# Question
Title: Are there any official rules for Bughouse?
I came across this question - Formal rules for two-player bughouse without a clock \- which asks if there is a formal way of breaking deadlock situations where one player on each side doesn't want to move, but nothing about formal or official rules. Do they exist? Has anybody tried to control this chess variant?

# Answer
> 8 votes
I found two sources. For fans of the USCF they have produced their US CHESS SCHOLASTIC BUGHOUSE RULES but not a grown up version that I can find.

The rather more serious Czech federation holds an annual bughouse championship in conjunction with their regular national championships as part of an annual chess festival. They publish their formal rules here.

These appear more serious and handle more difficult problems like formalizing storage of captured pieces and the way they are handled:

> 1.6 When a piece is captured, the captured piece is passed to the partner stuff-place immediately after the move is completed, not later than before the player's next turn. A player's "stuff-place" is an area reserved for pieces that the player can drop on the board. The player's stuff-place must be between his opponent's eyes and the player's hands. So the stuff-place is usually between board and player's hands.
>
> Before the game the players and arbiter should agree on the position of the stuff-place
>
> 1.7 A player cannot attempt to hide pieces from the opponent. During the whole game the players shall manipulate the pieces in such a way that both opponents are able to see all pieces. Only when captured pieces are transferred to partner's stuff-place or in the moment when player is moving or dropping piece on chessboard, a piece may be partially hidden in a players hand. However it must be clear to his opponents which piece is partially hidden and this moment must be as short as possible.
>
> 1.8 a) If a player hides pieces in an improper way (rule 1.7), his opponent (or partner of his opponent) is entitled to warn him to "show pieces".
> b) If a player drops a hidden piece, his opponent may restrict its use by the message "invisible", e.g. "invisible bishop". The opponent may then immediately start the player's clock and force him to make another move.
> c) A piece restricted in this way may not be used until the opponent allows (by the message "bishop visible now", for example). The opponent should allow it as soon as possible, in good sportsmanship.
> d) If a player repeatedly hides his pieces, his opponent (or partner of his opponent) may claim "repeatedly hiding" and the arbiter may impose some sanction. (rule 9.4.)
> e) If a piece is hidden through no fault of the player, and this drastically alters the game, the arbiter may order a new game.

Contentious issues around simultaneous checkmate are also handled:

> 1.9 When player is checkmated after taking any piece then if his partner has the move, he may drop this piece as his last move.
>
> 1.10 If both games finish at the same time, the results on both chessboards are counted up; **the team which wins on both chessboards wins the bughouse game. Otherwise the bughouse game is draw.**

> 2.2a The bughouse game is draw when player is taking a piece, then (in the next opponent move) is checkmated, his partner's move is in this moment, his partner is by dropping this piece (before his time is out) checkmating opponent or making draw by achievement of 3x repeated position (See 2.2.b).

There is no mention of stalemate for the obvious reason that a player can always put a piece on from the "stuff-place" or wait for a piece from his/her partner.

Also no mention of 50 move draw rule because, let's face it, pieces are always going to get taken and pawns are going to be moved and recycled and very quickly.

There is, though, a 3-fold repetition draw law.

---
Tags: rules, chess-variants, bughouse
---


title: How do you punish this opening?

text:
# Question
Title: How do you punish this opening?
I’m a fairly new player, with a FIDE rating of around 1000. I'm really wondering what’s wrong with this opening. It’s the Indian variation of the Nimzo-Larsen, but it’s a different line.

I like to play b3, Bb2 e3, d4, Bd3, Nf3, and Qe2, along with a3 or h3 if a knight threatens to go to b4 or g4. At this point, I’m ready to castle either way and enjoy a solid position. Of course, it doesn’t always go like this. Sometimes the order changes according to my opponent's play. But it seems really solid to me. Since it’s not a recognized line as far as I know, I want to know how to play against it.

```
[FEN "r2q1rk1/1bpn1pp1/pp1bpn1p/3p4/3P4/PP1BPN1P/1BPNQPP1/R3K2R w KQ - 0 1"]

```

# Answer
This is a recognised opening. It's the Colle-Zukertort opening by transposition. The normal move-order for White is **d4, e3, Bd3, Nf3, Nbd2** this is the Colle System, then **b3, Bb2** to end up with this structure.

In the Colle, White breaks open the centre with the freeing move **e3-e4** and gains piece play on the kingside which can turn into a king-side attack. White normally uses the e5-square for the knight in a Pillsbury/Stonewall style by following up with **f2-f4**. The bishop on b2 can come to life later on if Black tries to free himself with **.. c5** or **... e5**

With the g6-square weakened because of Black's **... h5**, White has the plan of **Ne5, f4, f5** threatening to exchange on e6 and now there's a hole on g6.

A quieter alternative is for White to play positionally with **c2-c4** and after exchanging on d5 playing down the c-file.
> 3 votes

# Answer
I guess the main thing "wrong" with the opening is that it doesn't press for an advantage. Stockfish at a depth of 22 gives the position above a -0.03, which is essentially equal. That's not surprising, since the position is almost symmetrical, except White has played a3 instead of castling.

The bishop on b2 has a very limited scope, and White does not control much space and isn't really attacking anything.

I'd say you shouldn't be so eager to prevent Nb4 or Ng4 unless there's a particular reason. If you wait to play a6 or h6 until *after* they play such a move, then they waste a move putting the knight back. But if you play it before it's necessary, then you're the one wasting a move. Also, a pawn on a3 or h3 can be a target in some positions. As it is, you've essentially given Black a tempo.

If I were Black in such a position, I'd be seriously considering a c5 push. (In fact, I may have already played it, since I wouldn't have wasted a move with h6.) Trading my c-pawn for White's e-pawn seems like a good idea if I can, since it gives me more center control, plus a half-open c-file which I could put a rook on. And opening the position somewhat when I'm slightly ahead in development doesn't seem to be a bad idea either.
> 1 votes

---
Tags: opening, counterplay
---


title: Do grandmasters think on every move?

text:
# Question
Title: Do grandmasters think on every move?
While watching Hikaru's Streams/YouTube (GM Chess Twitch Streamer), he's no doubt extremely impressive when it comes to recognizing patterns that win him material and forced mates in like 7+ moves. Things like this require extensive knowledge of certain key positions and a great load of pattern recognition to go on top of that. During or after the sequence, he goes over the sequence fairly briefly to explain his thought process to his viewers, and it's the type of stuff you watch and are really just amazed by. These are usually the flashy calculations that are showcased on highlight channels and things like that.

My concern is for the opposite type of moves, being the less subtle ones. Often, Hikaru will give no thought to a move and say something like "let's just go here" and it often turns out to be the best move there is (Once played a bullet game with 96 percent accuracy). On the surface, these moves don't look like they have any thought to them. Obviously, it doesn't straight up blunder anything, but it doesn't really give him an advantage either. This begs the question: when Hikaru plays these types of moves, does he innately know it's the best move based on his intuition, or is there some kind of hidden calculation/judgment that leads him to make the move? What reason goes into him playing that move?

This also leads to the more general question: do grandmasters have to have a reason for every move they play, or are some moves just "okay" and meant to pass the move to the opponent? Obviously, the opening is an exception to this but even so, there are underlying ideas of center control, development, etc. This might be wrong in some way, so if anyone could elaborate on this that would be great.

# Answer
> 21 votes
I will try to answer this in a different manner, the way I understand this topic.

Do we think on every signal, turn, fork when we drive?

Do we think every time we eat food or walk on the street?

The answer is yes, we do, but that thought process has moved to our reflexes to the extent that our brain does not let us know that it is doing a task (Thankfully!) unless there is a critical alert in our brain that puts us to think about the situation.

Just as a fact, the human brain takes 35000 decisions per day and not every decision we are aware, but is still taken.

Just like this, the Grandmasters have reached a state where the rudimentary positions are into their reflexes and they effortlessly play their game, to the extent that they invent positions and theories on the board itself. Reaching that state is "mastery"

# Answer
> 6 votes
I can also answer this from AlphaGo's perspective because we know fairly precisely how it works. We can then reason by analogy for the human perspective.

From a bird's eye view AlphaGo has 2 components, a neural network that looks at a snapshot of the board, and a Monte Carlo search step that uses the neural network output to search faster. Both the neural net and search produces (and optimizes for) an estimate of the probability of winning for every move. The key feature is that you can play chess with either of the algorithm components, or a combination. The Monte Carlo search on it's own has dreadful performance, but Deepmind computed the Elo rating of the neural network on it's own and it's pretty good at chess.

From the AlphaGo zero paper:

> Figure 6b shows the performance of each program on an Elo scale. The raw neural network, without using any lookahead, achieved an Elo rating of 3,055. AlphaGo Zero achieved a rating of 5,185, compared to 4,858 for AlphaGo Master, 3,739 for AlphaGo Lee and 3,144 for AlphaGo Fan.

Now for the analogy to human thinking. The Monte Carlo search does a lot of heavy lifting for AlphaGo and searches through at least thousands of combinations. Human search (thinking) is a lot slower than that, but the search strategy might be smarter. Still I think we can consciously look ahead at most 100 options, much less than a computer could. This leads me to believe that the subconscious (neural net) analysis makes up a larger percent of the total performance in humans. If we consider the Deepmind performance difference as a low bound, we'd be anywhere between 60% and 90% as performant subconsciously.

---
Tags: learning, strategy, psychology, grandmaster, calculation
---


# Question
Title: Big changes in engine's evaluation after considerable time
I hope this question hasn't been asked before.

I am looking for some examples where, say, the latest Stockfish or Komodo engine (or possibly some of the top NN engines) evaluates a position as plus or minus x for some time--possibly oscillating slightly near that point during that period--and then there is a big increase or drop in their evaluation.

What might be a suitable "for some time" period? I want to say more than a minute, but not more than 1 hour. Also, what is a "big" change in evaluation? I am not so sure about that, but let's say something like 3.0.

