title: How is Alpha Zero "more human"?

text:
# Question
Title: How is Alpha Zero "more human"?
I have a possibly naive question about AlphaZero. I have seen it described as playing in a "more human" style than other computers, but whatever it does, it gains about 100 ELO points by doing it. Kasparov, and many others, have claimed that a strong human in collaboration with a computer will beat a strong computer (perhaps by about 100 ELO??). So an obvious question is, how would AlphaZero compare with a "centaur" combination?

Having only looked at a few games, what I notice is that most computers play wide open games that maximize their own mobility, but AlphaZero seems very concerned to limit the opponents mobility. In a human player I would describe this as a matter of style, not more or less human.

# Answer
Page 5 in the paper has your answer:

> ... AlphaZero compensates for the lower number of evaluations by using its deep neural network to costs much more selectively on the most promising variations - arguably a more "human-like" approach to chess ...

"selectively" is the key word. What does that mean? Let's use this following position for our example:

> https://chess24.com/en/read/news/london-classic-5-caruana-shows-how-it-s-done

This is a recent game won by Caruana in 2017 London Chess Classic. The White bishop is under attacked, and you know you have to move it. But **where?**

Possibilities (not losing a piece):

* Bh4
* Be3
* Bd2
* Bc1

What was Caruana thinking?

> I felt like I would lose at some point, but when I saw, 25.Bc1 I suddenly started to get a bit more optimistic about my chances. I realised my position is bad, but at least I had a plan and that was really all I needed for some confidence in this position. When I saw this b3, c4 the position is double edged and I have some chances.

This is **human thinking**, and a "human move". Caruana **hadn't** considered Bh4, Be3 and Bd2 because they "looked" bad. He had been focusing **only** and **only** on the Bc1 move.

Humans play chess very **selectively**, we discard unreasonable moves because we don't have time to examine all possibilities equally.

* We discard Bh4 because it release the tension on the h6 pawn
* We discard Be3 because it blocks the two white rooks on the third rank
* We discard Bd2 because it blocks the White queen to the king side

That's what AlphaZero trying to claim in the paper. They claim their algorithm, although slower than Stockfish, is able to **selectively pick better** moves than Stockfish in the search. While Stockfish is faster, it wastes time on bad moves. AlphaZero is slower, but it's more precise (like what Caruana was doing).

For example, AlphaZero might spent 80% resources on Bc1, and 20% on all other bishop moves. Stockfish might give 25% for each move (Bh4, Be3, Bd2, Bc1).
> 37 votes

# Answer
Most strong engines emphasize looking very deeply, at the expense of having a superficial evaluation function. In the AlphaZero paper, they say that Stockfish looks at 70 million positions per second.

Human grandmasters look at very few positions indeed compared to engines, but they have a better feeling who is better in a given position.

AlphaZero looked at only 80,000 positions per second, so it spends much more time in its evaluation function.

That's the sense in which they meant "more human like", nothing more.
> 19 votes

# Answer
AlphaZero already seems to play like a regular "centaur" -\> correspodence GM with an engine assistance.

As an FM I'd get much more enjoyment of playing AlphaZero vs a regular engine.

One comparison would be it plays like Karpov would with perfect tactics. (Game 9 AlphaZero plays a piece down for 15moves which is very Tal like).

It is not just style, AlphaZero gives an impression of understanding positions better than Stockfish.

AlphaZero also does not suffer from Horizon Effect that ALL chess engines had suffered from until now. Time and again it is able to correctly evaluate a position more moves down than Stockfish does.

Here's an example:

```
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
[White "AlphaZero"]
[Black "Stockfish"]
[Date "2017.12.05"]
[Result "1-0"]
[Event "Alphazero vs Stockfish: AlphaZero - Stockfish"]
[Site "https://lichess.org/study/EOddRjJ8"]
[UTCDate "2017.12.06"]
[UTCTime "05:53:49"]
[Variant "Standard"]
[ECO "C11"]
[Opening "French Defense: Steinitz Variation #2"]
[Annotator "https://lichess.org/@/Spreek"]

1. d4 e6 2. e4 d5 3. Nc3 Nf6 4. e5 Nfd7 5. f4 c5 6. Nf3 cxd4 7. Nb5 Bb4+ 8. Bd2 Bc5 9. b4 Be7 10. Nbxd4 Nc6 11. c3 a5 12. b5 Nxd4 13. cxd4 Nb6 14. a4 Nc4 15. Bd3 Nxd2 16. Kxd2 Bd7 17. Ke3 b6 18. g4 h5 19. Qg1 hxg4 20. Qxg4 Bf8 21. h4 Qe7 22. Rhc1 g6 23. Rc2 Kd8 24. Rac1 Qe8 25. Rc7 Rc8 26. Rxc8+ Bxc8 27. Rc6 Bb7 28. Rc2 Kd7 29. Ng5 Be7 30. Bxg6 Bxg5 31. Qxg5 fxg6 32. f5 Rg8 33. Qh6 Qf7 34. f6 Kd8 35. Kd2 Kd7 36. Rc1 Kd8 37. Qe3 Qf8 38. Qc3 Qb4 39. Qxb4 axb4 40. Rg1 b3 41. Kc3 Bc8 42. Kxb3 Bd7 43. Kb4 Be8 44. Ra1 Kc7 45. a5 Bd7 46. axb6+ Kxb6 47. Ra6+ Kb7 48. Kc5 Rd8 49. Ra2 Rc8+ 50. Kd6 Be8 51. Ke7 g5 52. hxg5 { 1-0 Black resigns. } 1-0

```

AlphaZero plays the king to center 16. Kxd2! in a middle game correctly judging that Black will not be able to take an advantage of it.

It is able to correctly evaluate a piece sacrifice 30. Bxg6! while regular engines are unable to see that they are lost for a number of moves.

32. f5 is quite nice too.

There are other examples such as exchange Sacrifice in Game 3.
> 13 votes

# Answer
It is as easy to jump on a bandwagon saying Alpha-Zero's play is 'more' human than previous computer chess programs as it is to jump on the opposite wagon and say Alpha-Zero's play is entirely 'alien'. It's not clear that Alpha-zero's play is 'more human' especially given our human tendency towards anthropomorphism.

***Chess as a Struggle of the (human) Mind***

But in chess is this tendency true? Magnus Carlsen once spoke about how 'traditional' computers in general lack human creativity saying:

> "Chess is all about the struggle between human minds. That’s what makes it exciting. Computer chess is mechanical, dry and bland. The moves are very strong, of course, but there is no style. If you try to play against a chess computer, not only will you lose with a very high certainty, but you will also be bored in the process.

Magnus Carlsen didn't see evidence of human styles of play in traditional chess computers. So lets examine if Alpha-Zero's recent accomplishment has undone this perspective and moved us towards something more reminiscent of ourselves.

> If by 'human-like' you mean play 'exhibiting behavior more likely to appeal to our sense of anthropomorphism' does Alpha-zero's style seem more human? How do we really test this subjective myopic humans like to project upon non-human things? Lets ask - does the algorithm 'selectively pick better' or exhibit 'more human creative choice' in its style of play?

The algorithm's creators indicate that unlike Stockfish which uses an Alpha-Beta search algorithm, Alpha-Zero employs a Monte-Carlo tree search (MCTS) algorithm which accepts as input a weighted parameters θ built up from previous outcomes ~ Page 3. Mastering Chess and Shogi by Self-Play with a General Reinforcement Learning Algorithm).

So the algorithm doesn't exhibit choice at all. It actually engages in a random but probabilistic Monty-carlo search where the possible search paths available to it are increasingly prejudiced by previous outcomes. Did Alpha-zero choose to optimize its style of play this way or was that the choice of its programmers?

> Does Alpha-zero always have all possible moves available to it for consideration or are some moves prejudiced algorithmically in a way that mimics experience which can be interpreted by humans anthropomorphically?

Initially it had all moves available to it so its 'style' was entirely random. However as it's search is increasingly and optimally constrained by previous success or failure its style is actually changing towards the mode its programmers have shackled it with. Is this 'more human' though? Compare this to Magnus Carlesen who will sometimes choose less optimal moves because they are more creative:

> Magnus Carlsen: “I appreciate creating something unique”

***Chess as a Struggle of the (alien) Mind***

Humans can chose the criteria that drives their own style of play (for example I often chose impulse and error in my own style). Many see Alpha-zero's play in both chess and go as decidedly Alien. Nick Hynes, a grad student at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) observes:

> “What we’re seeing here is a model free from human bias and presuppositions: It can learn whatever it determines is optimal, which may indeed be more nuanced that our own conceptions of the same. It’s like an alien civilization inventing its own mathematics which allows it to do things like time travel...”

Likewise GM Peter Heine Nielsen told Chess.com:

> "After reading the paper but especially seeing the games I thought, well, I always wondered how it would be if a superior species landed on earth and showed us how they play chess. I feel now I know."

It seems that most react to Alpha-zero's emergent style of play as 'alien play', and not as 'more human'.

> Therefore there's reason to disagree with the answers above that say 'yes'.
> 9 votes

# Answer
## This is an incredibly interesting time to be alive.

Chess computers starting from the 1970s have been minimax-tree based search algorithms using alpha-beta pruning. These programs got stronger and stronger both because of advances in computer speed and parallelism and because of improvements in the heuristic eval function used to prune branches and select leaf nodes. But people have long noticed how materialistic and boring computer play is, and many people (myself included) thought it was impossible to encode "human" intuition into software.

*But have you seen these games?*

AlphaZero is exhibiting incredibly beautiful play, including several examples of material sacrifice for long-term positional advantage. This is reminiscent of some of the most beautiful games from human masters, but with unrivaled technical accuracy as well. This is the first example I've seen in my life of something that's **computer-generated and also has deep beauty**.

---

***The Centaur Claim:***

I've heard Garry say this many times, but it's just not true. Or at least, it won't be true any longer with AlphaZero on the scene.

Imagine this: there is a piece sac that has 10,000 relevant continuations, where 5,000 of them are purely tactical (yet mostly unrelated to one another) and another 5,000 that are mostly positional (yet mostly unrelated). How could a human sift through all of these variations without making a mistake? If AlphaZero can now look at these highly creative moves, what contribution could a human possibly make?

---

***The Last Frontier:***

There is one place left where brute-calculation will still beat deep neural nets: endgames. There is no amount of intuition that will beat a tablebase. But the endings that require a tablebase (because a search tree can't go deep enough to just calculate the right move) are pretty rare. And you could just plug a tablebase into AlphaZero, but that would destroy the purity of a "self-taught" engine, right?
> 6 votes

# Answer
Since humans lack ability to search deep, like traditional computer chess programs (fritz, stockfish et al), they create 'strategic principles' or thumb rules (center control, development, king safety) and concepts or tricks that are applicable in vast variety of situations in different ways, such as sacrifice, rooks connected, bishop pair, specific endings e.g how to corner the king with a rook and a pawn.

