title: The earliest possible knight fork

text:
# Question
Title: The earliest possible knight fork
I hope it's OK with a question on the fringes of existing opening theory.

If white wants to combine pawn moves `f4` and `b4` early in the opening, he has to be aware of the possibility of black snatching a pawn. One example is Larsen-Raizman from the 1958 Olympiad `1.f4 Nf6 2.Nf3 g6 3.b4`, where black could have gone `3...Nd5!?` with complicated play.

Even earlier possible pawn losses are `1.f4 d5 2.b4 Qd6` and `1.f4 Nf6 2.b4 Nd5`. I want to focus on this last variation.

```
    [FEN ""]
1.f4 Nf6 2.b4 Nd5

```

Before I thought this was good for black, but now I'm not so sure anymore. `3.e4 Nxf4 4.d4` looks like great compensation, although ironically I would prefer the b4 pawn back on b2. Black is better advised to play `3...Nxb4`, for instance `4.d4 d5`. A possible improvement for white is `3.d4` and after `3...Nxb4` start chasing the knight around.

Questions:

Is `2...Nd5` advisable for black?

How should white react?

# Answer
> 6 votes
This question led me to spend two hours of my life looking at a line that I most likely never will get to play. I went into it being quite confident that `Nd5` was a bad move simply because White would get too much development for the cost of a simple pawn. Analysing back and forth with Houdini has nevertheless convinced me that `Nd5` is perfectly playable.

**The similarities to the Sokolsky Opening**

To get a feel for the `b4` pawn it helps to understand a variation from the Sokolsky Opening. It goes like this:

```
[FEN ""]

1. b4 e6  2. Bb2 Nf6  3.b5

```

Here the pawn on `b5` is slightly annoying. It cannot be easily removed as `a6` can be answered by `a4` (it does not matter if the rooks are swapped off as White intends to castle short anyway) and `c6` can be answered by `e3` when Black must take away from the centre to remove the pawn.

In the game, however, Black can simply play `a6` in the similar position as White can't answer with `a4`:

```
[FEN ""]

1.f4 Nf6  2. b4 e6  3.b5 a6

```

So after `2...e6` White is only left with `3 a3`, which, although reasonable, is another pawn move on the wing. Black will be very solid after playing simple development like `d5`, `Bd6` and `0-0`. This is slightly better than one of the main lines of the Sokolsky Opening, which is not that good to start with (but where White often ends up playing `f4` later).

**Houdini 3 on `2...Nd5`**

The currently strongest engine on the planet is Houdini 3. When you let it analyse the position before `2...Nd5` to a depth of 25 it likes `2...d6` (claiming a small advantage for Black) the best (with `2...d5` as a strong second). `2...Nd5` does not come up as a top five alternative. Houdini is initially not impressed by grabbing the pawn.

**White plays `3 e4`**

Nevertheless, `2...Nd5` is still an interesting alternative and certainly gives more entertaining variations to look at. First let us take a look at what happens if White plays `3 e4` after `2...Nd5` and then Black takes the pawn at `b4`:

```
[FEN ""]

1.f4 Nf6  2.b4 Nd5  3.e4 Nxb4  4.c3 N4c6  5.d4 d5  6.Nd2 dxe4  7.Nxe4

```

To explain this variation it is important to know that Black's hope and main idea against a setup with f4-e4-d4 is to play `d5` and develop `Bc8` to `f5`or `g4`. In the variation above it turns out Black can't play either. `Bg4` simply hangs the bishop and `Bf5` runs into `Ng3` chasing it back. Here I (and Houdini) believe White has compensation for the pawn (although perhaps nothing more).

So, let us look at the alternative. Initially I was sure that `3...Nxf4` must be horrible for Black, but it turns out it is good after `4. d4 e5!`:

```
[FEN ""]

1.f4 Nf6 2.b4 Nd5 3.e4 Nxf4 4.d4 e5 5.dxe5 Ne6

```

As seen above, if White makes the natural capture on e5, Black just retreats the knight. Material is now even, but Black has two threats; The killing `Qh4+` and just grabbing the `b4` pawn. So Black will end up a pawn up with a much better pawn structure and no imminent attack from White.

Instead White must play:

```
[FEN ""]

1.f4 Nf6 2.b4 Nd5 3.e4 Nxf4 4.d4 e5 5.Nf3 Ne6 6.d5 Nd4 7.c3 (7.Ng5) Nxf3+ 8.Qxf3 a5

```

In the above variation please note that `6 Nxe5` runs into `6...Qxh4+`. The same idea works against `7 Nxd4`. And despite all the knight moves Black is left clearly better in this variation too. If you want to play this variation with White you need to try the chaotic `7.Ng5!?`, hoping to trap the knight at d4. Have fun analysing that.

**White plays `3 d4`**

I believe `3 d4` is a strong alternative for White. If Black takes the pawn on `b4` it transposes to a variation we have already looked at:

```
[FEN ""]

1.f4 Nf6 2.b4 Nd5 3.d4 Nxb4 4.c3 N4c6 5.e4 d5 6.Nd2 dxe4 7.Nxe4

```

So, as I mentioned in a comment to the question, perhaps Black can try the amazing `3...Nf6` with the simple plan of `d5` and `Bf5`. In this variation White will have more space, but also more weaknesses (and, no, Black is not behind in development):

```
[FEN ""]

1.f4 Nf6 2.b4 Nd5 3.d4 Nf6

```

**White plays `3 Bb2`**

Seeing that White will lose one pawn anyway, why not play a development move like and see which pawn Black decides to take? It seems that Black can just grab the `f4` pawn and get away with it. Let us see what happens if White tries to push Black off the board:

```
[FEN ""]

1.f4 Nf6 2.b4 Nd5 3.Bb2 Nxf4 4.e3 Ng6 5.h4 h5 6.Be2 d5 7.Bxh5 Qd6

```

White won the `h5` pawn, but now the threat of `Qg3+` is just killing White. Instead, if White tried some quiet development moves:

```
[FEN ""]

1.f4 Nf6 2.b4 Nd5 3.Bb2 Nxf4 4.e3 Ng6 5.Nf3 e5 6.Nxe5 Nxe5 7.Bxe5 Nc6

```

Black gets a small advantage by the precise `5...e5` which trades the not so optimally placed `Ng6` (Black is still a pawn up). Note that the alternative `3 Nf3` could easily transpose as it does not seem that White can improve much

**Conclusion**

The fork `2...Nd5` works out well for Black, despite Houdini's initial reluctance towards it. It seems White should play `3 d4` to equalise. I would certainly try `2...Nd5` should `1 f4 Nf6 2 b4` be played against me.

# Answer
> 2 votes
I think this depends on how you play chess as a human and how good the players are. Some people want to take every pawn they can and then they are defending their king, swapping pieces and then they win the game in the end game. Some want to give them away for some initiative (like white in our example). I think an engine will definitely play `Nd5` and grab the pawn(s).

I would play `Nd5` and take `b4` instead of `f4`, because white gets aggressive play after `e4 Nxf4 d4`, especially the half open `f` file is very nice.

If white plays `c3` after `Nd5`, I would take `f4`.

# Answer
> 1 votes
F4 is a reasonable opening move, to discourage Black's e5. He played Nf6 in a similar vein to discourage your e4.

But the followup move, b4, was bad. Not only does it allow the knight fork, but it has no relation to f4. (The fork is really the symptom, and not the disease). Most logically, you might follow with another move on the kingside such as Nf3 or g3. If you want to play on the queen side, the logical moves are Nc3, or d3, both of which would protect a future pawn on e4 from the knight on f6.

# Answer
> 0 votes
What white is doing doesn't make any sense, it's violating the simple rules of chess: dominating the center.

Nd5 isn't too bad, but the fork is bad i believe

```
    [FEN ""]
1.f4 Nf6 2.b4 Nd5 d3 Nxb4 Bd2

```

The knight is lost, if he's gonna retreat, white could start developing his peaces, and black is down in development.

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


title: Rules on castling, what is allowed

text:
# Question
Title: Rules on castling, what is allowed
I have learned about a move called castling, where you move the castle and the king to switch. Can anybody explain the rules? Thanks.

# Answer
Castling is done by moving the King two squares towards the Rook, and then placing the Rook on the square that the King skipped over. In order to castle, all of the following must be true.

* It's your turn.
* The squares between your King and your Rook are all unoccupied.
* You have not yet moved your King.
* You have not yet moved the Rook that you are using to castle.
* You are not currently in check.
* You will not end up in check.
* The square that your King passes through must not be under attack by an enemy piece (in other words, your King will not pass through check).
> 10 votes

---
Tags: rules, castling
---


# Question
Title: What is the proper way to ask for a draw?
I know that the rule states "The game is drawn upon agreement between the two players. This immediately ends the game." but what I'm interested in knowing the exact way to offer a draw because I've never played at a club (always played online, where you simply click the 'Offer draw' button). So do you actually say "Draw?" or "Do you extend your hand after you play your move?" Just wanted to know the norm.

# Answer
In tournament play, you make your move on the board, state your offer clearly (I say "I offer a draw" and make eye contact to make sure I am understood), then press your clock.
> 13 votes

# Answer
To add to the answer posted by @dfan (who is correct on all counts), the draw offer is only good for that move. If you make a move, then offer a draw, and your opponent makes a move, then the draw offer is implicitly declined.
> 4 votes

---
Tags: draw, etiquette
---


# Question
Title: Is there a name for the a position where King is on the first/last row and an enemy pawn is directly in front?
I'm trying to figure out if there is any name for this particular position so that it might be easier for me to research it more - not so much the rook as much as having king behind the pawn. I play queenside castle a fair bit and find that if given the opportunity to get into this position it usually is beneficial.

```
[fen "1k1r4/pPp5/8/8/8/8/8/7K b - - 0 1"]

```

Here it is in one of my games from yesterday. (I'm sure there were better moves for probably both of us, this is just to better explain since the above kinda looks like endgame)

```
[FEN "1k1r3r/pPbn4/4p3/8/3Pp1B1/2q3pP/2P1Q1P1/R3K2R w KQ - 0 1"]
1.d4 e6 2.e3 d5 3.Nc3 Bd6 4.Nf3 Bd7 5.h3 Qe7 6.a3 Nf6 7.b4 Nc6 8.Be2 O-O-O 9.Bb2 h5 10.b5 Nb8 11.a4 Ne4 12.Nxe4 dxe4 13.Ne5 g5 14.Nxd7 Nxd7 15.a5 f5 16.b6 Kb8 17.bxc7+ Bxc7 18.a6 f4 19.Bc3 fxe3 20.fxe3 g4 21.axb7 g3 22.Bxh5 Qg5 23.Bg4 Qxe3+ 24.Qe2 Qxc3+ 0-1

```

# Answer
There is no explicit name for this position, but it is known that the pawn can act as a line of defense for the king. Its presence can obstruct the other side from creating a path towards the king as the pawn cannot be easily targeted.
> 3 votes

---
Tags: terminology
---


title: What Is Controlling The Center?

text:
# Question
Title: What Is Controlling The Center?
I keep reading about the importance of controlling the center in an opening, however (and forgive me my ignorance), I'm unsure if control means to occupy the center squares or to position pieces such that they are attacking the center squares. If anyone could elucidate the concept of controlling the center, I'd be very grateful!

# Answer
> 6 votes
It means both. The 'center' is most common defined as d4, d5, e4, and e5. (The squares immediately around these are also sometimes included.) Pieces in the center have greater mobility and flexibility than those on the edges. The knight in the corner versus a knight in the center is the classic example. A bishop in the center may attack b8 and h8. The same bishop on g2 is still powerful, but can't immediately control the opponent's king-side.

Putting pawns in the center cramps the opponent and removes his options. If you control the center squares, you can begin thinking about working pieces into strong-points on the opponent's side of the board. Pawns on the the 5th rank can protect pieces on the 6th. These pieces are seriously in the opponent's business.

EDIT

It's hard to keep the queen or a rook in the center (during the middle game) since the opponent's minor pieces will probably be able to drive them away. Also, controlling the center doesn't mean your just plop your pieces and pawns in the center, but that you can *keep* them there. Finally, controlling the center is only a means to an end. Once your pieces are qualitatively better than your opponent's, you must strive for the win.

