and h- pawns will join in. Some files may get opened. The Queen may go to g6 via e8. Nh5-f4 is possible
2. If ..e5 is answered by dxe5, he hopes for play based on a Knight outpost at d4. The route could be a6-c5-e6-d4 A Pawn on c6 keeps any White piece out of the corresponding d5 square.
3. if the Pd4 does does not move after ..e5, Black hopes for pressure on the e-pawn with ..exd4, ..Re8 ..Nf6,..Nc5,..Qc7. Maybe eventually ..Rad8 and ..d5
4. If ..c5 is answered by d5, he hopes for a pawn storm on the Q-side with ..b5 and perhaps ..Rab8 and Qb6
5. If ..c5 is answered by dxc5,the objective might again be a Knight on d4, with the White Pawns weakened by ..a5-a4
6. If the Pawn does not move after ..c5, we can have a Sicilian formation.

This is a very incomplete and sketchy outline of the possibilities and the choice is part personal preference and part what White has committed to. They have to be considered in conjuction with each of the three Bisop placements (e3,f4,g5 and perhaps eventually h6)

The decisive factors in this instance stem from the three weak moves (e6,c6,Qc7) that allow threats of e5 and c5 to be generated following Bf4. The strength of this move does NOT lie in its strategic ideas, as the OP suggests. In fact generally speaking, f4 is usually the weakest of the three options because it allows ..e5 with tempo. It is the tactical alignments of the Bf4 and the Qc7 , also the Be2 and the Nh5 that give the move its power. At the end of the day White will have strategic advantages, but he will only get them by using tactics that are specific to this particular position.

Sometimes the strength of a player lies in recognizing that the normal rules do not apply. Although my six maxims are the ones that every Kings Indian player must know, none of them apply to this position. The slightly unusual move c5 is the one that has to be seen, and it is enabled only by the combination of three Black errors. These weaken the square d6 and misplace the Queen.
> 2 votes

# Answer
There's a myth in these Kings Indian type positions that Black wants a pawn on e5. Actually, that's not the case; Black wants to keep the long diagonal open for their bishop if possible, and having a pawn on e5 and then making a kingside pawn storm is just the choice they are forced into when they have to give up too much to keep the diagonal open.

If you play Be3, Black can play c5, and you're pretty much forced to concede that open long diagonal to Black. On the contrary, if you can force Black to play e5, that pawn won't ever leave that square. (Even if it has a chance to move, moving it exposes a weak backward pawn on d6.) With the center blocked, you have a chance to launch an attack on Black's disorganized queenside. (In contrast, your kingside defense is reasonably well organized and you don't even have to put your king there.
> 1 votes

---
Tags: analysis, strategy
---


title: How do you play blindfold?

text:
# Question
Title: How do you play blindfold?
I can do it okay using an empty board (like Luzhin). But I can’t picture 64 squares at once and their colors. Say black has N at b4. White can pin it to a black R on 8. Which file? What color square.

I can’t picture it instantly. I have to reason it. All I can do blindfold is based on reasoning. Eg, white KB is on a light square. I just memorize that. Or reason that it is 2 over from the light long diagonal which I just memorize is light. And I know white KB can unpin a f3 N, be blocked in by d3, defend e4, attack f7 from c4, pin a c6 N to e8, and infiltrate at a6. So I get that all those squares are light. And similarly or relatedly for black QB.

But what about the g1 to a7 diagonal. That one is a lot less “meaningful”. So to get b6 I might have to get its color from b5.

This isn’t direct visualization. Mental picturing. Now I'm sure everyone does a lot of what I just described to play blindfold. And I remember a comment once (which I can’t verify as fact) that for totally random chess positions on a board, GMs can’t memorize them at a glance much better than low level players do.

But still I assume some element of pure visualization is necessary that I lack. I know players rated much lower than me who do it much much much better than me. Maybe I can practice more. But I still end up doing more reasoning than picturing. Like subtracting two coordinates to calculate an odd or even difference to infer same color or not.

When you play blindfold, do you picture the whole board at once and concentrate on certain areas while still having the rest in view? Or is it you are using a flashlight that only illuminates small areas and specific relationships, and you have to scan around and think about what to check to know what’s going on? And do you practice testing or memorizing the colors of squares at random?

# Answer
> 1 votes
How to improve at calculation and visualisation? is relevant but concerns itself with the slightly different question of playing a normal game with only a weak ability to visualize. Following up on the information given will reassure you that in general weak visualization is no barrier to high achievement. But in a few people it is a permanent and unalterable aspect of who they are. If you are one of them, you should ignore most of the advice given about blindfold play; this usually assumes some visualizing ability and is not helpful if you cannot visualize at all. A difficulty that you face here is that most people suppose that others have an imagination that works just like theirs. Someone whose imagination is very different from yours will think that this is a badly worded question.

One piece of advice often given that I think is useful is that if someone names a square on the board like g4, you must be able to say without hesitation what color it is. As someone with quite literally no power to visualize I find this good advice but further find it helpful to "make friends" with all the squares. Here are some of the many things that I know about my friend g4.

1. g4 is white
2. g4 is a playable but eccentric opening move that weakens the squares f4 and h4
3. Against the Sicilian and Caro Kann it is sometimes part of an early Pawn Storm.
4. It is a square from which a Black Knight can attack f2.
5. It is a square from which a Black Bishop can pin my Nf3
6. Qg4 is sometime an effective response if in the opening Black leaves g7 undefended (with a number of specific examples)
7. Nf3-h2-g4 is quite common in the Lopez or Giuoco Piano
8. Pg4 supports an outpost Nf5.And I know how to get there.
9. Pg4 threatens g5 to eject defender Nf6 or to open a line by hooking on Ph6.
10. If I play h3 and g4 after short castling Black might sacrifice a piece.
11. Or he might force open lines with ..h5.
12. g4 after Be2 is a square I sometimes use to trade off my light Bishop.

I have never deliberately drawn up such lists, but they are there in my mind and very useful on the rare occasions when I attempt blindfold play. Even so, I am much weaker without sight of the board, but by now that is not a thing that worries me.

---
Tags: blindfold-chess, visualization
---


# Question
Title: Actual cases of a "frivolous draw offer"
Having been inspired by a recent question here, here is another.

FIDE §E11.5 prohibits "unreasonable offers of a draw". Some specific cases which might get frowned upon by your opponent, even if perfectly legal by the rules:

* Repeated draw offers are a relatively easy case for the arbiter, since (which is the whole point of that rule) you have to mark them on your game sheet. (Rule of thumb: No repeat unless the position has changed significantly.)
* Draw offer in a worse position: I would recklessly offer a draw against a GM e.g. in KNN/KRN, since I only have to survive 50 moves, and \>200 are needed for the win, so "standing worse" or "lost" is a nontrivial case.
* Finally, offering a draw against a much stronger player. I read about an actual case in a chess magazine (the stronger player did not complain to the arbiter, but to the public - a clear ?! move :-).

Please note that all these cases are judgmental, so don't bother to discuss where *you* would draw the line. They fall under the Preface catch-em-all "the laws can't rule everything, leave it to the tact of the arbiter". Thus, instead:

Can you link me to *actual* reports of such cases (chess magazines, websites), and how the arbiter ruled? (Since GM know the rules by heart...or so I hope..., I don't expect this to happen in a higher league. Also, you can always answer the frivolous offer silently by a move and a go-fly-a-kite face...)

# Answer
> 9 votes
Let's start by debunking some of the false assumptions in your post.

> Draw offer in worse position

The idea that this could be regarded as an "unreasonable draw offer" is nonsensical. Even when there is a material imbalance, which position is worse is often a subjective matter.