I am asking this question because, from my (very limited) experience, any dramatic changes in an engine's evaluation occur during the first 20 or so seconds. If an engine cannot find the deep tactics (or the deep positional play) during those first seconds then it is because the search tree has been pruned. (Am I right about this? I don't much about how chess engines operate.)

**Edit:** The drastic change in the evaluation should be a consequence of the introduction of a move not previously considered by the engine.

# Answer
> 7 votes
This happens often enough in engine tournaments that viewers have coined the terms "boom" and "moob" (for "eval explodes away from 0" and "eval implodes towards zero" respectively).

Here's the latest example of a boom from TCEC.

```
[FEN "8/kp6/6B1/p3p3/3r3P/q5P1/2Q2PK1/8 w - - 0 59"]

```

Leela, playing White, boomed from -0.46 the move before to -1.91 after playing 59. h5. That means this position (or one of the moves slightly prior) very likely meets your criteria, if you let Leela think for a sufficiently long time.

You can also see from the principal variations of both engines that Leela did not anticipate Komodo's move on move 58 - Leela predicted 58...Qd5+, but Komodo played 58...Qxa3.

If you're looking only for booms of more than +3, off the top of my head, this was another memorable boom.

```
[FEN "7Q/8/P3n1p1/2p3k1/6b1/5pb1/8/5K2 w - - 1 59"]

```

Leela, playing White, evaluated the position after 59.a7 as -0.06, then boomed to -14.28 after 59...Bf5 (Leela predicted 59...Nc7).

**Edited to add**: here's an example of a Stockfish moob from -1.38 to 0.00 after thinking for 4 minutes on TCEC hardware.

```
[FEN "r4k1r/p1pb2bp/2pp1nq1/4P3/3P3Q/2N5/PPP3PP/R4RK1 w - - 3 16"]

1.Rae1 Bf5

```

Stockfish had the Black pieces and its eval dropped after ...Bf5. Link to game with both engines' PVs if you want to see those.

# Answer
> 6 votes
This is a complicated position I had in a correspondence game. White to play and win. The engine evaluation rises and falls, occasionally hitting 0 again. Then it stays at roughly 1.5 for a long while until finally finding the breakthrough about 20 minutes in. Unsurprisingly, considering the full line is pretty insane.

```
[FEN "r5r1/1np3bk/1p1p4/3P4/bpP2PPp/P3N2P/1q1BQ2K/4R1R1 w - - 0 33"]

1. g5 Rge8 2. Qh5+ Kg8 3. Rg2 bxa3 4. Nf5 Rxe1 5. Bxe1 Bc2 6. Nh6+ Kh8 7. Ng4+ Kg8 8. Nf6+ Kf8 9. Nd7+ Ke7 10. Qg4 Nc5 11. g6 Rh8 12. Re2+ Kd8 13. Nb8 Ba4 14. Nc6+ Bxc6 15. dxc6 Qf6 16. Bf2 Re8 17. Ra2 Qe6 18. Bxh4+ Kc8 19. Re2 Kb8 20. Rxe6 Rxe6 21. Qg2 Re3 22. f5 Be5+ 23. Kg1 Rb3 24. Qa2 Bd4+ 25. Kf1 Rf3+ 26. Kg2 Rb3 27. f6 Rb2+ 28. Kf3 Rxa2 29. g7 Rg2 30. Kxg2 a2 31. g8=Q+ Ka7 32. f7 a1=Q 33. f8=Q Qg1+ 34. Kf3 Qd1+ 35. Kf4 Ne6+ 36. Qxe6 Qf1+ 37. Ke4 Qxf8 38. Qe7 Qxe7+ 39. Bxe7

```

# Answer
> 1 votes
Adding another answer since it meets every requirement by the OP and I believe they'll be interested.

```
[FEN "4nr2/5ppk/pn3q2/3ppNRP/1pr1P3/1P3P2/1KP3Q1/R7 w - - 0 42"]

```

Game 99 of the Season 20 TCEC Superfinal

Leela had +0.03 eval with this principal variation:

```
41....d5 42. bxc4 Nxc4+ 43. Kb1 dxe4 44. fxe4 Na3+ 45. Ka2 Qe6+ 46. Kb2 Nc4+ 47. Kb1 Rg8 48. Rg6 Qd7 49. Ka2 Qa4+ 50. Kb1 Qd7

```

And it boomed to +10.59 after 42. Rg6 and 3 minutes 27s thought.

Of course, it is TCEC hardware - their Leela ran at 92.1 knps. It's extremely unlikely OP (or anyone) can get anywhere near this speed. With weaker hardware, Leela's eval will be different.

*However* it is worth emphasizing that OP's actual question (about the engine changing its mind during the search) is not so clear, because Leela could very well suffer from tunnel vision and completely miss 42. Rg6. That's not to say that Leela never changes its mind, it does, but it's not as simple as "run Leela for 3 minutes and it will boom". That's especially the case since what Leela sees in 3 minutes is heavily dependent on what hardware you run Leela on.

Here's an article by GM Matthew Sadler on a different blunder by Leela in the TCEC Season 20 superfinal illustrating the difficulties with the question, and possibly providing another interesting position. To quote:

> Leave “my Leela” long enough (16.2M nodes searched) and its evaluation plummets: it sees that 79…Nb5 loses to the 80.Nf5 sacrifice and its assessment of its new top move (79…Bb5) is just 27.9% expected score (1 win, 3 draws and 6 losses). A big fall!
>
> However, if we look at “TCEC Leela’s” evaluation at this point…
>
> …it gives a WDL breakdown of 11.3% White win, 88.7% Draw and 0% Black win (0.16 is the conversion of this expected score to centipawns which the TCEC does to be able to compare easily with Stockfish). That’s just a slight disadvantage. Why is that?
>
> Well, “TCEC Leela” moved 79…Bb5 very quickly, taking just 34 seconds for its move.
>
> In that short time, it searched 2.3M nodes (10M nodes less than my 24 mins’ effort) and this was presumably not enough for it to see all the dangers in the position!

Position in question (I have taken the position one move earlier to have the board "right side up". White played 79.Bd3):

```
[FEN "5r1k/2nbq1rp/3p2p1/2pPp1P1/p3P3/P3NPQ1/1P2B2R/K6R w - - 3 79"]

```

---
Tags: engines, evaluation
---


# Question
Title: Are all grandmasters capable of playing blindfold?
There seems to be no shortage of stories about top rated players playing blindfold, either recreationally, or in tournaments. I'm curious whether *all* top players have this ability. Are there are GM-level players (current or former), for instance, known to *not* have any ability to play blindfold?

# Answer
As of this post all super grandmasters can play blindfold. For young GMs who are just starting out playing blindfold, they may not be super good at first but they should be able to pick it up quickly. Also, for old GM's it might be harder for them to play blindfold, as short term memory and spatial reasoning might be diminished. But most, if not all, GMs should be able to play blindfold chess.
> 2 votes

# Answer
Yes, unless they are very very old. It's probably not an exaggeration to say that essentially everyone rated over 2200 FIDE can do it, and many people who are lower-rated than that as well.
> 0 votes

---
Tags: grandmaster, blindfold-chess
---


title: Puzzle rush vs. Puzzles

text:
# Question
Title: Puzzle rush vs. Puzzles
I'm wondering what would be, in terms of efficient fast improvement, the best training module between puzzle rush (fast calculation and pattern recognition strengthening) and traditional timeless puzzle solving (deep calculation strengthening) ?

Does one become better than the other at some specific elo range or vice-versa?

I usually focus on timeless puzzles as I feel like deep calculation is very important for serious OTB classical/rapid games but wonder if it would be more time efficient to train with puzzle rush instead.

# Answer
I'd recommend starting off with traditional puzzle solving. Once you get to whatever your target range is and have a good accuracy rate (80-100%) *and* you can finish each of the puzzles in 45 seconds or less, move on to puzzle rush. Of course, when you get to 100 - 200 points below your target, and are accurate and quick, you could gradually start moving on to puzzle rush from the traditional puzzle solving.
> 2 votes

---
Tags: learning, tactics
---


# Question
Title: Positions in which only a single long sequence of correct moves avoids forced checkmate sequences
So for *n* steps, one player can only choose one out of many moves, because all others lead to forced checkmate sequences. Only one path from the root to the leaves of the game tree avoids a certain loss.

Does this concept have a name? Are there any known positions where this is the case?

# Answer
To start off, with such a requirement, the sequence would have to end in a draw. Well, more than most likely that is.

There is a similar concept from another question called the "Nunn Convention." It is a term to describe a move by one side that is the only way to draw, with the extra requirement that it isn't the only legal move. That extra requirement is what makes it "Nunn." It isn't quite what you wish for, but it is close.

The Matplus.net thread from which I learned the concept contains the below example. It is the record length of **32 plies** for such a "Nunn" sequence. It is from post number 19.

```
[Title "Geir Sune Tallaksen Østmoe, Matplus.net Forum 8/9/2019, White To Draw"]
[FEN "k1B5/r1p1p2b/nPPP2R1/BN2b1R1/2P2qp1/p7/P3P2P/6Kn w - - 0 1"]

1. Bb7+ Rxb7 2. Rg8+ Bxg8 3. Rxg8+ Nb8 4. Rxb8+ Kxb8 5. bxc7+ Rxc7 6. dxc7+ Bxc7  7. Bxc7+ Qxc7 8. Nxc7 Kxc7 9. Kxh1 Kxc6 10. Kg2 Kc5 11. Kg3 Kxc4 12. Kxg4 Kc3  13. h4 Kb2 14. h5 Kxa2 15. h6 Kb1 16. h7 a2

```
> 5 votes

# Answer
The sequence can be arbitrarily long if we allow repeated moves, e.g.

```
[Title "Every other White move allows mate in 1"]
[FEN "2B5/8/R7/4rp2/2P5/1PkP4/2p6/2K6 w - - 0 0"]

1. Re6 Ra5 2. Ra6 Re5 3. Re6 etc.