I think that alpha zero has independently reinvented many such concepts (percepts and concepts) and has also learnt tons of new ones - because its knowledge was not required to be built upon human evaluation functions and the strong minmax search which always assumes the opponent is a genius.

Of course, such principles themselves conflict in some situations, that is why various opening plays and pitfalls are carefully studied - eg don't develop queen too soon.

On the other hand, humans also notice that once you lose one piece (without exchange) you weaken your forces so they are extremely careful not to lose a piece without a compensation.

I think that Alphazero's play has liberated computer chess (and human chess) from the slavish fear of losing small material and overreliance on opening books and piece values.

Alphazero games show things like the 'strategic principles' like center control, development, space, initiative are far more important if your opponent is sloppy. In other words, 'sacrifice' is not really sacrifice but trading off a piece for gain in initiative, position, directed move.

Alphago (not the zero) relied on human evaluation, but alphazero sets up the entire chain of evaluation to 'search or simulation' as a single end to end process and comes up with totally new way of playing.

If you think about it, great masters of the past like Morphy, Fischer, Kasparov have been applauded for typically this kind of -counter-intuitive- play where they are not bounded by written-on-stone evaluation by take advantage of special situations that emerge. I think alpha zero's games have such 'wow' factor to it.

Why neural networks. While computer programs that use symbolic representation and discrete search can only use 'one' way of thinking, neural networks can parallelly process situations with alternate, conflicting evaluations and flip to the more valuable view in later layers.
> 3 votes

# Answer
More human in the sense that the moves it plays seem to coincide more or less with an human approach : play for long-term advantage, positional sacrifices, piece activity. There is an apparent convergence with human chess knowledge and accepted strategic principles refined over the centuries (e.g. it "discovered" many same openings). This is remarkable given the fact that AlphaZero has not been seeded with human-constructed chess knowledge.

But the similarities end here. AlphaZero takes it to the next level and does it better, and in ways humans have never conceived. AlphaZero possesses "superhuman" capabilities to quote the paper : "AlphaZero achieved a superhuman level of play \[...\]" (https://arxiv.org/pdf/1712.01815.pdf). In addition it doesn't have the weaknesses inherents to humans beings: concentration issues, fear, tiredness, feelings, intuition, etc. that limit humans. And its silicon brain allows for tactical combinations beyond human capabilities when necessary.
> 3 votes

# Answer
I want to say thank you to all who have responded to this question, often with subtlety and insight. The chief difference in the responses, it seems to me, is in the interpretation of the word human.

AlphaZero does not play human chess in the sense of oversights and miscalculations, but its "thought" process seem to correspond, in a heightened form, to how I think that most strong players think. You draw up, fairly quickly, a list of "candidate moves" that you would like to play, and for the strongest players this list is amazingly accurate, even playing something like a recognizably sensible game in one minute. The rest of the time is spent on asking, which of the moves on that list really work? Petrosian said that he felt most on form when the move he eventually played was the one he first thought of. We all know how satisfying it is when the move we most wanted to play turns out to be tactically playable. I can relate to the AlphaZero algorithm much more easily than I can to AlphaBeta search, which does not at all resemble what goes on in my head.

What seems most interesting is how the machine was able, by self-play, to recognize the promising candidates. That is where the potential lies for real revolution. I wonder whether this is only possible for domains like chess and go, where the objectives can be clearly defined. But I find it striking that AlphaZero seems to display purposeful play, but Stockfish has no idea what is going on.
> 1 votes

# Answer
The way I understand neural networks, A0's real advantage is its superior evaluation of board positions. This evaluation incorporates both short term tactical knowledge (which in a sense serves as a multiplier of the number of positions examined) and a superior evaluation of strategic value.
> 0 votes

# Answer
One thing I feel the whole discussion has missed is that A0 can play chess, shogi and go, all very well and all from self-training. This is much more human. Furthermore, in go it has revealed deeply new ideas to the top players (as I understand it). Other engines are very task-specific, A0 seems otherwise. I'd like to see it play chess960.
> 0 votes

# Answer
I don't think there is anything 'human' about Alpha. It just used much stronger hardware and played higher quality chess. The good opening moves it finds(for example, to fianchetto king side with Bg2) are fully due to its simulated opening book. Concepts that impressed me and that I have formulated in 'The Secret of Chess': http://davidsmerdon.com/?p=1970 , which Alpha uses for the first time among top engines, are advanced longer chains, for example the d4-e5-f6 chain that trumped a whole piece in the Bg6 sacrifice game, and central backward-makers, as seen in the French Defence games between both engines. Both concepts involve searching to great depths, and probably here Alpha was helped by its tremendous hardware. Otherwise, I see nothing human about its play. Many of the games were, admittedly, beautiful.
> -2 votes

---
Tags: engines, stockfish, elo, alphazero
---


title: Is this endgame position a draw?

text:
# Question
Title: Is this endgame position a draw?
It’s white to move.

```
[FEN "8/8/8/3k3p/3P3K/2P3R1/8/7r w - - 0 1"]

```

I was white, and this was a blitz game which ended up as a draw because I didn't know what to do. My friend and I later analyzed this position, and he suggested that if I had played Rh3! here, then I would've won (of course, if black trades rooks, white wins). But I wasn't convinced, as the trade wasn't forced at all, and judging by the black king's position, I thought black could hold with perfect play (i.e. keep his king where he is, and use rook checks/occupation of the f-file to stop the white king from getting too close to the white pawns). We gave up analyzing after a while, and used an engine to check the position, and it gave +3 to white, which would imply (I think) that there is a forced win. But machines still tend to be wrong, and after my friend played out the line given by Fritz 12, no progress was made by white. The black rook simply occupied the f-file, and the white king couldn't get close to the white pawns.

Is this a draw? If this isn't a draw, how can white win?

# Answer
> 17 votes
Yes, it seems to be drawn. First consider the following variation, but in particular the position after `2.Kxh5` first:

```
[FEN "8/8/8/3k3p/3P3K/2P3R1/8/7r w - - 0 1"]

1.Rh3 Rg1 2.Kxh5 Rg8 3.Rf3 Kc4 4.Kh4 Kd5? 5.Rf5+!

```

Here we don't even need to consult an engine because there is a better oracle to be had. This 6-piece position is covered by existing endgame tablebases, and you can confirm with a query that this is drawn. So we know for a fact that going this `1.Rh3` route leads to a draw. (White could try delaying the pawn capture and making a more productive immediate move, but it doesn't help, and just leads to play like that coming after `1.Kg5`, discussed at the end below.)

As to the idea behind Black's play from here, it is to keep the pawns at bay with the king, and as you intimated in your original post, to use the rook to cutoff the white king as much as possible. It's difficult to say much more about the exact drawing method here, because the play can be very complicated (one reason to love endgames, by the way). To give an idea, consider the position after `4.Kh4`. 10 of Black's possible moves keep the draw (including those that simply move the rook along the g-file), but the perhaps seemingly harmless `4...Kd5?`, putting the king back where it was, is suddenly a loss for Black in 41 moves, *but only if White plays `5.Rf5+!`*, as all other fifth moves again draw. One way to get a good feel for the correct and incorrect play (and for the general notion of how impenetrable optimal play in technical endgames can be) is to toy around with moves at the link I gave above.

White's only other first move option is `1.Kg5`, and it's not too surprising that this draws if winning the h-pawn immediately already draws. It's true that White avoids getting his king cut off on the h-file, but the cost of leaving Black with a distracting outside passed pawn is too high. The point is that the black king and rook can easily stop the pawns if the white king isn't helping out his rook. But now if the white king does try to get involved, say via ideas like `Kf6-e6` and pushing the d-pawn, Black can keep things level because she has her own passed pawn to play with.

# Answer
> 8 votes
While the accepted answer gives the correct evaluation of the position and a useful link, I think it is important to detail a little bit more the strategy in this interesting rook endgame.

First of all, it is important to notice that Black *cannot* keep the white king cut away from the pawns. Offering rook exchanges and hiding behind the white rook, the king will make its way until d2.

```
 [FEN "8/8/8/3k3p/3P3K/2P3R1/8/7r w - - 0 1"]

 1.Rh3 Rg1 2.Kxh5 Rg8 3.Rf3 Kc4 4.Kh4 Rg7 5.Rg3! Rf7 6.Kg4 Rf8 7.Rf3 Rg8 8.Kf4 Rf8! 9.Kg3 (9.Ke3 Re8)  (9.Ke4 Re8! {and the king has to go back}) Rg8 10.Kf2 Re8 11.Re3 Rf8 12.Ke2 Rd8 13.Kd2

```

Actually, if the white king could rather reach the upper part of the board in front of its pawns (say, e5 or d6), he would win, but as shown in the sub-variation above, Black can prevent this with frontal checks since the white rook has to stay on the third rank protecting its pawn on c3.

When the white king reaches d2, White has a strong threat of Re5-c5+, kicking the black king out of its blockading position. To save the draw, Black *must* react and prepare a check on the second rank, grab the Pc3 and reach a well-known KRPKR theoretical endgame:

```
 [FEN "3r4/8/8/8/2kP4/2P1R3/3K4/8 b - - 0 1"]

 1...Rh8! 2.Re5 Rh2! 3.Ke3 (3.Re2 Rh3) Kxc3 4.Rc5 Kb4 5.Rc8 Rh3 6.Ke4 Rh4 7.Ke5 Rh5 8.Kf4 Rh4 9.Ke5 Rh5 10.Kf6 Rd5

```

After 4.Rc5 the black king is cut one file away from the white pawn and White is aiming for a winning Lucena position. There are two possible defenses for Black:

a. frontal checks, which works when the pawn has not crossed the half of the board: Re8-d8-e8 etc harrassing the white king. White can prevent that with 5.Rc8!?

b: lateral checks, which works when the 'long side' of the pawn is available, i.e. when the defensive king is cut on the 'short side': it is the case here, so black can secure the draw by checking from the h-file 5...Rh3 6.Ke4 Rh4 7.Ke5 Rh5 etc. White cannot make any progress.

