# Question
Title: What do you do when you put your king in check and you don’t realise?
I moved my king as I wanted it to be in a safer location and after I did my turn my opponent realised that I put my king in check by accident and as the rules state you cannot put your king in check we did not know whether we should go back to my last turn or if my opponent had won the game.

# Answer
> 3 votes
You noticed immediately, which makes it very easy because in this case the rules are the same (apart from time penalty) for all forms of chess. In the first instance you have to take back the illegal move and make a legal move. If possible you have to move the piece you touched. So, if your king could legally move to another square that's the move you would have to make. If it could legally move to several squares then you could choose between them.

For a first offence your opponent gains time on the clock. At blitz this is 1 minute and for standard and rapid it is 2 minutes. A second offence loses the game. But note that these penalties only apply if you pressed the clock before your opponent noticed and told you. If you did not press the clock then there is no penalty. You just have to make a legal move with the piece you touched.

The rules governing this are the FIDE Laws of Chess. This is what they have to say:

> 7.5.1 An illegal move is completed once the player has pressed his clock. If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined, the game shall continue from the last identifiable position prior to the irregularity. Articles 4.3 and 4.7 apply to the move replacing the illegal move. The game shall then continue from this reinstated position.
>
> 7.5.5 After the action taken under Article 7.5.1, 7.5.2, 7.5.3 or 7.5.4 for the first completed illegal move by a player, the arbiter shall give two minutes extra time to his opponent; for the second completed illegal move by the same player the arbiter shall declare the game lost by this player. However, the game is drawn if the position is such that the opponent cannot checkmate the player’s king by any possible series of legal moves.

Those are the rules for standard time control where the moves are being written. Because the moves are being written down it doesn't matter if the illegal move is noticed after several more moves were played, you still have to go back to the position when the illegal move was made and make a legal move instead.

For rapid and blitz this usually isn't possible and so the rules say that the illegal move has to be flagged before the next move. Appendix A in the Laws deals with rapid and the rule says:

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

Appendix B deals with blitz and that says:

> B.4 Otherwise, play shall be governed by the Rapid chess Laws as in Article A.2 and A.4.

So, the rules are the same as for rapid, but for the penalties:

> B.2 The penalties mentioned in Articles 7 and 9 of the Competition Rules shall be one minute instead of two minutes.

# Answer
> 2 votes
In this case you would just go back to the last turn. In official tournaments, a rule used is you get a penalty on the first time you make an illegal move, and then if you make 1-2 more illegal moves (for FIDE it's 1 more) you lose the game. But assuming this game was just for fun, as it seems no arbiter was involved to help out, just take the move back and continue the game.

# Answer
> 0 votes
It depends on the tournament policy that you play. For some tournaments, there is a penalty such as losing the game if you have done 3 illegal moves. The procedure is generally like this: Your opponent should stop the clock and call the referee. The rest depends on the decision of the referee.

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Tags: rules, check, kings
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# Question
Title: I like to play 1. e4 but I dislike 1. ... c5. Can I continue with 2. c4?
I read a related but closed question here and I share a very similar feeling. I would love to play 1. e4 but I only feel comfortable when my opponent replies with 1. ... e5, or French, or Caro-Kann. I find 1. ... c5 too complicated and too risky for me as white.

Surely there is no way I can control what my opponent play but here is my thought: since I also like the English opening, when the game starts with 1. e4 c5, can I continue with 2. c4. aiming to reach the following position for white:

To me, this position is less risky and more solid for white than most lines in Sicillian. Is it a good idea to play 2. c4 after 1. e4 c5 if I am uncomfortable with Sicillian?

It seems that according to 365chess.com's statestics, 2. c4 is an unpopular move and the winning percentage for white is very low. So what's wrong with 2. c4 if I continue the game with the ideas of the English opening?

# Answer
> 10 votes
You can, but if you like most openings with 1.e4, it's probably not the most adequate choice for your "style" (the resulting position will be "slow" rather than a fast exchange of tactical blows. 2.c4 is a legitimate option, but here are a few alternatives you may want to consider:

* Find some line in the Open Sicilian: this is the ideal, but requires a lot of work to be put in tournament practice. I'd definitely go for it when playing "just for fun". There are a lot of crazy middlegames resulting from this option and you'll also "learn a lot of chess" from them.
* Play the Alapin with 2.c3. Still a solid, more positional option Probably more ambitious than 2.c4.
* Play the wild Morra gambit! (2.d4 cxd4 3.c3) This would be my favourite way to go if not for the fact that that Black can transpose to the Alapin if they want to.
* Play some f4-based scheme, like the Grand Prix (more aggressive) or the Closed Sicilian (more solid)

As a final consideration, there is nothing wrong with 2.c4. Don't blindly believe the Statistics. It could be that there is a player skill bias against 2.c4, or perhaps that players who opt for this line haven't often studied it deeply. Filtering for games at different ratings could dramatically impact the result. In my opinion, the main problem with 2.c4 is that Black can choose between a closed, symmetrical position with an eventual ...e5, or simply try to exploit the d4 square with ...g6, ...Bg7, ...Nc6-d4 and so on....

# Answer
> 7 votes
It is not the most ambitious choice, but should be playable. It has been played by 2500 rated players. Basically by playing c4 you weaken your dark squares and black could try to take advantage of it by the following set up.

```
[FEN ""]

1.e4 c5 2.c4 Nc6 3.Nc3 g6 4.g3 Bg7 5.Bg2 e6 6.Nge2 Nge7 7.d3 O-O

```

If you are fine with such position go for it. I wouldn't be too thrilled having that hole on d4. Also, black always has the option of playing d5 which I often find uncomfortable.

Two alternatives to avoid the sharp lines of the Sicilian:

* go for a Maroczy bind by following up your c4 with d4 later on. This is a very stable position.
* go for a Kings Indian Attack by playing 2. d3

# Answer
> 0 votes
There are lots of variants in the Sicilian that will fit into your game, just study them and find one you feel comfortable with. Sicilian is probably the most studied defense in chess, there's room for everyone

# Answer
> 0 votes
Going for c4 is pretty risky, while playing White. You are inviting the opponent to come and have a go at you through your weak Black Squares.

# Answer
> 0 votes
To answer your question- Yes you can. It's perfectly sound. You end up transposing to a Botvinnik system in the English Opening at some point. This is fine, but it's very slow, very closed, and may not be what you want out of your openings if you play e4. As suggested, your good variation choices go as follows: 1. Some Open Sicilian line- If you dislike 1.. c5, this is probably not what you want to go for. There's a substantial amount of theory, but these will probably suit your playstyle best. Some people (like me) don't like them either and choose one of the other options 2. Closed Sicilian lines (2. Nc3). 3. King's Indian Attack setups (d3, Nf3, g3, bg2, 0-0, etc) 4. Rossolimo (1. e4 c5 2. Nf3 Nc6 Bb5) and a way to deal with 2..d6 (Bb5+ is my recommendation here), and 2..g6 and 2.. e6. 5. Other "Anti-Sicilians" meant to avoid the Open.

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Tags: sicilian-defense, 1.e4, english-opening
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title: How are humans good at chess?

text:
# Question
Title: How are humans good at chess?
It is estimated that the total number of legal positions in chess is somewhere between 10^40 and 10^50. This is of course an enormous number. Computers today with reasonably good chess software can sometimes look 20 moves ahead to find the best continuation.

But (most) humans are incapable of such calculations. After each move, it is practically impossible to compute all the ramifications and variations. Therefore a move made by a human being is expected to be a very poor move indeed.

But this is not the case: looking at GMs games, those people are able to find the ''best'' moves recommended by top engines such as Stockfish, even though they obviously are not calculating billions of combinations per minute.

So what makes humans good at chess, if they are unable to see into the vast space of future variations? When looking at what GMs do better than amateurs, what I usually find is better ''intuition'' or ''feeling for the position''. But these can't be quantified. And GMs are obviously not psychic. So how can they find the best move most of the time? Chess masters often insist that they are not following an internal ''algorithm''. So what on Earth are they following?

How can humans be so good at chess?

# Answer
> 40 votes
Herbert Simon touched on this question. He received the Turing Award in 1975 and the Nobel Prize in Economics in 1978. His primary research interest was decision-making and is best known for the theories of "bounded rationality" and "**satisficing**".

Satisficing is a decision-making strategy or cognitive heuristic that entails searching through the available alternatives until an acceptability threshold is met. Simon used satisficing to explain the behavior of decision makers under circumstances in which an optimal solution cannot be determined.

In his paper Theories of Bounded Rationality (1972), Simon used "the **game of chess** as a microcosm that mirrors interesting properties of decision-making situations in the real world." Here are some useful quotes.

> On the average, at any given position in a game of chess, there are about 30 legal moves-in round numbers, for a move and its replies, an average of about 10^3 continuations. Forty moves would be a not unreasonable estimate of the average length of a game. Then there would be perhaps 10^120 possible games of chess. Obviously the exact number does not matter: a number like 10^40 would be less spectacular, but quite large enough to support the conclusions of the present argument.
>
> Chess players do not consider all possible strategies and pick the best, but **generate and examine a rather small number, making a choice as soon as they discover one that they regard as satisfactory.**

## The limits of rationality in chess.

> (...) three limits on perfect rationality were listed: uncertainty about the consequences that would follow from each alternative, incomplete information about the set of alternatives, and complexity preventing the necessary computations from being carried out. Chess illustrates how, in real world problem-solving situations, these three categories tend to merge.

## Satisficing and optimizing.

> The terms satisficing and optimizing (...) are labels for two broad approaches to rational behavior in situations where complexity and uncertainty make global rationality impossible. In these situations, optimization becomes approximate optimization - the description of the real-world situation is radically simplified until reduced to a degree of complication that the decision maker can handle. Satisficing approaches seek this simplification in a somewhat different direction, retaining more of the detail of the real-world situation, but settling for a satisfactory, rather than an approximate-best, decision. One cannot predict in general which approach will lead to the better decisions as measured by their real-world consequences. **In chess at least, good players have clearly found satisficing more useful than approximating-and optimizing**

# Answer
> 29 votes
Let's take a conversation. The number of sentences that could be said are infinite. The number of grammatically correct is still infinte, as is the number of logically/conversationally correct would be. The humans pare down what they say in any situation by intuition/experience. As chess players study what should be played, their task is much easier than you holding a simple conversation.

# Answer
> 25 votes
Humans try to understand a game like this, to formulate rules, try to recognize patterns of what worked in one position and apply them in positions they consider similar.