# Answer
> 2 votes
Controlling the center means your pieces are placed on the board in such a way that the center 4 squares can be attacked and controlled (as shown in the picture below). When pieces are placed in the center they have more mobility and control over major areas of the board (especially with knight) than when they are placed elsewhere.

Controlling the center does not mean that your pieces have to be in the center. Fianchetto is a good example on strategic placement of bishop so that center can be covered from far end of the board.

---
Tags: opening
---


# Question
Title: What is the highest known lower bound for mate in N from starting position?
**Edit**: It seems my question was not clear enough. Let me rephrase: What is the largest N for which we can knowingly say "chess, from the starting position, is not a forced mate in N moves"?

Chess is not solved, i.e. it is not known what the outcome from starting position is given perfect play.

However, if the starting position is win for either player, it is a mate in N for some N. Also by example, if we know for certain that the starting position is not winnable in 5 moves (for either player), 5 is a lower bound for N.

Roughly how deep is it feasible to search exhaustively from the starting position in practice? How high a lower bound for N is known?

# Answer
This is essentially the question of what is the game complexity of chess. Note that by finiteness, we know that chess *is* determined, but we do not know if the starting position is a win for white, a win for black, or a draw. The game complexity of chess is roughly the minimum number of positions we need to check in the game tree to determine the state of the initial position. This is known as the Shannon number. In the influential paper *Programming a Computer for Playing Chess*, Shannon estimated that the Shannon number is at least 10^{120). Note that the number of particles in the Universe is estimated to be 10^(80). To answer the question, we actually want to know the *height* of the game tree when the initial position becomes determined. We should also divide this height by 2, since a *move* in chess is typically considered a white and black move. The branching factor of the tree is estimated to be about 30. Thus, we can take the largest N such that 30^(2N) \< 10^(120).

**Answer.** By the back of the envelope, N=40 works. Coincidentally, this happens to be the length of an average game between grandmasters (although they often resign and do not actually play the game to conclusion).

**Edit.** The moral of the story is that I was trying to estimate an upper bound for your lower bound. The first part of Shannon's reasoning is not circular; he says that there are about 30 legal moves from each position, and this number is reasonably constant for the first portion of a game.

Thus, we can estimate the current *known* value of N (which is really what you are asking, let's call this N') to be at most log\_30 (C) where C is equal to the amount of computing power that has existed in the history of mankind. Even with conservative estimates for C, we get something like N' at most 20. In practice, I don't think anyone has carried out this computation very far up the tree, since a priori we know that the computation becomes infeasible after a very short height and it is not necessary to *exhaustively* search the tree to write good chess programs.

Note however, that you are asking a slightly weaker question, since it is possible that the initial state of the game is a draw with optimal play. So, one could get bounds for N by writing a program whose goal was to not lose for as long as possible. We could then play this program against the best programs or human players in the world and see what the length of a shortest game is. Again, this does not properly answer the question, since we cannot assume that our opponents are *playing optimally*. True optimal play requires full knowledge of the game tree, but we have seen that this is computationally infeasible. Thus, the best we can currently do is approximate an optimally playing opponent with a Kasparov or a very good chess program.
> 6 votes

# Answer
It's not true that the starting position is not winnable in 5 moves or less using the canonical definition of a full move in chess. It can be done in 2 moves via Fool's Mate.

To address your question, the strength of a chess engine is dependent on the software and hardware. In 1997, Deep Blue was a proof of hardware concept, a massively parallel supercomputer capable of evaluating 200 million moves per second with an average depth of 7-8 moves. However, in 2006, Deep Fritz running on a dual-core personal computer had equivalent results while only evaluating 8 million moves per second.

Today, the strongest supercomputer that has been applied to chess is Blue Gene. Using 131,000 processors, Blue Gene can calculate 280 trillion operations per second. Although there is no data to confirm the depth to which Blue Gene can calculate, I would suppose it would be quite deep. Of course, this is dependent on how long the computer runs.

However, we cannot in this case use the term 'exhaustive' when 'solving' and opening. A chess engine has no need to go to the end of the line when it is certain that the end result is decisive. In such, the program would exit when it became clear that the evaluation was clearly in favor of one side. This is known in theoretical computer science as Alpha-Beta pruning.

If I had to make a rough estimate, I would say that Blue Gene would be able to calculate around between 15 and 20 moves per second. Although its hardware and software is extremely impressive, we have to remember that the complexity of chess scales exponentially. According to recent estimates, the game-tree complexity of chess is at least 10^123 and the number of potential positions at 10^46.7.
> 3 votes

# Answer
Assuming there is a winning continuation from a given position and assuming perfect play, implies `N` is fixed and not bounded (otherwise its not perfect play!).

In this case one has to really work backwards - which is accomplished by Endgame Tablebase

*The tablebases of all endgames with up to six pieces are available for free download, and may also be queried using web interfaces (see the external links below). Nalimov tablebase requires more than one terabyte of storage space*
> 1 votes

# Answer
You may look here for a discussion. Of course you should not use the 50 move rule, but according to this forum, the record is hold so far by this position (black to move):

```
8/1r6/8/6n1/5k2/1b6/3K3N/7Q w - - 0 1

```

517 moves to a winning position and 525 to mate (best play by both sides). See here, entry 316. Thus this is a winning position with no win in less than 525 moves.

Let me also reproduce Bourzutschky's comments: "Even deeper 7-man endings may exist, but I doubt it. That such a great depth is still possible with so much firepower on the board suggests that even deeper endings may arise with 8 pieces, perhaps in krnnkbbn. This ending could be generated with 64 GB of RAM in a few months on a fast single CPU machine and about 5 terabytes of storage. Any takers?"
> 1 votes

# Answer
Edit: Sorry, looks like I misread the question. My guess is that any reasonable N is well outside the horizon of a computer. If we set up a very powerful computer to caluclate the starting position that's probably the only confident X we could show, let's say it could 10 million nodes per second after 10 days we could calculate 10 * 86400 * 10^8 nodes = 8.64 * 10^13 nodes. If we assume the average position in the first 20 moves has about 15 legal moves (lower because beginning has much less and probably even slightly lower because of alpha-beta pruning) which is only about 12 moves after 10 days (position only after move 6) so you see why this problem is ugly. However I think practical play probably suggests a much, much, much higher value. I'll take good money against any computer human combination you can come up with that I can not get checkmated in 20 moves (if that's my only goal).

Let's ignore that chess is most likely a draw. We must consider the rules under which chess is played in practice. In almost every tournament situation there's a 50 move rule in effect which states that the game is a draw if "the last 50 consecutive moves have been made by each player without the movement of any pawn and without the capture of any piece."

So this means we can have 49.5 moves per capture or pawn move. Each pawn can move up to 6 times and there are 15 pieces which can be captured for each side (although one piece must remain to deliver checkmate) so we can put an upper bound on the number of moves.

This works out to 49.5 * (8 * 2 * 6 (pawn moves) + 29) = 6187.5 So this means that IF chess is a forced win for white with adhering to the 50 move rule then it is in at most 6188 moves for white. I could probably lower this a tiny bit without doing too much by saying that all K + piece mates v K mates that are forced (Rook at Queen only) are doable in substantially less than 50 moves (I think about 16 playing around with Nalimov for some "tough" cases. So I think we can probably subtract 34 moves from that total confidently for 6134!

Therefore: **If chess is a forced win for white with adhering to the 50 move rule then it is in at most 6134 moves.**
> 0 votes

---
Tags: analysis, software, theory, chess-algorithms
---


# Question
Title: Is there software or a device that allows bookmarking positions to allow variation analysis?
I'm wondering if there is any chess software or portable chess computer that allows a position to be bookmarked while a variation is examined? For example, it's possible to download pgn for games analyzed in Chernev's logical chess. However, there isn't a diagram for every position, and occasionally the author outlines alternate moves and their consequences. While it's possible to follow through this analysis on a board and "unplay" the moves back to the point where this divergence from the actual game takes place, this can be time-consuming. What I'm looking for is the opportunity to bookmark a point in the game, follow the variation through, and then click back to the bookmark to continue on with the game, rather than clicking a back arrow for every move that was made. Thanks

# Answer
Chessbase is a commercial product that solves your problem. Any position in Chessbase is in essence a bookmark. You can just click on the move/position you want to go back to (all the moves are available visually beside the chess board). I believe the same functionality is available for free with Scid.
> 3 votes

# Answer
In the days before electronics, I managed this with a pocket magnetic set. I'd follow along playing the game on the board, and when I wanted to explore a variation I set the "return" position on the magnetic set to save until I was done and wanted to go back.

These days *every* chess database of any stripe will allow you to jump directly to a given move. So you follow along, create a new variation, follow it, and then with one click you jump back to the original position.
> 1 votes

---
Tags: software
---


# Question
Title: Where can I find images for vector chess diagrams?
Chess diagrams are simple, icon-based images and there's no reason they need to be raster images. I've seen many threads started on this topic throughout the web, always unanswered.

# Answer
Someone has just posted a collection of tools for creating vector chess diagrams on reddit. You can find them here. If anyone knows of some more resources like this I'd love to hear about them.
> 2 votes

---
Tags: notation
---


# Question
Title: Deciding on an n-variable for an Elo rating system
I have recently been looking into the mathematics behind the Elo rating system and its application to areas other than chess. I can understand almost all of it but I'm having a problem finding out the meaning of one of the values, and how it is determined. The value I'm talking about is the `n` value, which is supposed to be some number of rating points that a person `n` rated points above their opponent is expected to win ten times as often (If my explanation is not clear enough, it is represented by the number 400 - the value used in chess - in the fomulae on the wikipedia page).

This all makes perfect sense so far, but I was wondering how you determine that value when setting up a new system. For example, in chess the value of n is 400 - why was this number chosen and not something more 'round' like 100 or 500? About the only effect I can see that this number has is the increase in precision (though not accuracy) of the rating for higher values of n, and if this is the case, does the value really matter so long as it remains consistent?

# Answer
Since you referred to the wikipedia page, I assume you understand the probability calculation itself. If not, or if anyone else is interested, I could work through it. I assume that you are just interested in whether the value of 400 was chosen.

From a mathematical perspective, it is totally arbitrary. The value could be 1000, or it could be 1. If the number were larger, the rating scale would end up stretched out. If it were smaller, it would be compressed.

The number 400 works because it means that a difference of 100 points is a pretty meaningful difference. People can relate to that when they look at a rating. People tend to think in 100 point intervals, so if I say that my rating is "in the 800s", people have a reasonable grasp of my abilities, and can instantly make a meaningful comparison to someone who is "in the 900s." If we used 100 instead of 400 in the formula, then instead of 1300 vs 1200, we would be talking about 1225 vs. 1200. It would mean exactly the same thing, but it's easier to relate to that 100 point difference.
> 4 votes

# Answer
It appears to be basically historical. From Arpad Elo's *The Rating of Chess Players, Past and Present*:

> The present range originally took 2000 as the upper level for the strong amateur or club player, and arranged the other categories above and below (1.26)
>
> Category designations and proficiencies among federations have become generally more comparable with the adoption of the Elo system by FIDE and by many of its member federations, but the numbers assigned to any given level of chess proficiency remain entirely arbitrary. Both the class subdivision into 200 points and the choice of 2000 as the reference point were already steeped in tradition when this author arrived on the scene. \[...\] These features were retained for their general acceptance by the players. (1.27)

In particular, the Elo system was designed to produce ratings on approximately the same scale as the Harkness system, which had already been in use by the USCF since the 1950s. The ~200 points per class difference in the Harkness system falls out of the simple equations used to describe that system.
> 5 votes

---
Tags: rating, elo
---


# Question
Title: Is it beneficial to play blindfolded chess?
I've played only two blindfold games so far, but it was against someone who was maybe at a 1000 uscf rating strength, and hence was fairly easy to beat, and once against my friend, who's also rated about 1650, like myself. I also managed to beat him with a sneaky tactical shot, but it was a lot more challenging, as I found it hard to remember where certain pieces were. I've also read that while it benefits your board vision for tournament games, it puts too much strain on your mind to be beneficial overall. Is this true? Any other arguments for/against playing blindfold chess?

# Answer
**In my opinion**

I cannot speak to the health benefits or drawbacks of playing blindfold chess (which I find to be, in my opinion, baseless).