```

Naturally if the "certain loss" incurred by a deviation is allowed to take longer than mate in 1, there are simpler positions, even with only one Black pawn in addition to the two Kings; for example in the following position White must "find" 10 only moves before the first repeat, though it might take Black as long as 26 moves to punish a misstep:

```
[Title "Every other White move loses"]
[FEN "8/8/k5p1/8/8/8/K7/8 w - - 0 0"]

1. Kb2 Kb6 2. Kc2 Kc6 3. Kd2 Kd6 4. Ke2 Ke6 5. Kf2 Kf6 6. Kg2 Kf5 7. Kf3 Kg5 8. Kg3 Kh5 9. Kh3 Kg5 (9... g5 10. Kg3) 10. Kg3 etc.

```

I'm assuming that only one side's moves must be unique in this sense; if you want both White and Black to be walking such a tightrope at once, see **Rewan Demontay**'s example of a "Nunn sequence".
> 5 votes

# Answer
### depth=2 (+1)

I found this position, White has to make two moves (e3, e4) to avoid getting checkmated by Blacks pawn promotion and then has to move to h6 to avoid a draw by stalemate. After these three moves white wins by its own pawn promotion.

```
[Title "depth 3, white to move"]
[FEN "k7/Pp4p1/1P6/3p3P/8/1p2p3/pP3P2/K7 w - - 0 1"]

```
> 2 votes

# Answer
The moves themselves are technically forced, so that might be the concept to which you are referring (forced moves).
> 2 votes

---
Tags: problems, terminology, composing
---


# Question
Title: What is the solution to single-check chess?
Single-check chess is a variant where the first person to give check wins. There is a website that claims it has been solved, with white winning in four moves; however, I cannot find the moves anywhere.

# Answer
If you trust Stockfish's evaluation on lichess.org, using the "three check" variant where both sides already have two checks, White wins in 5 moves with 1. e4, 1. e3, 1. Nc3, or 1. Na3, and loses otherwise.
> 6 votes

# Answer
```
[FEN ""]

1. Nc3 e6 (1...d5 2. Nb5 Kd7 3. Nf3) 2. Ne4 Ke7 3. d3 f6 (3... Nf6 4. Bg5) 4. Bg5 fxg5 5. Qd2 Nf6 6. Qxg5

```

And it's check next move. Very far from the quickest or the most elegant solution, but this will do until somebody posts a good one.
> 3 votes

---
Tags: chess-variants, check, study, solving
---


# Question
Title: The Chess960 analogue in shogi, xiangqi, etc
Bobby Fischer said

> In chess so much depends on opening theory, so the champions before the last century did not know as much as I do and other players do about opening theory. So if you just brought them back from the dead they wouldn’t do well. They’d get bad openings. You cannot compare the playing strength, you can only talk about natural ability. Memorization is enormously powerful. Some kid of fourteen today, or even younger, could get an opening advantage against Capablanca, and especially against the players of the previous century, like Morphy and Steinitz. Maybe they would still be able to outplay the young kid of today. Or maybe not, because nowadays when you get the opening advantage not only do you get the opening advantage, you know how to play, they have so many examples of what to do from this position. It is really deadly, and that is why I don’t like chess any more.

and

> \[Capablanca\] wanted to change the rules already, back in the twenties, because he said chess was getting played out. He was right. Now chess is completely dead. It is all just memorization and prearrangement. It’s a terrible game now. Very uncreative.

and (emphasis mine)

> I love chess, and I didn't invent Fischer Random chess to destroy chess. I invented Fischer Random chess to keep chess going. Because I consider the old chess is dying, or really it's dead. A lot of people have come up with other rules of chess-type games, with **10x8 boards, new pieces,** and all kinds of things. I'm really not interested in that. I want to keep the old chess flavour. I want to keep the **old chess game**. But just making a change so the starting positions are mixed, so it's not degenerated down to memorization and prearrangement like it is today.

and from this interview in 2005

> You have to understand something about chess. Of course I'm better than Morphy. Why am I better than Morphy? I don’t say I have much more talent than him. I just know much more theory, right? If he came back today, and he could not open a book, let’s say, right? He would do badly even against masters, maybe. That has nothing to do with his talent though right? So when you say I'm better than so and so, it doesn't mean anything 'cause of all this theory in chess. Now if you were to ask if I were the most talented player that's something else.

**Question**: Do shogi or xiangqi suffer any of the same problems that chess does, according to Fischer, which led him to invent chess960? I mean are there any analogues of chess960 in shogi or xiangqi? I'm not asking about arbitrary variants. I'm asking really about variants created to address an such opening theory problem shogi might have.

Note:

Most of what I know about shogi and xiangqi is from tv series like Shion no Ou, but I really do not see how standard chess is unique in this or at least how shogi isn't the same this regard. Again, they are all mathematical and abstract strategy games that involve pieces on a board and have the same starting position of the pieces. (I believe it's the same with draughts/chequers, but of course in this case all the pieces at the start move the same. Maybe even go/baduk.) In each game, opening theory is I believe not only extremely viable to study but will dominate a very large portion of what a player ought to study.

Oh but I did read that shogi has extremely rare draws. That's fine, but as I understand chess960 wasn't invented mainly to reduce draws. I think the reduction of draws is a 2ndary goal or byproduct.

# Answer
> 5 votes
## Randomizing variants of Xiangqi

Xiangqi has numerous variants: here are three which involve randomization.

## Lucky Xiangqi

When I lived in Hong Kong, I saw numerous old guys playing Xiangqi in the villages - while their wives played Mah Jongg back home, I conjectured. About half the time, they would play a randomized version of the game, where all the pieces of a side except for the king start upside down, but on the 15 usual starting squares. Neither player knew which was which. Unlike Chess-960, there is no correlation between the two players' arrangements, so one might call it Xiangqi-115967627816040000, or if on friendly terms with it, Xiangqi-1.16E+17 for short.

**Detailed rules of Lucky Xiangqi**

According to a friend (ex-Hong Kong Xiangqi champion), a piece makes its *first* move according to its starting square and then flips to discover what it will be for the rest of the game. So a cannon on a horse square makes its first move as if it's a horse, and then behaves as a cannon for the rest of the game. The boundaries for elephants and advisers no longer exist. Pawns still may move sideways only when they are on the far side of the river, and the king cannot leave the palace.

There is now a random element, but this plays into the strategy. For example, if I have a chance to trade an unknown piece for a known piece, what are the relative values? This also removes both parity & boundary issues associated with elephants and advisers, which had always struck me as rather dull. As the game advances, more information is revealed and the game converges to regular Xiangqi, but in kinds of positions which are not normally reached orthodoxically.

The random element would not stop this version being classified in the Wikipedia list of Abstract strategy games that are not combinatorial. This category is defined as "including hidden information or set up, random elements (e.g. rolling dice or drawing cards or tiles) or simultaneous movement". Other hugely successful such games with a random element include Backgammon, Dominoes, Mah Jongg, Royal Game of Ur & Stratego.

My contact says Lucky Xiangqi has been developed for fun only, not because the opening theory of the orthodox game had been exhausted.

Here's a link which confirms that this is indeed a thing, but gives no more details: Lucky Xiangqi.

## Formation Xiangqi

According to this site a version similar to Chess-960 does exist.

**Detailed rules of Formation Xiangqi**

> One player's pieces are jumbled up, then placed randomly on one side of the river, except for the generals and advisors, which must be at their usual positions, and the elephants, which must start at two of the seven points they can normally reach. The other player's pieces are set up to mirror the first's. All other rules are the same.

There are 873,180 different starting positions. I have never seen this played. It retains the dull limitations on elephant and advisor movement of orthodox Xiangqi. I might offer a novel sub-version of Formation Xiangxi, "Reformation Xiangqi"? under which one can shuffle all 15 non-royal units, and ignore palace and river (except for king and pawns). But Lucky Xiangqi is much more engaging, as its popularity shows.

## Banqi

For completeness, I should also mention Banqi (aka: Half Chess, Blind Chess) although this is completely different game, that just happens to use a Xiangqi set and board.

It is played on the 8x4 squares of a half-board, rather than on the 10x9 vertices of a full board. Movement is just to an orthogonally adjacent square, but capturing depends on unit type (so: similar to Jungle, or to a lesser extent Stratego). Since every square is occupied at the beginning of the game, it is very random & chaotic like ferrets in a sack. But it works very well. I've actually played this one in Taiwan, back in the day, but I've never seen in it in Hong Kong.

# Answer
> 8 votes
For shogi and xiangqi, the answer is **no**. There is no analogue for western Chess960 in those chesses. Disclosure: I'm a decently strong player in all three.

The problems Fischer identified in those quotes you gave are that western chess favours the player with more opening preparation, and that there is no room for creativity. (Bear in mind that this is his own view as an insanely strong player who had reached the top level of the game back then.)

To answer the question from a broader context, I will give a little bit of history and cultural context to show why shogi and xiangqi, despite also suffering from the "dogma of opening theory", never arrived at randomisation of the start position as a solution - indeed, the opening theory is not even perceived as a severe problem.

(Also, I will keep the context to professional/master players; at the amateur level, really anything goes for openings in all of the chesses.)

## Shogi

Opening preparation is indeed important at the top levels. Historically the game has progressed from slower, cautious buildups favoured in the 17th-19th centuries, towards the more modern, faster game of the mid-20th century to today.

There are very sharp openings where one/both sides start attacking early and both players must walk tightropes (e.g. New Rapid Ishida; yokofudori/Side Pawn Picker; some lines of Gokigen Central Rook).

There are openings that have been examined to great depths (60 ply, even 80 or more ply) and involve many move order subtleties (Double Yagura games; Bishop Exchange; One-turn-loss Bishop Exchange).