Certainly at the level of expertise of the average arbiter you don't want arbiters making subjective judgements about the position. They are there not because they are good chess players who can make such decisions but because they know the laws of chess and have (or are supposed to have) the judgement to apply them.

Just a reminder: some years ago there was a proposal that FAs and IAs should be required at some stage in their playing career to have reached a FIDE rating of at least 1800. This was rejected. Few of them are actually strong enough players to have this level of chess judgement.

> Finally, offering a draw against a much stronger player

Some years ago I beat an IM level player (FIDE rating about 2400) when my rating was a humble 1900+. Is a 500 point rating difference enough for you? He would have ripped my hand off if I'd offered a draw in the 5 or 10 moves leading up to his resignation. Of course weaker players are allowed to offer draws to stronger players.

> Can you link me to actual reports of such cases (chess mags, websites), and how the arbiter ruled?

Of course not! Such a case would have attracted a warning at most. Even repeated infractions are unlikely to result in any action serious enough to make the news.

---
Tags: rules, history, draw, etiquette, reference-request
---


# Question
Title: What is the criterion for a chess set to be used in FIDE tournaments?
For example, a Harry Potter based chess set will never be used in a FIDE tournament. But that got me thinking: is there a specific set of rules/ criteria for a chess set to be used in a FIDE tournament? Does FIDE have any rules regarding this?

# Answer
> What is the criterion for a chess set to be used in FIDE tournaments?

Actually there are several criteria for this.

FIDE have published their relevant rules in Standards of Chess Equipment, venue for FIDE Tournaments, rate of play and tie-break regulations.

The first requirement is that the tournament organizer and the chief arbiter approve. So, if you want Harry Potter pieces you will first have to convince them:

> ### 1. Chess Equipment
>
> 1.1 The chess equipment offered by the organisers (hosts) of a FIDE or Continental Championship, Olympiad and other FIDE registered tournaments shall conform with the standards mentioned below, and **shall be approved by the Chief Organiser and the Chief Arbiter**.

Second, for high-level tournaments, the players also need to agree:

> 1.1.1. It is recommended, that the chess pieces, boards and clocks, used in the World or Continental top level competitions be approved by participating players.

Recommended, but not mandatory, is the use of Staunton style chess pieces:

> #### 2.3 Form, style of pieces
>
> Recommended for use in FIDE competitions are pieces of Staunton style.

So, Harry Potter style pieces are not completely forbidden! Although you will need to get organizer, chief arbiter and players to agree.

FIDE also have recommendations for the size and composition of the pieces:

> #### 2.1. Material
>
> Chess pieces should be made of wood, plastic or an imitation of these materials.
>
> #### 2.2. Height, weight, proportions
>
> The size of the pieces should be proportionate to their height and form; other elements such as stability, aesthetic considerations etc., may also be taken into account. The weight of the pieces should be suitable for comfortable moving and stability.
>
> Recommended height of the pieces is as follows: King – 9.5 cm, Queen – 8.5 cm, Bishop – 7 cm, Knight – 6 cm, Rook – 5.5 cm and Pawn – 5 cm. The diameter of the piece's base should measure 40-50% of its height. These dimensions may differ up to 10% from the above recommendation, but the order (e.g. King is higher than Queen etc.) must be kept.
> 5 votes

---
Tags: rules, fide, chess-set
---


# Question
Title: What is the largest n such that discrete forced mate in one through mate in "n" exist?
This is admittedly a bit of an obscure question, so I apologize for the awkward wording of the question. To begin, assume you are playing as White, and that a "forcing move" is any move that leaves Black with only one possible move.

Imagine a position where you have a mate in one. In addition, you also have a different move that gives black only one possible move that is *also* a mate in one. So, functionally, you have the option to play a mate in one or a mate in two. Extend this idea so you have a sequence of forcing moves that allows you to play a mate in one, mate in two, mate in three, and so on, all the way to mate in *n*. What is the largest value of *n*? For example, in the position below, White has a sequence of forcing moves that allow a mate in one, two, three, four, and five. Note that every move Black has in all variations is forced.

```
[FEN "6k1/8/8/4BQNB/8/8/8/6K1 w - - 0 50"]

1. Qf7# (1. Qh7+ Kf8 2. Qf7#) (1. Bf7+ Kf8 2. Qc8+ Ke7 3. Qe8#) (1. Bf7+ Kf8 2. Bd6+ Kg7 3. Qe5+ Kh6 4. Bf8#) (1. Bf7+ Kf8 2. Bd6+ Kg7 3. Qe5+ Kh6 4. Qd4 Kxg5 5. Qf4#)

```

For this position, there is a potential mate in six - 1. Bf7+ Kf8 2. Bd6+ Kg7 3.Qe5+ Kh6 4. Qd4 Nxg5 5. Qg7+ Kf5 6. Qg6# - but I am *not* counting this because the move 5... Kf5 is not, under this definition, forced. Black can also play 5... Kh5. To the best of my knowledge, there is not a series of forcing moves which allows for a mate in exactly six.

Of course, this position is not the end-all-be-all. I only created it for illustrative purposes. A position with mate in one through mate in fifty may exist, for all I know. Has anyone here heard of a similar problem before? If so, do you have any leads, or better yet, any ideas of your own?

# Answer
> 6 votes
Using wizardry to abuse the 50-move rule, I can make **n equal 3053.** White has a mate in one at any point and all of Black's moves are forced.

Here, White has 47 pawn moves and 14 pieces to sacrifice. The Black knight capture adds an extra move. This allows for (47+14)\*50+1=3051 moves. Promoting the h-pawn whilst having a mate in one requires careful maneuvering, but it is doable.

```
[FEN "7k/8/8/6QN/5P2/5P2/PPPPPP2/RNBKnB1R w - - 0 1"]

1. Kxe1

```

To add on the last two moves, the limit due to threefold repetition, the White king must move up before the sacrifice of the second White knight.

```
[FEN "8/7k/8/6QN/8/8/8/4K3 w - - 0 1"]

1. Ke2 Kh8 2. Ke3 Kh7 3. Ke4 Kh8 4. Ke5 Kh7 5. Ke6 Kh8 6. Kf7 Kh7 7. Nf6+ Kh8 8. Nh7 Kxh7 9. Kf8 Kh8 10. Kf7 Kh7 11. Kf8 Kh8 12. Qg7#

```

---
Tags: problems, checkmate, forced-move
---


title: Making the best move

text:
# Question
Title: Making the best move
It took me a while to realize, that my best move could actually be a blunder or a relatively insignificant move or the wrong approach etc.

I have the impression that there should be a recipe or some kind of a protocol for making the best move, is there such a thing, or is the idea not practical?

The chess engines can do it and they obviously are following some kind of algorithm for making the best move, so maybe we can do the same or something similar?

# Answer
> 3 votes
I'm assuming you're asking how to make a good move. As a 2000 elo rated player, I think I can answer this question. There are three situations:

1. It's the opening. Honestly I can't say much about this - as long as you play sound openings and know your stuff you'll most of the time be fine.
2. It's the middle game. In these positions, tactics are important - however, obviously most of the time tactics just do not exist in the position. This is when you use "check's, captures, attacks" to find candidate moves (best protocol that I know of that works for me) - in evaluating those candidate moves, ask yourself questions such as "does checking/attacking the king directly in this move push my agenda"? Does it develop my pieces onto advantages squares? And most importantly, does my opponent not have a satisfactory follow-up to my move? Most of the time at lower levels if a move "looks good" it probably is good. For example, a knight to e5 jump that attacks the opponent's queen, or a rook move that threatens to win a piece. There are small details that distinguish high level players and low ones - for example, stop randomly trading your bishops for knights, or being down an exchange is better than being down a piece. If you're playing a closed position, sometimes these moves are not obvious. What you need to ask yourself if "where do my pieces **want** to be? For example, look at your knight; what square does it crave? Is there a support point that it wants to exist on? It is impossible to make the best best move (which is quite often subjective), so the best you can do is follow certain principles.
3. It's the endgame - again, I cannot tell you everything here as most of this stuff you do have to understand yourself through books and studying. At the end of the day, there isn't a single protocol, instead it's the building of intuition and solid foundations.