And it turns out that that is possible, otherwise there wouldn't be humans of different playing strengths, everybody would just be guessing.

Then we *used* that knowledge to create engines like Stockfish; in the end they can't calculate all the way to checkmate either in most positions, and they have an *evaluation function* based on what we consider good. It's the same principle.

Only since completely new engines like AlphaZero, that start with zero knowledge about the game and have to work their way up themselves has that changed. It's interesting that the best of them are more or less on equal footing with Stockfish right now.

But the important thing is to turn this phenomenon around -- if it *weren't* possible for us to learn rules about the game of chess that work, then the game would have been very uninteresting and it *would never have become popular*.

E.g. imagine a game where you have to guess a whole number between 1 and 10^80. You get no hints when you get one wrong, you lose after a million wrong tries. Nothing can be learned, and nobody would play it.

If a game can be learned *perfectly* (like tic-tac-toe or Nim) then it probably won't become very popular either.

Chess is apparently in some sort of sweet spot.

# Answer
> 6 votes
# Interesting Chess

Given a board configuration, many expert chess players are able to reproduce the moves which produce that configuration. However, of the 10^40+ board positions, grandmasters would be hard-pressed to reproduce the vast majority of board states. Why is that? Well, that's because most of them involve obviously bad moves, like developing your king by itself to the center of the board, or sacrificing all your pieces willy-nilly. The games which produce these board states are *not interesting*. A much more difficult question is: "How many board states are *likely*?" What if that number is just 10^10 or so?

# Learning

Computer science has one powerful optimization trick. When performing an expensive computation which always has the same result for a particular input, the programmer can instruct the program to simply *remember the answer*. This technique is called "memoization". Then, the next time the computation is requested, the program "cheats" by returning the memoized value instead of wasting a bunch of effort computing something exactly the same way it did before.

Humans also have one powerful optimization trick, called the Hebbian Learning Rule, often summarized as: "Neurons which fire together, wire together." It is overly simple to say that this explains all human learning, because it doesn't. But it is, in a sense, the computationally simplest and most abstract way to capture what the memoization technique does: if a pattern of neural firing consistently produces the same result, let's take a shortcut and not do all the work we did the first time.

# Stockfish

Now, let's compare those tricks to what Stockfish does: brute force search of the game tree. Obviously, Stockfish is smarter than that. It can use an opening book, and endgame database, and it can prune branches of the game tree that are trivially silly. But there's one thing that Stockfish cannot do: it cannot say: "Wait a second! I've been here before. What did I do the last time I was here?" Stockfish has no memory (across games). Of course, this makes it useful for evaluating positions, because Stockfish's answer does not depend on which games it has already played. It will give you the same answer every time you evaluate the position, *even if it plays a game in which it discovers that its evaluation was inaccurate*.

# AlphaZero

So now we begin to see why AlphaZero can evaluate 1000x fewer positions, and still wipe the floor clean with Stockfish: AlphaZero does the simplest thing an intelligent system can do--it remembers the past. You cannot ask what the AlphaZero evaluation of a position is, because that is a meaningless question. Each instance of AlphaZero is unique, shaped by its history of games played. Instead of saying: "I'm going to pretend like I've never seen this board state before, and blindly search the game tree" it says: "Well, I've seen this board state 237 times, and I already know that 3 moves are significantly better than all the others I evaluated" (it doesn't actually know how many times it's seen the board state, except implicitly).

Incidentally, this one simple trick is also why humans are able to evaluate tens of thousands of moves fewer than computers, and still play a respectable game. A grandmaster is not a human who can evaluate 60,000 positions per second. A grandmaster is a human who can *remember* 60,000 board positions and strong lines of attack and defense from the most important ones.

AlphaZero plays more human chess than any program before it, because it actually *learns* chess. In a way, it probably understands chess better than any entity in the universe. Its primary shortcoming is a lack of communication ability. If it had language, and could describe its reasoning, we would likely be awed by its analyses. And yet, we would quite possibly be surprised how human-like those analyses turn out to be, while noting that there is still an element of alien sensibility borne from the ability to evaluate tens of thousands of moves per second.

The fact that AlphaZero runs on transistors which can switch a billion times per second, compared to the measly 3-5 times per second for the typical human interneuron suggests that in a sense, AlphaZero is much like a hyper-accelerated human. But to get back to your original question: human grandmasters *can* look into the vast space of future moves. They do so by *remembering* which of those moves are better than others, rather than computing them fresh every time. Of course, play is a combination of memory and tree search, so humans, like AlphaZero are also exploring new lines of play every time. But they have to be more economical in their search, and it shows.

# Answer
> 5 votes
"Intuition" is basically just pattern matching. We use our experience from past situations/chess positions that are familiar, in order to gain a "feel" of a current position. With this intuition, we can make up for calculating a relatively small amount by:

1) Being able to evaluate resulting positions in our calculations well.

2) Knowing what lines to prune in our mental calculation tree.

That being said, even the top humans are *far* below current Stockfish. And even though Stockfish is probably the best/second best in the world (with Leela), there's no telling how good objectively it really is. If it played against some agent that always made literally perfect moves, there's a good chance it wouldn't do that well.

There's also a kind of anthropic principle going on here. Humans wouldn't invent a game in which everyone who played it was guaranteed to do horribly. Imagine the number of theoretical games whose complexity exceeded chess (and any other game we play) by x orders of magnitude.

Finally, coming back to intuition/pattern matching, in a sense it can be quantified. Theoretically you could measure how good someone's memory is, how well/quickly they can detect when one event is similar to another, etc.

# Answer
> 5 votes
At one level, the answer is that we don't know how the human brain works. But something a bit more helpful:

The algorithm used by Stockfish (and other chess engines before the rise of deep neural nets) is called Minimax. The basic idea goes something like this:

1. Generate a tree of all possible moves as far out as resources allow.
2. For each final position in the tree, assign a score of how good that position is for you
3. Work backwards towards the present position, deciding at alternating levels either
    1. Whether I should make this move (it leads to a final position that is good for me)
    2. Whether my opponent would make this move (it leads to a final position that is bad for me)

And then there are ways to optimize these evaluations so you don't have to process the entire tree.

What the computer is very good at is step 1: coming up with a tree of all possible moves. What the computer is not very good at is step 2: figuring out how good a position is for you. Chess engines benefit from looking far ahead not only because that's closer to a checkmate, but also because it's easier to score an endgame position with less material.

Humans, it turns out, are better at step 2. We can somehow look at a midgame position and decide "this attack looks strong" or "my king-side looks weak" even though we haven't worked out an actual line of play that would exploit said strength or weakness. This is where people bring in pattern recognition and experience as somewhat fuzzy explanations of what human brains are doing.

So what the human player is doing is more "top down" than the computer's "bottom up". Instead of thinking about millions of possible outcomes and then starting to discard worse ones to prune the tree, we throw away branches as we build the tree when we decide that position doesn't look promising.

# Answer
> 4 votes
Good question, I've been curious about that myself. Humans have an extra plane to their reasoning. The first evaluation is that of strategical themes applicable to the position, and the next one is a tactical one of the paths selected above. Those who can perform the first step successfully can drastically narrow down the search space for the second step, where they can repeat the approach (strategy/tactics) to narrow it down even further. For those with top skills at both, the path to finding the best move will consist of just a handful evaluations as the search space can be reduced by orders of magnitude with each iteration.

# Answer
> 4 votes
# Making plans

(Pattern matching has been mentioned. Humans are good at it)

In addition we *make plans*.

For example, looking at a position we see that the opponent's king and queen is in a good position for a fork by our knight. However, the relevant square is currently guarded by an opponent piece.

So, we look for ways to make that opponent piece go away. Or maybe we can pin it.

Of course, if we just move a piece to pin it, it will be the opponents turn and they might do something devastating like moving their king out of harms way.

So, we need a move that is both a threat the opponent must reply to *and* sets up the fork we want.

And so on and so forth.

**The point is that while making a plan like this we are only looking at small number of moves and positions.**

It does not matter that *we* have other moves, we can ignore those. And part of the plan is to reduce the possible moves by the opponent.

The hard part comes next, checking if the plan holds water. Ideally the opponent's moves should be forced, but usually they have a few alternatives on each step. Are we really really sure all combinations of these alternatives are harmless?

Of course, looking at a position and seeing the possible weak spots we can plan to attack is just pattern matching again. This is why we can't have computers players make plans, they would waste time trying to set up utterly hopeless attacks. They would discard these plans are not working, but by the time they have discarded plan number several billion, they would have lost on time.

# Answer
> 3 votes
I am a very bad amateur chess player, but one thing I notice is that people are able to prove (in the mathematical sense) many things about a position, and grandmaster has a much more developed intuition (also on mathematical sense) and a much larger repertoire of thoerems to help prove (or extract) information out of a position than an average player. Due to proving a large number of things, a grandmaster is able to prune many branches of the search tree.

A trivial example about a theorem: after I captured the bishop of a beginner opponent, he said "oh, I thought it was protected by the other bishop", immediately me and a spectator said: "it is impossible, a bishop can never protect the other bishop". That is a very basic theorem a chess player learns very soon.

As the player advances, he learns much more intricate theorems and learn to intuitively spot patterns to use the theorems extract information. One theorem explicitly stated by a better chess player than me: a knight can never fork two pieces if they are on different color squares.

I still get confused, in endgame, if my king will be able to catch the pawn before promotion, or if I can promote my pawn before the opponent, but I imagine such things are immediately obvious to higher level players, due to more developed intuition and bigger repertoire of theorems.

I think this is the kind of information a deep neural network, like AlphaZero, is able to learn after playing too many games. And I disagree with Lawnmowner Man that it simply "remembers" the positions, and that all AlphaZero instances are fundamentally different. They are different because of the stochastic nature of a neural network training, but after too many games, they are able to extract higher level abstractions than simply remembering positions, and get to more or less the same set of most useful theorems and intuitions. A repertoire that is also shared by grandmasters.

# Answer
> 3 votes
## Spotting more complex or different types of patterns

Computers don't have a particularly easy time identifying the same patterns that humans can easily spot.

This is especially noticeable in something like Computer Vision. Computers have made a lot of progress in terms of recognising objects, but they are still probably worse than a young child at recognising even one or two different types of objects.

While any given board state in chess may not have as many parameters as a large image and it's can be solved in a more systematic way, a similar argument applies.

Computers and human brains just don't work in the same way.

Humans manage to spot some complex patterns in terms of which pieces or parts of the board are threats or weaknesses. Computers need to throw a ton of processing power to spot those same patterns, and even then they may still not be able to see the exact same patterns. They may go a different route and just try a bunch of different moves and play each of those out to determine the best one or doing something else.