Thus the king being cut on the short side is the decisive factor. Indeed, if in the starting position we move the central pawns one file to the right, White is totally winning:

```
 [FEN "8/8/8/4k2p/4P2K/3P2R1/8/7r w - - 0 1"]

 1.Rh3 Rg1 2.Kxh5 Rg8 3.Rf3 Kc4 4.Kh4 Kd4 5.Rg3! Rf7 6.Kg4 Rf8 7.Rf3 Rg8 8.Kf4 Rf8 9.Kg3 Rg8 10.Kf2 Re8 11.Ke2 Rh8 12.Rf5! Rh2 13.Kf3 Kxd3 14.Rd5 Kc4 15.Rd8 Rh5 16.Kg4 {The black rook lacks a i-file.} Re5 17.Kf4 Rh5 18.e5 {White progresses and will reach a Lucena position soon.}

```

# Answer
> 5 votes
This is a very late answer, but if you check 7-piece Lomonosov tablebases, it shows the original position is a draw.

Here is a link to the proof.

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


# Question
Title: How do I play the Colle System as white?
I started playing the Colle system as white about 3 months ago. I have played 9 league games with it and lost every one! The sequence of moves that cause me the most problems is 1.d4 d5 2.Nf3 Nf6 (note that black already has two units hitting the vital e4 square) 3.e3 Bf5 4.Bd3 Ne4. This might well be a bad move by black, but I have no idea how to play against it. Trying to dislodge the knight with f2-f3 would entail me having to move my f3-knight again and the pawn move would weaken my kingside.The only plan I use at the moment is to play Nbd2, c3 and Qc2 to force black to exchange. But that gets rid of my important d3-bishop and stymies any notion of continuing with a king-side attack.

# Answer
It would be easier to answer would you show us some of your games where you tried the f3-plan.

5.Ne5 or 5.0-0 aiming for a quick f2-f3 indeed make sense. However, I would argue that the most logical answer is to quit your Colle schemes (after all, Black has a strong grip on e4...) and switch to 5.c4 (or 5.0-0 first, followed by 6.c4)

After 4...Ne4 Black has played twice the same piece and reduced his control of d5. The early development of Bc8 has also left b7 unprotected, which may become a target to a later attack by Qb3.

After the approximative line 5.c4 e6 6.Nc3 (6.Qb3!?, 6.Qc2!?, 6.0-0) c6 7.Qc2 Black cannot maintain his e4-outpost:

7...Bb4 8.0-0

7...Nxc3 8.Bxf5 exf5 9.bxc3 and Black center will collapse to a later cxd5 and c3-c4.

7...Nd6 might be best but Black has lost some time. You can try to exploit this by giving a pawn with 8.Bxf5 Nxf5 9.0-0 followed by e3-e4, or play more conservatively with 8.b3. White must be slightly better.
> 4 votes

# Answer
Bf5 disrupts your plan to play Bd3 and eventually push e4, but it comes at some cost. The b7 square is no longer protected and black's bishop has left the queenside, so that's a good place to focus your attention. You should abandon your c3 plan and play c4 followed by Qb3 and work on the queenside.

Black is essentially playing a reverse London system, and a good plan against that system is to do exactly what I'm suggesting here, but here you're a move up.

Chess is a concrete game and a good player must be flexible. Black has pre-empted your original plan, but all moves leave a weakness somewhere and you should always look to see if it's something you can exploit.

Stubbornly sticking to a plan that has already been countered will lead to the sort of frustration and poor results that you say you've been experiencing. Instead use it as an opportunity. He's taken something away, but what has he given you in return?

Consider the analogy of an army with the task of seizing a castle. You have a plan of storming the front gate. When you arrive at the castle, however, you see that they have relocated most of their defenders to shore up the front. Would you just shrug your shoulders and continue with your plan, or would you think "If they've increased their presence here then the other side of the castle must be weak, so maybe I should change my plan and attack there instead."?
> 4 votes

---
Tags: opening, colle-system
---


# Question
Title: Why are these weak squares important in this situation?
I'm watching a video on weak/strong squares. I think that I understand the concept, but not exactly why they are important in this game (Carlsen-Karjakin):

The video explains how Carlsen maneuvered to outnumber Karjakin in number of pieces that can go into those squares. This includes exchanging his two bishops for Karjakin's two knights, in a game that a result of these changes, is opening.

My question is, why are these two squares so important? Specially `b5` is quite far from both sides' kings.

PS: Carlsen indeed moves his knight to `b5` later on.

# Answer
> 10 votes
The final position is a very typical position of **weak bishop against strong knight**.

The knight has good outposts on d5 and b5, where it is supported/protected by white pawns and cannot be challenged by any black pieces unless black sacrifices an exchange (rook for knight). Also the white knight is very mobile and can basically go wherever it wants.

In contrast, black's bishop is very passive and bound to the protection of the d6 pawn. It is hindered in activity by its own pawns and cannot attack any white pawn (because most all of them and all relevant ones are on light squares).

Furthermore black has very weak pawns which are relatively easy to attack/win. Of course care needs to be taken, because black occupies the only open file, but other than that only white has winning chances.

> My question is, why are these two squares so important? Specially b5 is quite far from both sides' kings.

The kings are both relatively safe and don't matter in this position. Basically to repeat what I wrote above: b5 and d5 are important because:

* white can put a **protected** knight there which **can not be challenged** (unless black sacrifices material
* if there is a knight on d5 or b5 it not only covers lots of squares, but also attacks the weak pawns (b6, d6, f4)
* thanks to the knight and white pawns on c4 and e4, black cannot exchange his weak pawns on b6 and d6
* the knight on b5 or d5 is very mobile and can easily move in case it is needed somewhere else

So the point/plan for white as stated in the video is to leave black with his weakest minor piece and conserve a white knight to take advantage of these weak squares.

Similar ideas appear in some lines of the Sicilian Najdorf, where white sometimes manages to exchange a dark squared bishop on f6 for a black knight, thereby reducing the number of black pieces that can cover the typical Najdorf hole (weak square on d5), while remaining with two knights and a light squared bishop all of which can take advantage of the weak light squares.

---
Tags: analysis, strategy, positional-play, carlsen, karjakin
---


title: Notes on Chess Piece Class

text:
# Question
Title: Notes on Chess Piece Class
I have following this tutorial http://www.chessbin.com/post/Chess-Piece-Representation to build simple chess engine right now .

at the very first step of Chess Piece Class there are many things confuse me.

why do we need many values to evaluate a chess piece for example :

pieceValue , pieceActionValue, AttackingValue, DefendingValue.

and is there any standard numerical values for evaluating chess pieces ?

Thanks

# Answer
> 1 votes
Chess engine algorithms are implementation dependent, thus there is no such thing as "standard numerical values". Unfortunately, you will need to come up with your own values. However, you can apply some common sense such as the piece value for a queen must be higher than a rook. If you're confused, please take a look at the TSCP source code. It's a very simple chess engine.

Everything you mention is standard in chess. When you play chess, you do look the attacking/defending pieces, right?

Please take a read on:

Modern chess engines such as Stockfish has **many** more evaluation terms. The difficulty in coding a evaluation function is the main motivation for machine learning (neural networks).

---
Tags: engines
---


# Question
Title: How do you 'calculate' compensation in chess
Here is another very difficult subject for me that I can't even begin to understand \[ incidentally, although I've been playing chess for over 50 years, my current ELO rating is only 1300, hence these questions.\]

The idea of 'compensation' comes up all the time in master games.

* How do you calculate it?
* It seems to be a comparison between material and position. But what positional element is the material equivalent of a pawn; the exchange; a piece; even the queen?
* Can the idea of compensation even be adequately quantified at all?
Given a position where, for example, one player sacrify a pawn to improve the position of a knight, would two GM's, say, Carlson and Giri, even agree as to whether the player has adequate compensation for the pawn, given their vastly different playing styles?

# Answer
> 1 votes
**Introduction:**

Your goal in the chess game, is to win. Having more *points* is good, only when it helps you win the game (e.g. check-mate your opponent) If sacrificing material improve your chances to win the game, then it is the right thing to do.

Compensation in Wikipedia

**Compensation includes:**

* Better pawn structure.
* The "two bishops", which refers to having bishops of both colors while your opponent does not. Almost all modern players consider having both bishops as an advantage, although historically there has been great debate as to how much of an advantage they constitute. The two bishops are most likely to show their power in the endgame.
* Better piece activity and/or better development (common in gambits).
* Having the enemy king open to future attack, either due to a loss of pawn cover or being trapped in the center of the board is often excellent compensation.
* Passed pawns are often decisive in the endgame.
* Connected and/or protected passed pawns are even more deadly.
* Control over key squares, diagonals, files, or ranks.

**Summary:**

There are several types of compensation.
The answer to *Is the sacrifice worth the compensation?* might depend on two factors:

* Is the compensation very straight forwards? (if so - it is clear to be good)
* The specific player profile (e.g. some players prefer open positions, and some closed positions) - if the new position after the sacrifice will be more suitable for the player - he'll have clear plan how to continue/win

---
Tags: theory, sacrifice
---


# Question
Title: Longest opening variation that you can memorize?
What is the longest opening line or variation, starting from the first move, that you memorized?

# Answer
> 2 votes
As black Sicilian Dragon 1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 g6 I don’t care to do more since at that point many variations can diverge heavily, but I expect 6. Be3 Before fianchettoing my bishop.

As white Ruy Lopez, Rio Gambit line 1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Nxe4 5. Re1 Nd6 6. Nxe5 Nxe5 7. Rxe5+ Be7 8. Bf1 This is just a fun one

And generally since there wasn’t any obvious objective a few things to add if you were looking for data or a suggestion (even though there is a high chance you out rank me)

• English Opening and King’s Indian are very powerful opening I plan on studying due to the success of AlphaZero

•Learning gambits are great for improving your ability to calculate attacks and general aggressive intuition

•My favorite way to practice openings is with friends or against Stockfish ai on Arena chess since you get similar variations, particularly I’ve found ~2200 range to be great for popular Sicilian lines

•Mainstream opening traps aren’t worth it to study (unless to avoid) since those situations are so well known they are often avoided, some obscure ones like when Bobby Fischer coined his famed opening trap

---

I believe it’s better to study opening theory as opposed to specific lines since it provides a stronger, flexible ideology for how to open, and with thousands of games it’s fairly common to remember them anyways

---
Tags: opening
---


title: What is 'space' on a chessboard?

text:
# Question
Title: What is 'space' on a chessboard?
I know, I know, this sounds like a ridiculous question, but bear with me.

As an example of my lack of understanding, let's take the advanced variation of the French defense.

```
 [title "Advanced variation of the French Defense"]
 [fen ""]

 1.e4 e6 2.d4 d5 3.e5

```

The opening books say something like "white advances their e-pawn to *gain space* in the center". Now, try as I might, I simply can't see where the extra space is that white has gained!

They can't use the `f6` square or the `e6` square as these are covered by pawns, knight and bishop. They can't use the `e4` square as that is covered by black's `e5` pawn. So where on earth is the *extra space* that white is supposed to have gained?