Each position has each of the own nuances, and therefore their own set of different plans. Of course this answer is quite glossy and doesn't cover a lot of things - but to answer your question, no, there isn't a single protocol. If there was, chess would be so simple and easy.
If you're wondering how computers think How do chess engines "think"? pretty much sums it up. It's either that, or computers are fed thousands of games and/or moves at once and a neural network "learns" from those games. Technically, we mere mortals do that but at a much slower pace. From what I can tell, humans really only benefit from computers like that at the highest level.

---
Tags: candidate-move
---


# Question
Title: When is a queen better than 3 minor pieces (or vice versa)?
Obviously a lot is going to depend on the exact position, but I'm asking if there are any general signposts - e.g. bishops usually get better than knights if the position is open, or in an endgame, but I can't say the same about Q vs 3 minors.

# Answer
The queen does a good job when there are a lot of weaknesses to attack, especially if the opponent's king is out in the open, so there are a lot of options for double attacks.

The pieces are generally stronger if they can coordinate and the king is still relatively safe. Earlier in the game that's usually the case.
> 10 votes

# Answer
A lot depends on whether there are other pieces involved and the pawn structure.

If you mean positions with Q alone vs three minor pieces then relative king safety comes into play. The side with the Q tries to expose the opponents king and harass it.

The Q alone side may need to create connected passed pawns to make progress since the pieces should easily cope with a single passed pawn by twice covering the square in front of the passed pawn.

However, the side with three pieces may need to only create a single passed pawn to create winning chances.

Also, the three pieces side would find it easier to create fortress type positions at least to avoid defeat.

Personally, I would prefer to play the three pieces for the previous two reasons.

But (there's always a but!) in blitz time formats I would prefer the Q!

(As an aside, I once drew a strong IM in a regular tournament game with only two pieces v Q and equal pawns by setting up a fortress.)

I don't have a chess database but someone who does may be able to research positions with just Q vs three minor pieces and provide some statistics.
> 3 votes

# Answer
Generally speaking the queen is going to be better when the opponent's king is exposed to checks and/or when the position is "loose" ie pieces and pawns hanging, pawn weaknesses etc.

If the side without the queen can hold the position together and push a passed pawn there isn't really anything the queen can do.
> 2 votes

# Answer
According to the Syzygy tablebase, the position is likelier to be winning for the queen than for the minor pieces.

* in KQ v KBBN, 48.9% of positions are wins for KQ, a further 2.3% are frustrated wins for KQ, 26.2% are drawn, and 22.6% are wins for BBN. (Frustrated wins are positions which are theoretically won, but in practice drawn because the defending side can get a 50-move draw.)
* in KQ v KBNN, 49.7% of positions are wins for KQ, 30.4% are drawn, and 19.9% are wins for BNN.
* in KQ v KNNN, 38.3% of positions are wins for KQ, 47.8% are drawn, and 13.8% are wins for NNN.
> 2 votes

# Answer
Please see in action the famous games from the grandmasters demonstrating the combat dynamics of a Queen versus three minor pieces. No English language can explain the entire dynamics. You must see it for your self.

https://www.chessgames.com/perl/chesscollection?cid=1016182
> 0 votes

# Answer
For me I belive that the Queen is worth 3 pieces for a variety of reasons,

1. It combines the functionality of the Rook and the Bishop, the Bishop, which act like snipers in the early-mid game, are very valuable, because of their sniper-like capability, whereas the rook is bad in the early stages of the game, because the board is crammed usually, conversely, in the Endgame, Rooks are better, because they allow you to occupy an area and put up a wall that the king cannot cross, by the definition of a bishop, since they are on a single color diagonal, it requires 2 Bishops to create an inescapable wall for the king, the Queen provides for both of these, by being able to snipe pieces on the outskirts with its bishopesque range, and it can wall of sections of the board at the endgame because it can cross multiple colors like the rook
2. This is more of an extension of the last point, but its your main offensive tool, overall, Rooks are best in the Endgame, Bishops and Knights are great in the Mid game, but the Queen can function almost anywhere, they also exceed in their ability I call the "Royal Attack" because of its long Range, devastating attacks and multitude of directions, it is often used to attack 3 or more pieces at one, where as the Knight can fork but not pin pieces, and the bishop can not fork but can pin pieces, the Queen combines all the functionality into 1, therefore in most situations, if you lose your queen, unless it was a mistake on you opponents move, thus leading to a delayed trade, or mate, its usually time to resign as most of you offense is gone
3. The Queen is also great at counter-attack, for example in this trap from the Queens Gambit:

\[FEN ""\]

1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 d5 5. Qa4+ Kf8 6. Qxb4+ Ke8
> -1 votes

---
Tags: strategy, queens, material-balance
---


title: Who makes the rules of chess?

text:
# Question
Title: Who makes the rules of chess?
We all know the rules we play competitive chess under. They are the FIDE Laws of Chess. Our individual federations in different countries may tweak the parts of the rules they're allowed to tweak (the ECF, for instance, overrides the FIDE "zero tolerance" by saying that if an organizer doesn't specify a default time then for standard time control it is 30 minutes) but basically we play by FIDE's rules.

Who makes those rules? Every 4 years or so FIDE has a major revision of the rules. The last major revision was in 2017 with a tweak to rapid and blitz in 2018. We were due a major revision last year, delayed no doubt by Covid. We should expect a new revision soon. What kind of people are going to be making those changes?

# Answer
The FIDE Rules Commission makes the rules and maintains them.

There we can see who is making the rules. We see that, in general, they are arbiters and mostly not very strong players. Here is a list with their arbiter qualifications (FA = FIDE Arbiter, IA = International Arbiter), ratings (when they have them) and titles.

**Chairman** \- Abdulrahim, Mahdi IA 1349 (standard)
**Honorary Chairman** \- Vardapetyan, Ashot IA unrated
**Secretary** \- Pahlevanzadeh, Mehrdad IA 2078 (standard)
**Councillors**
Khaled, Hassan IA unrated
Escafre, Stephane IA 1673 (standard)
Hoffpauir, Mike FA unrated
Turdialiev, Husan IA unrated
**Members**
Krasenkow, Michal IA 2576 (standard) GM
Cisse, Ibrahima \- unrated
Vergara Palomino, Jorge Luis IA 1975 (standard)
Press, Shaun IA 1946 (standard)
Saduakassova, Dinara \- 2468 (standard) IM, WGM
Md Haroon or Rashid IA unrated
Paulino Garcia, Wilfredo Antonio IA 1922 (standard)
Lehtivaara, Jouni IA unrated
Johann, Gregor IA 2003 (standard)
Underwood, Martha FA unrated
Polovina, Elena IA 2078 (standard)

So, those are the 18 people making the rules. One chairman, one honorary (?) chairman, one secretary, 4 councillors and 11 members.

Two have no arbiting qualifications, two are FIDE Arbiters and the rest (14) are all International Arbiters.