Humans do sometimes also consider different moves and mentally play those out, but at any given point there are different mechanisms at work to determine whether a board state is good or bad or whether a move is worth considering.

## Intuition and your subconscious

I show you a picture of a cat and you identify it as a cat. If I then ask you to explain to me exact why you think it's a cat, you may not have an easy time doing that (especially if you can't look at the cat while doing so). You may start to identify things like the whiskers or cat-like ears, but if I dig a little deeper you may not be able to explain exactly what "cat-like ears" means. I may also be able to show you an image of what is clearly a cat (even of the same breed) without those features, or a picture of something which is clearly not a cat with those features.

Your subconscious is probably doing most of the work in identifying the features of a cat and it just tells you "that is a cat" without giving your conscious mind much more information.

To bring this back to chess, you can look at a move and your subconscious can spot some patterns based on the rules or your experience watching or playing past games. You can use this to identify the move as good or bad without necessarily being able to justify it.

Going any deeper into it would probably shift the discussion a bit too far into psychology, neuroscience and/or computer science.

# Answer
> 2 votes
@Kortchnoi's answer is very insightful and worth a read.

It's also worth noting that a game between two *perfect* chess AI engines must always, in theory, end in a stalemate due to the min-maxing algorithm being mirrored on both sides.

On the other hand, two human chess players do not use the same "algorithm," and thus it could be argued that one player is simply better than the other. Moreover, humans make mistakes; a chess engine evaluates the possible game states and picks the "best" one, so it's not prone to human error in that sense.

One example from game theory that comes to mind is the pirate's dilemma, where the most reasonable choice is not always the one that a person ends up taking. Humans don't always think like AI—they base many of their decisions on fears, suspicions, and gut feelings, and chess is no exception.

# Answer
> 2 votes
As far as chess is concerned many people before me have given brilliant answers. But, additionally I would like to point out that many chess players employ, apart from theorems they have learnt through practice, a different strategy based on opponents.

Games are simulated in practice and rough plans are made.

One such strategy I typically use is guard pieces until other player makes a mistake then pounce on them.

Often players try to fight without queens to reduce the mental strain if given a chance to do so.

In a game motivations are important, if I find a player is trying to achieve a certain objective to deliver the checkmate I only think along those decision tree to either guard or trap them. Both players have a mental image of what the other is trying to achieve.

The game is usually decided on whether the other person has the correct picture or not, and whether we have enough knowledge and practice to foil their plan.

# Answer
> 1 votes
When talking about the strength of the human chess players, one normally forgets to mention that what they have is not only their own work. Most of it comes from many generations of others humans that have played and studied chess for many years and have added to the 'basic' modern knowledge of chess. Not that one doesn't have made many sacrifices to have such strength but it would be very different if one doesn't stand on the shoulders of giants :)

Stockfish is like an Godly Genius that has the mentality of a new born baby, the memory of an ant and the knowledge of chess player that just learned the rules (excluding the "artificial" extra opening books and end game library). Alpha zero is the same excluding that he has an excellent memory and, if given enough time, it can stand on its own shoulders.

Your question is similar to asking another one: Why has humans technology being so "low" for so many thousands of years and now it is accelerating like an explosion?

The science rules that gives us so much power, when we are so weak, are like the the knowledge in chess.

# Answer
> 1 votes
There's not much I can add to the other answers, but I want to make clear that both the number of legal positions and the search depth are misleading or even irrelevant metrics. About legal positions: In the king & rook vs. king endgame there are over 200000 legal positions (when not considering symmetries), but mating with the rook is easy enough that you probably need to see it executed just once and can memorize the algorithm. For rules like "a bishop pair is worth more than 2 bishops", you don't need to compare the vast number of positions with a bishop pair to the ones without it. In fact, you don't even need to look at 1 position, because you probably learned it from a more experienced player without reference to any particular position. It can also be derived logically from the properties of a bishop. Looking beyond chess, the number of legal Go positions is known to be about 2\*10^171 and the number of legal positions for Go on the smaller 9x9 board is about 1\*10^38. Does that mean that Go is more complex than Chess and that 9x9 Go is less complex? Without additional information, that judgment can't be made. It would even be easy to design a game that has more legal positions than Go, but is trivial to play. All these examples should make clear that the number of legal positions does not really tell you anything about the game, even if you restrict the positions to some subset like "positions with a bishop pair".

About search depth: Stockfish searches 60 million positions per second on the hardware used by Deepmind to compare it to AlphaZero, whereas AlphaZero only searched about 60 thousand positions per second. Both are of similar strength. And you could easily write a chess engine that uses Stockfish's highly optimized move generation, but replaces its algorithms for pruning and evaluating with some crap that results in this new engine playing like an average player with the same resources that Stockfish itself would use to play on world champion level. And even without calculating ahead at all, a human player will sometimes choose a move that agrees with the strongest engines (e.g. when the opposing queen takes your queen, the intuition tells you to retake the opposing queen). In other words: The quality of your move choices matters as much or probably more than the search depth.

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Tags: grandmaster, game-complexity
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title: The Evolution of the K-Factor

text:
# Question
Title: The Evolution of the K-Factor
The change in Elo ratings depends, among other things, on the K-factor (or development coefficient).

## Current rules

FIDE Rating Regulations effective from 1 July 2017 give the following values:

* K = 40 for a player new to the rating list until he has completed events with at least 30 games; and for all players until their 18th birthday, as long as their rating remains under 2300.
* K = 20 as long as a player's rating remains under 2400.
* K = 10 once a player's published rating has reached 2400 and remains at that level subsequently, even if the rating drops below 2400.

The same values have been in effect since July 1, 2014.

## Past rules

The Wikipedia page on the Elo rating mentions that FIDE used the following values before July 2014:

* K = 30 (was 25), for a player new to the rating list until the completion of events with a total of 30 games.
* K = 15, for players with a rating always under 2400.
* K = 10, for players with any published rating of at least 2400 and at least 30 games played in previous events. Thereafter it remains permanently at 10.

## My questions

1. When were these past rules enforced?
2. When was the change from K=25 to K=30 applied?
3. With the exception of this last change, have these values been applied since the beginning of Elo's creation?

I take the liberty of asking all these questions at once because they're related.

# Answer
The USCF implemented Elo's suggestions in 1960, and the system quickly gained recognition as being both fairer and more accurate than the Harkness rating system. Elo's system was adopted by the World Chess Federation (FIDE) in 1970. Fide used k=30 factor before July 2014.
> 1 votes

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Tags: rating, history, fide, elo
---


# Question
Title: Can one mate a lone king with Bishop and two knights without being aided by the attacking king?
In order not to overload the answer to this question, I split off the bishop+two knights part. So the question is: Is it possible to mate with a bishop and two knights without the help of the king?

# Answer
**Work in progress**

You can convince yourself easily, that mate is only possible in a corner of the board. We distinguish four cases:

* The corner is the same color as the bishop and the bishop mates
* The corner is the same color as the bishop and a knight mates
* The corner is the opposite color as the bishop and the bishop mates
* The corner is the opposite color as the bishop and a knight mates

For the following analysis we only consider unique positions that are not related by symmetry. Also we don't distinguish between similar positions of a bishop along a diagonal, if the same essential square(s) is covered.

---

Starting with the first case, bishop same color as the corner and the bishop mates. There are 5 distinct (up to symmetry) mating positions: 1.1a to 1.1e.

Doing a retro-analysis for 1.1a and 1.1b:

* White's last move was Bb7+ and the bishop came from c8 or a6.
* Black's last move was Ka8 and the king came from b8 or a7. The king was not forced to go to the corner and could have escaped to c7 or b6 instead.

Doing a retro-analysis for 1.1c, 1.1d and 1.1e:

* White's last move was Be4+ and the bishop came from somewhere along the b1-h7 diagonal.
* Black's last move was Ka8. If the king came from b8 or a7, it could have gone to b7 instead of the corner. If the king came from b7, it could have gone to (among others) c6 instead of the corner.

So in conclusion, it is not possible to force a mate with the bishop in the corner of the bishop's color.

---

The second case, bishop same color as the corner and the knight mates. There are 2 distinct (up to symmetry) mating positions: 1.2a and 1.2b.

* White's last move was Nb6+ and the knight came from a4, c4, d5, d7 or c8.
* Black's last move was Ka8. If the king came from b7, it could have captured Kxc6 instead (note that the c6 knight was not protected then).

**If the king came from a7 or b8, there is actually a longer series of forced moves leading to mate! Needs further invetstigation.**

## 2. Corner opposite to the bishop's color

# 2.1 Bishop mates

You easily see that there is not even a theoretical mating position for this case.

# 2.2 Knight mates

You easily see that there is not even a theoretical mating position for this case. In order to mate, one knight would have to check the king in the corner, say a8, the other knight would have to cover the light square b7 and the bishop would have to cover both a7 and b8 which it cannot.
> 2 votes

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Tags: checkmate
---


# Question
Title: Can someone explain the positional advantages for white?
```
[FEN "3r1rk1/7p/bq2ppp1/p1R5/Pp2P2P/4QB2/1P3PP1/3R2K1 w - - 0 1"]

```

As far I can see, Black’s bishop has more scope than the white one, White has some isolated pawns, and the Black pawns rule the 5th rank.S Since Black appears to be better here, then why does the engine show a better evaluation for White much more than I expected?

# Answer
> 7 votes
You evaluate the position *statically* which only rarely works. As for your static evaluation you are correct, that the black bishop is stronger and that the pawns take some squares on the fifth rank. On the other hand, white has two active rooks vs one black rook.Stockfish gives a static evaluation for this position of +0.76 if white is to move and +0.5 if it is black's move. So statically it is roughly equal with a slight advantage for white.

However, such static evaluation is only really useful (if at all) in quiet and/or closed positions. In open positions like the one here, where there are concrete ideas, the static evaluation does not tell you anything. You should look at least a couple of moves deep to see what plans white and black could follow.

White has at least three obvious ideas: play against the a5 pawn, against the week pawns on e6 and f6 or directly against the black king.

Black has no obvious plan other than exchanging pieces and (if veryvery lucky enter the white position with heavy pieces.

---

Concretely to your question:

**Black’s bishop has more scope than the white one**: True, the black bishop has more scope, but there is not much to do along that diagonal.