# Answer
It's not a ridiculous question. Before discussing your precise example, let's cover some basic grounds:

* Purely from an optimal play perspective: having more space translates into having more activity and thus more options for your pieces, and that's really the key point here. The more space your pawn structure provides, the more maneuvering possibilities you will have to re-route your pieces around the board to ever more optimal posts. Moreover, controlling more space also means eyeballing or covering your opponent's important squares, related to concepts such as "dark/light square control" in chess strategy. So it's really about the relative amount of space both sides control. For a trivial example, go to very basic cases, such as first moves, `1.e4`: what is the point very naively speaking? Not only it activates some of your pieces, but it also potentially takes away options from black, namely, it stops black from establishing a pawn on either `d5` or `f5,` therefore we say white is a tempo up, because it gets the first say in space control and thus partially dictates the types of subsequent positions.
* As for general ways of defining it, not necessarily restricted to optimal play in chess strategy, you can e.g., define space in terms of the number of possible legal moves you have, or the number of squares that are under attack by your pieces, so on and so forth, all compared to the other side.

Your position:

```
 [title "French defense example:"]
 [Fen "rnbqkbnr/ppp2ppp/4p3/3pP3/3P4/8/PPP2PPP/RNBQKBNR b KQkq - 0 3"]

```

In your example, there are very clear differences in terms of piece-activity thanks to the advanced white pawns on `d4` and `e5` in contrast to black's lesser advanced central pawns of `e6` and `d5`:

* white has activated both bishops, whereas black's `c8` bishop is facing a wall.
* white has enabled both knights to be posted centrally on `c3` and `f3`, whereas black's `f6` square has been taken away, so the knight is bound to go via the `e7` square, but you have both options of `f3` and `e2`!
* white's queen has a total of `6` legal possible moves at its disposal, black's queen is restricted to only `3!` Specially `Qf3`, `Qd3` and `Qg4` all very useful and common moves for the queen, all of which are symmetrically impossible for black, because of the lesser space created by the central pawns (which in turn also disabled the `c8` bishop in taking away the `g4` square from white's queen!)
* Last but not least, although both sides have committed to their central `e` and `d` pawns, black's prospect are further limited by the fact that in order to eventually create healthy space for their pieces, they're forced to undermine white's pawn chain with `f6` at some point. Meaning black's further pawn development is also being limited here, but white's are not.

Now all is not lost, because space alone doesn't dictate the outcome of the game and all still depends on how you decide to use that space, but the moral here is that having more **space** means having more **choices**, both in terms of possible **moves** *and* possible **strategies** to pursue.
> 22 votes

# Answer
Two things could be meant by space:

1. White has more space (basically one row more than black) to maneuver his own pieces **behind** his pawns, let's say around d2, e2, d3, e3. Compare this to black who has very little "space" at this point of the opening.
2. While's pawns on d4 and e5 attack squares in the opponent's half of the board, particularly the pawn on e5 limits the development options for black.
> 4 votes

# Answer
Look at the ranks. The player with the pawn on "x" rank has "x" amounts of space.

For example, in the French, Advance variation (1. e4 e6 2. d4 d5 3. e5) White has five ranks of central space, whereas Black has four.

White therefore has more central space in this position. Black's plan is to undermine this center so he can re-claim the space and induce weaknesses in White's position.
> 3 votes

# Answer
As a quick and dirty definition and to sum up the above written:

**The player who has more possible moves when being on his turn than his opponent has more "space". The larger the difference, the more significant is his "space advantage".**

*If "space" (as possible, so legal, moves) equals zero for one player, he lost the game when in check at the same time, otherwise (no check) the game is a draw by stalemate. If a players has only one possible move it is "Zugzwang".*
> 1 votes

# Answer
Consider the situation before and after **3.e5**.

Before this move, White has the squares e2, e3, d2 and d3 where he can put his pieces safely behind his pawns, and Black has e7, d7 and d6, so White has one more "safe" square than Black.

After the move, White still has the same four squares (as you point out in the question, e4 isn't a safe square) but Black only has e7 and d7. Perhaps you'd prefer to say that Black has lost space but White now has two more "safe" squares than Black, so he has gained space relative to Black.
> 1 votes

---
Tags: opening, strategy, theory, space
---


# Question
Title: Is it possible for stockfish to tell that mate is in X moves, when mate is in X + Y moves?
I know that it is possible for a chess engine to evaluate a position as mate in X moves, when in fact there exist a mate in smaller number of moves. But can the reverse situation happen?

For example the engine evaluated a position as mate in 8 moves, but actually the best possible mate is in 9 moves (or 10 or 13).

To be more concrete the engine is stockfish.

# Answer
> 2 votes
No, it isn't possible because, before Stockfish says it is Mate in 8, it views the position from the aspect of the losing side, i.e, the evaluation is the best that can be obtained by the losing side.

In other words, Mate in 8 is what happens if the losing side plays the possibly best defense. If the losing side plays sub-optimally, it could lose faster, but 8 moves is the longest possible postponement of Checkmate

---
Tags: engines, stockfish
---


# Question
Title: Weakest player to ever beat the mature Bobby Fischer?
Who was the weakest player to ever beat the mature Bobby Fischer in a tournament or match game? I understand that it's a bit hard to define the "mature" Fischer indeed, since he was incredibly strong even as a teenager, but I mean roughly, let's say, from the early 1960s on, e.g. not counting his very early years.

# Answer
> 9 votes
**Summary**:

Cesar Munoz from Ecuador is the last untitled player to beat Fischer, in 1961. Kovacevic is the last non-grandmaster to do that in 1970, but obviously he was already very strong. Janosevic in 1967 was a grandmaster but not the most famous of them. And Spassky in 1992 was not *that* strong anymore...

**Detailed answer**:

From 1960 onwards, Bobby Fischer lost 100 chess games that are registered here.

You can browse this list to pick whom you consider "the weakest" winner. About a half of the games were played in simultaneous displays so they don't qualify as *tournament or match game*s. The answer might also depends whether you include blitz and rapid tournaments.

Fischer lost a couple of games to non-grandmasters in 1960 (IM Bernardo Wexler) and 1961 (Cesar Munoz, *The unknown Ecuadorian caused a sensation in the preliminaries of the Leipzig Olympiad when he beat Bobby Fischer.*), but if we limit ourselves to 1963 onwards, my suggested answer would be Dragoljub Janosevic in Skopje, 1967. It seems any other person who beat Fischer after 1963 was a world-class grandmaster (technically Kovacevic was still an IM in 1970 when he beat Bobby Fischer in Bled, but he was already of GM-strength).

Since Janosevic was a (less famous) grandmaster not far from his peak in 1967 who also won games against Tal, Petrosian, Larsen, Bronstein and an aging Botvinnik, there is also an argument to be made that the weakest person to beat the mature Fischer would actually be former world champion Boris Spassky in Belgrade, 1992, when his level of play had already gone down.

---
Tags: tournament, fischer
---


title: Stockfish crashes on fen string

text:
# Question
Title: Stockfish crashes on fen string
I have created a GUI that communicates with a Stockfish 8 engine by passing it a FEN string. Everything works nice but on some specific FEN strings, Stockfish crashes. I don't have any clue why...

One of the FEN strings on which Stockfish crashes is

```
r2k1b1r/pp4p1/4QnPp/3p1B1P/2pPp3/3qP2N/5PKR/3nB3 b KQkq - 0 1

```

# Answer
> 2 votes
Very simple, your FEN is absolutely invalid. You shouldn't give castling rights in a position that you kings have already moved. This won't work.

---
Tags: stockfish
---


title: Is Nc6 good response to c3 Sicilian?

text:
# Question
Title: Is Nc6 good response to c3 Sicilian?
I used it sometimes and when I read about c3 Sicilian I found out that it isn't a good response to c3, why ? It seems like you develope a piece and add pressure on d4. I thought about it as good move. Thanks in advance.

# Answer
> 2 votes
I'm assuming you mean 2 c3 Nc6. It's helpful to give specific moves or positions.

If you do mean 2.. Nc6, historically white has been very successful with the natural (and stockfish-recommended) 3 d4.

In the LiChess masters database, for example, it shows that after d4 white has won a whopping 48% of the time while losing only 18%.

From looking through the top games in that database, black's pressure on d4 is insufficient and the knight ends up being misplaced on c6, with white typically using it as a tactical target with a later Bb5 as black attempts to untangle his position.

# Answer
> 3 votes
With 1. e4 c5 2. c3 white is aiming to create a strong center with pawns on e4 and d4 (after capture cxd4 cxd4).

2. ... Nc6 does not prevent white from playing d4 and the knight on c6 might later be kicked away by white playing d5. In any case after 1. e4 c5 2. c3 Nc6 3. d4 cxd4 4. cxd4 white occupies the center and is ready to develop his bishops. Black on the other hand is not fighting much for the center yet and still needs to make space for his bishops..

More principled replies to 2. c3 are 2.... Nf6 or d5 that take advantage of the fact that white cannot develop his knight to c3 anymore.

After 2... d5 3. exd5 Qxd5 black has a centralized queen which is not easy to attack (because c3 is played) and the game might develop into a typical isolated queen pawn game. If white choses to play 2...d5 3. e5, black gets a better version of the advance French, where the bishop on c8 is not blocked by a pawn on e6 yet.

After 2... Nf6 the game typically continues 3. e5 Nd5 where white gets a pawn chain on dark squares similar to the French, but black has an easy game attacking the chain with d6, Nc6.... and developing naturally. The same positions can also result from the Morra gambit.

Another option is to play 2.... e6 which might very well transfer into the French defense (but that's likely not something you are happy with if you are a Sicilian player).

---
Tags: sicilian-defense
---


# Question
Title: What move is better in this position, Ke7 or g6?
1.e4 e5 2.Nf3 f6 3.Nxe5 fxe5 4.Qh5 And in this position what move for black is better, Ke7 or g6 ? I know that such position will never occur in game between good players because after Nxe5, fxe5 is bad move because of the queen attack. But on one of YouTube chess channels in this position move g6 was said is better, but there wasn't explanation, is it so and why ?