What I can say is from experience. I have attempted playing blindfold chess when I was not a very strong player and found it challenging and not worthwhile. However, as my chess progressed I found playing blindfold to be a lot easier, and was even recently able to play a game to the 62nd move where I checkmated my friend. It took 90 minutes.

My main point is that that blindfold chess more than likely does not affect your chess ability. It is your chess ability that affects your blindfold chess.

**Here is are some conclusions from an in depth study**

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2972788/

In their review of the literature, Hearst and Knott document a number of notable conclusions that may surprise chess players and non-chess players alike:

- The general memory of chess masters, including those able to play many blindfold games simultaneously, is no better than that of the average person.
- Highly skilled players can form long-term memories of full-board chess positions within seconds of viewing them.
- High level chess skill (not just blindfold chess) requires a recognition-action repertoire of some 50,000 to 100,000 features of chess positions and associated responses.
- Some of the strongest masters find the actual sight of a chess position to be more distracting than helpful when thinking ahead during a game.
- Practicing blindfold chess improves sighted chess skill.
- Some of the strongest blindfold chess masters claim that the strength of their blindfold play is similar to that of their sighted play.

**Bonus material**

In case you really want to read up on the subject: http://www.wjh.harvard.edu/~cfc/Chabris1999d.pdf
> 15 votes

# Answer
I cannot speak for whether it ever improved my chess, but I did try several Chess Visualization exercises. (This was a few years back, and I was inspired by the Amber Tournament where Super GM's played Blindfold games that blew me away.)

If you do a web search for "Chess Visualization exercises" you can find many leads, and some of them are worth it. (I don't recommend spending money on any though. There's plenty available for free.)

One sample: Chess Eye

I found two uses for these:

1. When I had a few minutes to kill, I could attempt some of these exercises when I didn't have a board or computer in front of me.
2. The biggest value for me from these attempts at blindfold was that I could follow variations much more easily. If you watch high profile games on ICC, there will be a lot of people *kibbitzing* lines non-stop. Being able to follow them made me better appreciate the positions.

Other than that, I am not sure if full blindfold games have use, except to maybe impress non-chess players.
> 7 votes

# Answer
I would think developing your board vision must be somewhat useful although I doubt it means a significant difference in playing strength. Blindfold seems a handy way to improve board vision as it can be fun, and you have feedback when you forget the position. Intuitively, a nice benefit of improved board vision would be that it is easier to study. So many chess books and articles are provided with only occasional diagrams; consequently, readers are often utilizing the same board vision skills necessitated by blindfold chess.
> 5 votes

# Answer
From my personal experience playing Blindfold is absolutely beneficial. I tried it pretty consistently for several weeks many years back and suddenly, despite being rated around 1800, I was mowing through 2100 players at my local club at blitz. Blindfold can only help your visualization ability since you not only only have to visualize future moves but also the current position. And I find the "strain on the brain" argument to be utterly absurd.
> 5 votes

# Answer
From the following research I gather that the issue was/is under some debate though most people believe that it doesn't harm your health. I personally don't have an opinion on the subject.

In 1930 the USSR banned displays of blindfold chess because they thought it was bad for the health.

That same article states that:

> Botvinnik spoke out against it, which may be why his top student, Kasparov, has declined to test his blindfold play. Most of the Melody Amber players agree that it is more tiring than a regular game even with a faster time control.

I also found several older threads on the topic where the topic was debated. One on Chess.com and one on the Red Hot Pawn forums.

A user from the Red Hot Pawn thread found a study by several universities that goes into the subject on page 5. They state:

> Hearst and Knott (2005) generally find that supposed examples of serious health hazards from playing simultaneous blindfold chess are unfounded.

That study also says:

> Similar training procedures were a commonplace part of instructional techniques in the Soviet Union, and even the three Polgar sisters, now among the best woman players in the world (Judit Polgar, the youngest, competes at male world championship level), have commented on how learning blindfold play at the age of 5 or 6 helped them to develop certain chess skills. However, we do agree with Gobet that the causality goes both ways: blindfold practice may improve chess skill, and the ability to play blindfolded improves as general chess skill improves. There is hardly any master we know who cannot play at least one or two games blindfolded, even without any special training at that form of chess.
> 4 votes

# Answer
Based on my experience, absolutely!

In a nutshell:

* It improve your calculation and visual representation abilities
* It increase your capacity of concentration (you have to work quite hard to be able to play your first full blindfold game!)
* It boosts your self-confidence when you play regular over-the-board games
* and best of all, this fun and rewarding! Playing (and winning) a blindfold game against a family casual player will establish your Chess reputation in the family for the years to come! :-)

If you want to more about blindfold play in general, you can take a look at some post I wrote on this very topic:

1. http://improveyourchessornot.blogspot.ca/2013/04/the-black-art-of-calculation-blindfold.html
2. http://improveyourchessornot.blogspot.ca/2013/04/the-black-art-of-calculation-blindfold\_20.html

Cheers!
> 1 votes

---
Tags: learning, blindfold-chess
---


# Question
Title: Chess Pieces like classic 1997 "Pure Mate" ad
I used to have this print up on my locker in highschool, and have had a blown-up, framed version in my living room for the past several years.

I've recently started playing chess regularly again and was looking to buy a new board, and was wondering if anyone could recommend a place to purchase a similarly detailed set.

The ad is titled "Pure Mate" from 1997. I'm not sure if I'm allowed to link amazon or an outside site in these posts, but this if so here is the ad in question: http://www.amazon.com/Smirnoff-Vodka-Bottle-Chess-Pieces/dp/B00764VM14

# Answer
> 2 votes
Try these themed sets from House of Staunton. I don't see the set you're looking for, but you can expect whatever they have to be very high quality. I love the Isle of Lewis set.

http://www.houseofstaunton.com/chess-pieces/themed-chess-pieces.html?src=feature

---
Tags: chessboards
---


# Question
Title: A variant in the French defence advance variation
Consider the following beginning, quite typical of the advance variation of the French defense:

```
[fen ""]

1.e4 e6 2.d4 d5 3.e5 c5 4.c3 Nc6 5.Nf3 Qb6 6.a3

```

On what I have seen on the web, the recommended black's next moves are `6. ... Nh6`, or `6. ... Bd7`. But what about `6. ... f6` ? Lately this has been played regularly against me with the white pieces, and I don't know what to do. Any idea?

Thanks,

Joël

# Answer
Actually, the GM who taught me (Vladimir Kosyrev) plays c4! closing the structure then Na5 then Bd7 then Nb3, after Nxb3, you pin the N on b3 with Ba4! and you can leave the pin until the queen moves, of course castle long and f5 to break through on the king side

```
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 e6 2. d4 d5 3. e5 c5 4. c3 Nc6 5. Nf3 Qb6 6. a3 c4 7. Nbd2 Na5! 8. g3 Bd7 9. Bg2 Nb3 10. Nxb3 Ba4!

```

Feel free to look up Vladimir Kosyrevs french games in this position after 6... c4!
> 7 votes

# Answer
I think `6. ... f6` is probably the best move for black at this point. The responses I'd try are `7. Bd3` or `7. Be2` or `7. b4`. `7. exf6` seems like it just gives black an extra minor piece developed with Nf6, but it doesn't seem horrible either. `7. b4` looks the most interesting to me, followed by something like... `7. ... fxe5 8. dxc5 Qc7 9. Bb5` or `9. c4 Nf6`. Still doesn't feel too great for white, but at least you're almost even.

In *Beating the French Defense with the Advance Variation*, GM Andrew Soltis doesn't even discuss `6. a3` as an option. You might consider his recommended line:

```
[fen ""]
1.e4 e6 2.d4 d5 3.e5 c5 4.c3 Nc6 5.Nf3 Qb6 6.Be2

```

At this point, the `6. ... f6` move is reduced to 4th or 5th place for black's options, the best being:

```
[SetUp "0"]
[fen "r1b1kbnr/pp3ppp/1qn1p3/2ppP3/3P4/2P2N2/PP3PPP/RNBQKB1R w KQkq - 4 6"]
[StartPly "10"]

6. Be2 cxd4 7. cxd4 Nh6

```

You'll probably find yourself castling short soon, and maybe breaking out `a3` a few moves later when it will make black feel more pain.

Disclaimer: I'm by no means an opening expert. Just some ideas to try...
> 4 votes

# Answer
I'd suggest playing 7.Be2, followed by castling short soon. If black plays fxe5, just play dxe5 (even Nxe5 works, but you will simplify a lot, and not give black any problems), which deprives the knight of the f6 square. The g8 knight will likely take one of the h6-f5 or e7-f5 route to plop on h5, after which you may consider even Bd3, if you find the knight particularly annoying on that square. You could follow up with putting your rook on e1, preparing a later f4, etc. following Nimzowitch's overprotection idea of a central pawn.

I'd also suggest not playing 6.a3. It seems very passive, and doesn't create any threats, doesn't help your pieces develop, and creates a weakness on b3. The position looks as if white is playing the black side of some variation of a QGD Meran system with an extra tempo or two. Instead, you may consider aiming for ideas like 6.Bd3 or 6.Be2.
> 3 votes

# Answer
**Strengths**

Positionally White has just blundered a little by playing `a3`. `f6` takes advantage White neglecting to develop a piece and begins to work on attacking `d4` from the king side ( obviously there is pressure on `d4` from the queenside as well). Black is listed as having a slight `-0.28` advantage (23 moves).

**Weaknessess**

A player who is not experienced defending may lose to a king side assault after moving `f6`. However, to build the attack it requires White to sac a pawn, and that is all an experienced player needs sometimes to win the game. This would not be a gambit. Black is very strong at this point and `a3` should seriously be reconsidered.

**White's Response**

Play defensively. Although the position favors Black, it is still very slight, and an equal slip by the opponent will even the game out. No material has been lost yet. It is very important not to give in to Black's traps. Of which, there are many here, and all include dropping a pawn. Avoid taking first, unless it is absolutely forced. This game is going to continue on with White being forced over and over to make the correct move in order to properly develop and retain equal material.

There are, however, a few traps you may entice your opponent into

Offer a "free" pawn for a positional advantage.

*7. Bd3...*

This is a standard continuation of the position in question. Black will realize that by fiancettoing king side they can possibly win the pawn on `e5`.

```
[FEN ""]
1. e4 e6 2. d4 d5 3. e5 c5 4. c3 Nc6 5. Nf3 Qb6 6. a3 f6 7. Bd3 fxe5 8. dxe5 c4 9. Bc2 g6 10. Nbd2 Bg7

```

At this point, allowing Black to take the pawn gives White an undeniable advantage. Here is a continuation if Black takes.

```
[FEN ""]

1. e4 e6 2. d4 d5 3. e5 c5 4. c3 Nc6 5. Nf3 Qb6 6. a3 f6 7. Bd3 fxe5 8. dxe5 c4 9. Bc2 g6 10. O-O Bg7 11. Nbd2 Nxe5 12. Nxe5 Bxe5 13. Nf3 Bf6 14. Re1 Ne7 15. Ba4+ Kf8 16. Ne5 Kg8 17. Qf3 Nf5 18. Nd7 Bxd7 19. Bxd7 Kg7 20. a4 Rad8 21. a5 Qd6 22. Bxe6 Rhe8 23. Bf4 Qc6 24. Bxf5 gxf5

```

Otherwise, you may be looking at a long grueling, semi closed position:

```
[FEN ""]

1. e4 e6 2. d4 d5 3. e5 c5 4. c3 Nc6 5. Nf3 Qb6 6. a3 f6 7. Bd3 fxe5 8. dxe5 c4 9. Bc2 g6 10. Nbd2 Bg7 11. O-O Nge7 12. Qe2 Qc7 13. Re1 O-O 14. b3 b5 15. Bb2 Bd7 16. a4 a6 17. bxc4 bxc4 18. Ba3

```

---

*Summary*

What it all boils down to is, don't be overly aggressive, play defensively, and try not initiate a material trade (especially with pawns) when in this position. In my opinion, playing `a3` is what makes `f6` seem so disruptive, when the real result was a loss in tempo.
> 3 votes

# Answer
```
[FEN ""]
1. e4 e6 2. d4 d5 3. e5 c5 4. c3 Nc6 5. Nf3 Qb6 6. a3 f6 7. Bd3 fxe5 8. Nxe5 Nxe5 9. Qh5+ Ng6 10. Bxg6 hxg6 11. Qxh8

```
> -2 votes

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


# Question
Title: What are the common themes in the Catalan?
I have looked over some of the main lines of the Catalan in MCO-15 and feel pretty lost as to what's going on in them. What are some of the key positions and goals for either side? Or is the opening just too tactical to have any real unifying themes?