**White has some isolated pawns**: Neither player has isolated pawns. Please check what an isolated pawn is.

**the Black pawns rule the 5th rank.S:** They cover squares on the 5th rank, but hey that's just the 5th rank, i.e., on the black side of the board (in the starting position the pawns rule the 6th rank....). Also (and much more relevant here), since the pawns are next to each other they don't support each other anymore and the pawns on e6 and f6 are weaknesses. Typically, building such horizontal line of pawns to gain space is a good thing to do in the opening phase, when the pawns can be supported by pieces. Towards the endgame such pawn lines can often become weaknesses.

---

Assuming it is white to move,my engine says about +3, (which means white is clearly winning) and gives the following line: 1. Rxd8 Qxd8 (or Rxd8 which is slightly worse) 2. e5

If black captures fxe5 or allows white to capture exf6, he will end up with a very weak isolated pawn on e6 (in addition to the weak pawn on a5) and a rather open king (ideas with Qe5, Rc7 or h5 look very scary for black).

If black closes the position with f5, the engine likes to go for the a5 pawn by exchanging queens with Qg5. Another viable option could be h5 with an attack on the king. In any case, black is left with weak pawns on e6 and a5.

So in summary, it is basically black's weak pawns that make the difference.

If in the initial position you...

* move the pawn from f6 to f7, the evaluation improves for black to +2, because the pawn structure is much more stable.
* remove all the pawns on the a and b files, the evaluation improves for black to +1 only.

# Answer
> 3 votes
It seems to me the advantages for White would be that White's major pieces - the 2 Rooks and the Queen are aimed at the center - and even the minor piece - the Bishop - is aimed at the center too - even though its own pawn blocks its immediate reach. White has a pawn in the center also. The center being the sweet spot - d4 d5 e4 e5. Black has only a single major piece - a Rook - which can cover the center, and though Black has 2 pawns that cover a single square a piece of the center - it doesn't have the pawn positioned in the center alike its White adversary. White also has a space advantage, with its major pieces covering more of the board than Black - plus it has 3 pawns on the 4th rank - versus 1 Black pawn being on their own 4th rank - though it has one on its 5th rank. It seems to me the biggest advantage White has over Black would be that it's White's turn to move.

---
Tags: engines, analysis, positional-play, middlegame, evaluation
---


# Question
Title: What's the best alternative to the 'scoresheet' blunder checking strategy?
In Simon Webb's brilliant book, *Chess for Tigers*, he advises that a player write their move on their scoresheet *before* playing it. Then, right before you play your move, you check it one more time to ensure you haven't made a blunder. I used this strategy with great effect in my games, and it cut down my blunder rate considerably.

Unfortunately, Fide changed the rules, and now this kind of strategy is illegal: you have to write your move down after you play it. Is there a substitute for this strategy that still uses the scoresheet, but is legal under Fide rules?

# Answer
> 5 votes
I don't know of any proven method but here's one idea: you could try to imagine writing the move. Translate your move into algebraic notation, imagine the text on your scoresheet, maybe even trace it with your finger. Hopefully that will be enough of a pause in your train of thought to enable you to see the move from a different perspective, which I think is the rationale behind the "write before you move" approach.

# Answer
> 3 votes
> Is there a substitute for this strategy that still uses the scoresheet, but is legal under Fide rules?

According to 12.3a FIDE:

> 12.3a During play the players are forbidden to make use of any notes, sources of information or advice, or analyse on another chessboard.

Therefore, if any performed action is considered as *making use of notes*, it is a violation. This is confirmed by

> 12.4 The scoresheet shall be used only for recording the moves, the times of the clocks, the offers of a draw, and matters relating to a claim and other relevant data.

and the rule that you are probably referring to

> 8.1 ...
>
> It is forbidden to write the moves in advance, unless the player is claiming a draw according to Article 9.2, or 9.3 or adjourning a game according to the Guidelines of Adjourned Games point 1.a.
>
> ...

While there are many advices that can be given to substitute the scoresheet (visualization, writing mentally, etc), the current FIDE rules limit you severely.

So, can you come up with a substitute strategy? Definitely.

Consider algebraic notation. Ideally, you want to encode:

* the piece that moves: `K`,`Q`,`B`,`N`,pawn
* destination file: `a`,`b`,`c`,`d`,`e`,`f`,`g`,`h`
* destination rank: `1`,`2`,`3`,`4`,`5`,`6`,`7`,`8`
* `O-O`, `O-O-O`
* sometimes, origin file/rank in case of ambiguity
* optionally, capture, check, mate, `e.p.`

For the purpose of blunder checking, one can certainly sacrifice optional symbols, consider the frequency of the notation with the origin file/rank (ex., `N2e4`) to be negligible. By using only pen and the scoresheet, you can easily specify the destination:

With enough practice, positioning the pen and the scoresheet according to the map identical to writing `b4` on the scoresheet.

You can encode the moving piece (king, queen, bishop, knight) by, say, buttoning and unbuttoning your suit, using a third object on the table, and many other ways.

This approach is very similar to writing the notation in your mind, rather than on the scoresheet, but it uses the physical objects.

Disclosure: I do not use this approach.

# Answer
> 2 votes
I know there is such a rule but in practice, even if in serious tournaments it's not necessarily enforced. I had a game in World Open at Philadelphia a few years ago and my opponent wrote on his score sheet before making any move. I was debating if I should report and finally I reported to TD and TD warned him. The next time he did that I reported again and nothing happened. So the next time it happened I ignored it and did not report. So if you really want, you can still do it at your own risk. It's unlikely the TD is going to forfeit your game. The worst is probably a warning or something.

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Tags: rules, blunder, scoresheet
---


# Question
Title: Why move the queen’s rook to defend d-file instead of king’s rook?
In this position, why is it better to move the queen’s rook to defend the d-file instead of the king’s rook? Moving the king’s rook to the d-file becomes more challenging. Is it important to leave king’s rook behind to support the king? Is control of the f-file more important? I am curious about the logic behind of choosing the queen's rook in such situations.

```
[FEN "3rr1k1/pp3pbp/1n4p1/4P3/3P2b1/B4N2/P3BPPP/R4RK1 w - - 0 1"]

1. Rad1

```

# Answer
> 3 votes
White needs to find a way to make use of his extra pawn, because it is hard to see any other plan. His dream would be to play d4-d5-d6, but this is not yet possible because a) d5 is under Blacks control, and b) the Pe5 would hang. Having the Rooks on e1 and d1 would address both of these issues, and that would be a motive to choose Rad1, but there is still play in this position and White needs to be accurate. Whites K is extremely safe, so that is not a concern. There is no reason to worry about Bxf3. The resulting "weak" pawns do not matter because they cannot be attacked. Best in this situation seems be Bb5 which forces either Bd7 or Nd7, both of which reduce the effectiveness of Blacks blockade. A plausible continuation after 1..Nd7 would be 2. Ng5 threatening Bc4, 2..h6, 3.Ne4 intending Nd6. So Black will have to play ..Bd7, and then White can play Bxd7 and reorganize at leisure. He might consider putting the KR on d1, followed by a Knight move and f4. The QR is then free to occupy the c-file. It is too soon to analyze to a clear conclusion, but I would certainly expect White to win.

This discussion is based on specifics of the particular position, and not on appeal to any general principles. That is almost always the way to go.

# Answer
> 2 votes
A better answer in response to the general question being asked might be as follows:

*It is often strategic to position the rooks on the d1-e1 squares, which allows them both to support the center files. Naturally the Queen's Rook must be moved to d1 - and the King's Rook to e1, remembering that only the Knights have an ability to jump pieces.*

---
Tags: analysis, positional-play, rooks
---


# Question
Title: Why does FIDE recommends using German numbers and piece names for blind and visually impaired?
While reading FIDE version of the rules, I stumbled upon *Appendix E: Rules for play with Blind and Visually Handicapped*.

There, in E2.1:

> The moves shall be announced clearly, repeated by the opponent and executed on his chessboard. When promoting a pawn, the player must announce which piece is chosen. To make the announcement as clear as possible, the use of the following names is suggested instead of the corresponding letters, algebraic
>
> A - Anna, B - Bella, C - Cesar, D - David, E - Eva, F - Felix, G - Gustav, H - Hector
>
> Ranks from white to black shall receive the German numbers:
>
> 1 - **eins**, 2 - **zwei**, 3 - **drei**, 4 - **vier**, 5 - **fuenf**, 6 - **sechs**, 7 - **sieben**, 8 - **acht**
>
> Castling is announced “**Lange Rochade**” (German for long castling) and “**Kurze Rochade**” (German for short castling).
>
> The pieces bear the names: **Koenig**, **Dame**, **Turm**, **Laeufer**, **Springer**, **Bauer**.

So, FIDE recommends using German for announcing moves when tournaments with blind/visually handicapped participants take place.

A quick search did not allow me to answer the question of why is it like that and why German (not, say, French) was chosen. I also wonder, since when did those recommendations are present in the rulebook.

# Answer
> 3 votes
Not sure but maybe it is because International Braille Chess Association headquarters are in Germany, also as far as I know ( My knowledge is on the basis of Chess Base India's videos ) players are free to announce their moves in any language as long as both of them agree, German names are used only if the players are not able to reach any mutual agreement.

---
Tags: rules, fide
---


# Question
Title: Refutation of the Blackmar-Diemer gambit?
Is there an accepted refutation of the Blackmar-Diemer Gambit, **1. d4 d5 2. e4** or what is the strongest line for Black to prove that the gambit is unsound?