There are openings which have gone even further, to survive in the ecosystem around it. (Fujii System was analysed literally all the way to mate in some lines by its inventory, Fujii Takeshii 9-dan.)

But yet, in the middle of all this, there is still room for creativity and variety. By the 1990s, of the two main styles, Static Rook was seen as the superior choice over Ranging Rook. The great player Habu Yoshiharu sparked something of a renaissance by playing Ranging Rook as an upstart young challenger in a title match - and winning. Since then different Ranging Rook styles, and even double Ranging Rook games, have never truly fallen out of favour at the professional level, even when engines overtook humans and universally preferred Static Rook.

There is more than enough to analyse, and still more creativity to be had (especially in double Ranging Rook games) - there was not a need for randomised shogi. This is of course not even mentioning arguments from tradition - there is no way that one can redo national culture by randomising the start position.

(Oh, and yes, randomised shogi would *heavily* disrupt existing opening theory, at least with regard to concrete moves.)

## Xiangqi

Even before I talk history, the simple logistics of it is that xiangqi pieces don't randomise well. The kings, advisors and elephants are bound to the few points they can leap to, and are almost worthless if randomly shuffled away; the cannon movement means that they also don't randomise well, since on the first move already captures may be possible.

Now the history. Again, opening preparation is important at the top level. This should be no surprise again, as top players do like to seek any advantage they can get.

In ancient times (think 800 years ago), xiangqi was thought to be a win for red, the first player - classical manuals do some analysis on opening traps and games for red to win with central cannon versus screen horses, or opposing cannons (either one).

Fast forwarding to more modern times, there was the same sort of status quo from chess and shogi at one point: it was thought that black had trouble neutralising red's initiative, and the only defence against a central cannon was screen horses. The theory debates in this flowed from the 1930s onwards in national tournaments in China, with multiple red and black setups tested in battle.

In the 1960s, Grandmaster Hu Ronghua decided to revisit a "busted" opening. Was the Fan Gong Ma defence for black really losing? With tons of effort into research and with sheer playing strength, GM Hu Ronghua managed to bring the dead opening back to life, winning big tournament games with it and drawing other masters to try it. Again, this brought forth another period of experimentation that has not quite died down; even today, masters are exploring more than ever other red openings than a central cannon, with more fertile ground waiting to be explored.

---
Tags: chess-variants, chess960, shogi, xiangqi
---


title: I am trying to understand chess moves

text:
# Question
Title: I am trying to understand chess moves
Hi I am trying to learn chess, and when I review my moves, I just don't understand how Nd4 is a good move and how nh4 is a blunder.

Thanks.

# Answer
> 11 votes
14.Nxd4 takes a pawn on d4, *and* it attacks the bishop on h5. So if black takes back with 14...cxd4, then white has 15.Bxh5, leaving white a pawn up (knights and bishops have roughly the same value). And if black wants to avoid this with 14...Bxe2, white can take back with the knight on d4 (15.Nxe2) so that it is safe too; again, white wins a pawn. And if black retreats the bishop, white retreats the knight, and is again up a pawn.

14.Nh4 does not win a pawn, so that already makes it a bad move when winning a pawn is available. But that is not all: black can first exchange bishops (14...Bxe2, forcing 15.Qxe2) and then *fork* the bishop on f4 and knight on h4 with 15...g5, winning a piece and opening lines against the white king.

That makes 14...Nh4 a blunder.

More importantly, I am not a chess.com user, but can't you press on those magnifier icons to see the line the engine has in mind after each move?

# Answer
> 0 votes
14. Nh4 is a blunder since after 14..., Bxe2 to save the bishop (the bishop could also retreat to f7 or e8 to save itself), 15. Qxe2, the pawn fork 15..., g5 will win a piece for Black (this fork could also be made after the bishop retreated, again winning a piece), whereas 14. Nxd4 (discovering an attack on the bishop) will win a pawn for White after 14..., Bxe2 (to save the bishop) 15. Nxe2. The bishop could also retreat in this last line to save itself, but the Black "d" pawn would still be lost to the knight, which could then immediately retreat to save itself. Incidentally, these actions (duscovered attacks, forks, along with several others such as pins) are known as tactics, skill at which is considered one of the most importanct elements for chess success. It can be developed by working on tactics problems, which are readily available online.

---
Tags: analysis, knights, blunder
---


title: Why is this a checkmate?

text:
# Question
Title: Why is this a checkmate?
I'm new to chess and I'm confused about a puzzle I was practicing.

As you can see my black queen has put the white king in check, but I'm confused how this is possible if a rook is right next to my queen and could capture me next turn. Am I missing something?

# Answer
> 81 votes
To get out of check, the king needs to move to a square that isn't attacked by any opposing pieces, or you need to capture/block attacking pieces such that the king is no longer under attack on its current square.

Since the queen is attacking the king and both of the unblocked squares it can move to, white needs to capture the queen to get out of check here. The only two pieces in position to attempt this are the king and the rook. The king cannot do because it would be attacked by the black rook if it did, and the rook cannot do it since it would expose the king to being attacked by black's dark-squared bishop.

This situation is called pinning: the bishop has "pinned" the rook (even if the queen weren't there) because moving the rook would expose the king to capture, and it is illegal to make a move which places your own king in check. This term is also used when the piece you expose by moving is a high-value piece other than the king (typically a queen or rook), but in this case it's not illegal to make the move, it's just a bad idea most of the time.

# Answer
> 26 votes
Rook at d2 is pinned by the bishop at g5 and hence the rook can not capture the black queen at c2 checkmating the white king at c1.

# Answer
> 26 votes
Since you are a beginner in chess first you need to understand the term **pin** in chess.

> In chess, a pin is a situation brought on by an attacking piece in which a defending piece cannot move without exposing a more valuable defending piece on its other side to capture by the attacking piece.

Now, coming to your answer: Rook cannot capture the queen at f7 as the rook is pinned by the the bishop at b4 and the rook cannot move from the b4 square. Hence, this will be a checkmate.

# Answer
> 12 votes
The original goal of chess was to capture the opponent’s king. The idea of “checkmate” follows this: you may as well call the game won/lost once capture next turn is inevitable. So you’re checkmated if whatever you do, your king would get captured next turn — i.e. if every move you can make would leave your king still in check.

In your example: There are two ways white can stop the original check, by capturing black’s queen with either the white king or rook. But each of those would leave the king in check from some other black piece — either black’s bishop, or black’s right-hand rook. So whatever white does, their king would still be in check afterwards, and so black would be able to capture it (if we still played on till the final capture).

Other answers mention terms like *pinning* to describe why the black rook can’t capture the white queen here. Those terms are useful for describing and understanding games, but they’re secondary to the main point here. The *concept of checkmate* is that it’s when whatever a player does, their king will still be in check.

# Answer
> 7 votes
White can't move their rook from d2 as your bishop at g5 will capture the white's king.

# Answer
> 2 votes
When your King is attacked, it can escape in any of three ways.

1. it can flee, i.e.move out of check
2. interpose a piece between itself and the attacker
3. capture the attacking piece.

In your example, the King cannot move out of check since it has no escape square, being cut off by the edge of the board and its own pieces, cannot interpose a piece since there's no intervening square between it and the attacking Queen, and cannot capture the attacking Queen with its King since the Queen is protected by the black Rook on c8, and also cannot use its Rook to capture the Queen, since the Rook is pinned to its King by the Black g5 Bishop. Hence it is in checkmate.

---
Tags: rules, checkmate, puzzles, pins
---


# Question
Title: Can the pawn take the rook in this position?
I have a question regarding the way that pawns are allowed to attack. Sorry I’m a beginner, but me and my friend are playing and I don’t want to make this move if I’m not allowed to. I have a picture of how it is. I’m clear he’s white, am I allowed to attack his Rook?

# Answer
Pawns are a pretty complex piece. They can make the following types of moves:

* Move one square forward, if that square is not occupied by any other piece.
* Move two square forward on their first move, if neither of those squares is occupied by any other piece
* Capture a piece diagonally in front of it
* Capture an enemy pawn "en passant".
* When they get to the 8th rank, they can "promote" to a Queen, Rook, Knight or Bishop

So, in the position you're showing, your pawn can capture either the enemy rook or the knight, but not the pawn right in front of it.
> 8 votes

# Answer
Since you are a beginner in chess, first you need to know how pawn capture other pieces in chess. The pawn is the only one of the chess pieces that can capture other pieces in a method that’s different from how it normally moves. There are two ways a pawn can capture:-

1. **The pawn captures by moving one square diagonally forward to the left or right.**
2. **En passant capture** https://en.m.wikipedia.org/wiki/En\_passant

So, in the above picture black pawn can capture either White's rook or the knight.
> 3 votes

---
Tags: rules, beginner, pawns
---


# Question
Title: What is the farthest away a game can be from a guaranteed checkmate?
What is the maximum number of moves away from checkmate that a player can be where checkmate is guaranteed? There are many positions that are a guaranteed win for a player if played perfectly, right? (Obviously there is not a guaranteed win from the first move). My question is: *What is the furthest amount of moves one can be from guaranteed checkmate, when the shortest amount of moves to checkmate is taken?*

Let's assume you are white and have, say, a bishop and a knight left and black is down to just the king. (there is a way to get checkmate with a bishop a knight, so checkmate is assumed to be *guaranteed*). Now, one set of moves could take say 40 moves to get checkmate from this point, but the least number is say 19 moves away. Now, my question is asking what the most amount of moves to guaranteed checkmate is, but you have to take the route to checkmate that has the least amount of moves, so 19 would be the case *from the point where the bishop and knight are the only pieces other than the kings left*.

I apologize for the lengthiness of this question, I couldn’t think of a good way to ask what I’m asking. This question derived from wondering if black or white could win every time from the first move but obviously that isn’t the case. The main question is at the end of my first paragraph.