# Answer
4...g6 is technically better, because it only loses a rook at once due to 5.Qxe5 Qe7 6.Qxh8, leaving White with a winning position, while after 4...Ke7 5.Qxe5 Kf7 6.Bc4+ Black will have to give even more material to postpone checkmate: 6...d5 7.Bxd5 Kg6 8.Bxb7 Bxb7 9.Qf5 Kh6 10.d4 g5 11.h4 +-

As said by the OP, 2...f6? and 3...fxe5? are the bad moves in this line.
> 2 votes

---
Tags: opening, opening-traps
---


# Question
Title: White to play and checkmate in two moves
It’s White to play and checkmate in two moves.

This puzzle was created by Frank Healey, and published in 5 Family Herald on 7/17/1858.

```
7R/1B1N4/8/3r4/1K2k3/8/5Q2/8 w - - 0 1

```

# Answer
Use the fact that the rook is pinned, and that the king has few squares left; I'm thinking that 1.Rd8 Kd3 (only possible move) 2.Nc5# should be the solution.

```
[White "NN"]
[Black "NN"]
[FEN "7R/1B1N4/8/3r4/1K2k3/8/5Q2/8 w - - 0 1"]

1.Rd8 Kd3 2.Nc5#

```
> 35 votes

# Answer
Black is not in check, but still only has one move:

Check mate.
> 3 votes

# Answer
Move the rook onto the same row as the king, king moves to the only possible square, checkmate by moving the bishop to a6?

1. Rh4, Kd3 2. Ba6#
> 0 votes

---
Tags: problems
---


# Question
Title: Should you state your rating if you want to play in a simul?
Gary Kasparov complains in Johannesburg simultaneous exhibition

Is Gary right to be angry? Should you state the rating while playing in a simul? Isn't simul supposed to be a fun place where everyone gets to play their favorite player? Are there such rules in simul?

# Answer
> 7 votes
First off, Kasparov is not a big fan of losing. That's an important detail. I wont weigh in too much on his personality, but if you look at the comments on that video, there are quite a few strong opinions about what kind of person he is.

I don't know what the rules were for that simul, but if they were the same as the Kasparov's current website:

> Players must be true amateurs who have 1999 ELO points or less, no exceptions. No player who has ever held a Rating of 2000 or over is permitted--it is contrary to the spirit of the simul and to the agreement. No coaching or computer assistance is permitted.

So if the organizers in Johannesburg were operating under these rules, then indeed they were out of line.

If you watch the whole thing, it looks like the under 2000 rule may not have been in place back then, but he did specifically ask the coordinators to tell him who the strongest player was. It appears they did not take into account a coach helping these players during the simul, and so they pointed elsewhere.

In some sense, it does make sense. At the GM level, you are always playing to your opponent. You have to know something about them. He was playing on assumptions about the capabilities of his opponent, and those assumptions turned out to be false.

On the other hand, you are right about this event being something that's supposed to be fun. I know I generally agree with it, but not everyone does. Kasparov does seem to care that a player can walk away claiming "I beat Kasparov" when Kasparov was not playing his best at the time. Instead, he was playing a version of Kasparov designed to do "something else," whether that's saving time for other boards or trying to teach the amateurs something about chess. We don't know what his purpose for being at the event was, but we do know he values his name and he values his record.

---
Tags: simultaneous
---


# Question
Title: Simltaneous checkmate and draw claim on the 50th move
This question is for aspiring rules lawyers.

The FIDE's new laws of chess, effective Jan. 1, 2018, patch ambiguities and other subtle problems. I like the new laws. When it comes to game mechanics, I hope that the new laws remain permanently, so may I now ask a totally pedantic technical question regarding a ridiculous but (as far as I know) legal situation?

Under the new laws, suppose that

* you have made 50 moves since the last pawn move or capture,
* I have made 49 moves since the last pawn move or capture, and
* it is my turn to move.

Suppose that my 50th move checkmates you. Ridiculously however, suppose that—simultaneous with my move—I claim a 50-move draw. Do I read the laws right: this game is a draw?

Before answering, you might compare law 9.3.1 against law 9.6.2. The new laws are more carefully worded than the old laws were, so I am unsure that the effect in question is a mere unintentional artifact of unfortunate wording. I *suspect* that the effect might be deliberate, rather.

Can you shed any light in the matter?

Of course, I am not asking why a checkmating player would choose to waive the checkmate in favor of a draw, but am only probing an odd corner of the laws' logic.

See also this related question and answer from before the recent changes in the laws.

**UPDATE**

It turns out that my question is a duplicate of the linked question, if you look at it the right way. Morever, an answer to the linked question quotes Geurt Gijssen, an authoritative source. Gijssen answers the question indirectly by answering the inverse question. If I read Gijssen correctly, then a player can indeed claim a 50-move draw while checkmating, *and in that case the draw claim would take precedence.*

Weird, eh?

One could question the relevance of Gijssen's comments, since Gijssen (if I recall) retired before the most recent revision cycle, except that the revision seems to come to address questions Gijssen himself had considered or raised.

This sort of question is interesting if one is, for example, programming a computer interface for online chess play, for the programmer must implement the law in question the one way or the other. Just leaving it ambiguous would probably not be a reasonable option in that context.

I also note that players reading the rule in this very question thread are reaching opposite conclusions regarding the rule's meaning in the present case. Academic questions like this can be significant from a rules-logical perspective (as anyone who has programmed game rules into a computer might verify), even if the situation the question targets might never arise during over-the-board play. No game rule *wishes* players to reach opposite conclusions regarding its meaning, does it?

Two computer programs with different understandings of the rules might deadlock, if set to play one another, for example.

**FURTHER UPDATE**

The answers have been really interesting, at least to me.

An actual arbiter in this thread has now persuaded me to the opposite conclusion. He has persuaded me that the checkmate would take precedence, after all.

Unfortunately, one probably cannot but conclude that the rule is ambiguous in the sense that the rule evidently supports reasonable, experienced players to reach opposite conclusions regarding the rule's meaning in this instance.

# Answer
> 5 votes
I would let the checkmate stand but the true answer is that it does not matter. The player has the right to offer a draw at any time and the claim according to article 9.3 is also a draw offer. You are concerned with a peculiar situation where player A wants a draw and does not want to win, for whatever reason, while player B does not want to draw (even at the cost of a loss). Therefore, the question you really ask is whether claiming a draw according to article 9.3, if the intended move delivers a checkmate, can secure you the draw. Abstracting away from the possibility that you can choose any other legal move and claim on that basis, the answer to that question is that yes, there is a way.

You can claim the draw as you proposed and if the arbiter rejects the claim because the checkmate stands then you simply let your time run out and the game is a draw because the opponent cannot checkmate you by any series of legal moves. This is since you have committed to play the checkmating move thus there is no way how the opponent could checkmate you as they are going to be checkmated on next move. A catch is that not all arbiters may be comfortable with this interpretation and they may declare the game lost for you even though they shouldn't. But this situation will never happen anyway, right? It is purely of academic interest.

I would let the checkmate stand for two reasons.

1. Consider this variation on your question, you claim the draw as you proposed but the intended move does not deliver a checkmate but rather captures a pawn. Again, as you point out, the move has not yet been made, hence, the pawn is never captured. Still the claim should be rejected. To assess the validity of the claim you need to consider the position as if the move had been played. I would apply this reasoning to the checkmate situation. If there is a checkmate after the intended 50th move, the validity of the claim cannot be assessed since the game will have finished. Of course, you can choose another move and claim the draw.
2. Article 9.6.2 explicitly says that the checkmate takes precedence, therefore, I would apply it to article 9.3.1 too (not 9.3.2 since the game would have already finished once the checkmate is on the board). The crux is whether article 9.3.1 omits to mention this precedence intentionally. If this was so then what would the intention be? The intention would have to be to allow the player to secure a draw instead of the win and this is pointless as I explained earlier. Therefore, this difference in the wordings is not intentional, in fact, article 9.3.1 does not require it while article 9.6.2 does. In the situation described in 9.6.2 the player does not have the option not to claim, the amendment protects the stronger player here.

It does not really matter though. Imagine 50 moves without a capture or moving a pawn have already been played. Then the player can either claim according to 9.3.1 as you proposed or they can claim according to 9.3.2 even though they could deliver a checkmate next move. In the latter case it is an unambiguous draw. It does not make much sense to obtain to different results depending on which way you claim the same thing (yes, I am undermining my earlier arguments) but either way you get something out of it that does not make much sense. But again, no one forces you to claim a draw with a checkmating move. In fact, this may trigger a punishment according to article 12.9 for putting chess in disrepute.

I am afraid you misunderstand Geurt Gijssen's answer. He did not answer your question at all, he said that the player having the move would not make the claim, because it does not make sense, and the opponent is not allowed to make the claim, because it is not their move. It does not follow from his answer that he would agree with the claim if the player really made it.

# Answer
> 8 votes
The Laws of Chess say:

> 9.3 The game is drawn, upon a correct claim by the player having the move, if
>
> a) he writes his move on his scoresheet and declares to the arbiter his intention to make this move, which shall result in the last 50 moves having been made by each player without the movement of any pawn and without any capture, or
>
> b) the last 50 consecutive moves have been made by each player without the movement of any pawn and without any capture.

So you don't claim the draw WHILE you checkmate but BEFORE you make the checkmate move. Therefore there is no checkmate, but the game is drawn.

If you don't claim the draw but execute your checkmate move, your opponent cannot claim a draw by 9.3.b) because the game is finished by your checkmate.

# Answer
> 3 votes
It appears that 1.4.2 and 5.1.1 on that page would take precedence.

> 1.4.2 The opponent whose king has been checkmated has lost the game.
>
> 5.1.1 The game is won by the player who has checkmated his opponent’s king. This immediately ends the game, provided that the move producing the checkmate position was in accordance with Article 3 and Articles 4.2 – 4.7.

---
Tags: fide, 50-move-rule
---


title: Does checkmate over ride 50-move rule?

text:
# Question
Title: Does checkmate over ride 50-move rule?
If a move reaches the 50-move rule and gives checkmate at the same time, does the checkmate take priority over the draw?

# Answer
Checkmate overrides the 50 move rule.

Fide Handbook Article 9.3:

> The game is drawn, upon a correct claim by a player having the move, if:
>
> a. he writes his move, which cannot be changed, on his scoresheet and declares to the arbiter his intention to make this move which will result in the last 50 moves by each player having been made without the movement of any pawn and without any capture, or
>
> b. the last 50 moves by each playerhave been completed without the movement of any pawn and without any capture.

The player making the move that mates could claim a, but he of course won't do it because he is about to win. The player losing *does not have the move* after the checkmate, so he cannot claim the draw.

This interpretation is also confirmed by Geurt Gijssen, in his column An Arbiter's Notebook from 2006:

> Regarding your remark about the 50-move rule: only the player on move is entitled to claim a draw, but he is not forced to claim it. So if the 50th move produces checkmate – the checkmate stands.
> 15 votes

# Answer
You are allowed to make 50 moves to achieve mate.

If you make 51 moves, your opponent can claim a draw.

You do not make a move to create the move violation, if you have not mated or otherwise ended the game before 50 moves have been made, the player on move may claim a draw.
> 1 votes

# Answer
The FIDE later updated the laws, after which a duplicate question was inadvertently asked (by me) on this site. The answers to the duplicate are interesting, considerate and *contradictory.*

This suggests that, unfortunately, there may exist no common understanding as to what the rule in question actually means.