# Answer
The simplest refutation is 2...e6, the french defense, one of the most stable openings for black. It is also fine to accept the gambit 2... dxe4, but you have to know some specific traps....
> 3 votes

# Answer
Not an expert, but I'd say the onus is on the gambiteer (White) to prove anything. W is delaying development and must waste time to capture the pawn later. Black has natural moves like Nf6 and Bf5 which both develop and delay W's capture of the pawn (and can possibly even hold on to it). W is just giving away some of the opening advantage. I don't think Black can expect more than this. W can also choose to give up a pawn altogether with f3, exf3, Nxf3 with in-adequate compensation.
> 2 votes

# Answer
Just accept it. the traps are the only thing you have to know except the opening principles.
> 0 votes

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Tags: opening
---


# Question
Title: Does GM Larry Kaufman's "principle of the redundancy of major pieces" truly exists? Or could this effect be caused by the number of Pawns instead?
The following is an extract from *The Evaluation of Material Imbalances* by GM Larry Kaufman. I put in bold characters everything that was important for this question.

https://www.chess.com/article/view/the-evaluation-of-material-imbalances-by-im-larry-kaufman

> THE EXCHANGE
>
> Now let's move on to discussing the Exchange (rook for knight or unpaired bishop). **My research puts its average value squarely at 1¾ pawns (a tiny bit more when its a knight).** Most authors value the Exchange at either 2 (the standard value) or at 1½ (Siegbert Tarrasch, GM Edmar Mednis, GM Larry Evans), so my value is right in the middle. World Champion Tigran Petrosian actually claimed the Exchange was only worth one pawn, and former challenger David Bronstein said the same when the minor piece was a bishop, but in such cases the bishop pair is often involved. When the side down the Exchange has the bishop pair, my data shows he needs only 1.15 pawns to make things even; perhaps this case is what Petrosian and Bronstein had in mind.
>
> I note for the record that the authors who put the Exchange at 1½ pawns are right on the money if they are averaging in the cases where the side down the Exchange has the bishop pair, but it think it is much better to regard the bishop pair as a separate component of the material balance.
>
> TWO FACTORS
>
> The value of the Exchange is influenced by two factors. **First of all, the presence of more major pieces on the board favors the minor piece. In general, with no major pieces traded, the Exchange value drops to 1½ pawns, and if the minor side has the bishop pair just one pawn makes things even. But with queens and a pair of rooks gone, the Exchange is worth slightly more than its nominal value of two pawns, or about 1½ when opposed by the bishop pair.** Also important is the number of pawns on the board, especially when the minor piece is the knight. With most of the pawns on the board the Exchange is worth less; each pawn trade helps the rook. Rooks need open files!
>
> **So if you have a rook for a knight and two pawns, even though you are nominally a quarter pawn behind in material, you should try very hard to exchange major pieces, in contravention to the usual rule that the side ahead in material seeks exchanges.** I had a game with USCF Executive Director Mike Cavallo in the World Open in which he sacrificed the Exchange for some compensation. I was not at all sure of victory until he allowed me to exchange the extra rooks, after which I won in just a few moves. Had he known this principle, he could have put up a good fight.
>
> TWO MINOR PIECES vs. ROOK AND PAWN(S)
>
> **All of the above applies with even more force to the case of two minor pieces vs. rook and pawns; the side with the rook wants very much to trade major pieces, even if he is a bit behind in material. Why this should be so is subject to debate; my explanation is that having more than one major piece is somewhat redundant - in many games there may only be time to employ one major piece on an open rank or file. Having at least one major piece (preferably a rook) to bring to an open line may be critical, but having two may be wasteful.**
>
> All in all, this section is a very important one; imbalances involving the Exchange are fairly common, and the effect of major piece trades on the evaluation is quite significant. **While nearly everyone above novice level knows the value of the bishp pair, I suspect that even many masters are unaware of the above "principle of the redundancy of major pieces."** **As for rook and knight vs. two bishops and pawn, with nothing else but pawns on the board, the rook's side has a mild advantage, but add a rook to each side and the game is dead even. In general, with other pieces on the board, this imbalance should be considered even, with only a trivial edge for the rook's side.**

So if I understood correctly, Kaufman found that when you had only one major piece that is a Rook it is worth slightly more than usual. But when you have three major pieces your two Rooks are worth slightly less than usual. And when you have two major pieces, your Rook(s) is as powerful as usual. He called this "the principle of the redundancy of major pieces".

But I am doubting about the true cause of this effect. What if it was the number of Pawns that determined the power of the Rook(s) instead?

If you had few Pawns, there would be a high probability that you would also have few major pieces... and therefore if your lone Rook seem more powerful than usual it could be because you have few Pawns (which would cause your Rook to have a lot of open files).

If you had a lot of Pawns, there would be a high probability that you would also have three major pieces... and therefore if your two Rooks seem less powerful than usual it could be because you have a lot of Pawns (which would cause your Rooks not to have many open files).

Maybe he is correct and it truly is the number of major pieces that cause this effect, but I believe there is not enough evidence to support this, and it could simply be the number of Pawns that cause this effect instead...

What I also don't get is why he says that having a Queen (which is also considered as a major piece) would reduce the power of your Rook(s). She may be half rook, but she's also half Bishop, so she doesn't necessarily need open files to function well (each time she's on an open file she gets kicked by an opponent's Rook anyway). So if his "principle of the redundancy of major pieces" is indeed correct, could it be defined instead as: If you have two Rooks both your Rooks are slightly less powerful than usual ; if you have only one Rook your Rook is slightly more powerful than usual. (And the Queen would have no part in this principle.) ?

My third and final point is: Are there other GMs who are fully aware about the existence of this principle? Is that principle actually taught by chess coach? Is that principle really important or is it only the mysterious and dubious invention of one single man?

# Answer
> 9 votes
In Kaufman's full article, the rook's value is dependent on the number of pawns on the board (as does the knights value). The value of the rook increases as the number of pawns decreases (the value of the knight decreases as the number of pawns decrease).

So he takes into account the variation of the rooks value as pawns decrease, and thus his "redundancy of major pieces" is observed in his statistical analysis.

Of course, the actual values in a particular position depends on that particular position.

# Answer
> 3 votes
As a rule of thumb, when down the exchange(or have two pieces for a Rook), you don't exchange Rooks as they are redundant. On the flip side, if one Rook on the seventh is good, two Rooks on the seventh is crushing. Even if all the pawns have evacuated the seventh(second) rank, the Rooks still have power by attacking from behind.

A pawnless endgame with this imbalance is a theoretical draw. One pawn for each side and the Bishop is not on the same colour square as the Pawn, this position is considered a draw. The more pawns on the board, the less likely it is a draw. The more pawns left on the board, the more targets for the Rook to attack.

I believe it was Capablanca who stated that the secret to winning up the exchange was to give it back at a time when you could also win a pawn.

All of this boils down to that everything depends on the position, that is the placement of the Rooks.

As an observer of young players, it amazes me that they try to get the Nc7+ fork. They know the rook is worth 2 points more than the knight, but they don't know how to use the rook. Assigning static values is meaningless without listing every situation/exception.

Point Count Chess (PCC) was a 1950s-1960s publication, devised by Israel Albert Horowitz and Geoffrey Mott-Smith. This shows a system of trying to assign a value to a chess position. But as our knowledge grew, some the the points have changed value, including some going from negative to positive.

Every chess rule has an exception, including this one.

# Answer
> 2 votes
In Michael Steans excellent book "Simple Chess" he introduces the idea of each stable Pawn structure having the "capacity" to support a certain number of pieces. If your pawns lack capacity, your pieces will feel cramped. They lack mobility and "step on each others toes". Obviously you should work to bring about exchanges. Perhaps even more importantly, if your opponent lacks capacity, you should deny them any exchanges. Applying this to the Rooks, you can even let your opponent occupy the open files. If their Rooks cannot use the files to penetrate, they just get in the way of other pieces. "Capacity" does not replace other positional concepts, but it can be a useful addition.

---
Tags: statistics, evaluation, queens, rooks, point-value
---


# Question
Title: What arrangement of 8 each of these 4 different compound leapers has the "strongest coverage properties" on a 16x16 board?
The 4 compound leapers I'd like to look at are:

What arrangement of 8 of each of these 4 compound leapers (a total of 32 pieces) has the "strongest coverage properties" on a 16x16 board, defined as such?:

* Any square that a piece can attack is counted as being covered once per piece
* A square occupied by a piece is not covered by the piece occupying that square
* Sort first by # of squares covered once; then by 2x, 3x, up to highest cover count

For example, an arrangement of pieces that covered 256 squares at least once each and covered 96 of those squares at least twice each would by this definition be considered "stronger" than an arrangement that covered 252 squares once and 112 squares twice; the higher at least twice-covered square count doesn't matter if it covers less squares at least once each, and so on.

If any riders were in the mix (rooks and bishops are examples of rider pieces; rooks the (0,1) rider and bishops the (1,1) rider), I would add that "a square that a rider's path to is blocked is not covered by that rider"; my intention is for this definition to be generalized to any combination of pieces on a board of any dimensions.

(I should double-check; is this "strongest coverage arrangement" I'm defining already a thing which there is another name for?)

# Answer
This is the best arrangement that I've been able to find by hand. It covers 248 squares at least once; missing the 8 squares which are the 2 knight moves outwards from each of the center 4 squares. If I've counted right, I believe it covers 148 of those 248 squares at least twice each. I don't expect triple-covered squares to be a tiebreaker for this question and it's difficult to do by eye, so I admit to not personally counting which and how many squares are covered at least 3 times each in this arrangement.
> 1 votes

---
Tags: chess-variants, mathematics, unorthodox-pieces
---


# Question
Title: What should the practical meaning of "blunder" be?
There have been questions about the reliability of computer evaluation, and famous cases in which computers miss-evaluate positions have been given. What I want to ask is more related to the practical aspect of the evaluation, rather than its effectiveness.

As humans, we may find moves that put our opponents in deep trouble, or lead to positions we may personally enjoy, even though computers may label this moves as blunders. A classical example is Tal's knight sacrifice in the sixth game of their match. Humanly speaking, the move may be considered brilliant due to the creative inspiration it shows, and the practical effects of it (for the position gets complicated and rich in tactical motives, in which Tal felt comfortable). To a computer, though, it is disastrous; artificial intelligence can not feel discomfort nor prefer certain positions above some others, and quickly finds the correct refutation to the sacrifice.

In a practical sense, for a player looking to eliminate blunders (which is a goal dictated to many beginners), what does this actually *mean*? Is it correct to label as a blunder all refutable moves that severely worsen one's position, as engines do? Or is it more appropriate to use the word blunder in a more pragmatical sense, by referring to refutable moves that severely worsen one's position, and whose refutation can be actually achieved by a human opponent? In other words, how *pure* should the concept of *blunder* in chess be?

I know the question is somewhat philosophical, and I do not expect definite answers.

# Answer
> 7 votes
The definition of the word is rather subjective, since it depends on how much you value objectivity vs practicality. I think it seems reasonable to take both aspects into account. For example, a move that gives up a pawn on the spot (and offers no compensation) could be considered a blunder. Objectively it's clearly a poor move, and practically it's easy to refute: the opponent just takes the pawn, and that's the end of the story.

Meanwhile, a move that objectively loses 2-3 points, but forces the opponent to play 10 difficult moves in a row in order to exploit it (and if they don't play these moves, they will be much worse), may be considered "interesting" or "dubious". Objectively the move is even worse than the previous example, but practically there's a high chance it will work.

Judging the practicality of a move also depends on the time control of the game. In a blitz game, you can get away with a lot more than you could in a long OTB game. But you could also get away with a lot more in an OTB game than you could in a correspondence game with engines. The example above with giving up 2-3 points would definitely be labelled a blunder in correspondence.