Edit: 50 moves without a pawn push or a capture does not trigger a draw.

# Answer
The position with the longest known sequence away from checkmate has a mate in **595 moves**. It is a computer-verified extension of the 8-piece table record found by Lutz Neweklowsky.

By "verified," I mean Stockfish agrees with the moves that occur until the 8-piece position occurs, and then we know 100% it is correct from there. While we can't know defintely the first 4 moves are 100% the best, since 14-piece databases aren't here yet, it is best to accept them as it is at the limit of our technological capabilities.

```
[Title "Mate In 595 Moves"]
[FEN "7R/8/8/8/q7/p2B1KB1/P2pRQn1/3knB2 w - - 0 1"]

1. Qxe1+ Nxe1+ 2. Bxe1 dxe1=N+ 3. Rxe1+ Kxe1

```
> 12 votes

# Answer
I doubt that anyone will be able to give you a definitive answer beyond this one, but the longest known win from the end of a game is a famous 549-move 7-piece tablebase win. Until we get to 8-piece tablebases, this is probably the longest anyone can prove.

You can see that position, and all 549 moves here.
> 9 votes

# Answer
UPDATE:

An important update on 8-Men Tablebase by Marc Bourzutschky.

http://arves.org/arves/index.php/en/2-ongecategoriseerd/1509-8-men-tablebase-first-explorations?fbclid=IwAR2BwvtDqDsu\_2HIZjzHKWGgzJg42e1SX1SugBV\_fLxr8KfQ3rfp3iOt1C4

This is worth reading in detail, but one point demands quotation:

An important question is at what point the chess board becomes so crowded that adding more pieces does not lead to longer winning lines due to the increased likelihood of shortening captures. My results suggest that we may already be at or close to this saturation point: the longest winning line for 8-man endgames without pawns appears to be “only” 400 moves. \[...\] After generating about 15% of the pawnless endings I’m quite confident to have captured the longest ones. While 15% seems like a small subset at first blush, most other piece configurations have large material differences between White and Black so that long lines are unlikely.

**Q**: How long is the longest forced checkmate in chess?

**A**: We will probably never know but the naive extrapolation based on multiplication by number of moves is no longer impossible. It is even conceivable that we already know the longest forced mate in all of chess, which occurs with 7 pieces.

## 50/75 move-rules don't apply

Firstly, let's definitively remove one distraction: 50-moves (or 75-moves). The Codex for Chess Problem Compositions states:

> Footnote 12.
>
> Presently the rules defined in the 1 Jan 2018 version of the FIDE Laws are valid. \> Relevant for compositional chess are articles 1 to 5, 9.2 and 9.3.

This *includes* 50 moves-rule, but *excludes* 75 moves-rule. However:

> Article 17 – 50 Moves-Rule
>
> Unless expressly stipulated, the 50 moves-rule does not apply to the solution of chess compositions except for retro-problems.

These conventions are specifically crafted to support the kind of endgame analysis being discussed in this SE question.

The answers are very different from a superficially similar SE question where the 50 move-rule is taken into account.

## Extrapolation from 7-man

The 7-man case is solved at 549 moves, and ingenuity has pushed this back a few more moves (as of Jan 2021, 535 moves). The real breakthrough will come from tablebase development for the 8-man case. We don't know what the answer will be, but there is some intelligent extrapolation possible from existing results.

The Lemonosov webpage stated as long ago as 2014:

> Many show interest in what to expect from 8-man endings. First, take note that the longest 6-man mate took 262 moves (KRN-KNN). Moving to 7-man endings doubled \[the value\].

Of course, as the number of pieces increases, it maybe that the opportunity for stalemate increases and tends to dominate. There is no indication that this is happening at 7-man database level. We are not just limited to the 32-piece starting position, of course, we are looking at any legal position where no captures have yet taken place. So chess as whole might be a draw, while at the same time there might still be some very long forced checkmates in 32-man positions.

I imagine (and it can't be more than this) that such positions might lead themselves very quickly to exchanges, because the board is so cluttered). But I have no idea, and (absent some stupendous breakthrough in quantum computing) humanity will never know.
> 6 votes

# Answer
Here you can find a mate in 555 moves by me (Lutz Neweklowsky).

In this kind of chess compositions we don't have a 50-move-rule.
> 5 votes

---
Tags: engines, endgame, theory, checkmate, records
---


# Question
Title: Is there software which generates novel chess opening traps?
Opening traps can sometimes lead to quick wins, but fail against opponents who are prepared or have time to calculate. Thus...

**Question**: Is there software which generates novel chess opening traps?

I didn't easily find anything via Googling `chess opening trap generator`. Perhaps there's some inherent limitation which makes it not worthwhile or even impossible to do so.

# Answer
I am sorry, but you can not create any novel chess opening traps because all were already discovered in a certain range of moves. Also, I want to mention @RemcoGerlich's comment that even if there was an undiscovered opening trap then a computer couldn't recognize that it is a trap.

Instead, you could try to use an engine to look up moves that lose but are difficult to comprehend by humans.
> 1 votes

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


# Question
Title: Feedback and advice on a slav position for White
I play d4 with White and against the slav/semislav I start with the order of d4,c4,e3,Nc3 usually. But when I face the 3...Bf5 variation in the slav I do 4.Nf3. My problem is with a certain variation where I can't play Nh5 trying to capture the the light-squared bishop at the right time as illustrated in this variation:

```
[FEN ""]
1.d4 d5 2.c4 c6 3.e3 Bf5 4.Nf3 e6 5.Be2 Nd7 6.Nc3 Bd6 7. O-O h6 8. b3 Ngf6 9. Bb2 O-O 10.Rc1
Qe7 11. h3

```

After move 7...h6 I really don't know for which pawn structure I should go for. I noticed that Radjabov went for a b3 system and played the moves that I suggested up. But Black is better out of the opening and this really pisses me off! I mean I'm playing with White, I should have a slight advantage. My dark-squared bishop is bad, and Black's bishops are well developed! I would really appreciate your feedback about this position after move 3...Bf5 or 5...Nd7. How White should set up his pieces? and what are the general plans in these positions? In the variations where I'm allowed to play Nh5 to capture the bishop, I always do it. But if I can't, this is where I get stuck. btw I also checked the move 4.cxd5 cxd5 5.Qb3 or 5.Nc3 and then 6.Qb3

```
[FEN ""]
1.d4 d5 2.c4 c6 3.e3 Bf5 4.cxd5 cxd5 5.Qb3 (5.Nc3 Nf6 (5...e6 6.Qb3)(5...a6 6.Qb3)6.Qb3)

```

but I'm not sure about it. Let me know what you think.

# Answer
After 4.cxd5 the Queen cannot take because of 5.Nc3 Qa5 6.Bd2 which renders black in a horrible game (Stockfish says +1.4). So black has to play 4.cxd5 cxd5 5.Qb3 which either wins the pawn on b7 or forces black to play Qd7 (or Bc8)

```
[FEN ""]
1.d4 d5 2.c4 c6 3.e3 Bf5 4.cxd5 cxd5 5.Qb3 Qd7 6.Nc3 e6 7.Nf3 Nc6 8.Bd2

```

However, this is 0.0 or maybe +0.1. So it is not desirable for White. Instead, I advise you to play 4.Bd3

```
[FEN ""]
1.d4 d5 2.c4 c6 3.e3 Bf5 4.Bd3 Bxd3 5.Qxd3 e6 6.Nf3

```

or 3.cxd5. Even though it is frowned upon as a Remis variant.

```
[FEN ""]
1.d4 d5 2.c4 c6 3.cxd5 cxd5 4.Nc3 Nc6

```
> 1 votes

---
Tags: opening, slav-defense, semi-slav
---


# Question
Title: How is a perpetual check reached in this puzzle?
This puzzle on chesstempo caught my eye. We play as White:

```
[FEN "4Q/4p1bk/1p1qp2p/p1p1n2B/4P/2P3B1/PP4P/6K b - - 0 1"]

1. Nf3

```

**Side Note:** *The answer is of no importance here, so no spoilers from me. :)*

The puzzle is tagged with , yet I cannot see the perpetual check here. It has been discussed in the comments under the puzzle:

> * Why not just gxf3 and after Qxg3+, run away with the king to the left board edge and hide between pawns?
> * Because he can’t hide. When the king reaches c2, the black queen attacks from e2. When the king is on b3, the queen moves to b5, and perpetual.