**The Catalan Opening (E01-E09)**

```
rnbqkb1r/ppp2ppp/4pn2/3p4/2PP4/6P1/PP2PPBP/RNBQK1NR w KQkq - 0 4

```

# Answer
I have played the Catalan for something like 25 years, and to me the big secret explaining the opening's popularity is the following: You can expect a massive score against weaker players.

The key strategic factors in a successful Catalan are:

1) You achieve control/dominance over all four central squares, something rarely seen in other openings. (By the way this explains why the Catalan set-up isn't so effective with a black bishop on `f5`; white has too little control over `e4`.)

2) Long-term pressure against black's queenside, in part exerted by the bishop on the diagonal. In the end something is going to break.

These factors make it possible to turn up unprepared for a game Sunday morning during a weekend tournament and have a winning position before the first cup of coffee. In other words, great opening!

For books that focus on philosophy and not too much on concrete moves I can recommend the series *How Wojo won*.
> 10 votes

# Answer
The Catalan usually results in black exchanging his d5 pawn on c4, which leads to some pretty clear strategic goals on both side.

* White plays for control of the e4 square to support the e-pawn, and pressuring the d5 pawn with pieces.
* Black's freeing lever is c5, and thematic play centers around this push. If black can succeed, he often tries to expand his queen-side pawns to form an a6-b5 pawn chain, and develops his c8 bishop to b7, opposing whites.
* If white can prevent the c5 push, it becomes backwards or semibackwards on the c file, and white builds up pressure with his major pieces there.
> 8 votes

# Answer
Please get yourself a copy of Avrukh's 1.d4 book and also see the games of Anand-Topalov 2010 World Championship match, which are really instructive for seeing the themes of the Catalan. If you want to follow a strong exponent of the Catalan, check out Kramnik's games.
> 5 votes

---
Tags: opening, theory, 1.d4, catalan
---


# Question
Title: Are there games between top computers which uncovered never-seen-before ideas?
Are there games between top computers which uncovered never-seen-before ideas?

And if so, how can humans notice?

**Addendum:** I understand the position of James Christopher in his answer, but my question goes a little beyond that. It is possible for the computer to find a winning move without understanding the idea behind it, and thus to win the game. If afterwards a human notices that the move discloses a new theme or idea never before seen, that would qualify as a positive answer.

**Addenddendum:** We have a linguistic problem here. Let me clarify: The computer does not need to *have a new idea* or even understand what it is doing. But it can find a move that wins the game, and later, when people analyze what happened, they realize "oh! this move wins *because* of such-and-such!" The computer does not need to know that it forked the king and queen, it just evaluates the material gain and decides that the knight move is best. **We** call it a fork and add a section in the basic tactics chapter.

# Answer
> 10 votes
My answer is - Yes. A simple example is the use of endgame tablebase. Many positions, which were thought to be drawn, now have a winning line. IMO this is a new idea. One day computers might uncover that castling is bad - it is a new idea, doesn't matter if it was achieved by brute force.

ps: even though computers work on fixed algorithms, they can uncover new ideas. Same algorithm can return different results when run for longer duration and/or better hardware. In the end, chess is deterministic and finite.

# Answer
> 1 votes
Computers are based on algorithms written by humans, which are based on knowledge and concepts known to humans. They do not work based on abstract chess ideas. Computers are not known for creativity, so I would say that the answer to your question is no.

They will certainly find moves in a position that GMs have not thought of before, but that is not the same as a new chess idea.

# Answer
> -1 votes
Interesting question,

In my opinion computers dont play chess but do something that just looks like it. The way they do it is simply through number crunching algorithmes. It must be said that in their programming there are some heuristics that could be seen as rudimentary ideas about the game.

To answer your question I am sure computers produced moves that showed something new about the game but they didnt uncover any ideas. Computers can not think and ideas belong to the realm of humans. So to notice an idea needs someone to interpret the move or sequence of moves and form some sort of generalisation.

Besides opening innovations and improved endgame analysis computer chess is rather killing a lot of ideas by showing that many positions are defensible after all.

---
Tags: engines
---


title: Professional games that ended with mate

text:
# Question
Title: Professional games that ended with mate
What are some professional games where the losing side did not resign before receiving mate?

And how sure are people of the record? In old books they did not care much for complete historical accuracy, so a reference that makes the mate story believable would be better.

# Answer
Quite a few games here. There are many games with top players that ended in mate.

http://www.chessgames.com/perl/chesscollection?cid=1001021
> 3 votes

# Answer
Most of the games that end in checkmate are where the weak side allows checkmate for whatever reason (he thinks it's a nice win / checkmate, to ruin the publishability of the game, etc), but the strongest example I can think of where a player allowed mate on the board accidentally is Deep Fritz vs Kramnik: http://www.chessgames.com/perl/chessgame?gid=1440796
> 4 votes

---
Tags: history
---


# Question
Title: Will computer knowledge reach a perfect game, after expanding prepared openings/endgames?
If computers just check in an openings-DB what to do in the first 10, 15 or even 20 moves, and if they just check the endgames-DB at the endgame; wouldn't it reach a point where they have a DB of perfect games that goes from opening to endgame?

# Answer
> 5 votes
To my mind, what you are asking is can a computer ever "know" the correct move and evaluation in every conceivable position. Without such complete knowledge, it wouldn't be possible to play perfectly because every evaluation is dependent on evaluations of the multitude of possible upcoming positions. This perfection is what endgame tablebases provide. Outside of contexts where distance to mate can be calculated, tablebases are the only context in which computers have a "perfect" understanding of a position. For reference, 5 piece tablebases (e.g. 2 kings and 3 other pieces) require 7 GB of storage. 6 piece tablebases require 1.2 TB, and 7 man tablebases are only recently completed and require 140 TBs. To solve chess completely, you would need a 32 man tablebase.

The problem is comparable in fictional magnitude to the calculation of the "Ultimate Question of Life, the Universe, and Everything" as depicted in Hitchhiker's Guide to the Galaxy. In that case an entire planet, was devoted to identifying the question. It seems an equally pointless and gargantuan task to attempt to "solve" chess.

Just to put your mind at ease... even though computers may play well above the level of the best humans today, there are still plenty of decisive games between top level computers today. Check out the ongoing TCEC tournament. Clearly, computers are still quite capable of mistakes.

# Answer
> 3 votes
I will try a more serious answer because the discussion becomes pointless if we resort to empty arguments. Yes, the Universe may be finite, and yes, the "Ultimate Question of Life, the Universe, and Everything" may need a full Earth and 7.5 million years to solve... so what?

Let's do some quick numbers. Each of the 64 squares can be empty or hold one of 12 different pieces (R, K, B, Q, K, and P in black and white), so the total number of positions that you could set is at most

13^64 = 196053476430761073330659760423566015424403280004115787589590963842248961.

That is about 2 x 10^71 different positions. Of course this is a huge overestimate, because most positions are fake (we should eliminate positions with three or more kings, nine or more white pawns, pawns in the eighth rank, quadruple checks, etc). Let's take the square root:

13^32 = 442779263776840698304313192148785281,

or about 5 x 10^35. By taking the square root we are pretending that for each legal position there is a chess Universe worth of distinct fake positions. This is probably an underestimate, so the true answer must be somewhere in between these two numbers. Now we can confidently say that computers cannot study every legal position in a reasonable time. Even the "tiny" 13^32 is too large...

Wait! so am I arguing against myself? No! Computers cannot analyze every position one-by-one. BUT that is not the only way to solve chess. We humans are reasonably smart. In fact, smart enough to have invented chess. What I suggest is the possibility that people may find shortcuts; rules of thumb that eliminate many cases at a glance. We already have many trivial ones; for instance "K+Q vs K always wins". More sophisticated rules could be found by yet-unknown arguments, perhaps supported by computer tables.

Solving chess by analyzing all positions is brute force, and impractical. Solving chess in a smart manner may still be possible, and I do not see any obstacle. In fact, I do expect computers armed with faster processors and better chess knowledge may become provably perfect within 50 years.

# Answer
> 1 votes
Chess is a finite game. Lots and lots of positions, but finite. Eventually, with enough computing power, **yes**, computers will be able to play a perfect game. When will that happen? That is a different question. It could be less than 10 years if enough breakthroughs in algorithms and hardware are made. It could take 50 years. Who knows?

# Answer
> 1 votes
The game will not be solvable for a long time. In fact, it will *never* be solvable unless insanely radical hardware advancements are made. The search tree is too deep and too wide. Since we're talking about 'solving' chess, not 'winning the game', heuristics will not do; every move played - every one of them - must be evaluated to completion.

Choose the fastest processor you know of, multiply its speed by 1000 and you are really no closer to solving this problem. Multiply it by a million instead. Still, no closer from any practical sense.

Right now the new hotness in computer architecture is called a 'quantum computer'. They are still very primitive. The gist is that they can manipulate objects that are in multiple states. So theoretically, a pawn could be on a2 and a3 at the same time. With decades and decades of development, this could yield unheard-of efficiencies. Or, like bubble memory, it could fade away not long after making a splash.

---
Tags: engines
---


# Question
Title: How can I train myself in pawn endgames?
I'm looking for a chess program which offers to play pawn endgames to improve myself.
For example, can I force Fritz 13 to play pawns endgames? If so, how can I achieve this?

# Answer
Any chess-playing computer program that allows you to set up positions can be used. And yes, Fritz is especially suited for this.

You have several options:

1. Set up the position yourself (using board/position set up). Choose any position that you want to get better at. Save that position and play against the computer.

1a. I used to do this for simple pawn endings. I'd play both colors until I figured out some aspects of the pawn ending.

1b. I'd often set up one side with an advantage (say an extra pawn) and see if I could win easily. (Since the computer plays well, this is not easy to do in practice.)
2. You can start collecting some endgame positions, from a book or from around the web, create a small endgame learning database for yourself, and practice.
3. In this video (be sure to watch) Nigel Davies recommends Silman's *Complete Endgame Course* (I find most things by Silman to be very good.)
4. Finally, if you don't mind spending a little, "Fritz Endgame Trainers" (DVD or software add-ons) that ChessBase sells are quite good. (Just buy one at a time, and be sure to read the reviews to see if it is at the right level for your needs.)

Hope that helps.
> 6 votes

---
Tags: software, endgame, training, pawn-endgame
---


# Question
Title: Can I win this Rook and Pawn vs Bishop endgame?
I'm playing white and I've been unable to get the black king out of the corner. Does black have a guaranteed stalemate or is there some way to force him out the corner?

```
[fen "5K1k/6R1/7P/8/8/8/2b5/8 w - - 0 1"]

```

# Answer
> 11 votes
This position is in fact drawn (which you can confirm e.g. by looking the position up in an online endgame tablebase). The key for Black's defense is to maintain the bishop on the b1-h7 diagonal, which prevents White from doing things like (1) moving the king to g6 (for threatening an eighth rank mate) or (2) pushing the pawn to h7 to threaten checking the black king out of h8 and queening the pawn. Black is able to keep the bishop on this diagonal, or at least be able to come back to it after moving away, and this keeps White from making any progress.

Here is just one line illustrating how White could win if Black were to go wrong with the placement of the bishop. After `1...Ba4??` White has a won position, but only by the move `2.Rg2!` which keeps the bishop from returning to its defensively optimal diagonal. And that's the idea behind White's play in the rest of the line given: keep the bishop from coming back to that diagonal (e.g. with `4.Re2`, `5.Rd2`, `10.Re5` denying the bishop's return) until it's too late and the pawn push has already been arranged.

```
[fen "5K1k/6R1/7P/8/8/8/2b5/8 w - - 0 1"]

1.Kf7 Ba4?? 2.Rg2! Bb3+ 3.Kf6 Bd5 4.Re2 Bc4 5.Rd2 Bb5 6.Rd4 Bc6 7.Kg5 Bb5 8.Rd8+ Kh7 9.Rd5 Bc6 10.Re5 Ba4 11.Re7+ Kh8 12.h7 Bc2 13.Kh6 1-0

```

# Answer
> 5 votes
Draw. The white king can never occupy g6/7/8, and thus there is no way to attack both h7 & h8 at the same time, thus no way to chase the black king off the h file, nor any way to support the advance of the pawn to h7, which much be covered twice for it to advance as the black bishop can stay on that diagonal.