So all in all, a blunder could be considered a move that is clearly objectively bad, but also rather easy to refute in an actual game.

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


# Question
Title: Why are chess.com opening names and notations seemingly mismatched?
I often see something like the above when playing chess online. When I played Ruy Lopez and my opponent played Classical Variation, but I transposed us to Four Knights Game Spanish Variation, I had castled in between the Classical move and the transposition (Move 4).

It seems the reason the opening name says "5. O-O" because it one of the openings where the order of moves doesn't matter. But is this a bug in chess.com or intentional for the opening name to be mismatched with the move numbers?

# Answer
> 6 votes
I think this is intentional. The opening name alludes to the position reached, not the route taken to get there. The principal move order to reach this position is to start with the classical variation of the Spanish variation of the four knights game and play 5. O-O.

It wouldn't make sense to say `Four Knights Game: Spanish Variation, Classical Variation, 4. O-O` because if you had reached it from that route then you wouldn't have castled on move 4. While it would make sense to describe it as a Ruy Lopez with 4. O-O, it would be undesirable to list the same position under two different openings.

# Answer
> 5 votes
The opening variation is decided based on the position reached and not on move order. The expression 5. 0-0 is just to indicate the variation and has nothing to do with what you played. For example, imagine that for the Ruy Lopez, it showed the move after 3 moves. So when you play 1.e4 e5 2. Nf3 Nc6 3. Bb5, it would say "Ruy Lopez, 3. Bb5" because that entire expression is already stored. So it cannot happen that after 1.e4 Nc6 2.Bb5 e5 3. Nf3, it would say "Ruy Lopez, 3. Nf3" or "Ruy Lopez, 2. Bb5". It doesn't mean that you played Bb5 on move 3.

---
Tags: opening, online-chess, notation
---


# Question
Title: Can someone explain the playing style of the great Jose Raul Capablanca?
I have heard that he plays intuitively(maybe based on themes), but can someone give an example?

How did he manage to reach such heights despite his laziness for calculations?

Doesn't that mean even a mediocre player can reach great rankings if he just plays intuitively?

# Answer
Only if your intuition is good enough:)

You overlook the training and experience he had. Emanuel Lasker said he did not memorize anything he can deduce.

From my playing over his games he was a quiet patient positional player who could mix it up if the situation forced him to do that.
> 3 votes

---
Tags: strategy, tactics, capablanca, capablanca-chess
---


title: Facing irregular or uncommon openings

text:
# Question
Title: Facing irregular or uncommon openings
How do you deal with this? I'm a bit of a chess perfectionist, and I always want to play the best move, so when I go up against an irregular opening, I don't do badly, but it's hard be 100% sure you made the best move in the opening, and that really bothers me psychologically.

My current method for dealing with these types of situations is to just follow the basic opening principles, but at my level I feel like this is not detailed enough or too vague, since I always try to strive for a certain level of understanding in every position. What can I do to be more flexible in this area of chess? Are there more detailed guides for playing against uncommon openings?

Even though I don't necessarily play badly, I really want to learn to be "comfortable" in all positions. How would I achieve this? Is the answer to play beginners since they tend to play strange openings all the time? I've already done this, but I still don't seem "comfortable" enough. Maybe its all in my head?

# Answer
What you describe is the best advice to meeting an unusual opening: play by the principles.

In terms of resources, there are 2 I can think of:

* Beating Unusual Chess Openings by IM Richard Palliser. By 'unusual', Palliser really means anything other than 1. e4 or 1. d4, so he covers from Black's point of view:

> The respectable (English Opening, Reti and King s Indian Attack) through to the offbeat (Nimzo-Larsen Attack, Bird s Opening) and the totally bizarre (Orang-utan, Grob)
> 6 votes

# Answer
You are prepared for popular opening lines as you studied guides about them, but you are lost when you are out of the book. This indicates that you lack opening strategy and piece improving skills and you should work on them.

Memorizing and playing best opening moves won't help you to improve your chess. Actually, if you don't understand why a particular move is the best, you can't take advantage of resulting position. Let's say you played perfectly in the opening, after the opening you are on your own and you have to take advantage of resulting position, but you won't be able to as you don't understand deeply what you achieved in the opening so far. So instead, you should improve your overall chess ability to be able to play in any random position.

For this very reason, Fischer suggested 960Chess. He was complaining about that chess is getting more and more an opening memorizing game.
> 1 votes

# Answer
If you face something unexpected in the opening it is important to **stay calm.** It is unlikely that the new move is a super-strong novelty which will make you lose immediately.

Also you should avoid getting into the opposite mindset. We all know that things like the Grob are bad for white, but this does not mean that you can easily refute it and get a winning position. In many cases what you get even with perfect play is just a small advantage.

From a chess point of view, if you don't know theory you have to play on **general principles and avoid tactical traps**. Training both of these will help you not only when you encounter new openings, but also when playing the openings you know after you run out of book moves.

Also in many cases, particularly in less ambitious irregular openings, you can just play a ***system*** that you are familiar with: e.g. (depending on the situation) a Sicilian dragon setup or a Kings Indian or...
> 1 votes

# Answer
I used to play 1.b4 with some regularity and success. It worked extremely well against two kinds of opponent. One kind reacts by going on the defensive, and playing safety-first moves which give them a cramped position. The other kind believes that they can find a refutation over the board, consumes a great deal of time, and eventually gets nowhere (I would not play anything actually known to be refutable.)

The sensible reaction is not to get into obscure tactics that your opponent is likely to be prepared for. However, if you play well, you are probably under less pressure than you would be in a mainstream opening. So you may be able to choose slightly more aggressive piece placements than you normally would, such as Bd6 rather then Be7.

If you allow your normal thinking style to be disrupted by an unusual opening, then your opponent has already achieved one of their main objectives
> 1 votes

# Answer
I am afraid there is no good answer. If your opponent is playing an unusual opening intentionally, he or she has probably done so precisely so he or she is more prepared than you in that opening. I was once clobbered by a Grob. Aside from the standard "play by established principles", you'll also have to watch for any tricks and traps. The most important thing is probably to go over the game carefully afterward so you are better prepared if you encounter the same opening again. (Another one that got me, but only once, was the Blackburne Shilling.)
> 0 votes

# Answer
When in doubt, I like to play solid and defensive, d3, b3, Bb2 etc. which works against almost anything as long as you keep an eye out to play c4. I've gotten crushed by traps in the Grob many times!
> 0 votes

# Answer
The question is a bit too broad and it all depends on the actual opening, but the rule of thumb I follow in such situations is to develop knights as early as possible and build a position that will give me control of the centre of the board (basically to control e4 (e5 as Black) and fields close to it).
> 0 votes

# Answer
A good dvd is A Black Repertoire Against Offbeat Openings by Nick Pert on Chessbase.
> 0 votes

# Answer
Many openings are rare, so I'll just talk about Bird's and Larsen's. For the Larsen's, just e5, the Bird's, d5, the From's gambit is not so good, according to Stockfish.
> -1 votes

---
Tags: opening, psychology
---


title: Why is Ne2 better than Nf3?

text:
# Question
Title: Why is Ne2 better than Nf3?
I played Nf3 for attacking on king side which is about to castle having some plans to make a battery in future after castling but I feel Ne2 is making a block for Re1 at some point. Any suggestions?

```
[fen "rnbqk2r/pp3ppp/2p3n1/3pP3/3P4/2PB4/P4PPP/R1BQK1NR w KQkq - 0 1"]

```

# Answer
> 9 votes
While the knight wouldn't be badly placed on f3, playing Ne2 keeps your f2-pawn unblocked, allowing you to push it up the board. If the pawn reaches f5 then you will have an overwhelming position. Also, on e2 the knight could go to g3, helping to control the f5-square while eyeing the h5-square.

# Answer
> 7 votes
After Ne2 you are set up for 0-0 and f4-f5, which looks like a dangerous plan.

After Nf3 Bg4 is possible. Notice how the bishop doesn't have nice squares after Ne2.

# Answer
> 6 votes
Both the other answer have a valid point.

Either way the rook is blocked on the e-file, so logic dictates the the f-pawn should be pushed, and the knight on f3 would block the rook there.

On e2, the knight protects c3. Although this isn't an issue now, an unexpected Qa5 could disrupt your plans.

Another factor to consider is the future of the knight. From f3, the knight's only future is g5, which is a good, protected square. From e2, the knight's future is f4, to exchange a defender, or g3-\>h5. Both these paths are good, but the f3-g5 path is better.

BTW, without any calculation, Ba3, which keeps the king in the center, should be the best move.

# Answer
> 3 votes
Nf3 and Ne2 are both very good moves, which consolidate White's advantage. I don't see why Ne2 should be preferred over Nf3 on general considerations.

1. After Nf3! White can follow with Ng5, and/or h4. Nf3 is a very concrete and direct move.

* Bg4 does not solve Black problems. After h3, White gains the pair of bishops in a very open position.
    * 0-0 runs into problems for Black after Ng5 (1.Nf3 0-0 2.Ng5 f6 3.Nxh7! is crushing!!)
2. After Ne2, white can continue with Ng3 or f4, but it's much slower (by the way White can also play f4 before any knight move!).

Here are some illustrative examples of these two different approaches.

## 1.Nf3

```
[fen "rnbqk2r/pp3ppp/2p3n1/3pP3/3P4/2PB1N2/P4PPP/R1BQK2R b KQkq - 1 1"]

1... Bg4 (1... O-O 2. Ng5 Qe7 (2...f6 3.Nxh7!+-)  3.Qh5 h6 4.O-O! hxg5 5.Bxg5+-) {with a crushing attack}  {does not solve Black problems} 2.h3 Bxf3 3.Qxf3 O-O (3... c5 4.O-O Nc6 5.Ba3! cxd4 6.Rfe1! Qa5 7.Bxg6 hxg6 8.e6+-) 4.h4! f6 5.Bxg6 hxg6 6.Ba3 Re8 7.h5! {with a decisive attack}

```

## 1.Ne2

```
[fen "rnbqk2r/pp3ppp/2p3n1/3pP3/3P4/2PB4/P3NPPP/R1BQK2R b KQkq - 1 1"]

1... c5 2.O-O O-O 3.f4 f5 (3...cxd4 4.Nxd4 Nc6 5.Ba3+-) 4.dxc5 Nc6 5.Be3+-

```

# Answer
> 1 votes
There are 3 main advantages of Ne2 over Nf3. Other commentators have mentioned the first 2

1. Denying the Bishop on c1 from getting active, if white can maintain this restriction on the black light-squared bishop then black will effectively be playing down a piece
2. f4 -\> f5 (which is a powerful idea in this position) is much snappier if there is not a knight restricting the pawn's movement.
3. a Ne2 -\> Ng3 -\> (Nh5 or Nf5) is more dangerous than a Nf3 -\> Ng4 plan because it targets the dark squares around the future black king position, that are much weaker. Black would struggle a lot with defending the g7 if white builds up pressure there and if black plays g6 his position is toast since all of white's pieces would be able to find homes on threatening squares next to black's king

---
Tags: learning, problems, positional-play, knights
---


# Question
Title: Which gambits have been most successful?
Besides the Queen's Gambit (which isn't really a gambit anyway), which gambits have been most successful as far as winning percentage and usage at high levels of play?