The irony is that players with opposite interpretations of the rule can perhaps agree that the answer you are now reading were wrong, insofar as each opposite player believes the rule in question to be unambiguous, but unambiguous in opposite ways!
> 1 votes

---
Tags: rules, checkmate, draw, 50-move-rule
---


title: How is this scenario a draw?

text:
# Question
Title: How is this scenario a draw?
Firstly, I'm very very bad at chess. I've known *how* to play for most of my life, but I've never been good, so I'm trying to get good by playing against easy computers.

I commonly end in draws with situations like the following:

```
3k4/8/1N6/2P2Q2/4R3/R5B1/P3K1P1/5B2 w - - 0 1

```

I'm *really* not convinced this is a real draw. I have both Rooks and my Queen left, so I should be able to box the King in easily. But maybe I'm wrong, maybe it's impossible for me to win.

So if I'm wrong, I'd like to know why. If not, why does the computer consider this a draw?

# Answer
> 15 votes
With black to move, he is not in check but he also has no legal moves. There is no square where his king can go without putting himself in check, and that would be an illegal move.

That situation is called **stalemate** (Wikipedia), and it is an immediate draw by the rules of the game. You've boxed him in too well.

As to why stalemate is a draw see Why is stalemate a draw? , and there are also a lot of further questions if you search the site for "stalemate".

---
Tags: learning, draw
---


# Question
Title: Is a forced draw by 50 moves possible with Bishop and Knight endgame?
Except for the variations where there is a capture or fork possible for the defending side, is a position possible where this kind of endgame will last more than 50 moves? Is somewhere a calculation in moves done what is the worst possible situation?

# Answer
> 8 votes
It takes at most 33 moves to win this endgame from any position (excluding positions where bishop or knight can be captured). See https://en.wikipedia.org/wiki/Bishop\_and\_knight\_checkmate and references there.

So, no, a forced draw is not possible in this endgame. However if the defending side is playing perfectly (e.g. an engine with tablebase), it could be very hard to win this for a human within 50 moves if you start from one of those 33-moves-to-mate positions.

---
Tags: endgame, knight-endgame, 50-move-rule, bishop-endgame
---


# Question
Title: What are the most common squares to be overworked?
Generally are there any distinguishable patterns you look find in the opening that you recognize as weak, or exploitable. Or generally any openings that provide the over-bearing sense of duty on a piece?

# Answer
Prior to castling, f2/f7 are the most exploitable squares in the game, because they are defended by only one piece: the king. That's why so many king-stuck-in-the-center games are rounded off by a piece sacrificing itself on those squares.

On the queenside, the c2 and c7 squares also have problems, because of a tactical sequence like this:

```
1. Bf1-b5+ Qb6xb5
2. Nd5-c7 (forking the queen with either a king on e8, or a rook on a8)

```

But these tactics happen less often than tactics on f2-f7, because the queen is usually a better defender than the king.
> 1 votes

# Answer
In the French Defense, Tarrash variation, \`1.e4,e6 2.d4,d5 3.Nd2, Nf6 4.e5,Nfd7 White must carefully guard d4 and e5 as Black will play c5, & Nc6, & possibly Qb6. One scheme for White is Bd3 & Ndf3 & Ne2 & c3 (not necessarily in that order) & be willing to play ef6 if Black plays f6 (which can result in a weak Black pawn on e6).
> 0 votes

---
Tags: positional-play
---


title: Jaenisch/Schliemann Gambit

text:
# Question
Title: Jaenisch/Schliemann Gambit
Is the Jaenisch/Schliemann Gambit being played or it has become out of fashion?

PS: I am a club player (FIDE ~1800) and occasionally use it to success.

# Answer
It depends what level you're talking about. At the top level with super GMs, it's more or less out of fashion in serious games. They either choose the Berlin or some other main line (like the Closed Spanish).

In the -2000 section though, it's still a viable opening. If you know it well enough then it's a good weapon to catch your opponents off guard. I would recommend learning another line to play against the Spanish though, so that you can alternate between it and the Jaenisch. If someone were to spend a serious amount of time preparing for you, they could cause some problems. If you have multiple lines though, it makes preparation much more difficult.

I looked up the Jaenisch's stats in the Mega Database, and it actually stores fairly well. White only scores slightly over 50%, and this is a normal stat for most main lines. Also, some top level guys have played it before (Aronian, Radjabov, Carlsen, Ivanchuk). While they don't play it regularly, it's still a testimony to the viability of the Jaenisch.
> 3 votes

# Answer
I'm not sure how many times it needs to be played by players of what caliber in what period of time to be considered "in fashion", but chess.com's database shows one game in 2017 where this was played and both players were rated over 2500. For 2016 it shows ten such games, including several 2700-level games.
> 1 votes

---
Tags: opening, gambits, ruy-lopez
---


# Question
Title: What if White declines the Volga Gambit?
```
rnbq1rk1/p3ppbp/3p1np1/1ppP4/2P2B2/2N2N1P/PP2PPP1/R2QKB1R b KQ - 0 8

```

In the above position, Black gets a solid initiative and easy play on the weak White queenside pawns after `1.cxb5 (1. Nxb5? Ne4!)`.

But White can decline with `1.e3`, intending `2.Be2`, `3.O-O`. Should Black respond with `1...Nbd7`, waiting for White to take the pawn?

# Answer
> 4 votes
The position you've shown looks at first glance to be a poor side-line of the Benko (Volga) gambit for white, both the timing of `h3` and `Nc3` seem out of place. For instance let's reach that position (somewhat sensibly) by the following line: (annotated)

```
 [title "A path to OP's Benko gambit sideline"]
 [fen ""]
 1.d4 Nf6 2.c4 c5 3.d5 b5 4.Nf3 g6 5.Bf4 Bg7 6.h3 {h3 is well unnecessary here, in Benko the c8 bishop doesn't target the g4 square anyway, and if the f6 knight wants to re-route to e5 it doesn't have to go via g4, but d7. Thus, h3 is a waste of a tempo when white is already behind in development} (6.Nbd2 O-O 7.e4 {is much more to the point if you don't want to accept the gambit}) (6.e3 {yet another possibility, Nbd2 Be2 O-O are in queue unless black does something active} d6 {black cannot allow d6}) d6 7.Nc3 O-O 8.e3 {this is your suggestion: it doesn't really work here as you c3 knight is misplaced if you don't want to accept the gambit, now b4 comes with a tempo and your knight will end up either on the rim or hindering your own pieces} (8.Nxb5 {seems to be the most sensible choice, not damaging your pawn structure and not offering black to play a6 getting rid of its weak pawn and activating the bishop via a6-f1 diagonal.} Ne4 9.Nd2 {Not giving black chance to take on b2} Qa5 {pinning the knight and preventing Nc3 and preparing to take on b2 again} 10.Qc2 {sure visually it doesn't look great for white, but we're holding for the moment.}) (8.cxb5 a6 {accepts the gambit again but allows for the usual follow-up with a6-bxa6-Qb6 etc}) b4 {when the knight is on d2, b4 is less dangerous because you'll still be able to challenge it with a3 in time} 9.Ne2 Ne4 {g7 bishop alone is dominating the position, white lacks in development and dark square control, without any real other compensation to speak of} 10.Nd2 Nxd2 11.Qxd2 a5 {I think at this point black's advantage is quite clear.}

```

To conclude the above analysis in short key takeaways:

* This is generally not a desirable Benko line for white. `6.h3` seems well out of place, white should be pushing to complete development (so that you can quickly start challenging black's queen-side or creating play in the center, none of which is possible with your king still on `e1`.)
* `7.Nc3` is not the way to go if you don't want to accept the gambit, you're allowing `b4` without any repercussions for black, and your knight will be mis-placed. `7.Nbd2` is a much better try. If you want to stick to `7.Nc3` then it's best to start considering accepting the gambit, either `8.Nxb5` or `8.cxb5` each with their own merit and far more playable than `8.e3.`
* After `8.e3 b4` white is objectively behind: the knights seem out of coordination, the bishop on `f4` is staring at a wall, there are no clear pawn breaks for white, the queen-side is permanently weak and there are no quick ways of creating counter-play on the king-side as we're far behind in any attempt to challenge the `g7` bishop (`Qd2-Bf4` battery is not possible with `e3`, nor is there any re-routing for the bishop to return to `d4-g7` diagonal). This also answers your **main** question: Black should not respond by `Nbd7` after `8.e3`, instead **`8...b4`** is the **main** move to consider, exploiting the mis-placed `c3` knight while increasing your grip on the dark squares, leaving no real ways for white to challenge the `g7` bishop (note `b4` is also stopping any future attempts at `Bd2-Bc3`)
* Small recommendation (for the white side): avoid the `Bf4` side-lines, none of them are really interesting for white, in fact in many of the Benko variations the bishop belongs to its original `c1` square for a long time as `b2` is continuously under pressure. Instead consider the `5.Qc2` variation if you don't want to accept the gambit, which can roughly go as follows: `5.Qc2 Bg7 6.e4 d6 7.Be2 O-O 8.O-O`. I think after going through some of the possible side-lines of this variation, you can convince yourself that this is a much more sound continuation for white. Alternatively, accepting the gambit is known to yield the best play for white, namely lines such as `5.cxb5 a6 6.bxa6 Bxa6 7.Nc3` (black does have a different kind of compensation now, but by accepting the gambit we've prevented `b4` altogether and revived chances to challenge the dark-squares) `7...Bg7` and many ways for white to continue.

Welcome to ask additional questions, either regarding the analysis or more related to the black side of the Benko gambit.

---
Tags: opening, gambits, benko-gambit
---


title: How to decide when is a3/h3 needed?

text:
# Question
Title: How to decide when is a3/h3 needed?
a3/h3 are frequently used to prevent the bishops from pinning the knights.

I always have a hard time deciding whether to play them or not. Playing them loses moves and tempo while not playing can also sometimes become annoying (for example, if the knight is pinned after the bishop has already moved OR worse, if the bishop cannot come back to remove the pin).

Can the experts here help the rest of us with some thumb rules and/or examples?

# Answer
> 7 votes
Let's stick to one color, white here, and everything we'll say will generally hold true for black as well.