---
Tags: analysis, endgame, draw, rook-and-minor-endgame
---


# Question
Title: Parsing PGN files - when can a move be shortened?
I'm writing a PGN file parser, and need to know in which situations you don't need to write the rank/file of a piece that makes the move. I can think of the following:

* only one piece can conduct the move according to the rules of movement (i.e. attempting to move a bishop horizontally - that's obvious).
* both pieces can move to the given square, but all but one are obstructed by other pieces
* all but one of the pieces are pinned and moving them would expose the king to check

Anything else I'm missing?

I'd also like to add some seemingly ambiguous situations:

Black to move. Is Nc5+ valid PGN, or would it be Nbc5+? Is Nc5 valid, or would it be Nec5?

Black to move. Is Rg7# / Rg7+ valid PGN, or do I need to specify the rank here?

What if two pieces can move to the same square, but one of the moves would result in threefold repetition, and the game doesn't stop instantly?

What if two pieces can move to the same square, one of those moves forces a mate-in-one on the moving side, and the move is labeled "!!"? :)

# Answer
> 11 votes
From the PGN specification (http://www6.chessclub.com/help/PGN-spec):

> Neither the appearance nor the absence of either a check or checkmating indicator is used for disambiguation purposes. This means that if two (or more) pieces of the same type can move to the same square the differences in checking status of the moves does not allieviate the need for the standard rank and file disabiguation described above. (Note that a difference in checking status for the above may occur only in the case of a discovered check.)

This means you have to specify files respectively ranks in your two diagram examples.

My understanding is that you need to disambiguate in the last two situations you describe as well.

---
Tags: rules, notation, pgn
---


# Question
Title: Where can I find good information on the ideas/themes behind certain opening lines?
I'm looking for some information on the ideas or themes behind different opening lines. E.g. Queens Gambit / Slav defence .. white tries to accomplish X and black tries to do Y without books of theory covering every variation. I'm just looking for general ideas e.g. White's black bishop is very strong - Black will try to trade it off ... or fight will be around isolated pawn etc etc. thanks (I'm a 1700 player)

# Answer
> 1 votes
I highly recommend the book *Fundamental Chess Openings* by Paul van der Sterren. It is a comprehensive survey of the chess openings with an emphasis on themes.

*Understanding the Chess Openings* by Sam Collins is a similar book and is also pretty good but FCO is more comprehensive.

The original book along these lines was *The Ideas Behind the Chess Openings* by Reuben Fine but it is very dated now (it was originally written in in 1943).

---
Tags: opening
---


title: About Sultan Khan

text:
# Question
Title: About Sultan Khan
I know the standard facts about Sultan khan's life. He was servant to a wealthy Indian military guy who let him play in tournaments whenever he traveled to England. Sultan Khan was a really strong player who originally had learned to play with slightly different rules (about promotion and stalemate eg). He won the British Championship and defeated Marshall, Flohr, and Capablanca. When players were invited to his masters house, Sultan Khan was expected to serve them, even though he was their better at chess!

What I am looking for is the lesser known facts about him. Any picture, story, or other reference is welcome. Please quote your sources.

# Answer
Lots of info, pictures, and fun facts here: http://www.chesshistory.com/winter/extra/sultankhan.html
> 6 votes

---
Tags: famous-players
---


# Question
Title: Chess engines' .dll files usable in C# projects
Are there any free/paid chess engine .dll files that could be used in a C# project as a reference?

# Answer
> 3 votes
C#? Probably not any upper tier engines. Chess engines tend to be written for speed and are largely written in C, C++, or assembly.

I googled and found this. And this. And this.

# Answer
> 6 votes
Take a look at the C# port of Stockfish by bpfliegel. To my knowledge it is complete (was able to compile and run it) and even though it has not been updated in 11 months at the time of this post it is certainly much stronger than the other engines listed. When I tested its perft function it on my machine it was only a factor of 1.5 slower than the original C++ implementation.

---
Tags: engines, programming
---


# Question
Title: What type of hardware is the most important for analysing with Houdini?
I am going to analyse a lot of games with Houdini 3.

The system on which I am going to analyse it is really powerful, but I am curious, what is the most important type of hardware for such analysis?

* CPU
* RAM
* GPU

I am willing to buy some additional computational power, but if needed.

Up till now I have read this and was not able to find the answer.

If someone has any results or have done a strong analysis with Houdini, please give your insights.

# Answer
> 6 votes
You have not read enough of Houdini's online user manual. First look at the 2.1 Installing Houdini page.

Specifically, it says you'll get 30% faster performance with 64-bit over 32-bit. It says it's optimized to use up to 6 cores. And Intel i5 will run it faster than an equivalent speed AMD Opteron. Their home page says it will use up to 4 GB of RAM for hash memory. Obviously from that, you'll want to get the highest clocked Intel i7 you can find with a 4th generation CPU.

But if you get Houdini 3 Pro instead of Houdini 3 Standard, it supports up to 32 cores and 256 GB of hash memory and NUMA-architecture (whatever that is). Their example performance comparison shows on a 16-core dual AMD Opteron-6128 box that Pro has a 20% speed gain over Standard. With the Pro version, you'll want as many cores as you can get, because that's the number of threads you'll be able to run at once. Intel i7 will likely be better than AMD for the Pro version as well.

Definitely read everything in the online Houdini 3 User's Manual, especially section 3 about its configuration. That tells you how to optimize it.

# Answer
> 5 votes
CPU is by far the most important here. RAM is very cheap so I guess that you have between 8 and 16GB meaning that this will not be a bottle neck. You absolutely need a multiprocessor version of Houdini if you care about performance. Otherwise it will only use 1 of your 4 cores.

I think this is highly unlikely for home PC, but multiple processor would speed up your analysis a lot. Chess programs are doing very well when it comes to parallel processing and utilising resources.

If you have 1 processor, I would suggest buying a very good cooling system for it and overclocking it to higher clock. i7 2600k can easily run at 4.5 GHz.

# Answer
> 2 votes
The next most critical point is to ensure that you have a 64-bit operating system and use the 64-bit version of the engine. Well designed engines like Rybka (and Houdini is a derivative of Rybka) will see a performance gain of as much as 70% from switching to 64-bit architecture.

# Answer
> 0 votes
The answer of your question can be found by logic. When you play chess, the most important organ is your brain because you mostly need to think about positions. For computers, that's the same, which hardware refers to brain? CPU of course!

Moreover, nowadays, computers can have multiple brains (cores) and chess engines can be compatible with it. Thus, more your processor has cores, better is for analyzing positions.

You speak about Houdini but it's the same for other chess engines like Rybka, Fritz and so on.

---
Tags: analysis, engines
---


# Question
Title: Why is algebraic notation called algebraic?
How does algebra relate to this chess notation?

Why do they call this chess notation **algebraic**?

# Answer
> 6 votes
I think that Jonathan Garber is right. Much of algebra has to do with equation in an x y coordinate plane which is very similar to the way that algebraic notation denotes specific squares on the board. I have however not been able to find any specific source of the information.

# Answer
> 3 votes
Algebraic notation is quite old. It is based on a system created by Philipp Stamma (c.1705–55) *before* descriptive notation started to evolve. There is no indication that anyone with a mathematical background had anything to do with its development or spreading, so my best guess is that they called it "algebraic" simply because it uses coordinates. The funny thing is that there is nothing algebraic about coordinates. If anything, it should be called "geometric notation", but somehow "algebraic" sounds better; as if it is more accurate.

In brief, I strongly suspect that they **just** called it "algebraic".

# Answer
> 2 votes
Algebra is more than simply a branch of mathematics. The central element of it is using symbols as abstractions, the way the notation uses letters and numbers to represent the squares, as opposed to the systems where the square is more concretely described, as "King Bishop 4" for example.

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Tags: history, notation
---


title: Best websites for correspondence chess?

text:
# Question
Title: Best websites for correspondence chess?
I've had some bad experiences with Chess.com recently. What are some good alternative websites for correspondence chess? I'm particularly looking for:

1. No time limit
2. Email notifications when it is your turn
3. Ideally, you should be able to make moves by replying to notification emails (with a simple expression like e2e4)

Thoughts?

# Answer
> 4 votes
Apart from chess.com, here are a few others:

There are many out there...

---
Tags: websites, correspondence-chess
---


# Question
Title: How to represent chess state with a bitboard
I'm interested in programming a chess engine and using bitboards to represent the state of the game. I know there are a few open source chess engines that use bitboards, but its not so easy to look at the code and understand what is going on. I'm looking for good reference material on how to represent all the state in bitboards.

Clearly explaining how to maintain the state of the game using bitboards, and especially how to generate a list of valid moves from any given bitboard, or supplying good references to such an explanation will earn you the green check mark.

# Answer
The best resource for chess engine programming is the Chess Programming Wiki, which has a large section on bitboards. Everything you need to make a bitboard-based engine is there, although it's rather spread out and sometimes written by people for whom English is a second language.
> 14 votes

# Answer
What programming language do you want to use?

To implement a bitboard in C#, use System.UInt64. This can hold 64 bits, 1 for each square of the chess board. This value type lends itself to many fast bitwise operations.

This is a good bitboard tutorial.

Here are some examples from my own C# chess engine. As you can see from the code, it can take a while to wrap your head around using bitboards, but they are typically very fast, especially for position evaluation.

Example 1 - Bitboard definition:

```
internal UInt64 WhiteKing;
internal UInt64 WhiteQueens;
internal UInt64 WhiteRooks;
internal UInt64 WhiteBishops;
internal UInt64 WhiteKnights;
internal UInt64 WhitePawns;
internal UInt64 WhitePieces;

```

Example 2 - Bitboard initialisation:

```
// Initialise piece bitboards using square contents.
private void InitPieceBitboards()
{
    this.WhiteKing = 0;
    this.WhiteQueens = 0;
    this.WhiteRooks = 0;
    this.WhiteBishops = 0;
    this.WhiteKnights = 0;
    this.WhitePawns = 0;

    for (Int16 i = 0; i < 64; i++)
    {
        if (this.Squares[i] == Constants.WHITE_KING)
        {
            this.WhiteKing = this.WhiteKing | Constants.BITSET[i];
        }
        if (this.Squares[i] == Constants.WHITE_QUEEN)
        {
            this.WhiteQueens = this.WhiteQueens | Constants.BITSET[i];
        }
        if (this.Squares[i] == Constants.WHITE_ROOK)
        {
            this.WhiteRooks = this.WhiteRooks | Constants.BITSET[i];
        }
        if (this.Squares[i] == Constants.WHITE_BISHOP)
        {
            this.WhiteBishops = this.WhiteBishops | Constants.BITSET[i];
        }
        if (this.Squares[i] == Constants.WHITE_KNIGHT)
        {
            this.WhiteKnights = this.WhiteKnights | Constants.BITSET[i];
        }
        if (this.Squares[i] == Constants.WHITE_PAWN)
        {
            this.WhitePawns = this.WhitePawns | Constants.BITSET[i];
        }

        this.WhitePieces = this.WhiteKing | this.WhiteQueens |
                           this.WhiteRooks | this.WhiteBishops |
                           this.WhiteKnights | this.WhitePawns;
        this.BlackPieces = this.BlackKing | this.BlackQueens |
                           this.BlackRooks | this.BlackBishops |
                           this.BlackKnights | this.BlackPawns;
        this.SquaresOccupied = this.WhitePieces | this.BlackPieces;
    }
}

```

Example 3 - Move generation:

```
// We can't capture one of our own pieces.
eligibleSquares = ~this.WhitePieces;

// Generate moves for white knights.
remainingKnights = this.WhiteKnights;

// Generate the moves for each knight...
while (remainingKnights != 0)
{
    squareFrom = BitOps.BitScanForward(remainingKnights);
    generatedMoves = Constants.ATTACKS_KNIGHT[squareFrom] & eligibleSquares;
    while (generatedMoves != 0)
    {
        squareTo = BitOps.BitScanForward(generatedMoves);
        moveList.Add(new Move(squareFrom, squareTo, Constants.WHITE_KNIGHT,
                              this.Squares[squareTo], Constants.EMPTY));
        generatedMoves ^= Constants.BITSET[squareTo];
    }
    // Finished with this knight - move on to the next one.
    remainingKnights ^= Constants.BITSET[squareFrom];
}