However, I do not think this is quite right. b5 is protected by the White queen. So, where and how is perpetual reached on this board? I would appreciate a hint instead of the full solution. :)

# Answer
I think that Kf2 is actually the winning move for White and the perpetual results after gxf3.

```
[FEN "4Q/4p1bk/1p1qp2p/p1p1n2B/4P/2P3B1/PP4P/6K b - - 0 1"]

1. Nf3 gxf3 2. Qxg3+

```

Now the White king can not escape the perpetual even though the Black king is very close to checkmate.
> 1 votes

---
Tags: puzzles, check, perpetual
---


# Question
Title: How could I have prevented this long drawn out game?
Consider the following game. I am black.

```
[FEN ""]
1. e4 g6 2. d4 d5 3. e5 e6 4. Nf3 b6 5. Nc3 Bb7 6. Bg5 Be7 7. h4 Nc6 8. Bd3 Qd7 9. Qd2 O-O-O 10. Nb5 f6 11. exf6 Bxf6 12. a4 h6 13. Bxf6 Nxf6 14. Bxg6 a6 15. Nc3 h5 16. Qg5 Rdf8 17. Ne5 Nxe5 18. Qxe5 Ng4 19. Qg5 Rxf2 20. Bxh5 Rxg2 21. Bxg4 Rxc2 22. Qe5 Rg8 23. Bxe6 Re8 24. Bxd7+ Kxd7 25. Qxe8+ Kxe8 26. Nxd5 Bxd5 27. b4 Bxh1 28. h5 Rh2 29. Rd1 Rxh5 30. Kd2 Bc6 31. a5 bxa5 32. Re1+ Kd7 33. bxa5 Rxa5 34. Rg1 Be4 35. Rg7+ Kd6 36. Kc3 Rb5 37. Rg4 Bd5 38. Rg6+ Be6 39. Kd3 Kd5 40. Rg5+ Kd6 41. Rg6 c6 42. Ke4 a5 43. Rh6 a4 44. Rh8 Rb4 45. Rd8+ Kc7 46. Re8 Bd5+ 47. Ke5 Kb6 48. Rb8+ Ka5 49. Ra8+ Kb5 50. Rb8+ Kc4 51. Rh8 Bg2 52. Rh2 Rb2 53. Rh4 Re2+ 54. Kd6 Re4 55. Rh2 Rxd4+ 56. Kc7 Rd2 57. Rh4+ Kb3 58. Rh8 a3 59. Rb8+ Kc2 60. Ra8 Kb2 61. Rb8+ Kc1 62. Rb4 a2 63. Ra4 Kb1 0-1

```

I would say that both of us are at about the same skill level. The game started out okay. White was being more aggressive and I ended up more defensive than I would have liked during the opening (let's say the tenth move). By move 27, white has a slight advantage but he makes a blunder and loses one of his rooks. Assuming neither of us wants a draw, here are my questions,

* I have only a rook and a bishop. Just to make sure, it is difficult to force a mate with a rook and a bishop, right? Against a rook? Is my only option promoting to a queen and then mating him?
* By move 37, my intuition was that the (sole) white pawn on d4 would become problematic. Forcing a mate with only one rook is impossible so white has no choice BUT to promote to a queen. Therefore, I have to take that pawn and then work on getting my pawn promoted. Was this a reasonable strategy or was I being too cautious? Is there a better decision I could have made at this point?
* I was also unwilling to sacrifice one of my pawns because I didn't want to put all of my eggs in one basket. Was this reasonable or overly cautious?

I eventually took his pawn. The best case scenario is a draw for him now. By move 63, the forced mate is obvious to him and he finally resigns. My main question is,

**Was there any way to force a win and end the game quickly after move 30? Any path to a quick decisive victory?**

The game became very long and drawn out, probably because I was not being bold enough. This was correspondence chess so the game lasted like two months longer than it had to. My intuition is that I could have ended it sooner but I still can't actually see how. Is my intuition correct? Any comments in general to improve my game are also welcome.

# Answer
Very simple. Learn endgames.

If you knew much about endgames then you would know that in rook and pawn endgames your rook belongs behind your passed pawn. Knowing that on move 39 you wouldn't have played the pointless Kd5. Instead you would have played 39...a5 with the intention of following this with 40...a4 41...Ra5 and then just keep pushing the a pawn.

Note that your opponent's best plan was also to put his rook behind your passed pawn. That would make it impossible for you to put your rook behind the pawn and make it very difficult to push. Fortunately your opponent was equally ignorant of endgame theory.

Time spent learning endgames will gain you more points than anything else you could spend the same amount of time on.
> 11 votes

# Answer
I think I need to first clear up a misconception you have:

> Forcing a mate with only one rook is impossible so white has no choice BUT to promote to a queen.

> I eventually took his pawn. The best case scenario is a draw for him now.

**This is false**. A king and rook can, in fact, force checkmate upon a lone king. You should learn the technique ASAP. (It may be unlikely that he could do so considering all the extra material you have, but you need to be aware that it *could* be done.)

> I have only a rook and a bishop. Just to make sure, it is difficult to force a mate with a rook and a bishop, right? Against a rook? Is my only option promoting to a queen and then mating him?

Yes, that's very difficult and possibly impossible to force, depending on the position. (It's also very difficult to properly defend, for what it's worth.) You may run into issues with the 50 move rule. Promoting to a queen - or forcing your opponent to give up their rook to stop you from queening - is your best option.

> Therefore, I have to take that pawn and then work on getting my pawn promoted. Was this a reasonable strategy or was I being too cautious? Is there a better decision I could have made at this point?

Taking that pawn at that point was not strictly necessary, but it's a reasonable thing to do. If that pawn does queen you're in big trouble. If your concern was not drawing out the game, it probably would have been quicker to concentrate on advancing your a-pawn until he had to give up defending that pawn in order to stop you, at which point you might have been able to take it for free.

> I was also unwilling to sacrifice one of my pawns because I didn't want to put all of my eggs in one basket. Was this reasonable or overly cautious?

It depends. If you saw a clear path to queening a pawn, then sacrificing some other pawn in this situation would be perfectly reasonable. But if you didn't, then keeping as much material as you can is just common sense. There are many pawn and rook vs rook endgames which are draws with best play, and many king and pawn vs king endgames which are draws with best play, and if you wound up with your bishop and a-pawn against a lone king *that* could be a draw if the enemy king is well-positioned (your bishop doesn't control the queening square so you can't force the enemy king out of the corner if it gets there first) and you don't want to accidentally end up in one of those situations.
> 8 votes

---
Tags: analysis, learning, strategy, endgame, tactics
---


title: Four way chess -checkmate

text:
# Question
Title: Four way chess -checkmate
My friends and I have been playing knightmare chess in a four player variant. We were playing with the stipulation that when a player is checkmated, after his turn he removes his king from the board and his pieces change allegiance to the last player to cause checkmate.

I had caused checkmate on a player. An opponent between my turn and the checkmated player moved his bishop to cause check on the same king I had checkmated. He staked a claim to this player's pieces. I refuted his claim on the basis his bishop did not cause checkmate, only check while my pieces actually did cause checkmate. Who would get the pieces?

By definition, check is a move where a peice is threatening on his opponents next turn. According to this, I argued that I caused checkmate and was entitled to his peices.

# Answer
> 3 votes
I will need to make an educated guess as to what rules come closest to what you have described, and I think it is that:

1. You are checkmated whenever your king is attacked and if it were your turn next, you would not have any moves that would result in your king not being attacked.
2. An opponent causes checkmate on you, if at the start of their turn you are not checkmated, but at the end of their turn you are.
3. If at the start of your own turn you are checkmated, then your king is removed from the game and the opponent who last caused checkmate on you will gain control of your pieces.

Under these rules, merely piling on a check while it was already checkmate would not cause checkmate.

The rest of this post is background and further analysis of checkmate, that informed my answer and may help to understand it:

According to Wikipedia, it was the Persians who abandoned king capture and introduced warning of check in order to not accidentally end the game. So let's go back in time before the introduction of checkmate and reanalyse.

In two-player chess checkmate is a situation where at the end of your turn all parties are certain that you will (be able to) capture the king on your very next turn (and in two-player chess there exist no reasons not to actually capture the king). Because of this certainty of how the next two turns will play out (a doomed evasive move and a certain king capture), there is no point in actually playing those moves, so both can be (and have been in FIDE chess) eliminated from the game with no detriment to the game. (Very much the same thing happens when a player forfeits the game upon realizing that the game is lost and there is no point playing any further.)

But if there are three or more players a third party can intervene on behalf of a threatened king and (unless the game ends when the first king is captured) there may be more pressing matters than capturing an opponent's king left in check (like defending your own king). These differences make it impossible to say with certainty when king capture is actually going to take place before it actually happens, thereby invalidating the reasoning which allowed us to eliminate king capture from the (end of the) game.

It is of course possible to try and use a definition of checkmate that is equivalent to the full checkmate described above in two-player chess also in chess with three or more players. Indeed checkmate is usually defined in an operational way that is equivalent to full checkmate in two-player chess: your king is attacked and you have no move that will result in your king not being attacked.

When you try to use that definition in multi-player chess you will need to think about on which player's turns one can be checkmated. If your king is attacked and you have no move that will result in your king not being attacked, because it is not even your turn, are you checkmated? Apparently that was something you rejected, but then it becomes hard to say who checkmated you. It is possible for example that the player before you causes your king to be attacked by moving one of their pieces out of the way of a third player's piece, and even causes you to not have any moves that result in your king not being attacked, even though they are not even checking you with any of their own pieces. Have they checkmated you? I think most people are inclined to say yes. But if you want to know if they caused checkmate or not, then you need to be able to say whether or not you were already checkmated before their turn or not. Thus you need a way to determine checkmate even when it is not your turn.

One extreme is to say that every check from a player not immediately before you is checkmate (because as it is not even your turn you have no moves to remove that attack). Another way is to pretend that it were your turn and see if you could do something. I have recently even read rules for multi-player chess where it actually becomes your turn if you are checked, and the player whose turn it would have been had you not been checked continues after you (and you may or may not forfeit you actual next turn).

# Answer
> 1 votes
Checkmate is when the King is in check and no move would be able to remove him from check. If the Bishop check is a move that delivered checkmate, even if he was checkmated before, is the last checkmate and the pieces would be his.

# Answer
> 1 votes
I nearly agree with @hkBst, who says that one should determines the beneficiary at the beginning of the mated player's turn, by asking who would be able to actually capture the king (in the pre-Persian format). This would certainly give a unique result.

The removal of the king may also cause discovered checkmates to happen to as many a 4 other players in the game, if the board were large enough. And when they are eliminated for each of them that could result in another 3 discovered checkmates happening. Thus a cascade of checkmates might happen and the original mater might never have to move again.

Alternatively, the elimination of the king might create a discovered mate of the original mater himself! Does this mean that the original mate was illegal? I don't think so, in that the removal of the king in this case behaves like the mated player's move.

I also can't resist pointing out that the questioner says that under their rules, the mated king is removed **after** that player's turn. This suggests that the player gets to make some "last dying move", illegal in the sense that it doesn't avoid check, because it can't.