Two are master strength players (one GM and one WGM/IM), five are moderately strong (1900-2100), one is average strength (1673), one is weak (1349) and the rest are unrated.
> 21 votes

---
Tags: rules, fide
---


# Question
Title: Is it possible to manually input a command to Arena Chess GUI?
I want to manually input a single UCI command into my modded version of Stockfish to access my added functionality(a chat feature) and the incredibly useful `eval` command and then get the output. I'm using Arena Chess GUI, but I'm free for any other software recommendations.

I have seen some interesting stuff at Extras \> Run Command line and Extras \> Run Command but how am I supposed to use them? I don't even know what they do specifically, but seem something relevant.

Why am I not checking the documentation? Because there's none. I got Arena from http://www.playwitharena.de/ and there are only download links and there's also no documentation that came with my copy of Arena. And, third party docs are no way going to cover such technical stuff. I've tried, but found nothing.

And btw, this doesn't contain the `stockfish` tag because I'm using Stockfish but the question itself isn't engine specific. My version of Arena is 3.10beta for Linux.

# Answer
```
1. Open arena
2. Load engine
3. Press Engines->Log window
4. Press commands under Engine Debug window
5. In the dropdown textbox, input command like uci, etc. then press send button.
6. Also you can press help button to get help.

```
> 1 votes

---
Tags: engines, arena
---


# Question
Title: Three Knights vs one Queen, which is better?
Suppose the end game contains three knights and king *only* for white, and one queen and king *only* for black. Which side is considered to be in a stronger position?

Value-wise, the knights are worth 9 points, while the queen is worth 8, so I would have considered white with three knights winning. However, I played this against the computer, and found my knights very ineffective, so I’m not sure.

If the answer depends on who is to play and the position of the pieces, that can be stated, but let’s not assume the pieces start in a highly specific configuration.

# Answer
> 3 votes
The queen is not usually assigned a value of 8 pawns, rather often between 9 and 10 pawns. Of course the question still stands, assuming this roughly equal material balance who has the edge?

Let's consider two scenarios how the position could simplify: One is the queen sacrifices itself against a knight, or gets won by a knight fork for a knight. In this case one side stays with two knights against just the king. With no other pieces this is an easy draw for the lone king.

The other scenario is the queen wins a knight. In this case there exists a fortress for the knights like so https://lichess.org/analysis/4k3/8/8/3NN3/4K3/8/8/q7\_w\_-\_-\_0\_1 (e.g. Ke4 Ne5 Nd5 against a king on e8). The idea is the two knights block the opponent king from approaching. (as a funny aside, since both positions are a draw, in some sense blundering the queen for free in this position is not a mistake, it's a draw before and afterwards) It is worth noting that this position might not always be reachable for the knight side, so if the pieces start out in unfortunate positions it may not be possible to reach this setup. Yet, with an extra knight the vast majority of positions will be a draw.

To conclude, this position is very drawish, neither side has almost any winning chances. In blitz both sides may have slight winning chances; the queen side might win a knight while keeping the opponent away from the fortress position, conversely it might blunder the queen to a knight fork without getting a knight back. However, overall I would still see the chances as roughly equal.

It might be interesting to look at adding more material for both sides. I suspect if you give both sides a pawn or two, the side with the three knights might have the advantage as knights are quite efficient at blocking checks, and their sheer number might overload the other side from defending their pawns sufficiently often, all the while pushing the own pawn. But without pawns, the knights are simply not enough to win.

Addendum: Since it was requested, here are the stats from the tablebase, note that those are very misleading since many positions are unlikely to be reached in practice: With the knights to move, (1) draws, (2) wins for the knights, (3) wins for the Queen, (4) would be wins for the Queen but prevented by the 50 moves rule.

(1): 2704444173

(2): 1164961530

(3): 796423773

(4): 746382

With the queen to move:

(1): 1478314845

(2): 42978066

(3): 2554099491

(4): 1078938

As can be seen by the huge difference between the knights to move and the queen to move, the vast majority of these are decided by tactics straight away, which is why being to move is a huge advantage in a *random* position. In practice however, you wouldn't really consider them as static endgames but rather trading down into a smaller endgame straight away.

If you want to argue that way you can see that the queen indeed wins more often, likely because 3 knights have a lot of options to be very misplaced on the board.

---
Tags: theory, point-value, queen-and-knight-endgame
---


title: Best method of remote tutoring?

text:
# Question
Title: Best method of remote tutoring?
My tutor and I are exploring ways of doing lessons over the internet, and to our surprise, there isn't an immediately obvious way to do this on lichess or chess.com. What we were looking for is an analysis board that we can both move pieces on at the same time with maybe a chat room too (though we could just call each other, so that part isn't a deal breaker).

Is anyone aware of such a site/program? Worst case, we can do a screenshare and I can just watch him move pieces on his screen, but that is definitely less than ideal.

Surely this problem has been solved since I can't imagine we are the first to encounter it. I hope I am just overlooking something obvious.

# Answer
> 10 votes
Have you tried lichess studies ? They can be used exactly like that. Let me give you an overview of how it works.

First you need to create a study, which you can do by heading to https://lichess.org/study/ and clicking in the green plus button.

## Multiple Members

As the What are Studies page explains, you can invite people to your study:

Let me quote the page that explains what these studies are:

> Invite friends to analyse that new trendy opening. Invite your coach to teach you something. Invite 20 students to your lesson. Why not?
>
> If your study is public, anyone can review it; invited members can chat, and invited contributors can update the study.
>
> If your study is private, only invited members can review it, and invited contributors can update the study

## Moves, Symbols and Arrows

The study members can create moves, or delete them. Any move anyone does changes the board that all other members see. Any move can have arrows to point possible moves or threats as well as symbols which are the red circles that normally are used to point key squares:

## Comments

Any move can have comments, and these will be identified by who made them:

## Annotations

The moves can also have the common chess notation:

## Chat

There is also a chat, in case anyone wants just to say anything that isn't a comment to a move:

## Chapters

This feature is solely available in studies, and allows you to have multiple chapters over the same study. It is useful in many scenarios like when you want to try several different ideas with quite some depth and extended analysis while keeping the main line clean. You could have the analysis of all your games in a tournament within the same study, and turning each game into a chapter.

## Engine

As you would also probably be expecting, there is a feature to use an engine evaluation any time you need it. At the time of this answer the default engine is Stockfish 9.

# Answer
> 3 votes
You could use FICS with the Babaschess interface for this purpose. Setting up an analysis board in the starting position is as simple as typing the command "examine" in the command window. This will create a board on the server which you have control over. Others can view your activities on this board by typing "observe \[your username\]" in the command window. Then if you want to give a friend looking at your board authority to move the pieces as well, you write "mexamine \[friend's username\]" in the command window.

This analysis board will come with a dedicated chat which can be used if you like, but I prefer to use Discord and talk directly with my analysis partner when doing analysis since talking is much quicker than typing in my case.

When you want to finish your analysis of the current position you can use the command "unexamine". Note that on FICS you can only be analyzing one game at a time with the "examine" command, so if you want to move onto another game/position to analyze you have to end the current analysis first.

If you have a game stored as a pgn file that you wish to analyze you can do this as well on FICS in Babaschess very easily. This is as simple as logging in, going to "File"-\>"Open PGN file"-\>\[Navigating to and opening your pgn file\]-\>\[Choosing your desired game in the pgn file and selecting "Open as" instead of "Open"\]-\>\[Selecting "Examine on the server"\]. By doing this, you upload the game to the server, enabling you to quickly go back and forth between different interesting moments in the game to analyze.