```

Example 4 - Calculate material score:

```
// Material score from scratch, in centipawns from White's perspective.
internal static Int32 ScoreMaterial(Board position)
{
    return BitOps.BitCountWegner(position.WhitePawns)   * Constants.VALUE_PAWN +
           BitOps.BitCountWegner(position.WhiteKnights) * Constants.VALUE_KNIGHT +
           BitOps.BitCountWegner(position.WhiteBishops) * Constants.VALUE_BISHOP +
           BitOps.BitCountWegner(position.WhiteRooks)   * Constants.VALUE_ROOK   +
           BitOps.BitCountWegner(position.WhiteQueens)  * Constants.VALUE_QUEEN  -
           BitOps.BitCountWegner(position.BlackPawns)   * Constants.VALUE_PAWN   -
           BitOps.BitCountWegner(position.BlackKnights) * Constants.VALUE_KNIGHT -
           BitOps.BitCountWegner(position.BlackBishops) * Constants.VALUE_BISHOP -
           BitOps.BitCountWegner(position.BlackRooks)   * Constants.VALUE_ROOK   -
           BitOps.BitCountWegner(position.BlackQueens)  * Constants.VALUE_QUEEN;
}

```

Example 5 - Calculating piece mobility:

```
// Calculate mobility score for white knights.
remainingPieces = position.WhiteKnights;
while (remainingPieces != 0)
{
    squareFrom = BitOps.BitScanForward(remainingPieces);
    mobilityKnight += BitOps.BitCountWegner(Constants.ATTACKS_KNIGHT[squareFrom]
                                            & unoccupiedSquares);
    remainingPieces ^= Constants.BITSET[squareFrom];
 }

```
> 11 votes

---
Tags: engines, software, open-source, bitboard
---


title: Have we found every existing tactic?

text:
# Question
Title: Have we found every existing tactic?
Is it possible that there are missing or unstudied tactics, waiting there to be found?

Maybe some of them have been played only by GMs and in so few times that they don't get to have a name on their own, maybe the rest of the world just see them as 'just another brilliant move'.

What I am saying is, if we were all geniuses and GMs, do you seriously think the number of known tactics would remain the same? Maybe they are so complex that they cannot be learned by books, but by experience.

Or, should I stop watching conspiracy movies?

# Answer
> 6 votes
The type of complex tactic you are thinking of is called a combination. A combination is a forcing series of moves to create some sort of advantage; some would also say that a combination must begin with a material sacrifice, but this is besides the main point. If you are interested in combinations, look at the games of Mikhail Tal, for one, who has been called "the wizard of combinations" for his daring, speculative sacrifices which often led to his opponent cracking under the pressure of searching out the one saving defensive resource; or Alekhine, "the genius of combinations", whose combinations, if not as daring as Tal's, were perhaps more sound.

Wikipedia gives the following example of a combination:

```
r1b2r2/p2p2kp/1pn1p3/8/1PP5/P2K1P2/2Q4P/R4B2 b - - 0 1

1... Rxf3+ 2. Ke4 (2. Ke2 Nd4+) (2. Kd2 Rf2+ 3. Be2 Rxe2+! Kxe2 Nd4+) d5+!! 3. cxd5 (3. Kxf3 Nd4+)  exd5+ 4. Kxd5 (4. Kxf3 Nd4+) Be6+ 5. Kd6 (5. Kxe6 Nd4+) (5. Kxc6 Rc8+) (5. Ke4 Bf5+) Rd8+ 6. Kc7 (6. Kxe6 Nd4+) (6. Kxc6 Rc8+) Rf7+ 7. Kxc6 Rc8+

```

In light of the impending disaster, White in fact resigned on move 3 (Move 22 in the actual game between G. Stepanov and Peter Romanovsky).

# Answer
> 3 votes
Feast your eyes on this position:

```
8/1r6/8/6n1/5k2/1b6/3K3N/7Q b - - 0 1

1...  Rd7+ 2.  Kc3! Bd1 3. Qf1+! Bf3 4.  Qc1+! Kf5 5. Kb2! Rb7+ 6. Ka3 Ra7+ 7. Kb4 Rb7+ 8. Ka5 Ra7+ 9. Kb6 Rb7+ 10. Ka6 Re7 11. Qf1 Re6+ 12. Ka7 Re7+ 13. Kb8 Re8+ 14. Kc7 Re3 15. Kc8 Rc3+ 16. Kb8! Kf4 17. Qg1! Ne4 18. Nf1! Rb3+ 19. Ka7! Rd3 20. Qh2+! Kf5 21. Kb8 Nf6 22. Nd2! Bd5 23. Qf2+! Ke5 24. Qe2+ Kd4 25. Ka7 Nd7 26. Qg4+! Kc5 27. Qg1+! Kb4 28. Qb1+! Kc3 29. Qc1+ Kd4 30. Qb2+ Kc5 31. Qc2+! Kd4 32. Qa4+ Kc5 33. Qa5+ Kd4 34. Qb4+ Ke5 35. Ka6 Kf5 36. Qb1 Ne5 37. Kb5! Bc6+ 38. Kb4! Bd5 39. Qf1+ Kg6 40. Qe2 Kf6 41. Qh5 Ke6 42. Qg5 Nc6+ 43. Kb5 Ne5 44. Qh6+ Kf5 45. Nf1 Bc6+ 46. Kb4 Rd4+ 47. Kb3 Rd3+ 48. Ka2 Bd5+ 49. Kb1! Nc4 50. Qh5+! Kf6 51. Qh4+ Ke6 52. Ng3! Rb3+ 53. Kc1! Rc3+ 54. Kd1 Re3 55. Nf1! Ra3 56. Qf4 Kd7 57. Ke1 Kc6 58. Qh6+ Kc5 59. Kf2 Rb3 60. Qh8 Ra3 61. Qb8 Kc6 62. Qb1 Rc3 63. Kg1 Ra3 64. Qc2 Kb6 65. Qf5 Kc5 66. Qf8+ Kb5 67. Qe8+ Kc5 68. Qe2 Rf3 69. Qe7+ Kd4 70. Qg7+ Kc5 71. Qg5 Kc6 72. Qh4 Kb5 73. Qe7 Kb6 74. Qb4+ Kc6 75. Qe1 Ra3 76. Qf2 Rf3 77. Qd4 Kd6 78. Qh4 Kc5 79. Nh2 Ra3 80. Ng4 Ra1+ 81. Kf2! Ra2+ 82. Kg3! Ra3+ 83. Kf4 Rf3+ 84. Kg5 Be6 85. Nf6! Ne5 86. Nh5 Rf5+ 87. Kh6 Ng4+ 88. Kg6! Ne5+ 89. Kh7 Rf7+ 90. Kh6! Ng4+ 91. Kg5 Ne5 92. Qa4 Rf5+ 93. Kh6! Bc4 94. Qa5+ Kd4 95. Qb6+ Kd5 96. Qd8+ Ke4 97. Qd1 Ke3 98. Qc1+ Kd4 99. Ng3 Rf6+ 100. Kh5 Kd5 101. Kh4 Rg6 102. Kh3 Bd3 103. Qf4 Rg8 104. Qb4 Bc4 105. Qd2+ Ke6 106. Qh6+ Kd5 107. Qh7 Kc5 108. Kh2 Rg6 109. Qe7+ Kd5 110. Qd8+ Ke6 111. Qf8 Kd5 112. Kh3 Bb5 113. Qa3 Bc6 114. Kg2 Rf6 115. Kh2 Nf3+ 116. Kh3 Rh6+ 117. Kg2! Nd4 118. Qe7 Kc4+ 119. Kg1! Rg6 120. Qf7+ Re6 121. Qf4 Kd3 122. Qf1+ Kc3 123. Qc1+ Kb4 124. Kh2 Rf6 125. Kh3 Bd7+ 126. Kg2! Bc6+ 127. Kh2 Rf3 128. Qd1 Kc5 129. Nh5 Kd5 130. Qh1 Ke6 131. Qg1 Ke5 132. Qg7+ Ke4 133. Qc7 Kd5 134. Nf4+ Kc4 135. Qb8 Rc3 136. Qa7 Be4 137. Qb6 Bc6 138. Qa6+ Kc5 139. Nd3+ Kd6 140. Nb2 Rb3 141. Nd1 Nf3+ 142. Kg3 Nd4+ 143. Kf2 Rf3+ 144. Ke1 Kd5 145. Qb6 Kc4 146. Qa7 Bb5 147. Nf2 Nc2+ 148. Kf1 Bc6 149. Qa6+ Kc5 150. Qa2 Nd4 151. Kg1! Rf5 152. Kh2 Rh5+ 153. Kg3! Rg5+ 154. Kf4! Rf5+ 155. Kg4 Bf3+ 156. Kh4 Rh5+ 157. Kg3 Rg5+ 158. Kf4 Rf5+ 159. Ke3! Re5+ 160. Kd3 Be2+ 161. Kd2! Kb4 162. Qg8 Bb5 163. Qg4 Re2+ 164. Kc1! Kc4 165. Nd1! Rc2+ 166. Kb1 Rd2 167. Qc8+ Bc6 168. Qg8+! Kb4 169. Nb2 Be4+ 170. Ka2! Nb5 171. Qb3+! Ka5 172. Ka1! Bd5 173. Qa4+! Kb6 174. Qb4! Rd4 175. Qe1 Be4 176. Nd1 Rc4 177. Qe3+ Kc6 178. Kb2 Rc2+ 179. Kb3 Nd6 180. Qh6 Rc5 181. Nc3 Bd5+ 182. Kc2 Kd7 183. Qg7+ Kc6 184. Kd1 Bf7 185. Kd2 Bc4 186. Ke1 Ra5 187. Qf6 Rf5 188. Qg6 Kc7 189. Qg7+ Rf7 190. Qg3 Kc6 191. Qg2+ Kc7 192. Qh2 Kc6 193. Qh1+ Kc5 194. Qh8 Re7+ 195. Kd1! Re8 196. Qh2 Re3 197. Kc2 Rd3 198. Qe5+ Kc6 199. Qh5 Rg3 200. Qa5 Rh3 201. Kd2 Rh2+ 202. Ke3 Rh3+ 203. Kf4 Rd3 204. Na4 Rd4+ 205. Kf3 Rd3+ 206. Kg4 Rd4+ 207. Kh3 Ne4 208. Qa7 Be6+ 209. Kg2! Rb4 210. Qa6+! Kd5 211. Kf3 Kd4 212. Qe2 Kd5 213. Ke3 Bd7 214. Nb2 Bb5 215. Qh5+ Ke6 216. Nd1 Nf6 217. Qh3+ Kf7 218. Kd2 Rd4+ 219. Kc1 Rc4+ 220. Kb2 Rb4+ 221. Ka3 Ra4+ 222. Kb3 Rd4 223. Nc3 Bc4+ 224. Kc2! Be6 225. Qe3 Rh4 226. Qa7+ Kg6 227. Ne2 Rb4 228. Kc1 Rc4+ 229. Kb2 Rb4+ 230. Ka3 Rb3+ 231. Ka4! Rf3 232. Qd4 Bd7+ 233. Kb4 Be6 234. Qc5 Bd7 235. Qd6 Bg4 236. Nd4 Rd3 237. Kc4 Re3 238. Nc6 Bc8 239. Qh2 Re4+ 240. Kc5 Bb7 241. Qg1+ Kh7 242. Na7 Rg4 243. Qh2+ Kg6 244. Nb5 Rg2 245. Qh3 Rg5+ 246. Kb4 Bg2 247. Qh2 Bd5 248. Nd6 Ne4 249. Nc8 Nf6 250. Qd6 Rh5 251. Qc7 Kg5 252. Qe5+ Kg6 253. Qe3 Kh7 254. Qd3+ Kg7 255. Nd6 Rg5 256. Ka4 Rh5 257. Qg3+ Kh7 258. Kb4 Kh6 259. Ka3 Rg5 260. Qc3 Kg6 261. Qc2+ Kh6 262. Nf5+ Kh5 263. Qd3 Kg6 264. Ng3+ Kf7 265. Qe3 Rg8 266. Nf5 Ra8+ 267. Kb2! Ra2+ 268. Kb1 Ra6 269. Qe7+ Kg6 270. Nd6 Rb6+ 271. Kc2 Rb3 272. Qe5 Rf3 273. Kd2 Bc6 274. Nc4 Bd5 275. Ne3 Be4 276. Ng4 Bb7 277. Qe6 Kg5 278. Ne5 Rf2+ 279. Kc3 Rf4 280. Nf7+ Kg6 281. Nd6 Be4 282. Kd2 Rf2+ 283. Ke1 Rf4 284. Qc4 Kg5 285. Qe2 Bg6 286. Qe5+ Kg4 287. Ke2 Bf5 288. Qa1 Nh5 289. Ke3 Bc2 290. Qa8 Bg6 291. Qd5 Ng3 292. Nc4 Nf5+ 293. Ke2! Ng3+ 294. Kd2 Kh3 295. Qc6 Re4 296. Qa6 Re2+ 297. Kc3 Be4 298. Qd6 Kg2 299. Kb4 Bf3 300. Ka5 Nf5 301. Qc5 Be4 302. Kb6 Rc2 303. Qb4 Kf2 304. Ne5 Ke3 305. Nd7 Nd4 306. Qa3+ Ke2 307. Ne5 Nf5 308. Qa6+ Kf2 309. Qa4 Ng3 310. Qb4 Ke3 311. Nc4+ Kd3 312. Nd6 Ke3 313. Ka7 Bd3 314. Qb6+ Kf3 315. Qd4 Be4 316. Kb8 Re2 317. Nf7 Bf5 318. Ng5+ Kg2 319. Qd5+ Be4 320. Qb3 Bf5 321. Qf3+ Kh2 322. Qb7 Re8+ 323. Ka7! Re2 324. Qd5 Rf2 325. Nf3+ Kg2 326. Nd2+ Kh3 327. Qc6 Kg4 328. Qc3 Rf4 329. Nc4 Re4 330. Ne3+ Kg5 331. Qc5 Re6 332. Kb8 Re8+ 333. Kb7 Re6 334. Kc7 Re4 335. Kc6 Re8 336. Kb6 Re4 337. Ka5 Re6 338. Kb5 Re4 339. Nd5 Nh5 340. Ne7 Ng3 341. Qc1+ Kh4 342. Qh6+ Kg4 343. Nd5 Kf3 344. Qf6 Kg4 345. Qg7+ Kf3 346. Qc3+ Kf2 347. Qc5+ Kf3 348. Ka5 Bg4 349. Nf6 Rf4 350. Qc6+ Kf2 351. Nd5 Re4 352. Qf6+ Bf3 353. Nf4 Ne2 354. Nd3+ Ke3 355. Ne5 Rf4 356. Qb6+ Nd4 357. Kb4 Ke4 358. Nc4 Kf5 359. Qh6 Be2 360. Ne3+ Ke5 361. Qh8+ Ke4 362. Qe8+! Kf3 363. Nd5! Re4 364. Qf7+ Kg3 365. Qg6+ Kf3 366. Nf6 Rf4 367. Qh5+ Kg3 368. Qg5+ Kf3 369. Kc3 Nb5+ 370. Kb3! Rc4 371. Nd5 Nd4+ 372. Kb2 Rc2+ 373. Kb1 Ke4 374. Nf6+ Kd3 375. Nd7 Bf3 376. Ne5+ Ke2 377. Qh4 Rd2 378. Nc4! Rd1+ 379. Kb2! Rd3 380. Qg5 Rb3+ 381. Ka2! Rd3 382. Qe5+ Kf2 383. Nb2 Rd2 384. Qf4 Ke2 385. Kb1 Bg2 386. Nc4 Rd3 387. Qh2 Kf1 388. Qh7 Rc3 389. Kb2 Rc2+ 390. Ka3 Rc3+ 391. Kb4 Ne2 392. Ne5 Rh3 393. Qf5+ Ke1 394. Nd3+ Kd2 395. Nc5 Rg3 396. Qh7 Ke3 397. Qd3+ Kf2 398. Qc4 Rc3 399. Qh4+ Rg3 400. Ka5 Kg1 401. Qe7 Kf2 402. Qf6+ Ke1 403. Qh4 Kf1 404. Qd8 Ke1 405. Nd3+ Kd2 406. Nb4+ Kc1 407. Qe7 Kd2 408. Qd6+ Ke3 409. Nc2+ Kf2 410. Qe7 Rf3 411. Qh4+ Rg3 412. Ka6 Bh3 413. Qf6+ Rf3 414. Qa1 Rd3 415. Qe1+ Kf3 416. Qb4 Kg3 417. Qe7 Kf2 418. Ka5 Rc3 419. Qf8+ Rf3 420. Qb4 Rc3 421. Qb6+ Kg3 422. Ne3 Nf4 423. Nc4 Rf3 424. Qc7 Rf2 425. Qg7+ Kh2 426. Qe5 Kg3 427. Qg5+ Kh2 428. Kb6 Bg2 429. Ne3 Bh3 430. Qe5 Kg3 431. Nd5 Kg4 432. Qd4 Kg3 433. Qe3+ Rf3 434. Qe5 Kg4 435. Nf6+ Kg3 436. Ne4+ Kg2 437. Qc5 Ne2 438. Qc4 Nf4 439. Qc2+ Kh1 440. Qc5 Bg2 441. Nf2+ Kh2 442. Ng4+ Kh3 443. Qg5 Rb3+ 444. Ka5 Ra3+ 445. Kb4 Rf3 446. Ne5 Nd5+ 447. Kb5 Rf4 448. Kc5 Be4 449. Nc6 Rh4 450. Qd2 Kg4 451. Qe1 Bg2 452. Qe6+ Kg3 453. Nd4 Nf4 454. Qb3+ Kh2 455. Qe3 Rh5+ 456. Kd6! Rd5+ 457. Ke7! Nh3 458. Qd2 Kg3 459. Qc3+ Kh2 460. Qe3 Rg5 461. Qe2 Nf4 462. Qf2 Rg4 463. Nf5 Nd5+ 464. Ke6 Rg6+ 465. Kd7 Rg4 466. Qe1 Nf6+ 467. Kc7 Ne4 468. Qc1 Rg5 469. Qf4+! Kg1 470. Ne3 Rg7+ 471. Kb6 Rg6+ 472. Ka5 Rg5+ 473. Kb4 Rg6 474. Qe5 Bf3 475. Qa1+ Kh2 476. Qb2+ Kh1 477. Qc1+ Rg1 478. Qc8 Rg3 479. Qh8+ Kg1 480. Qa1+ Kf2 481. Qd4 Rg5 482. Nf5+ Kg2 483. Qb2+ Kh3 484. Ne3 Rh5 485. Nf1 Kg4 486. Qg7+ Kh3 487. Qg1 Rh4 488. Ka3 Rf4 489. Qh2+ Kg4 490. Ne3+ Kg5 491. Nd5 Rf7 492. Qe5+ Kh4 493. Ne7 Ng5 494. Ng8 Ne4 495. Nh6 Rf6 496. Nf5+ Kg4 497. Ne3+ Kh4 498. Kb4 Rb6+ 499. Ka5 Rf6 500. Qh2+ Kg5 501. Qh7 Ng3 502. Qg7+ Rg6 503. Qe5+ Kh6 504. Qf4+ Rg5+ 505. Kb6 Be2 506. Qf8+ Kh7 507. Nd5 Bc4 508. Nf6+ Kg6 509. Nd7 Nh5 510. Qd6+ Kh7 511. Qe7+ Kh6 512. Qe3 Be6 513. Ne5 Bd5 514. Qd4 Bg8 515. Qd2 Nf6 516. Nf3 Nd5+ 517. Kb7 Kg7 518. Qxg5+