This would allow a mated player in some circumstances to select which of the opponents would inherit all the pieces. In a multi-player game like Diplomacy, selecting which of one's attackers will be the beneficiary is a very real threat, which can discourage attack and keep small fry alive. This is perhaps the most apposite possible example of the chess saying that the threat is more powerful than its execution, in that this can only be triggered if the player has definitively lost.

Can one capture pieces one has inherited, or are they now part of one's own force? If the latter, then it's possible that one might be stalemated as a result of inheriting pieces that one can no longer capture.

Finally, how *do* stalemates work in this game? Are the pieces frozen? Can they re-awake later potentially? Does the stalemated player need to hang around in case they are brought back to life?

So many questions about this brilliant mechanism...

---
Tags: checkmate, chess-variants
---


title: Center Game: Von der Lasa Gambit

text:
# Question
Title: Center Game: Von der Lasa Gambit
I am looking at this game and saw this opening.

```
[FEN ""]
1.e4 e5 2.d4 exd4 3.Bc4 Bc5 4.Bxf7+ Kxf7 5.Qh5+ g6 6.Qd5+ Kg7 7.Qxc5

```

The 3.Bc4 is new to me. I think people usually play 3.Qxd4. So, my questions are:

1. What is the idea behind 3.Bc4? Simply put pressure the f7 square?
2. It seems that 3. ...Bc5 allows White to sacrifice the bishop because he could take a bishop back at 7.Qxc5. Are there any other reasonable moves for black after 3.Bc4?

# Answer
> 4 votes
**3. Bc4** is one of those fairly regular moves that defer the opening selection of the Scotch Gambit (**1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4**) and the Danish Gambit (**1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4**). **3... Bc5?** is a well-known mistake because of the **Bxf7+** followed by **Qh5+** sequence.

That's why Black's move is normally **3... Nc6** or **3... Nf6**.

---
Tags: opening, gambits, center
---


title: Quickly losing a queen in style

text:
# Question
Title: Quickly losing a queen in style
I accidentally ran into this game again.

```
[FEN ""]
[startply "7"]

1. e4 e6 2. d4 Qf6 3. e5 Qf5 4. Bd3

```

What would be the fastest way to lose a queen by a direct attack on it (i.e. no pin, no discovered, no mate threats, etc.), when it has a maximum of 27 moves, but all 27 squares are attacked by the enemy? I estimate around 20 moves and very silly play. Avoid prematurely hanging the queen (or mate in 1) if possible.

# Answer
Treating the queen as a king, **31 plies** is done.

```
[FEN ""]
[startply "31"]

1. c4 d5 2. Qa4+ Nc6 3. d4 Bh3 4. g4 Rb8 5. Na3 b5 6. Nxb5 a6 7. Qxa6 Nxd4 8. Nxd4 f5 9. Nxf5 Nh6 10. Nxh6 dxc4 11. Be3 c3 12. f4 Qd7 13. Nxh3 Qd8 14. Nf2 Qd5 15. Rd1

```
> 8 votes

---
Tags: problems, records, queens
---


title: The value of less common moves

text:
# Question
Title: The value of less common moves
If you look at openings explorer, you can see the most popular moves and their respective win percentages. Most lines have top 2 or 3 moves that number in the (ten) thousands. However, there are moves less common (100s of games) with better percentages. What is the best way to think about this problem? If you take two alternatives with equal win percentages but one is much more common, is it better to play the less common because your opponent is less likely to be familiar with it? Alternatively, should you not play it because it's less popular for a reason, and that reason is that it's not as good?

Here is an example: https://www.chess.com/openings/Kings-Indian-Defense-Normal-Variation-4.e4-O-O

5. Nge2 has the highest win percentage, but it is not very popular.

# Answer
> 8 votes
There are many reasons why percentages are misleading. They can mean that the move is more often played when white is stronger than black, or in situations where a draw isn't what white wants, or there is a trap that many people fall into but that can be avoided, or lots of different reasons. Maybe it used to be considered good in the past until some novelty was found that refutes it, and then people stopped playing it.

For *your* game, what matters is how *you* will score playing it. That depends not on the results other people had with it in the past, but on how good your moves in the rest of the game are going to be.

So much more important than the winning percentage is *how well you understand the idea behind the move*. 5.Nge2 there is a bit odd since it doesn't pressure e5 and blocks the white bishop; but in return you keep options open with your f-pawn (you can still transpose to the Samisch, basically). *Is that what you want? Do you think you can make the best of those pros and cons? Do you understand what black can do to make use of the cons, and are you ok with that?*

That's the sort of thing you need to be asking instead of looking at percentages.

Although of course if they are extreme and you don't know why, that may be a hint that there is something you need to figure out.

Also, the problem with "is it better to play the less common because your opponent is less likely to be familiar with it" *with a move that you are not familiar with*, is that you are certain that you will be giving yourself that disadvantage, but there is still a chance that your opponent actually knows the move well. So only do that with sidelines you actually investigated a bit first.

# Answer
> 4 votes
Well, if people don’t see those moves often people don’t know how to react to them. Also keep in mind that the win percentage can sway easily due to the small amount of people playing that move.

# Answer
> 4 votes
> is it better to play the less common because your opponent is less likely to be familiar with it? Alternatively, should you not play it because it's less popular for a reason

Neither.

You would do best to understand that the only popularity contest that is important in your games is which positions you find easier / more fun to play. Play the moves that lead to positions you like not the ones that other people like. They are not playing your game. You are playing your game.

Of course to do this you will need to learn and understand which moves lead to which kinds of positions. Doing this, improving your positional understanding, is an important part of improving as a player.

---
Tags: opening, kings-indian
---


# Question
Title: Starting positions in Chess960 where black is definitely worse
In article in wiki about chess960, it is stated that:

> It has been argued that two games should be played from each starting position, with players alternating as White and Black, since some initial positions may offer White a bigger advantage than in standard chess. For example, in some Chess960 starting positions White can attack an unprotected black pawn after the first move, whereas in standard chess it takes two turns for White to attack and there are no unprotected pawns

But what are these positions? Is there a comprehensive study of some of them?

# Answer
> 11 votes
I asked myself the same question a year ago.

I found this interesting page: http://computerchess.org.uk/ccrl/404FRC/opening\_report\_by\_white\_score.html#table\_start

With statistics for every 960 positions based on 144,300 games played by 123 engines.

Apparently the position that gives the biggest advantage to White is RKNQBBNR with a White score of 63.9%.

Note that on the previous page the standard position has a White score of 56.0%. I once read that the true White score in standard chess is 55.5% for GM games. Since these two numbers are pretty close it would seem that the statistics of the previous page are meaningful and pretty accurate.

Also, someone once told me that if we just inverted Knights and Rooks then White would have a big advantage: NRBQKBRN. But the previous page actually says that White only scores 47.4% in that position, so maybe he was wrong.

Anyway, I seriously doubt there exists a position where White has an advantage of +0.50 or more. And every single one of the 960 positions are very probably just draws with best play.

# Answer
> 4 votes
I built this analysis over more than 4.5 millions of games played in Chess960 variant: https://github.com/welyab/chess960-win-by-position-setup

The most unbalanced setup is RNBKRBQN where white has 51.44% of win, and black 44.75% of win.

At general, white has a win rate of 49.17%, and black with 47.1%. There are more information on github repository.

# Answer
> 4 votes
This question was put to the Norwegian supercomputer Sesse in 2019, which analyzed each opening position using Stockfish 9 to a depth of 40.

Its conclusion was that there are four initial positions that give white an advantage of 0.5 or better. The maximum imbalance (worst for black) is BBNNRKRQ which has an evaluation of +0.57 in white's favor.

| position | eval |
| --- | --- |
| BBNNRKRQ | 0.57 |
| NNRKQRBB | 0.52 |
| NNRBKQBR | 0.50 |
| QBBRKRNN | 0.50 |

A side note: none of the 960 possible starting positions had an evaluation in black's favor. They're all even or favor white.

See more details in this article on chess.com.
And this report on blogspot.

# Answer
> 1 votes
While probably all 960 positions are a draw with best play, some positions give White the possibility of entering a position that forces Black to play exact, in order to not get in material disadvantage. In other words, White can make immediate threats that must be countered correctly. You can see this page for the motives you have to look out for:

https://lichess.org/study/UQTwIHXt

These are not the only starting positions with that motive but they are prototypical.

---
Tags: theory, chess960
---


# Question
Title: In verbally describing a move, can you simply say: “B4f to Q5e?”
I don’t have a picture to upload.

# Answer
> 3 votes
Since the standard algebraic notation dictates that we write Bf4 and Qe5 instead of the other way around, you normally just say "Bishop (to) f4", "Queen (to) e5", and so on. If we have a pawn capturing something, say "fxe5", it's normal to say "f takes e5" or "f e5" for short; if instead a piece takes something, say "Nxe5", it's normal to say "Knight takes (on) e5".

In general, you should never change the order when speaking from how letters are written in notation. As noted in the comments, some people tend to use very compact notation describing moves, i.e. "fe" instead of "fxe5" when there is no ambiguity, and you may hear some people therefore say "f e" instead of "fxe5", for instance.

Edit: I just realized that I misunderstood your question, and will therefore add an addendum to answer your specific question.

In the case you have a bishop on f4, and it takes a queen on e5 (I strongly suspect this is what you're asking about), you just say "Bishop takes (on) e5"; as long as there is no ambiguity in what you're describing you don't have to mention from which square the bishop moved, and it's never necessary to declare which type of piece the bishop took.

Edit 2: As noted in the comments, if there is no ambiguity (often there will not be) people may say "\[Piece\] takes \[Other piece\]" when a capture occurs; in the given example it would become "Bishop takes Queen". As noted, this can be practical when describing a sequence of captures on the same square.