Finally, if you wish to analyze a specific position on FICS this can be done as well by typing the command "bsetup" in the command window. This will open up a dialogue box where you can choose which side to move etc. and when you're happy with your initial settings for the board you can setup any legal position you'd like to analyze. When you've finished setting up the board to the desired position you write "bsetup done" in the command window, which will then make your position into an examined game on the server by default.

# Answer
> 3 votes
Another option, released in 2022, is Classroom on Chess.com.

According to the news article about its release, it is an easy-to-use all-in-one tool for remote tutoring. The features are:

* Built-in video and voice chat
* Ability to load games from library collections, student archives, PGNs etc.
* Full control over board settings and other options (e.g., allowing specific students to move with White, Black, or both)

You need to be a Chess.com premium member if you would like to host more than one student though.

# Answer
> 2 votes
An option could be to use Team Viewer, which allows remote control of a computer. That way, you could both be using your tutor's Chessbase software (which he probably has). For voice chat, you could simultaneously use Skype or whatever other VOIP service you prefer.

---
Tags: online-chess, online, teaching
---


# Question
Title: Infinite sequence of consecutive checks allowing more pieces (say 9+ queens)
This is a task related to this question: Theoretical limit for the number of consecutive checks?.

By a sequence of consecutive check, what we mean is white giving check, black replying with a check, white replying to that with a check and so on. Note that we are talking about a theoretical situation so that 50 move rules or three-fold repetition are irrelevant.

In the linked question, he is asking for the longest sequence of consecutive checks with two conditions:

1. Initial position should be legal
2. Initial position should not contain promoted pieces.

Suppose we remove the 2nd condition, and relax the 1st one to allow more pieces than legally possible (say, 9+ white queens or 3+ white knights). **With these relaxations, is it possible to have an infinite sequence of consecutive checks?**

I think the answer to the above question is no (but no complete proof yet).

If such an infinite sequence is there, it should contain a loop for sure. Therefore, the sequence cannot contain pawn movements or captures.

A second question is to construct longest such sequence. Alexey Khanyan's record 54 with conditions 1 and 2 may be surpassable because we relaxed them. (By the way, even with conditions 1 and 2, Khanyan himself thinks that 54 can be improved).

PS: For this question, I am not interested in involving fairy chess pieces or chess variants.

# Answer
> 6 votes
There are no infinite sequences; in fact, I'll show that there is no loop even on an infinite board. Thanks to Umlin for starting the proof, and alphacapture for getting me thinking about monovariants.

Terminology: I will say two squares are "in line" with each other if they lie on a common rank, file, or diagonal. A "direct" check is a non-discovered check; i.e. a check given by the piece that is moved. A "stationary" piece is a piece that never moves for the entire loop.

**Preliminaries** (observed by other people): To get an infinite sequence, you need a loop. This rules out captures, pawn moves, and castling. As Umlin pointed out, any king move must discover a check, but a king can't discover check while remaining in line with the opposing king. So if a king moves once, neither king can ever move again, which makes a loop impossible. Thus the kings never move. Since there are no captures and no king moves, every move must block a check. In particular, this means every check must be blockable; e.g. no double checks or knight checks. (Checks discovered by moving a knight are okay.)

**Step 1**: At any given time, consider the number of pieces that are either checking or x-raying their enemy king. (That is: queens in line with the enemy king, rooks orthogonally in line with it, and bishops diagonally in line with it, regardless of how many other pieces are in between.) Since the kings themselves never move, this quantity will only change by at most one at a time; namely, the piece that is moved. I claim it never decreases. If it did, this would mean we're moving a piece that is x-raying the enemy king to a place where it isn't attacking or x-raying the king. But a piece that is already x-raying the king can't discover check. This means that we are giving neither discovered nor direct check, contrary to our goal.

Since the quantity in question never decreases, it can never increase either if we want to form a loop. This means that we never move a non-x-raying piece to a square where it does x-ray or check the king. This has multiple consequences for different kinds of pieces:

First, queens can't discover check, so every queen move gives a direct check. By the previous paragraph, every queen move must come from an x-raying square.

For the same reason, if a rook or bishop ever moves into a direct check or an x-ray, it must have come from an x-raying square. But rooks and bishops can't move from one checking/x-raying line to another in one move, and staying on the same line won't be a check. So rooks and bishops (along with knights, as we saw earlier) can *never* move to or from x-rays or direct checks. In other words, every rook or bishop that ever gives a check or x-ray must be a stationary piece. Every rook, bishop, or knight *move* must be a discovered check, going from one non-x-raying square to another.

As a consequence of the above, every move, regardless of the piece, must come from a square in line with the enemy king: queens move from x-raying squares to checking squares, and other pieces always give discovered check. Every move must also end on a square in line with the friendly king (in order to block check). So in order to form a loop, every move must both start and end on squares that are in line with both kings. This significantly restricts the squares that we can use.

**Step 2**: Using everything from step 1, we now consider different cases for where the kings could be, and look at the possible moves in each case.

**Case 1**: The kings are orthogonally in line with each other. Then up to rotation and stretching, the board will look like this:

The marked squares are the only ones in line with both kings, so every move must be from one of these squares to another. (There may of course be stationary pieces on other squares to provide discovered checks.) In fact, no piece can move to one of the starred squares: you can't block a check by stepping behind the enemy king, and you can't discover a check from behind your own king.

White queens can't deliver checks on squares 2, 3, 4, or 6, since there's no permissible square on which black could block such a check. So white queens can only move between the squares marked 1, 5, and "-" (there may be more than one of the latter). Since there are no legal moves between these squares, white can never move a queen. The same goes for black. In particular, every move must be a discovered check, not a direct one.

If there is ever a check given along the line between the kings (labeled "-"), the checking piece must be a stationary rook or queen. Once this check is discovered, it must be blocked. The blocking piece can then never move again, as it has no way to discover a check through the stationary rook or queen. This can't happen in a loop, so there are no checks along this line, and thus no pieces ever move to or from it. So all moves are from numbered squares to numbered squares.

Next, since rooks and bishops can't move to or from squares where they check or x-ray the enemy king, there are no possible bishop moves, and the only possible rook moves are between squares 3 and 4. There are also no knight moves. (If we shrank the board by a factor of 2, knights could go e.g. between squares 1 and 6, but that would also have the effect of putting the kings on adjacent squares.) So at most one player will be able to shuffle a rook back and forth, and the other player will have no permissible moves at all. Therefore case 1 is impossible.

**Case 2**: The kings are diagonally in line with each other. Then up to rotation and stretching, the board will look like this:

(I'm allowing an infinite board, so I'm not concerned about whether there's actually room to discover a check by moving a piece from square 1, for example.) This case is ruled out by the exact same argument as in case 1, except with the words "bishop" and "rook" switched. (Note that knights could move e.g. between 1 and 4 if we shrank the board by a factor of 2, but again this would mean the kings are on adjacent squares.)

**Case 3**: The kings are not in line with each other. Say the kings are separated by a squares horizontally and b squares vertically, where a \> b \> 0. I've illustrated the case a = 4, b = 2 on an 11-by-11 board below:

A word of warning: this picture will look different if you change a and b. The differences that affect sliding pieces are as follows. Squares 5 and 8 only exist if a and b have the same parity. Additionally, if a = 2b (as in the diagram), then squares 4/9 are vertically in line, and squares 3/9 and 4/10 are diagonally in line. If a = 3b, then squares 4/8 and 5/9 are vertically in line, and 4/9 are diagonally in line. Otherwise, none of these pairs are in line.