# Answer
> 15 votes
According to these statistics from 4 million games, the Marshall Gambit of the Semi-Slav defense is the most successful with 58.4% wins. I only counted gambit openings that had more than 1000 occurrences in the database.

The least successful gambit appears to be the Latvian Gambit with only 41.1% wins.

Note that since the database does not discriminate against older games, the statistics may not necessarily reflect the possible outcome of an opening if it were played today.

# Answer
> -1 votes
According to Stockfish, the best is the Fried Liver Attack (+1.57), and the worst is the Latvian gambit (+1.61) for black, the worst is not the Halloween Gambit, although it's almost there.

---
Tags: opening, gambits
---


# Question
Title: Does 1. e4 e5 2. Nf3 f6 have to be a bad opening?
There seems to be a pretty nifty attack for White after `1.e4 e5 2.Nf3 f6`:

```
[FEN ""]

1.e4 e5 2.Nf3 f6 3.Nxe5 fxe5 4.Qh5+ g6 5.Qxe5+ Qe7 6.Qxh8

```

I've played as White with this opening several times, always to my advantage (usually Black panics and plays `4 ... Ke7`, soon after which he finds ample reason to resign). But once someone played as shown above, and went on with

```
6. ...     Nf6,
  etc.

```

to try and put my queen on the spot. Presumably he intended to follow up with moves such as `...b6`, `...Bb7` or similar, `...Nc3` or similar, `...O-O-O`, and then `...Bg7` forcing Qxd8. Since it was a blitz game, best play was not made, and he made a mistake allowing my queen to escape, but it got me thinking. Is there some way Black can recover from `1. e4 e5 2. Nf3 f6?`

My question especially regards `1. e4 e5 2. Nf3 f6 3. Nxe5 fxe5 4. Qh5+ g6 5. Qxe5+ Qe7 6. Qxh8` (as shown above) - is there a way to trap White's Q? Or is `3... fxe5` simply a bad move? Should `2... f6` be avoided altogether?

# Answer
After

```
1.e4 e5 2.Nf3 f6 3.Nxe5 fxe5 4.Qh5+ g6 5.Qxe5+ Qe7 6.Qxh8 Nf6

```

with ideas of trapping the queen, `7. d3` followed by `Bg5` or `Bh6` and there won't be any issues getting the queen out, e.g.:

```
7.d3 d5 8.Bg5 Nbd7 9.Nc3 b6 10.0-0-0 Bb7 11.e5

```

Black can try to minimize the damage after `2...f6?` with something like `3.Nxe5 Qe7`

You aren't losing the exchange any more, but you've still destroyed your position with `...f6`.

`2... f6` should be avoided.
> 15 votes

# Answer
White has a forced win of a bunch of material after either `4... g6` or `4... Ke7`, but if you're into silly "psychological" justifications for moves, you could argue that `4... Ke7` makes White think a little harder to find the win, while Black can prep it.

```
4. ... Ke7
5. Qxe5+ Kf7
6. Bc4+ d5
7. Bxd5+ Kg6
8. h4 h6

```

This is the only line that leaves White with an *overwhelming* advantage; for instance, one game between relatively weak players continued:

```
8. Qg3+? Qg5
9. Qxc7 Ne7
10. Qd6+? [h4!] Kh5

```

(Feng-Sloan 2010)

After which Black *looks* hopeless...

...but is actually just bad.

However, you may already know that if White plays correctly up to `8 ... h6`, they have a killer 9th move that picks up material. Here's a diagram as an exercise for the reader:

(answer)
> 11 votes

# Answer
This opening is also known as the Damiano Defense and it is just bad.

In the line you gave, where black plays `6... Nf6`, white's best plan is to play `d3` and `Bg5`. Black can't move the bishop because it is pinned (so the queen can't be trapped until black castles).
> 5 votes

# Answer
No, the Damiano Defense does not lose by force so it's not a bad opening.

If you analyze it with a computer you won't be able to find a variation that wins for white against best play.

After `1.e4 e5 2.Nf3 f6 3.Nxe5`, playing `3...fxe5` will lose for black but playing `3...Qe7` will hold the game. For example check out the game Fischer vs McGregor, 1964 (here's a version with commentary on YouTube), which ended in a draw.
> 3 votes

# Answer
The damiano cannot protect the pawn and weakens kingside. Just say, damiano himself is pretty annoyed by it getting named after him.
> -1 votes

---
Tags: opening, strategy, queens, captures, damiano-defense
---


title: Do the new chess AIs play gambits?

text:
# Question
Title: Do the new chess AIs play gambits?
Do the new chess AIs, such as Alpha Zero and Leela Zero, play gambits?

By *gambit,* I do not mean a merely nominal gambit like the mainline Queen's Gambit, but rather a genuinely speculative offer of opening material like Evans' Gambit, for example—or like the gambit @Akavall gives below.

# Answer
Sure, this line of Queen's Indian came up:

```
[FEN ""]
[White "AlphaZero (Computer)"]
[Black "Stockfish (Computer)"]

1. Nf3 Nf6 2. d4 e6 3. c4 b6 4. g3 Bb7 5. Bg2 Be7 6. O-O O-O
7. d5 exd5 8. Nh4 c6 9. cxd5 Nxd5 10. Nf5 Nc7 11. e4 d5
12. exd5 Nxd5 13. Nc3 Nxc3 14. Qg4 g6 15. Nh6+ Kg7 16. bxc3
Bc8 17. Qf4 Qd6 18. Qa4 g5 19. Re1 Kxh6 20. h4 f6 21. Be3 Bf5
22. Rad1 Qa3 23. Qc4 b5 24. hxg5+ fxg5 25. Qh4+ Kg6 26. Qh1
Kg7 27. Be4 Bg6 28. Bxg6 hxg6 29. Qh3 Bf6 30. Kg2 Qxa2 31. Rh1
Qg8 32. c4 Re8 33. Bd4 Bxd4 34. Rxd4 Rd8 35. Rxd8 Qxd8 36. Qe6
Nd7 37. Rd1 Nc5 38. Rxd8 Nxe6 39. Rxa8 Kf6 40. cxb5 cxb5
41. Kf3 Nd4+ 42. Ke4 Nc6 43. Rc8 Ne7 44. Rb8 Nf5 45. g4 Nh6
46. f3 Nf7 47. Ra8 Nd6+ 48. Kd5 Nc4 49. Rxa7 Ne3+ 50. Ke4 Nc4
51. Ra6+ Kg7 52. Rc6 Kf7 53. Rc5 Ke6 54. Rxg5 Kf6 55. Rc5 g5
56. Kd4 1-0

```

I got this game from chessgames.com: game
> 7 votes

# Answer
Most chess engines don't play dubious gambits, or gambits with serious material loss(like the Halloween gambit.)

I found two games where Stockfish and Houdini played each other to draws in the Evans Gambit at these links:

In fact, Komodo has played the King's Gambit against Stockfish!

```
[FEN ""]
[White "Komodo (Computer)"]
[Black "Stockfish (Computer)"]

1. e4 e5 2. f4 exf4 3. Nf3 Be7 4. Nc3 Bh4+ 5. Ke2 d6 6. d4 Bg4
7. Bxf4 Nc6 8. Qd3 Nge7 9. Kd2 Bf6 10. e5 Bf5 11. exf6 Bxd3
12. fxe7 Qd7 13. Bxd3 Nxe7 14. Raf1 O-O 15. Kc1 a6 16. h4 b5
17. h5 b4 18. Nd1 Nd5 19. Bd2 a5 20. Nh4 c6 21. Rf3 Nc7
22. Nf5 Ne6 23. d5 cxd5 24. Nde3 Nc5 25. Nxd5 Nxd3+ 26. Rxd3
Rae8 27. Rf1 f6 28. h6 g6 29. Nfe3 f5 30. Nc4 f4 31. Rxf4 Rxf4
32. Bxf4 Re1+ 33. Kd2 Re6 34. b3 Qd8 35. Kc1 g5 36. Rg3 Rg6
37. Be3 Kf7 38. Rf3+ Ke6 39. Ncb6 Rxh6 40. Bd4 g4 41. Rf1 Qh4
42. Nc7+ Ke7 43. Kb2 Qg5 44. a4 bxa3+ 45. Kxa3 Qg6 46. c4 a4
47. Ncd5+ Ke8 48. Re1+ Kd8 49. Re7 Qd3 50. Bc3 1-0

```

Gambits do happen, just very rarely.
> 6 votes

# Answer
From what we've seen of Alpha Zero, the answer appears to be yes. Its games showed it playing gambits where there was no immediate way to reclaim the material. Often, Alpha Zero's compensation was just long-term active piece play (or some positional edge). As an example, see the game posted by Akavall. In that game, Alpha Zero sacrifices a Knight, and just gets long-term compensation for almost the next 20 moves.

Alpha Zero plays more "intuitive chess" because it is a constructivist machine (it learned the game by playing with itself over and over again). None of its strategies were given by its human programmers, meaning that Alpha Zero must have learned "active piece play" is more important than mere material.

Comparatively, constructionist engines like Stockfish and Houdini (which just follow rules given by their human programmers) are unable to play more intuitively, since they're bound by these rules. The moves they choose are based off their evaluations of positions, and these evaluations must follow strict rules. For example, a Knight is worth "3 points", space advantages of x amount are worth "x points". This severely limits the intuitive capabilities of these engines, which is why they don't tend to play "true" sacrifices as often as constructivist engines like Alpha Zero.
> 3 votes

# Answer
**Update 31 May 2020**

If left alone, the trained Leela nets play a very predictable set of openings. These openings, however, are not gambits - instead they go for the best & most solid lines that never lead to unbalanced positions.