```

This is black to move, and white to mate(!) in 517 moves. This is the longest known forced mate discovered so far, part of the 7 man tablebase projects. That is to say that there exists a single combination here that makes the most complicated combinations seen on the board look trivial, that can't even be comprehended by the strongest humans, or the strongest computers without tablebases, and this with just 7 pieces left in play. I suspect that there are many such amazing combinations. Imagine what we could find with a 32 piece tablebase?

# Answer
> 2 votes
It depends on the criteria you use to say two tactics are the same thing. If I play a combination tomorrow, in some position that's not played before, and the details of where the pieces are is just slightly different, is it a new tactic?

Endgame studies have been described as crystallized versions of tactics; only the tactic, nothing else. I don't think the last original endgame study has been composed already.

# Answer
> 1 votes
If you mean by tactics things like forks, pins, overworked pieces etc. the answer to your question is yess. There is only so much you can do with these wooden pieces. Ofcourse when combining these tactics over more moves the sky is the limit.

# Answer
> -1 votes
No, since Chess is not "solved", the resulting tactics are not solved. There are just too many permutations and combinations..pun!!

---
Tags: tactics
---


# Question
Title: How can a drawish opening be fashionable?
dfan's answer to this question suggested the following. Why would a specific opening become popular as the method of choice to play for a draw? Wouldn't it be better to select an obscure out-of-fashion variation that leads to a draw? That way you always have the chance to catch your opponent unprepared and score an extra 1/2 point.

# Answer
If I choose a well known drawish opening, it sends two messages to my opponent:

1. Offer me a draw and I'll accept it
2. If you play for a win, you'll just smash against my rocks. If you try too hard, you'll lose. If you don't, you'll probably just get a draw anyway.

Of course, some opponents won't care and will fight for the win while others will be more than ready to throw in the towel, especially if there's a rating difference in the opponent's favor.

This really only applies to master play. Amateurs make enough mistakes that nothing is drawish, nothing is safe.
> 4 votes

# Answer
Because an obscure variation is just that -- obscure. It is far less understood and analyzed, and so you cannot be confident in your ability to play lines that lead to the outcome you want. In a well known opening, you can play the lines that you know most likely lead to certain positions.

In response to your edit:

In order to be confident in playing the lines of an opening, you would have to be well-studied in it. If you are playing at high level chess, your opponent most likely will know that you play these lines, and will prepare for it.
> 3 votes

# Answer
It's difficult to give a general answer why one opening is more popular than another. I can try to give some reasons in the specific case of Berlin vs Petrov that prompted your question.

In the Petrov the following line is popular for white.

```
[fen ""]
1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.Nc3 Nxc3 6.dxc3

```

This might be theoretically fine for black, but from a practical point of view white is very much in control. White may have prepared a dangerous novelty to use at a later stage in the opening, and black has to react over the board. There is almost no upside for black as white can play for a win with little risk.

The Berlin

```
[fen ""]
1.e4 e5 2.Nf3 Nc6 3.Bb5 Nf6 4.O-O Nxe4 5.d4 Nd6 6.Bxc6 dxc6 7.dxe5 Nf5 8.Qxd8+ Kxd8

```

on the other is much more flexible. Black has almost as many different possible set-ups as white has. Compared with the Petrov, here it is much more difficult for white to prepare specific lines. White frequently goes wrong even at the highest levels. I think Aronian once commented that he sometimes plays the Berlin when he wants to win with black.
> 3 votes

# Answer
Specific openings become popular as a way to play for a draw (among grandmasters!) because those openings tend to lead to very drawish position (few unbalances).

Playing less popular lines is a different subject, with pros and cons -- the opponent may not remember too much about it and that may be an advantage, on the other hand you won't have much experience with them either, and unpopular openings are usually unpopular for a reason -- they're often worse than the popular ones. In fact your opponent may well know the exact reason why it's unpopular.

But those are trade-offs associated with playing unpopular openings at all -- not of playing them when trying to achieve a draw. Your question boils down to "why play popular openings at all?" Well, if one line is seen as having the biggest chance of success at the moment, then that line is going to be popular.

People don't choose a line based on popularity, but based on how good they think they can do with the positions they lead to.
> 3 votes

---
Tags: opening, draw
---


title: What's with the Petrov?

text:
# Question
Title: What's with the Petrov?
The Petrov or Russian opening is seldom seen these days:

```
[fen ""]

1. e4 e5 2. Nf3 Nf6

```

Why? Is it fully refuted? Or merely uncomfortable for Black?