**Rule of thumb:** On the one hand, you generally don't want to move your king-side pawns (such as `h3`) when you've castled short, unless you have to, and we will expand on what "have to" entails here. The immediate exception to that is when you decide to fianchetto your king-side bishop, e.g., in the Catalan where then you play `g3`. On the other hand, your queen-side pawns (assuming you've castled short) are to be used more actively to either gain space or prevent an spatial expansion by your opponent. (*the rule is naturally to be taken with caution, chess rarely lends itself to these kinds of generalizations*)

The more common cases are when a bishop is pinning your knight on `g4` and `h3` is an immediate way to try and challenge the bishop, asking it where it wants to go. But there are cases where `g4` is not being exploited for a pin but rather as an intermediate square to re-route a knight (to `e5` for instance). In either case, if the pin is problematic to deal with, which may be so if you've already made a commitment with your light square bishop and it cannot return to `e2`, or if the knight re-routing would be an improvement for your opponent, then you really want to play `h3` in a **prophylactic** way to prevent all of that. Here's an example in the Benko gambit:

```
 [Title "Benko gambit declined - preventive example"]
 [fen ""]

 1.d4 Nf6 2.c4 c5 3.d5 b5 4.Nf3 g6 5.Qc2 Bg7 6.e4 d6 7.h3 {Stopping any future knight re-routes to e5 via g4, and specially securing e3 for the c1 bishop. Bg4 is altogether less of a concern here in comparison}

```

And below you find two prophylactic examples of `a3` and `h3` where they are purely strategic and intentional:

```
 [title "a) Nimzo-Indian b)London system - (deliberate examples)"]
 [fen ""]

 1.d4 Nf6 (1...d5 2.Nf3 Nf6 3.Bf4 e6 4.e3 Be7 5.Nbd2 O-O 6.h3 {this is largely to secure the h2 square so that we can preserve our dark square bishop for instance against Nh5.}) 2.c4 e6 3.Nc3 Bb4 4.Qc2 O-O 5.a3 {white by choice, not forced, plays a3 to resolve the pressure on c3 in order to finish development more deliberately, with choices such as Bg5 becoming easier to make} Bxc3+ 6.Qxc3 b6 7.Bg5

```

Then there are **reactive** cases where *tactically* one may not have a choice but to challenge a piece on `g4` or `b4` respectively, in which case although there's no doubt your opponent would be forcing your hand into playing `h3` (`a3`), but you will have to include that move and accept a small set-back. Extreme cases are when a mate is threatened, e.g., a queen on `h5` and knight on `g4.`

**Why moving the castled-side pawns would generally be a set-back?**

Main reason for that is two-fold: First, as obvious as it may sound, you'd be permanently committing to a pawn structure, second and tightly related to the first, you'd be creating targets for your opponent. The latter may be, to name a few, in the form of weakened dark squares, for instance if there's a dark-square battery on the `c7-h2` diagonal that you'd want to preferably deal with by playing `g3`, but having previously played `h3` may make that difficult and `g3` would expose `h3` *and* `g3` itself to potential sacrifices. Another type of target would be, a pawn push on the king-side by your opponent, challenging `h3` with `g4` attempting to undermine your king-side pawns and open a file towards your king.

The **takeaway** here can be generalized: pawn moves in chess are always a commitment, the later you have to commit to them, the more pawn structures you can opt for, and conversely, the sooner you commit to one, be it willingly or forced by your opponent, the earlier you create targets for your opponent. Targets are not always weak pieces/pawns (such as back pawns, or isolated ones), but they can also be strategic targets that can be exploited in your position, prime example being weakened-black/white-squares, or more abstractly, your pawn-breaks in the position can become limited, and the few remaining ones can more easily be prevented/delayed by your opponent, which ultimately means you will have a hard time undermining your opponent's structure and creating active play. This is closely related to space control in chess, which you can read more about here. With all of this in mind, now you can see for example why the English opening is generally is hard to face: it is extremely versatile in pawn structures it can lead to, consequently, the opponent has a harder time to resolve the dilemma of which plan to opt for! Instead, `e4` and `d4` openings are more committal by definition (as we start by moving a central pawn already), so we can more reliably establish *systems* against them

Now let's take an extreme example where our rule of thumb is being perfectly illustrated:

```
 [title "Michael Adams vs Garry Kasparov, Linares 2005"]
 [fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Be3 e6 7.Be2 Qc7 8.Qd2 b5 9.a3 Bb7 10.f3 Nc6 11.O-O-O b4 12.axb4 Nxb4 13.g4 Be7 14.g5 Nd7 15.h4 Nc5 16.Kb1 Rb8 17.h5 O-O 18.g6 Bf6 19.Rdg1 Ba8 20.Bg5 Be5 21.gxh7+ Kxh7 22.Nb3 Nxc2 23.Nxc5 Na3+ 24.Ka2 Qxc5 25.Na4 Nc2 26.Kb1 Qa3 0-1

```

Notice how Kasparov pushes with `a6-b5-b4` on the queen-side in order to launch his attack on white's long castled king and yet *never* moves any of his king-side pawns until the end as to avoid giving white *any* entry-points or targets. Notice how Adams had to play earlier `a3` in order to prevent `b4` as it would force his `c3` knight to be mis-placed in turn weakening the `e4` support. And having committed to `a3` is precisely the target Kasparov used with `b5-b4` to open the `b`-file, which he then exploited beautifully. This is a cherry picked example, but it's very appropriate here because all of our previous points culminate in one game! More generally, Sicilian players are accustomed to this type of pawn structures (i.e., knowing not to commit their king-side pawns and just push as fast as possible on the queen-side).

# Answer
> 5 votes
**NEVER** say never. Rules of thumb are just that. White very commonly plays h3 at an early stage in many variations of the Ruy Lopez, even before Black has committed his K. What often makes this safe is that Black may have already disarranged his own Q-side pawns by ..a6 and ..b5, so he is unlikely to castle over there.

I remember learning this rule of thumb for White in the Lopez. Do not play d4 if Black can answer with ..Bg4, because then your center will be under attack. But if Black plays ..Bg4 early, go with d3, because then your center is not under attack and you can manoeuvre ..Nd2-f1-e3 with tempo against the misplaced (?) Bishop if you have not played h3.

The answer to your question is that h3 (or any other move) is good if it forms part of an integrated plan. Rules of thumb like the ones quoted by Glorfindel or Phonon or myself are useful if they start your planning off in a good direction, but the thing about plans is that you must be prepared to change your mind (and perhaps change it back again). To reinforce a point made by Phonon, I have always admired (but not always remembered) the advice of James Mason,"You have 48 pawn moves. Spend each one as if it was the last dollar between you and starvation".

Reasons **not** to play h3 in the Lopez; 1. It encourages a charge by the Black g-pawn (but is that anything more than just a bit scary? Does Black have backup?) 2. It weakens f4 to occupation by an enemy Knight because g3 will now hang the h-pawn (Is that Knight currently anywhere near f4?) 3. It may lose time for executing a desirable manoeuvre elsewhere (but does that matter if the manoeuvre is merely delayed and cannot actually be prevented?)

(Who said that h3 was "provincial timidity occasioned by metropolitan excitement?", Staunton?)

Reasons **for** playing h3 in the Lopez; 1.To prevent Bg4 (if this was really a threat) 2. To prevent Ng4 and secure stability for a B on e3, 3.To remove back-rank anxieties 4. To keep more pieces on the board (if Black is already cramped. 5. to prepare g4 (if you are the one ready with a pawn-storm.) 6. As a waiting move (If Black is trying not to commit to some decision but you want them to reveal it) 7. To drive off an attacking Knight before reinforcements arrive.

There can be many more and often they are in conflict. What you must do is try take all of these into account (and combine them with decisions about your c-pawn, for example) until you have a harmonious plan (Much of this will eventually become instinctive, as part of your "chess vision", the pieces will look neat and organized.) Then try to remain consistent with that plan (accentuate the positive, eliminate the negative) until circumstances change; be very alert for that moment. If your plan does not work, recognize that you have been outplayed by a better planner (unless you just missed a Knight fork). The focus of a postmortem should not be "Was this a good move?" but "was this a good plan?" Rules of thumb are invaluable as reminders in the early stage of planning. Ask, What is the usual situation? How might this be different?

# Answer
> 3 votes
1. **Never** do it in front of your castled king (or on the wing where you want to castle), if the opponent hasn't castled yet or castled on the other wing. Doing so weakens your king's fortress and is an open invitation for a storm by the b- or g-pawn.
2. Generally, in open games (after 1. e4 e5), and especially with Black, the loss of tempo involved in a (preemptive) a3/h3/a6/h6 will be heavier than in closed games. Actually, I have a hard time thinking of main line openings where this move is played to prevent the bishop from coming to b4/g4/b5/g5. **That alone should be a reason not to play it.**
3. Playing it *after* the opponent moved the bishop (e.g. 3... a6 in the Ruy Lopez, 4. a3 in the Sämisch variation of the Nimzo-Indian) is usually less of a problem, because it forces the bishop to retreat or be exchanged with the knight, giving you the bishop pair.

---
Tags: opening, pawns, knights, bishops, pins
---


title: What is the winning move here and why?

text:
# Question
Title: What is the winning move here and why?
```
B1b2rk1/p3pp1p/6p1/q1Pp4/3b1B2/2n4P/P2Q1PP1/2R1K2R b K - 0 17

```

Stockfish rates this position as -2.94, so Black is clearly winning. Or is it so clear? After 1... Bxf2+ 2. Qxf2 Ne4+ 3. Bd2 Nxf2 4. Bxa5 Nxh1 5. Bxd5, White obtains the Bishop pair in an open position and a passed pawn. This is not the winning move. (Actually, there are two: The alternative is 1... Qxc5.)

However, I cannot fathom how Black is better. Sure, material is even in terms of points, the White LSB is locked in and eventually Ba6 will be played, but when is *eventually* and how?

# Answer
`Bxf2+` gives away all your advantage because of the precise line you mention. The correct move is `e5` (to protect your bishop with tempo, note `1...e5 2.O-O exf4 3.Qxd4` doesn't work because of `Ne2+` fork), followed by `Ba6`, preventing castling and attacking the trapped `a8` bishop. Notice `Bc6-Bd7-Bg4` doesn't really save the bishop as shown below: (covering some side-variations as well, rather called for as it's a very concrete position)

```
 [title "1...e5"]
 [fen "B1b2rk1/p3pp1p/6p1/q1Pp4/3b1B2/2n4P/P2Q1PP1/2R1K2R b KQq - 0 1"]

 1...e5 (1...Qxc5 {also a good move with similar threats except the queen discovery} 2.O-O Ba6 3.Rfe1 Rxa8 4.Be3 Bxe3 5.Rxe3 d4 {easily winning: two pieces and a pawn for the rook, together with a passed pawn and dominant knight}) (1...Ba6 {The immediate Ba6 is not good enough probably but it's a fun line, the idea with Ne2+ forking bishop and knight while still taking on a8.} 2.Qxd4 Ne2+ 3.Qd2 Qxd2+ 4.Kxd2 Rxa8 5.Be3 Nxc1 6.Rxc1 {still a pawn up but it's opposite colored-bishop so always big drawing chances.}) 2.Bh6 Ba6 3.Bc6 (3.Bxd5 Rd8 4.Bf3 Bxf2+ {wins on the spot for black}) (3.Bxf8 Bxf2+ {however white recaptures loses on the spot} 4.Kxf2 Ne4+) Rc8 4.Bd7 Rxc5 5.Bg4 Bxf2+ 6.Qxf2 Ne4+ {and you're winning the house.}

```
> 4 votes

---
Tags: tactics
---


# Question
Title: What merit is there to the so-called "Swiss gambit?"
The "Swiss gambit" refers to the idea of intentionally lowering one's performance at the beginning of a Swiss-system tournament, to one degree or another, in order to have an easier path through the later stages of the tournament. E.g. a highly-rated player in a field could take a half-point bye in the first round (instead of a likely win) in order to likely be paired against weaker competition for the next few rounds than would have happened otherwise.