Again, every move must start and end on numbered squares. But note that white queens can't go to squares 4, 5, 6, 9, 10, or 11, as checks on those squares couldn't be blocked. Accordingly, the only possible white queen moves are 1-3-2 and 7-8-12. But those aren't actually possible: the moves 2-3 and 7-8 are parallel to the black king and can't be checks, while the moves 1-3 and 8-12 are parallel to the white king and can't block checks. So white queens can't move, and of course the same is true of black queens. In particular, all checks are discovered checks with stationary attackers.

Next, white bishops can only move to squares 2, 3, 4, 6, 10, and 12, since they can't move into checks or x-rays. The only possible moves among these squares are 6-4 and (if a = 2b) 4-10. The former is impossible because it wouldn't block a check. So the only possible bishop moves are 4-10 for white and symmetrically 3-9 for black, and these only work if a = 2b.

Similarly, white rooks can only move to squares 1, 5, 7, 8, 9, and 11. The possible moves among these squares are 9-11 and (if a = 3b) 5-9. The former is impossible because it wouldn't block a check. So the only possible rook moves are 5-9 for white and symmetrically 4-8 for black, and these only work if a = 3b.

It's a real pain to figure out what knight moves are possible. I'll spare you the casework and just give the answer:

* lots of them, if (a, b) = (2, 1);
* 3-5-10-8-3, if (a, b) = (3, 1);
* 3-9 and 4-10, if (a, b) = (3, 1) or (3, 2);
* 4-9, if (a, b) = (3, 2), (4, 1), or (5, 2).

At this point, we've effectively enumerated all possible king configurations and all possible moves that can be made; we just have to show we can't make a loop out of these moves. The following lemma helps with the casework:

**Lemma**: Whenever a piece moves to square X, there must at some point be at least two non-stationary pieces on the ray starting at the white king and passing through square X. (The same is true for the black king.)

*Proof*: If a *white* piece moves to square X, it must in doing so block a check which is given by a stationary black piece along the specified ray. It must move again later in order to form a loop, but before it does so there must be another piece blocking this check, as claimed. If, on the other hand, a *black* piece moves to square X, there must again be a stationary black piece attacking on this ray (so that the moving piece can later move again with discovered check), and there must currently be another piece blocking the check (so that the white king was not already in check before black's move).

In all cases except for (a, b) = (2, 1), there are very few possible moves (enumerated above), and the lemma is enough to rule them out. If (a, b) = (2, 1), then the board is as below, where squares 5 and 8 don't exist:

In this case, the lemma implies that no piece can move to squares 1, 2, 6, 7, 11, or 12, as each of these is the only permissible square on some ray extending from either the white or black king. So the only permissible moves in this case are 3-10 (for a knight), 3-9 (for a black bishop), and 4-10 (for a white bishop). Using the lemma again, no piece can move to squares 3 or 10 (as squares 1 and 12 are no longer usable), so we have no moves left. This is a contradiction, so a loop is impossible.

# Answer
> 3 votes
### No, it's impossible to have an infinite sequence of checks

Let's remember that there are 3 ways to parry a check :

1. Move the King to a safe square
2. Capture the enemy piece giving the check
3. Move a piece between the King and the enemy piece giving a check (except against a Knight check as it can jump over pieces)

2 and 3 aren't sustainable over an infinite number of moves, because the chessboard has finite space, only 64 squares and necessarily less pieces than there are squares. So the only way to get an infinite cycle of checks going would be for both Kings to escape checks with method 1, by continually moving them.

This also implies that the King movement gives check. Since Kings can't come into contact, that means their movement must deliver a discovery check from a long range piece. This in turn, implies that after each move, both Kings stay aligned over some axis (rank, file, or diagonal), otherwise there would no longer be any discovery checks for lack of an alignment.

Let's say we're in such a position and it's Black to move. To summarize the constraints, the Black King must :

* Be on 1 of the 8 lines passing by the square where the White King is (otherwise it can't deliver a discovery check), and
* Move to another of these 8 lines (otherwise White won't be able to deliver a discovery check), and
* Follow normal rules of chess, e.g. move only one square in any direction and not on a square where it would be in check

Let's say the White King is on e4. The only way to move from one of the 8 lines passing by e4 to another by jumping only one square is to either go to or from one of the 4 squares diagonally adjacent to the White King : d5, d3, f3, f5. But because these squares are in contact with the White King, it's not possible for the Black King to perform such a move. It can't be on these squares because the position would be illegal, and it can't move there because the move is illegal. So it's impossible to follow these constraints.

Hence, from all the above, I'd conclude that under the normal rules of chess, **it's impossible for both players to perform at all an infinite cycle of checks**. This is also valid under the 2 conditions you mentioned in your question, as they don't affect the reasoning used here.

# Answer
> 2 votes
As Umlin proved, it is impossible to have infinite mutual checks. However, that is with the standard set of chess pieces. With **fairy** chess pieces, it is indeed possible to have an infinite series of checks by both sides. I remembered a simple example from Tim Krabbe's Diary Entry #120, entitled "Mutual Discovered Perpetual."

In the example, the knights are acting as Nightriders, knights with an infinite range in one direction, aka line pieces. Both sides can mutually give check forever.

```
[Title "Arthur John Roycroft After T. R. Dawson The Problemist 7/1976"]
[FEN "8/8/3rr3/4k3/8/3K4/8/2N2N2 w - - 0 1"]

1. Ke3+ Kd5+ 2. Kd3+ Ke5+ 3. Ke3+ Kd5+ 4. Kd3+ Ke5+

```

For reference, the original publication can be seen in The Problemist Archves on the British Chess Problem Society website. It is also in the Die Schwalbe Chess Problem Database.

---
Tags: problems, check
---


title: Is this move illegal?

text:
# Question
Title: Is this move illegal?
I'm currently writing my own chess game with my own AI and have a Question about a move:

Here, Purple moved his Pawn from F2 -\> F3, which allowes the Green Queen on H4 to capture the King, and I wondered if the F2 -\> F3 move is illegal or if it's just an oversight of the player which lost him the game.

# Answer
The rules governing chess are the FIDE Laws of Chess. This point is explicitly covered in **Article 3: The moves of the pieces**

> 3.9.2 No piece can be moved that will either expose the king of the same colour to check or leave that king in check.

The move f3 violates this rule because it exposes the king to check. As such it is an illegal move. Your program should not allow illegal moves so should not allow this move in just the same way that you do not allow the pawn to move from f2 to f5 in one move.

In a real game when an illegal move is made the move must be taken back and a legal move made in its place. In competition chess there are also penalties for making illegal moves.
> 11 votes

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


# Question
Title: Pawn went forward, capturing pawn that stayed parallel. Chess.com bug?
I decided to play a game against a real player in chess.com app. I played black.

At some point of the game I had a pawn on f5 and white had a pawn on e5. White captured my f5 pawn with the e5 pawn by moving the e5 pawn to f6!.

Is that a bug or a feature? I played for a while with bots and can’t remember they made such tricky moves.

```
[fen "rnbqkb1r/p3pppp/2p5/1p2P3/3PpP2/8/PPP1Q1PP/R1B1KBNR b - - 0 1"]

1...f5 2. exf6

```

# Answer
This is a legal capture using the "en passant" rule. According to the FIDE Laws of Chess:

> 3.7.4.1 A pawn occupying a square on the same rank as and on an adjacent file to an opponent’s pawn which has just advanced two squares in one move from its original square may capture this opponent’s pawn as though the latter had been moved only one square.
> 4 votes

---
Tags: rules, chess.com
---


title: Analyse a blunder

text:
# Question
Title: Analyse a blunder
Black (me) to move.

I took the knight at f3 with my knight at e1. However, Lichess analysis shows that this move is a blunder, and suggests to take the bishop at g2 instead.