# Answer
There is nothing wrong with the Petroff and it is still used regularly at the highest levels. If it is less popular than it used to be (and I'd have to check the data before claiming that), then that would likely be because it is usually played when Black is trying to make a draw, and these days the Berlin variation of the Ruy Lopez is the most popular way to try to achieve a draw against 1.e4.
> 3 votes

# Answer
What's "wrong" with the Petroff is that it is "boring," and associated with playing to draw, because it is somewhat symmetrical.

Most people, even Black, like to play to win, and when they do, their choice is "sharper" Sicilian, or French, or even certain variations of the Ruy.

I remember people using it in my high school days (forty years ago) when they were ahead in the tournament, and just wanted to finish with a good score.
> 2 votes

# Answer
I wouldn't call any of those moves *wrong*, but I would say it is a bad idea for Black to move `2. ... Nf6`.

If you are an optimistic player who thinks that White and Black are even at first glance, my Houdini counters by saying White is already **one point ahead**.
In one classical game, it goes like this: **`C42 Russian Game: Classical`**

```
[FEN ""]
1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 Be7 6. Bd3 f5

```
> -3 votes

---
Tags: opening, petroff-defense
---


# Question
Title: Make checkmate with pawns without promotion
I have a chess puzzle here:

```
[FEN "7k/8/8/4KPPP/8/8/8/8 - - - 0 0 "]

```

> Can White force mate without promotion?

And if such exist, where can I find some more chess puzzles like this, which feature particular and restrictive directions?

# Answer
> 4 votes
As Daniel indicated in a comment, the answer here is that, **no**, White cannot force checkmate without promoting at least one pawn. Enough toying with the position makes this pretty clear, intuitively. The only way it could possibly be done would be to keep the black king in the corner it's in, and while doing so, to then checkmate by advancing the pawns. The intuitive reason this isn't feasible is because the white king is the only option for keeping the black king from running to the other side of the board, but while he's doing that, there's not enough support behind the pawns to advance them for checkmate.

But I want to point out that if one finds that intuitive explanation unconvincing or unsatisfying, there is a more rigorous way to demonstrate that White cannot force checkmate from your position without promoting, and that is to do a little bit of retrograde analysis. (Incidentally, the retrograde analysis subfield of chess problems provides some of what you ask for at the end of your post, namely problems with a very particular sort of solution.) Basically, all I mean is that we should work backwards: with the given material on the board, there's only a small handful of positions that could possibly be our final checkmate position. Thus, if we can show for each of those positions that there couldn't be a forced win that ends that way, then we know it can't be done.

For instance, here's a non-promotion checkmate position with the given material:

```
[fen "5k2/5PP1/4K2P/8/8/8/8/8 b - - 0 1"]

```

But I claim we couldn't possibly *force* Black into this position: the final move would have to have been `100.g7#` (where I just picked 100 arbitrarily), the move before that would have to have been `99...Kf8` (moving from either e8 or from g8), and the move before that had to be `99.f7+`. OK, so we know that White must have played this `99.f7+` with the black king either on e8 or on g8. But if the black king was on e8, he could have instead played `99...Kd8` in reply, and if the black king was on g8 then he could have instead played `99...Kh8` in reply. The point is that, either way, White couldn't actually have forced Black into that final checkmate position.

Alright, so that's one possibility down. There are others of course, but a similar retrograde analysis for each of those will confirm that none of them can actually be forced, and that's all you need for an airtight proof that White can't force checkmate from your initial position without promoting a pawn.

---
Tags: analysis, problems
---


# Question
Title: Rating calculations for Anand-Carlsen world championship
I have some interesting questions that have to do with the rating changes and calculations for the Anand-Carlsen world championship.

First, some preliminary information:

Carlsen's live rating: **2870**, Anand's live rating: **2775**

If Carlsen wins a game, he gains **3.7 points**; draw **-1.3 points**, loss **-6.3 points**.

If Anand wins a game, he gains **6.3 points**; draw **1.3 points**, loss **-3.7 points**.

The match will be 12 games, with the winner being the first to 6 points. Therefore, **the number of standard rated games in the match can vary** based on all the **ordered** possibilities of wins, draws, and losses.

My questions are:

**1. What are the possibilities for Carlsen to cross 2900 in live rating?**

**2. What are the possibilities for Anand to cross 2800 in live rating?**

**3. What are the upper and lower bounds for Carlsen's rating in the match, given the stipulations?**

**4. What are the upper and lower bounds for Anand's rating in the match, given the stipulations?**

Thanks!

# Answer
The answer for 1 is NEVER, because even if Carlsen has the theoretically best possible tournament with 7-0, his rating would go to 2895.9 only.

The answer for 2 is if:

```
Anand wins the match 7-0, making his rating 2819.1

```

OR

```
Anand wins the match 6.5-5.5 (order of game results does not matter) by:

6 wins, 1 draw in a 7-game match: new rating = 2814.1
5 wins, 3 draws in a 8-game match: new rating = 2810.4
4 wins, 5 draws in a 9-game match: new rating = 2806.7
3 wins, 7 draws in a 10-game match. new rating = 2803.0

```

The answers for 3 and 4 are:

Carlsen's maximum rating, 2895.9, is attained if he wins 7-0, and thus Anand's minimum rating, 2749.1. Anand's maximum rating, 2819.1, is attained if he wins 7-0, and thus Carlsen's minimum rating 2825.9.
> 1 votes

# Answer
First, note that the final ratings depend entirely on the score of the match, not on the particular games. For example, if they each win a game, their ratings will change by the same amount as if they draw both games. This may seem like a coincidence but it's just a consequence of the way that FIDE ratings work.

Here is the entire table of possible results. The columns are Anand's match score, Carlsen's match score, Anand's post-match rating, and Carlsen's post-match rating. The results are sorted by post-match rating.

```
  A   C  A_rat  C_rat
0.0 7.0 2749.1 2895.9
0.5 6.5 2754.1 2890.9
1.0 7.0 2755.4 2889.6
1.5 6.5 2760.4 2884.6
2.0 7.0 2761.7 2883.3
2.5 6.5 2766.7 2878.3
3.0 7.0 2768.0 2877.0
3.5 6.5 2773.0 2872.0
4.0 7.0 2774.3 2870.7
4.5 6.5 2779.3 2865.7
5.0 7.0 2780.6 2864.4
5.5 6.5 2785.6 2859.4
6.0 6.0 2790.6 2854.4
6.5 5.5 2795.6 2849.4
6.5 4.5 2799.3 2845.7
7.0 5.0 2800.6 2844.4
6.5 3.5 2803.0 2842.0
7.0 4.0 2804.3 2840.7
6.5 2.5 2806.7 2838.3
7.0 3.0 2808.0 2837.0
6.5 1.5 2810.4 2834.6
7.0 2.0 2811.7 2833.3
6.5 0.5 2814.1 2830.9
7.0 1.0 2815.4 2829.6
7.0 0.0 2819.1 2825.9

```

Therefor the answers to your questions are

1. None.
2. He needs to win the match with 7 points, or with 6.5 points with Carlsen scoring at most 3.5.
3. 2895.9, 2825.9.
4. 2819.1, 2749.1.
> 10 votes

---
Tags: rating, world-championship, elo, carlsen, anand
---


title: How do you analyze master games?

text:
# Question
Title: How do you analyze master games?
One of the pieces of advice (usually from masters) that I see over and over is that I should be analyzing master games. But how do I do that?

Most of the tactics are over my head (obviously the simpler ones I can see). I can see strategical ideas all over the place, but my ideas are probably wrong. Without someone walking me through what to look at it's hard to understand.

What should I be looking for? What should I look to learn?

# Answer
It really depends on where your skill level is at. If you play rated Federation chess or happen to be buzzing around your favorite online server, you'd probably fall into a rating class or have a rating that serves as a great predictor of your skill/strength level.

With that being said, **here's** a category-based answer to your question (using the USCF classes and typical online server ratings).

( I'm only going up to class C as I'm currently a B player who's done his time climbing the ladder =\> is therefore *somewhat* qualified to make these recommendations :) )

**USCF E (1000-1199) or 1200-1400 ICC/FICS with Slow Time Controls:**

* Avoid just looking at Master games with no textual explanations. There is ZERO value for somebody at your strength level.
* Avoid game books that contain no annotations/text descriptions for each move.
* Avoid player game collections (e.g. My Best Games - Vishy Anand) and focus on the **few** Instructional + Annotated game collections out there.
* Totally avoid any book containing games played AFTER the 1900s.
* Avoid game books that don't print out a diagram every 2-3 moves.
* Always go over the game with a board or a computer.
* A lot of these books mean well but often drown you in a ton of variations. It is fine to skip over this part and just get to the move that was played! :)
* If you are using a computer, keep the engine off. You don't need it at your current strength level.
* Get used to covering up the next move and playing "guess the move". You'll want to do this for every game you ever look at going forward.
* Pay attention to the opening **PRINCIPLES**, don't even dare try to memorize openings or worry about the nuances. It really doesn't matter at this stage ... the principles alone are sufficient.
* Write things down on paper or use a database application. The minute something feels vague or does not make complete sense to you, write down your question. Don't immediately read the author's explanation. Come up with your best answer. Then .. and only **THEN** read the text. You'll be able build a great foundation and start thinking for yourself. It will also boost your confidence when your own ideas are in sync with what was played.
* Go back to this game a week later and review it again. It should feel like a grocery store you've visited in another city a year or so ago. You'll feel comfortable but not enough to not notice something or find a new question worth asking. Review your previously asked questions ... do the answers now seem obvious? If so, you're making progress!
* Finally : Always find a strong-er player or ask a credible forum about a position that stumps you. Even some well written instructional books may not completely explain why a certain move was played in a given position.

**Recommended Books:** A First book of Morphy (Rosario), Chess Master vs. Chess Amateur (Euwe)

**USCF D (1200-1399) or around 1400-1600 ICC/FICS with Slow Time Controls:** Same as above, except now:

* You can and should use a computer engine to look at other tactical possibilities that the book did not go over.
* You can start looking at pre-1950s games, but still avoid contemporary games/the modern era.
* Practice finishing off the game vs. a computer from the position at which one of the Masters resigned. For fun, try to win it at blitz time controls! If this is becoming a struggle, seek help from a stronger player to show you the correct technique (which was bloomingly obvious for the Master who resigned :))
* There are some very famous games in chess history that every "Russian schoolboy" knows. Google them out and play through them.

**Recommended Books:** Chernev's Logical Chess and his Most Instructional Games of Chess.

**USCF C (1400-1599) or around 1600-1800 ICC/FICS with Slow Time Controls:**

* Same as above, but you can finally start poking around at what the big boys of modern chess are doing. You still want to read books that are intended to be instructional, not just a showcase of somebody's favorite games.
* You should have a set of pet openings (repertoire). Seeking out games of Masters who play your opening makes sense.
* Make sure you now work through the variations those books tend to spit out. They are quite insightful and show you how much calculation is often needed in critical positions.
* Focus on players who often play very natural and beautifully elegant games without tons of complexity. (Capablanca, Fischer would be good examples)
* Start focusing on the endgame aspect of their games. Especially how the winner strategically transitions into the endgame he WANTS, making the correct piece trades at the right time.

**Recommended Books:** Weeramantry's Best Lessons of a Chess Coach.
> 6 votes

# Answer
Here is some commentary by IM Jeremy Silman, who is also well known for his work in chess instruction.

And opinions from various chess players:
> 4 votes

# Answer
if you want to look at master games, you should look at ones where black has a bad advantage. as my chess teacher have said, common ones where the masters play with the Guicco Piano, The Spanish, The Scandinavian, etc.

When you study the games, don't look at where they move the piece. look at the thinking behind it. As I have previously stated, these games, black has the disadvantage. Study more closely at black and how he blunders so that it might improve your tactics. Examine everything!!

At the end, memorize not in,y the game, but the strategies and tactics all behind it. Therefore, when you come across a similar game you are playing against someone else, it is a good thing. Not only that, but also learn how when you are playing as black, you learn how to not blunder.
> 1 votes

---
Tags: analysis, master-games
---