It certainly shouldn't be the case that it's *always* a good idea, or Swiss-system tournaments would be very poorly conceived. But depending on where a given player sits ratings-wise in the field, and the exact distribution of the ratings of players in the tournament, it is not inconceivable that such a Swiss gambit could increase a player's expected final score. Of course, intentionally giving points away at any point could obviously decrease the expected score as well. This is all I am asking for here:

> Has any serious research been done concerning scenarios in which a Swiss gambit is/isn't effective, probabilistically speaking, in the sense of raising/lowering the gambiteer's expected tournament score?

Pointers to any legitimately mathematical (and mathematically legitimate) discussions of the matter would be most appreciated, as would the creation of such in an answer of course.

# Answer
> 9 votes
I tried writing a crude pairings/results simulator, to see whether taking a bye could increase a top player's score. When generating pairings, the program ignored pairing history and color (which I realize can matter, but I didn't want to have to program it to go back and redo pairings if there was a conflict - this is a crude simulator, not an actual pairings engine!) But it was able to handle pairing people in a scoring category with the usual top half/bottom half method, as well as the all-important "pairing up" of the top person from the lower category with the bottom person from the higher category if there was an odd number of players in the higher score category.

I assumed a uniform ratings distribution through whatever ratings range I selected. I used the "Standard winning expectancy" formula at the bottom of page 11 in this document. I did not account for fatigue. I assumed a draw probability of half of the probability that the higher-rated player would lose (for example, if the expected score was 0.75 according to the formula, I assumed a win would happen 70%, a draw 10%, and a loss 20%. For even matches with 0.5 expected score it would be 40% - 20% - 40%.) I set the program to run 100000 tournaments at a time, to get a good average.

The Swiss gambit pretty much always decreased a high-rated player's overall score regardless of the number of players, rounds, or rating spread (unless I set the draw probability parameter to zero, which is unrealistic.) At best it had only a small negative effect on the final score. Although the player's performance in later rounds was indeed better due to weaker opponents, that performance did not quite overcome the nearly half-point lost. The top players were better off playing in all the rounds.

For example, in a simulation of an 8 round 200 player tournament, with player ratings ranging from 200 to 2000, the 2000-rated player had an average score of about 6.35 if they did not take a bye. If they took a first-round bye, the average was only about 6.24.

However, for some small tournaments with large point spreads and a certain number of players, although the average score dropped, the probability of placing first actually increased. For example, in a 5 round 32 player tournament with players rated from 200 to 2000, taking a first round bye decreased the average score from 4.23 to 3.95, but increased the probability of taking clear first from 33.2% to 34.7%. I'm not sure if these are artifacts of an imperfect pairing engine, though; the exact pairings matter more in such situations. In *most* of my simulations the decrease in score corresponded with a lower probability of taking first (and the decrease was somewhat larger than the increase shown here.)

Interestingly, although it also wasn't effective compared to playing all the rounds, it seems that taking a half-point in the second or even third round often gave a slightly better score than taking one in the first round, especially when the ratings spread was large (in the 8 round 200 player example, they scored about 6.26 by taking the bye in the second or third round, as opposed to 6.24 by taking it in the first round.) The first round has a top half player against an easy opponent; why skip a game you'll almost certainly win, instead of skipping the next one where your opponent may have something of a chance?

So, overall: The average score decreases when using the Swiss gambit. The odds of winning the tournament *might* go up in certain specific scenarios, but I'd need a better program to say for sure, and if there is any such effect it's sensitive to the *exact* number of players.

# Answer
> 2 votes
It would help to know the motivation of the gambiteer. It never occurred to me to game the Swiss system, or that it was even gameable. Does the gambiteer want prize money? Rating points?

I've seen far too many Swiss systems at the class level where the winner had a perfect score. It's hard to believe that the goal is to win the tournament when the gambiteer voluntarily loses 1/2 point.

Let's start off by agreeing that surely, it is possible to get an easy 2nd and 3rd round if a player honestly loses or draws in the first round. The question becomes, can a cheater manipulate the system in a meaningful way.

So, let's assume for the SG (Swiss Gambit) to work:

```
1. it's a class-level tournament (my world.)
2. all players have the exact same rating.
3. the ratings are accurate.

```

I don't believe the SG would yield a positive result in this case; at best, the gambiteer would play people who might be off their games. However, it's much more likely he'd just be playing someone who lost. At the class level the games are almost always decisive.

Thus, I draw the conclusion that the SG only works dependably if there's a wide range of rated players. In large tournaments where players are grouped by class (D and under, C, B, A, Expert) I can't imagine a measurable result; the maximum difference between ratings is 200 points.

So, I posit:

```
1. it's a class-level tournament (my world.)
2. the brackets must include players of wildly different ratings
3. the ratings are accurate
4. the point of cheating is to get prize money

```

#1 implies draws are rare. This becomes important once the ratings are widely distributed. If the gambiteer secures the only draw, in round 1, he'll almost certainly end up playing in the "0-wins" bracket since the only other player with a draw would be his opponent and you can't be paired twice in a Swiss. And because of #2, the "0-wins" bracket will contain mostly lower rated players.

#2 implies a small tournament where there aren't enough players to fill out class-specific brackets.

#3 is a dicey assumption since I'd expect a cheater to sandbag his rating. I'd also expect a cheater to also play with a cheesy style designed to knock out less experienced players. For example I've seen players talk during play, make really fast moves in an attempt to psychologically rush the opponent, etc. This is probably not germane to the discussion, however.

#4 is my assumption of the motivation. This means the gambiteer wants to win the remainder of his games and be alone at the top. It doesn't do much good to get a cut of 3rd place with 5 other people. Because it's probably a small tournament (else #2 may not be true) the gambiteer needs very good score.

As I work through this, I begin to understand the SG. The SG exploits the Swiss method of

```
a. pairing people with the same scores
b. not allowing duplicate pairing, and
c. splitting the brackets in half by rating and pair the top of the top with the top of the bottom.

```

So the gambiteer scores a factional point in rd 1 in the hope he's always paired with someone in the group with the lesser score. So in round 2, he's paired with the "0/1" group. Further, he'll be paired with a player whose rating puts him in the middle of that group.

Consider the last round of a 5-round Swiss: The gambiteer, at 3.5 points, will be playing a middling 3.0 scorer. Compare this to the others at the top - two 4's battling it out. The Gambiteer is going to probably come out on top of one of them. The *worst case* scenario is that the 4's draw and all three of them share 1st, 2nd, and 3rd places.

Conclusion #1: I'm convinced it is easily possible to materially manipulate the 2nd round of tournaments that meet criteria #1 and #2.

Conclusion #2 - the SG is real in theory if dicey in practice. Draws, drop-outs, and the leeway allowed to the TDs can ruin the gambiteer's day.

Solution - group draws with the category above them, not below them. This will stop the SG in its tracks. That is, in rd 2, the gambiteer would be playing winners, not losers. Further, because of their scores, the gambiteer would be playing someone at the bottom of the top half of the group. Probably not the intent and certainly not a path to a prize-by-cheating. In fact the first-round draw works against him now as he always gets paired up. This may be too harsh. It could be in rds 2 and 4 the fractional scores would get paired up and in rd 3 they would get paired down.

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Tags: statistics, tournament
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# Question
Title: What is a good plan for Black when White surrenders the center?
```
rnbq1rk1/ppp1ppbp/5np1/2Pp4/3P4/2N1PN2/PP3PPP/R1BQKB1R b KQ - 0 6

```

In the above position, White has ineffectively surrendered control of the d5 square with 1. c5?. All of his pieces are not developed onto the queenside and he is unable to make use of his space advantage.

Would a good plan be for Black to play ...a5, preventing b2-b4 (which supports the c-pawn) and Bg4, Nd7, Re8, c6, Qc7, and eventually e7-e5?

# Answer
In positions like this (while the a1 rook is undefended), a typical plan is to play immediately 1...b6 and reply to 2 b4 with 2...a5, the idea being that white cannot defend the b4 pawn with a3.

In order to analyze the consequences of this plan, I'd check the following:

* bxc5, dxc5 would give black's bishop the long diagonal and should be preferable for black
* cxb6 axb6 (or cxb6) does not seem so clear to me, because the light squares on the queenside get weak. Assessment might depend on whether black can take advantage of the half-open a file and/or can put his queenside pieces to good squares without giving white too much play on the light squares.
* 1. ...b6 2. b4 a5 3. b5 Does not look attractive for black

So it seems that black does not get anywhere on the queenside, which leaves the pawn break with e5 as the most reasonable alternative. The idea would be to either open the long diagonal for the bishop (if white captures on e5) or to create a weak pawn on d4 (if black captures exd4, exd4).

There is not much white can do to prevent black from playing e5 sooner or later. The next white moves are pretty much predictable (develop pieces, castle, push pawns on queenside...). The question is how black wants to prepare e5.

* 1. ... a5 is probably a good idea because it hinders white's natural plan of pushing the queenside pawns
* c6 vs Nc6: the pawn on c6 would protect d5 which could be important after white captures dxe5; The knight on c6 looks a bit unnatural, particularly if white manages to create a pawn storm. On the other hand from c6 a knight could put pressure on the d4 pawn.
* Bg4: with all white pawns on dark squares, this bishop could be strong. You might not want to exchange it too soon.
* Re8: probably a good square for the rook

Taking into account all this and potential tactics such as white sacrificing a pawn on c6 (if black plays Nbd7), etc, I believe the best options are:

* Re8, Nc6, e5
* Re8, c6, Nbd7, e5
* c6, Nfd7, e5 (but black might delay his development too much here)

ALl of these could be combined with Bg4 depending on how much you value bishops vs knights. Personally I'd go with the Re8, c6, Nbd7, e5 plan
> 1 votes

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Tags: center
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