IMO, I am winning no matter I exchange the knight or bishop, but I feel hard to understand why exchanging the knight f3 is a blunder?

```
[FEN "r1bq1rk1/pp3ppp/4p3/2Pp4/2P5/P1B2NP1/3NPPBP/R3nRK1 b - - 0 1"]

1...Nxf3? (1...Nxg2!)

```

# Answer
> 5 votes
> why exchanging the knight f3 is a blunder?

It obviously isn't a blunder.

I suspect you've made the mistake of thinking that if the website tells you that it evaluates Nxf3 as fractionally lower than Nxg2 then that means that Nxf3 is a blunder. It isn't. A blunder is when your large positive advantage turns negative. A blunder loses you the game from a roughly equal position or throws away a winning advantage. It is not when the evaluation changes slightly against you.

---
Tags: analysis, problems, evaluation, blunder
---


title: Can Black draw by perpetual check?

text:
# Question
Title: Can Black draw by perpetual check?
In this position, from the game Carlsen-Radjabov, it is White to move. Is it possible to get rid of the checks?

```
[Title "Carlsen-Radjabov, World Blitz Championship, Moscow Russia, 11/18/2010"]
[FEN "7B/5p1k/6p1/3P2Kp/2n1P3/5P2/6q1/Q4N2 w - - 0 1"]

```

# Answer
> 2 votes
> Can Black draw by perpetual checks?

Only if white blunders, doesn't see Kf6 and instead plays Kh4. Yes, Kf6 allows black to capture the bishop on h8 but that leads to a swift mate. Blacks best try is to keep taking pawns and checking but eventually he has to exchange queens to avoid mate and White still has one pawn left plus the extra piece to give him the win.

```
[title "Carlsen-Radjabov 2010 Blitz"]
[fen "7B/5p1k/6p1/3P2Kp/2n1P3/5P2/6q1/Q4N2 w - - 0 1"]

1. Kf6 Qxf3+ (1...Kxh8 2. Kxf7+ Qb2 3. Qa8+ Kh7 4. Qg8+ Kh6 5. Qxg6#) 2. Ke7 Qxe4+ 3. Kf8 Kh6 4. Bg7+ Kh7 (4...Kg5 5. Qc1+ Kg4 6. Qxc4 Qxc4 7. Ne3+) 5. Qc1 g5 6. Qxg5 Qg6 7. Qxg6 fxg6 8. Ne3

```

---
Tags: analysis, draw, check
---


# Question
Title: What is the highest possible number of pawn captures in a game?
What is the highest number of pawn captures possible in a game?

# Answer
Each side has 15 pieces that can be captured, for a total of 30 captures. But after the last pawn capture, there must be a pawn remaining on the board. Therefore, no more than 29 captures are possible.

29 pawn captures are possible through the following sequence. First, the knights are captured, followed by the rooks, bishops, queens, and lastly the pawns. Finally, Black's passed pawn can then go ahead promote to a queen. Then it can move in to get captured by White's remaining pawn in the 29th pawn capture of the game.

```
[FEN ""]

1. Nc3 Nc6 2. Nf3 Nf6 3. Nd5 Nd4 4. Ne5 Ne4 5. Nb6 Nb3 6. Ng6 Ng3 7. axb3 axb6 8. hxg3 hxg6 9. Ra5 Rh4 10. Rc5 Rf4 11. Rc6 Rf3 12. Rh5 Ra4 13. Rf5 Rc4 14. Rff6 Rcc3 15. bxc3 bxc6 16. gxf3 gxf6 17. Ba3 Ba6 18. Bh3 Bh6 19. Bd6 Bd3 20. exd3 exd6 21. Be6 Be3 22. dxe3 dxe6 23. Qa1 Qa8 24. Qa3 Qa6 25. Qc5 Qc4 26. bxc4 bxc5 27. d4 cxd4 28. c5 d3 29. cxd6 cxd6 30. cxd3 c5 31. d4 cxd4 32. cxd4 e5 33. dxe5 dxe5 34. f4 Ke7 35. fxe5 fxe5 36. f4 exf4 37. exf4 g5 38. Ke2 gxf4 39. g4 f5 40. gxf5 f3+ 41. Ke3 f2 42. Ke2 f1=Q+ 43. Ke3 Qe1+ 44. Kd3 Qe6 45. fxe6

```
> 11 votes

---
Tags: problems, pawns, records
---


# Question
Title: Moving a game up or down the SCID database list
Is there a way to move an individual game up or down the database list or give it a new game number in the list?

# Answer
> 3 votes
There is a workaround to organize the games in a database if you don't mind playing a bit with the text files (PGN files) where the games are stored. This works well in **ScidvsPC**:

1. Go to Tools \> Export All Filter Games \> Export Filter to PGN
2. Use a name for the file you can identify quickly. For example myfile.pgn
3. Open the PGN file with any text editor.
4. Locate the game you want to move. Cut and paste it in the new position you wanted in the file (database). Save and close the text editor.
5. Run the program **pgnscid** as follows: `pgnscid myfile.pgn mybase`
6. This will create a new database with the name `mybase`. The database consists of three files with different extensions: `mybase.sg4`, `mybase.sn4`, and `mybase.si4`.
7. Rename these files with the name you want for your database but keep the extensions. For example: `nepo.sg4`, `nepo.sn4`, and `nepo.si4`.
8. Open the database in **ScidvsPC**.

It is not as easy as just pressing an arrow button that says move UP or DOWN, but it works.

# Answer
> 1 votes
SCID orders the items in the order that imported them. You can modify the sort order in the list of games. Click in the column names to change the sort order or to reset the sort. But you can't change the individual position of a game in the list.

And what columns can be shown, seems to be hard coded. But if you add a collection of games that are numbered, say on the event tag, it is possible to sort that database by that tag.

---
Tags: database, scid
---


# Question
Title: Can I move a piece somewhere else if I left it but didn't press the clock?
Can I move a piece somewhere else if I left it but didn't press the clock?

Suppose I touch my queen and then move my queen, keeping it on a square, and take my hand off. Then, before I press the clock, I realize that it's a wrong move. Thus, I move the queen to a different square and then press the clock. Is this allowed, or do I have to play the queen on the first square (if my opponent calls the arbiter)?

I am getting conflicting answers. An official answer would be appreciated.

# Answer
When I first started playing competitive chess 50 years ago what you describe was standard practice in blitz but not allowed in standard time control chess. Nowadays it is not allowed at all except in the case that moving the piece was not legal, for instance because it left your king in check or placed your king in check.

According to the current FIDE Laws of Chess:

> 4.7 When, **as a legal move or part of a legal move**, a piece has been released on a square, it cannot be moved to another square on this move.

**Legal** and **illegal** moves are defined so:

> 3.10.1 A move is **legal** when all the relevant requirements of Articles 3.1 – 3.9 have been fulfilled.
> 3.10.2 A move is **illegal** when it fails to meet the relevant requirements of Articles 3.1 – 3.9

There are two cases when the requirement for the move to be legal would allow you to take the move back, indeed *require* you to do so.

The first is if your king ended up being in check after your move:

> 3.9.2 No piece can be moved that will either expose the king of the same colour to check or leave that king in check.

The second is if you move a piece in a way it is not allowed to. You can take the move back if, in your example, you moved your queen to a square it is not allowed to move to, for instance you moved the queen like a knight:

> 3.4 The queen may move to any square along the file, the rank or a diagonal on which it stands.
> 18 votes

# Answer
No, you may not move that piece to another square even if you have not yet pressed your clock.

From the FIDE Laws, art. 4.7.:

When, as a legal move or part of a legal move, a piece has been released on a square, it cannot be moved to another square on this move.