For example, if you let Leela play against itself, there's a good chance you'll see Ruy Lopez Berlins every game (depends on the exact net).
> 2 votes

# Answer
I found a few stockfish vs. alphazero evans gambits.
> -1 votes

---
Tags: engines, gambits
---


# Question
Title: How can I know if the chief arbiter has "cheated" in the pairings and possibly report it?
Few years ago, I participated in a local, FIDE-rated tournament. In its first round, the chief arbiter paired the players 4 times (yes, I saw the 4 different pairings and changed four opponents before I started the game!).

This was only the start; in the next years, arbiters from this club (even those who had an FA title!) started doing more "cheats", like manual pairing players, clearly in favour of their club's ones. How do I know? - I've made a script in Perl to calculate the pairings for the first round in a Swiss-system, but the output is different from the reality (e.g. pairing the first with the second, the third with the last, etc.).

I find this annoying and unfair, since I get paired with unbeatable opponents each time. I think that if I ask them for explanations, they'll deny everything and they will say that I have not got proof. The tournament is on Chess-Results, where everyone can download the Swiss-Manager file.

Is it possible to know if they "cheated" from the `.TUNX` Swiss-Manager file and possibly report this case to the national chess federation? If not, how can I approach this situation

# Answer
> I participated in a local, FIDE-rated tournament. In its first round, the chief arbiter paired the players 4 times

This has happened to me too, although not as many as 3 repairings that I am aware. As an arbiter I've also done repairing in the first round although only ever in small local events. I would try very, very hard indeed to avoid doing this in a norm event. Normal procedure for the first round in a norm event to avoid this happening is to require the players to register their presence before a certain time and do the pairings when this time is reached. Any player who doesn't register in time is excluded from the first round.

There is a unique problem in the first round of a tournament in that usually it is possible as a player to ask for and be granted a half point bye and players will often choose to miss the first round. This information goes to the organiser who should pass it on to the arbiter but often some of this information "goes astray". With luck this is discovered before the round starts. In that case the correct procedure is to redo the pairings taking into account the updated bye information.

Sometimes this information isn't discovered until the round has started. In this case some players will have sat there with no opponent because the opponent requested a bye but that information got lost. They will be awarded the full point. When you look at the pairings the next day you will see that these players are shown not having an opponent in round one (even though when the round was played they did) but each getting one full point instead of the half point they would get for a bye. Any time you see more than one player get a full point bye you know this is what happened.

The organiser and arbiter can try and be strict and say byes must be agreed the day before but then half an hour before the first round is due to start a player rings up to say that there has been an accident on the motorway, he is going to be delayed and won't arrive in time to play his game, can he have a half point bye?

When this happens, again, the arbiter should repair using the new information. This can be annoying but it is real life.

Now modify the scenario slightly. This time the round has started but it is still before the default time and again a player phones up. He is giving a lift to another player and again they will miss the round because of an accident. They are not paired against each other so two players are sitting at their boards without opponents. As the arbiter, what is the best thing to do? As long as the organiser wrote in the tournament conditions that in this situation the players can be repaired then the correct thing is to repair the two players without opponents. The only way to do this is manually. If the two players without opponents are seeded 2 and 3 then the pairings will be changed so that 2 plays 3 and the two missing players who may be 56 and 57 each end up getting a half point bye.

> How do I know? - I've made a script in Perl to calculate the pairings for the first round in a Swiss-system, but the output is different from the reality

I'm an FA so I don't need to write a Perl script to check the pairings but as a player I have several times looked at the results from the previous round and calculated who I should be playing in the next round because the pairings are slow coming out. On one occasion the published pairings agreed with my calculations but were changed the next morning when I came to play and on several others they did not correspond. I ended up paired against somebody completely different! It has also happened to me in large, prestigious events where I do not expect such things to happen. How could this be?

Well, it is actually very simple. Take a very large tournament in a very small place with few local players like Iceland or Isle of Man. Most of the local players will be entered. This is their big chance to play new people without having to travel. With all these other players from distant and often exotic locations they really don't want to miss out and play their clubmate who they play several times a year, if not month.

If it is not a high level tournament like a norm event then it is reasonable to approach the arbiter (ideally before the event starts) and say "I don't want to play other islanders. Please don't pair me against them". This is reasonable and understandable and in every case where the pairings don't match my calculations I have found that such a thing explains the difference.

In the case where the pairings were changed on me I suspect that an initial error was made and a "forbidden pairing" which had been requested hadn't been entered correctly and players who had requested not to be paired against each other had this happen, noticed and then asked the arbiter to correct this.

> Is it possible to know if they "cheated" from the .TUNX Swiss-Manager file and possibly report this case to the national chess federation?

In the case of a norm event then, yes, it should be possible and was done for the big Gibraltar tournament a few years ago when Hou Yifan complained that she was paired against too many women. (Spoiler alert: she was wrong) However for smaller tournaments this is not really possible unless you have all the information including bye requests, late bye requests, missed bye requests and requested forbidden pairings.

As an aside I did play in a tournament a few years ago where they openly cheated on the pairings and the prizes! They even announced before the first round that they were going to do this. It wasn't FIDE rated and it wasn't nationally graded and all I could do was complain to them loudly and vow never to play in one of their tournaments again.
> 6 votes

# Answer
Do you have proof of cheating? It is more likely he had to use discretion to best satisfy the pairing rules due to the number of people/rounds and other factors.
> 0 votes

---
Tags: rules, tournament, swiss-pairing
---


title: Help needed to find the big mistake

text:
# Question
Title: Help needed to find the big mistake
Below is a a game in which I played as black. A chess engine analysis told me that I made big one mistake. Can someone point out what it is?

```
[FEN ""]

1. d4 b6 2. e4 Bb7 3. Nd2 g6 4. Bd3 Bg7 5. Ngf3 e6 6. O-O Ne7 7. Qe2 a6 8. Re1 d6 9. c3 Nd7 10. Nf1 h6 11. Ng3 b5 12. Bd2 Nb6 13. Rad1 Rb8 14. b4 Na4 15. Rb1 c5 16. e5 cxd4 17. cxd4 d5 18. Rec1 Rc8 19. Be1 h5 20. h4 Bh6 21. Bd2 Bxd2 22. Qxd2 Rxc1+ 23. Rxc1 Nc6 24. a3 Ne7 25. Qc2 Nc6 26. Bxg6 fxg6 27. Qxg6+ Kd7 28. Qg7+ Kc8 29. Ng5 Qf8 30. Qxf8+ Rxf8 31. Nxe6 Rf7 32. Ne2 Nb2 33. Ng5 Nd3

```

# Answer
There's more than one mistake in this game, but the biggest one is the last move: 33...Nd3. Probably this is the mistake that was pointed out. It allows White to win a piece (e.g., 34.Rxc6+ Bxc6 35.Nxf7). A better move would have been moving the rook away with 33...Rf5.
> 4 votes

---
Tags: analysis, middlegame
---


# Question
Title: Which is better-Stockfish 10 or AlphaZero?
I know **AlphaZero** (an AI) is one of the best top chess engines but **Stockfish** is also improving. Which one is better at chess?

# Answer
> 21 votes
We can't say for sure since AlphaZero is a private engine, i.e. we don't have games between it and the latest versions of Stockfish. Still, if AlphaZero hasn't improved since it was unveiled, it will likely lose to the latest version of Stockfish. That's because AlphaZero beat Stockfish 8 by +155 = 839 -6, which is an elo difference of about 50. The latest versions of Stockfish are capable of beating Stockfish 8 by about 150 elo (see also this). It's true that elo isn't transitive (i.e. engine A can beat engine B, which beats engine C, but C could still beat A in a match); however, the differences are so large that it would be incredible if AlphaZero is capable of beating the latest versions of Stockfish. You ask about Stockfish 10 (not latest Stockfish), which still beats Stockfish 8 by 100 elo, so it should be capable of beating AlphaZero as well.

Having said that, Leela Chess Zero is an engine based on AlphaZero techniques. It incorporates many new innovations not in the original paper, and therefore should be stronger than AlphaZero. Indications are it's competitive with Stockfish, and (for now at least) stronger: it won the most recent version of the Top Chess Engine Championship by five games - an elo difference of about 15.

Caveats:

1. In the world of computer chess, 100 games is an incredibly small sample size. Engine developers regularly need tens of thousands of games to conclusively say that one engine is stronger than the other. These games are played at bullet time controls, which isn't really chess as us humans understand it. Still, we can't play ten thousand games at long time controls - that takes too long - so we have to be satisfied with 100.
2. Stockfish continues to improve. As of time of writing, Leela has kinda stalled while a new net is being trained. So while Leela was (probably) stronger two months ago, it might not be the strongest engine *right now*.
3. Stockfish is not Leela's only competitor. In fact just two seasons ago, Leela actually failed to qualify for the superfinal, losing out to AllieStein. Like Leela, AllieStein is a neural network engine; unlike Leela, AllieStein includes human knowledge. Plus, as of time of writing, all three of Leela / AllieStein / Stockfish are behind Stoofvlees in the qualification tournament for the superfinal.

You might be interested in the ongoing Season 18 of the Top Chess Engine Championship, live games are available here.

**tl; dr:** AlphaZero is probably inferior to Stockfish 10, and even more so to the latest versions of Stockfish. Leela is at least competitive with Stockfish, and there's a good chance it's stronger (right now) as well. For the question "who is the strongest engine right now?", the situation is fluid; there are several engines that could all claim to be #1 at any one time. For the foreseeable future, this situation is likely to remain the case.

**Edit**: Deepmind acknowledges that AlphaZero would probably lose to the latest versions of Stockfish and Leela. They don't perceive it as a challenge, however, because they're not a chess engine company and don't view having the best engine as a big deal.

**Update:** with wins in the last four TCEC championships, Stockfish is probably the strongest engine right now, up to small sample size effects (see first caveat above).

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Tags: engines, stockfish, alphazero
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title: Why is b3 a blunder?

text:
# Question
Title: Why is b3 a blunder?
```
[FEN "r2q2nr/p3kppp/3bp3/2p2b2/Bn1P4/1P2PN2/4NPPP/R1BQ1RK1 b - - 0 13"]

```

I dont see whats wrong in b3 I am making some space to bring black bishop into game attacking nb4

# Answer
I wouldn't call it a blunder, as White still has a large advantage after 1.b3. But more efficient is 1.dxc5 Bxc5 2.Bd2. Here White's attacking the knight, but has only spent one tempo developing his bishop. Your idea with 1.b3, 2.Ba3 would take two tempi.

In this kind of position where the opponent's king is vulnerable, each tempo matters more. You want to take advantage of things before the king gets to safety.
> 4 votes

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Tags: learning, blunder, attack, closed-position
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