(Art. 4.7 continues with further laws regarding captures, castling and promotion.)
> 5 votes

# Answer
You didn't ask, but note "legal" in the answers: if you made an illegal move, and did not press the clock, you may and must change it, and usually (modulo §E11.5, "Do not distract your opponent in any way!") get scot-free. In German even the part on the board ("Zug ausgeführt") and on the clock ("Zug abgeschlossen") have different names in the FIDE rules to easily distinguish these actions (I didn't memorize the English names).
> 5 votes

# Answer
It is not allowed to change your move: https://www.fide.com/FIDE/handbook/LawsOfChess.pdf

"When, as a legal move or part of a legal move, a piece has been released on a square, it cannot be moved to another square on this move."
> 4 votes

---
Tags: rules, pieces, otb-chess
---


# Question
Title: What would be the ELO of modern-day centaurs?
The last public ranking of chess centaurs was in 2014, and only compares centaurs to each other. As of 2018, what would be the ELO rating of the best centaurs compared to the best humans and chess engines?

This is similar to this question, but two differences:

* It is specifically about if centaurs beat computers, which is a subset of this question
* The top answer is about a GM with a computer who does *not* have any training as a centaur, while we know that good centaurs have very different skills than good humans do.

# Answer
Chess centaurs is not correspondence chess because centaur matches are played under the classical time controls. Unfortunately, centaurs is dead because the best strategy is just follow the engine moves.

In classical time controls, there's generally no advantage for human assistance. Humans are too slow, too clumsy etc ... we need more time.

This is 2018, centaurs matches are absolutely meaningless. They are like computer matches with dumb human intervention. Computer engines play stronger than human+computer unless the human player has sufficient time to digest the positions.

The answer to your question is the **same ELO as the engine itself**.
> 4 votes

# Answer
In this 2015 article Magnus Carlsen agrees with the interviewer's claim that the best computers surpass human playing ability:

> Interviewer: Both chess - and more recently the Asian game of Go - are now played better by computers than by humans, even by the very best like you. Does that take away the magic of brain games like chess?

> Carlsen: Yes, to some extent it takes a bit of the mysticism away. **But as for chess, we've known for a long time that computers are better, so the computer never has been an opponent**. It's a tool to help me analyze and to help me improve at chess.

However, there are rare times when a human will play a move over the board that the engines being used by analysts in real time do not find. For example, in this video analysis of Kramnik v Leko 2004 WCC Game 8, the commentator's engine fails to find Leko's brilliant move 25 ... Qd3.

```
[FEN ""]
[Event "2004 World Championship Match Game 8"]
[White "Vladimir Kramnik"]
[Black "Peter Leko"]

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5 7. Bb3 O-O 8. c3 d5 9. exd5 Nxd5 10. Nxe5 Nxe5 11. Rxe5 c6 12. d4 Bd6 13. Re1 Qh4 14. g3 Qh3 15. Re4 g5 16. Qf1 Qh5 17. Nd2 Bf5 18. f3 Nf6 19. Re1 Rae8 20. Rxe8 Rxe8 21. a4 Qg6 22. axb5 Bd3 23. Qf2 Re2 24. Qxe2 Bxe2 25. bxa6 Qd3 26. Kf2 Bxf3 27. Nxf3 Ne4+ 28. Ke1 Nxc3 29. bxc3 Qxc3+ 30. Kf2 Qxa1 31. a7 h6 32. h4 g4

```

This fact suggests that perhaps a world-class human player could occasionally find moves that improve the play of one of the best computers. But it seems that for the most part, the human would go against the recommendation of the computer at great risk. A centaur match today would probably be quite boring.
> 2 votes

---
Tags: history, elo
---


# Question
Title: Is there a sequence to force a draw in crazyhouse?
I have heard that there is something like a 9 move sequence to force a draw in crazyhouse. Is there such a sequence?

# Answer
Not only is there no "9 move sequence to force a draw" in Crazyhouse, but it is quite possible - rather likely in fact - that a draw cannot be forced in Crazyhouse in any number of moves, because Crazyhouse is a win for White.

The first thing to note about Crazyhouse is that it is a more, not less, complex game than chess in the sense of having a larger gametree: much larger, indeed, because for every piece you can drop, there are a great many empty squares you could probably drop it on (thus, the average branching factor of Crazyhouse is probably more than double that of chess). Crazyhouse is regarded as quite similar to Shogi in this sense. Gametree size isn't all that matters for strategic depth - how easily the gametree is pruned by a player also matters; there's no indication that Crazyhouse's tree is any easier to prune than that of standard chess.

All this to say, it's inconceivable that any human player of Crazyhouse could be anywhere near the game's theoretical skillcap. The best humans get clobbered by the best engines pretty much 100% of the time, like in chess. So much for a simple 9-move way to force a draw.

Now, there is also some evidence that Crazyhouse is a theoretical win for White. As AlphaZero improved at Shogi it was found that its win-rate as Black (the first-mover in Shogi) actually increased. I don't know much about the current engine scene in Shogi but I'd be interested to hear whether this trend has been sustained. In Crazyhouse, there is some evidence that as you increase the strength of engines, whether by lengthening the time-control or by using a better (more recent) engine, the White win-rate increases. Empirically, it seems fairly likely that you cannot force a draw in Crazyhouse at all. (At least, unless you're White, in which case you can probably force a win too; and in any case, these are far beyond the horizon of calculation for any human or currently feasible engine.)
> 6 votes

---
Tags: strategy, chess-variants, draw, crazyhouse
---


# Question
Title: How to understand which positions result from certain opening
I was watching Irina Krush's great lecture on YouTube and, at 20:06, she asks "Which opening is this position from?" The answer is apparently the Sicilian, which made me wonder. How do you understand which middle game positions result from certain openings?

In the video example, I am guessing that the absence of Black's c pawn and the fight against the d5 square may have given it away. But can't that be the result of a different opening as well? Also, can we reverse engineer *every* middle game position to an opening, or do some openings result in obvious middle game positions?

# Answer
> the absence of Black's C pawn and the fight against the D5 square

That's more or less it. This kind of position is most probably the result of a Sicilian. Could it be something else? It can, but the Sicilian is the most likely opening.

> can we reverse engineer every middle game position to an opening

No. This position for example is a middlegame with no clear signposts as to what opening led to it.

```
[FEN "rn1r2k1/pp2qppp/8/8/3N2n1/1N2P3/P1Q2PPP/R4RK1 w - - 0 18"]

```

Here's another example. It should be decently clear which opening this game began with. If not, imagine Black playing ...f5 and White taking with exf5.

```
[FEN "r1bqk2r/pppn2bp/3p4/3Ppp2/2P5/2N1BP2/PP4PP/R2QKB1R w KQkq - 0 12"]

```
> 6 votes

# Answer
The biggest clue is the pawn structure. Allure's first diagram hints that is was a Grunfeld due to the queenside pawns. (Although since there are so many transpositions that the opening can change on a move's notice.) The further the game proceeds, the harder it becomes to guess the opening.

As a teen, I played the Blackmar–Diemer Gambit, which had the trait of white missing the e and f pawns. However, black could transpose into the French or the Caro-Kann, making a d pawn into an e pawn opening.
> 2 votes

# Answer
Some positions have clues which at least rule out certain openings, even if they don't identify one specific opening. For example, if a pawn is still at home, then the opening wasn't one in which that pawn moves or gets taken.
> 1 votes

---
Tags: opening, middlegame, transpositions
---