# Answer
> -1 votes
Brief remark on ambiguity in notation: bishop moves are quite rightfully non-ambiguous as each has its color. They differ from knights and rooks in this regard: with a duo on the board, you need to pay extra attention to the position of the other one to determine whether or not it could reach the same destination after a moving or capturing.

---
Tags: notation
---


# Question
Title: Chess problem by A. G. Kopnin - Russian notation explanation needed
```
[Title "Alexey Grigorievich Kopnin - mate in two - 1948"]
[FEN "nR1rB3/2PPPN2/bbk1N3/1p2p3/1p2P1nq/1K1Pp3/7B/8 w - - 0 1"]

```

(source)

In this problem, it’s white to move and mate in two. What is the solution?

In the link (source) there is also a solution but it is in Russian notation and I do not understand it. (Maybe I would not understand it even if it was in English notation) I need to see the exact moves explicitly.

Here is the Russian solution:

```
1.d4! (угроза 2.d5#)
1…ed 2.Kfd8#
1…K:c7 2.Ked8#
1…C:d4 2.cdK#
1…Kf6 2.edK#
1…Л:b8 2.d8K#
(1…Л:e8 2.deФ/C#)

```

What move is the "1…ed" for example? There are just two columns "ed" but what is the row number and what piece should be moved and where?

# Answer
> What move is the "1…ed" for example?

"ed" indicates that an e pawn takes a d pawn.

> Maybe I would not understand it even if it was in English notation

It is actually in algebraic notation. If you follow the link you will find that it even tells you what the Russian abbreviations are for the pieces!

From there it is easy to work out that this is what it means:

```
[Title "Alexey Grigorievich Kopnin - mate in two - 1948"]
[FEN "nR1rB3/2PPPN2/bbk1N3/1p2p3/1p2P1nq/1K1Pp3/7B/8 w - - 0 1"]

1. d4 {threat d5#} exd4 (1...Nxc7 2. Nexd8#) (1...Bxd4 2. cxd8=N#) (1...Nf6 2. exd8=N#) (1...Rxb8 2. d8=N#) (1...Rxe8 2. dxe8=B#) 2. Nfxd8#

```

Note that "mate in 2" means that white mates in 2 moves exactly against any defence. Hence listing all the possible black replies to the first move.
> 7 votes

# Answer
I'd be interested to see this position come live in a real game; I have found 4 potential variants;

The Solution I found was

```
[Title "Alexey Grigorievich Kopnin - mate in two - 1948"]
[FEN "nR1rB3/2PPPN2/bbk1N3/1p2p3/1p2P1nq/1K1Pp3/7B/8 w - - 0 1"]

1. d4 Rxb8 2. d8=N

```

I think what the Russian text is doing is describing the different moves eg';

1. d4 Nxh2 2. d5#
2. d4 NxH2 2. d8N#
3. d4 Rxb8 2. d8N#
4. d4 Rxb8 2. d5#

So i am assuming that they are just listing different solutions; The idea seems to be to underpromote to a knight, or push the d-pawn

Edit;

Its Russian Notation ( https://en.wikipedia.org/wiki/Algebraic\_notation\_(chess) ) Kp = King (sometimes can be Kr) Ф = Queen Л = Rook С = Bishop К = Knight p = Pawn

So 1…Л:b8 2.d8K# in English notation would be 1... Rxb8 2.d8=N#
> 3 votes

# Answer
After

> 1.d4 (the first move that enables mate in 2)

the 'optimal play' for black is to either march to promotion or to capture the pawn

* **The optimistic best move**

> 1...e2 That's actually the "best" move choice: black is now only *one step from queening* his pawn. Any other possible piece move black has would be a *direct* contribution to black's demise; a self-inflicted blow. So *ceteris paribus*, black wisely keeps on pursuing his own goals and races for the new queen, as if following some principle of *lesser evil.*

* **The pessimistic best move**

Alternatively,

> 1...exd4 That's also active play. This capture removes the pawn, correctly identified as the most imminent death threat black has in the moment. Here black does not go for the queen, hence that pessimism.
> 2 votes

---
Tags: problems, notation
---


# Question
Title: Does it change anything to play blindfold chess for a "good" chess player?
It's been a long time since I wanted to ask this question to a professional player but as I don't know any, I thought maybe this was the right place to ask: Does it change anything to play blindfold chess for a "good" chess player ? How much is the level of play impacted when you play like this? Also I would like to learn to play blindfold, is there any good way to improve this ? Thank you very much.

# Answer
GM Alexandra Kosteniuk on a stream today mentioned how her father would encourage her to solve studies and puzzles by visualising the solutions and then say, setting it up on a board and then solving it blindfolded.

So if you're already at a stage where you can look at a puzzle on a screen and work out the solution without moving any pieces, the next step is to solve puzzles taking a glance at the board and then doing it blind.

This will help you in learning to retain the board in your mind, and having a guide like knowing it is a mate in 3 for example, will be a crutch so you can build up performing more complex calculations.

After you have managed this blindfold problem solving, you can then try playing blindfold chess. There are programs that help to train for this - off the top of my head, I know Lucas Chess offers a feature like this.

Even if you never play a blindfolded game against a real opponent, practicing it the right way can help your visualization and memory, thus helping your overall performance in any game.
> 3 votes

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


title: Depth problem in stf 12

text:
# Question
Title: Depth problem in stf 12
I don't understand something about depth in STF 12, in fact i thought it was basically the number of anticipated half moves, but when I run it, I sometimes have results with higher depth and less moves, for example:

info depth 48 seldepth 51 multipv 1 score cp 23 nodes 19440223582 nps 9584151 hashfull 1000 tbhits 0 time 2028372 pv e2e4 e7e6 b1c3 d7d5 d2d4 g8f6 e4e5 f6d7 c3e2 c7c5 c2c3 d8b6 a2a3 b8c6 b2b4 c5d4 c3d4 a7a5 b4b5 b6b5 e2c3 b5b6 g1f3 b6d8 f1d3 f8e7 c3b5 f7f6 e5f6 d7f6 e1g1 e8g8 f1e1 c8d7 c1f4 f6e4 f4c7 d8e8 d3e4 d5e4 has 40 half moves anticipated while

info depth 43 seldepth 47 multipv 1 score cp 28 nodes 7457369869 nps 9860163 hashfull 1000 tbhits 0 time 756313 pv e2e4 e7e6 d2d4 d7d5 e4d5 e6d5 g1f3 g8f6 f1d3 c7c5 c2c3 f8e7 e1g1 e8g8 h2h3 b8c6 f1e1 f8e8 c1g5 h7h6 g5f6 e7f6 d4c5 e8e1 d1e1 d5d4 d3e4 d8e7 e4d5 e7e1 f3e1 c8e6 d5e6 f7e6 c3d4 f6d4 b1c3 a8d8 a1d1 d4c5 d1d8 c6d8 e1f3 has exactly 43 half moves anticipated

The opposite can also happen beacause i found on the net (however not in stf12):

info depth 65 seldepth 97 multipv 1 score cp 8 nodes 17288598093977 nps 9446437 hashfull 999 tbhits 0 time 1830171180 pv c2c4 c7c5 g1f3 b8c6 d2d4 c5d4 f3d4 g8f6 g2g3 e7e5 d4b5 f8b4 c1d2 a7a6 b5c3 d7d5 c4d5 f6d5 f1g2 c8e6 e1g1 d5b6 c3a4 b4d2 g2c6 b7c6 a4b6 d8b6 d1d2 e8g8 d2c2 f7f5 b1c3 f5f4 c3a4 b6a7 a4c5 a7f7 c5e6 f7e6 c2e4 f8f6 b2b3 f6h6 a1c1 e6h3 e4g2 h3e6 c1c4 a8d8 f1c1 f4g3 h2g3 d8d2 c4c6 e6c6 g2c6 h6c6 c1c6 d2a2 g1f1 g8f7 c6c7 f7f6 f2f3 a2b2 c7a7 b2b3 a7a6 f6e7 a6a7 e7f6 f1f2 b3b2 f2e3 f6g6 a7a6 g6g5 which has a 78 half moves anticipated.

Could you explain me where it comes from?

Thanks!

# Answer
A chess engine's depth used to denote how many half moves it calculates ahead (roughly speaking), however this has long not been true anymore. Traditionally you would search one depth at a time, so first 1 ply deep, then 2 plies deep, then 3 and so on, each iteration increasing the depth by one ply. Modern engines however have various search heuristics which lets them search deeper in relevant positions and less deep in less important positions. Because of that, the iteration counter that is still called depth there, is hardly representative of the actual depth of the main line. (also of course the depth of the different calculated lines can be very different)

One thing that (AFAIK) still counts for something is the "seldepth" number, which denotes the deepest line looked at. However that number too is not too relevant, one line being calculated very deeply doesn't necessarily tell much about the other lines.
> 3 votes

---
Tags: engines
---


# Question
Title: Polyglot opening book: getting incorrect moves
I am in the process of adding an opening book to my C++ engine and I hit a problem. Here is what I have:

* The Perfect2021.bin opening book that I would like to use.
* The function that creates the polyglot hash for the board. I tested this with many boards, and it is correct.

Now I would like to retrieve and for now only print all the moves my engine can make in a position, according to the book. I tried it with the following method:

```
move opening_book::getBookMove(const chessboard& board, const game_information& info) {
        uint64 boardKey = polyKeyFromBoard(board, info); //get key for board
        std::cout << "Finding moves for board key: " << std::hex << boardKey << std::dec << std::endl;
        unsigned short moveKey;
        //list moves from the book
        for(polyglot_book_entry* entry = entries; entry < entries + entriesNumber; entry++) {
            //apparently I need to swap bits for these
            if(boardKey == swap_uint64(entry->boardKey)) { //found the board in the book
                moveKey = swap_uint16(entry->move);
                unsigned short fromFile = (moveKey>>6)&7, fromRank = (moveKey>>9)&7,
                               toFile = (moveKey>>0)&7, toRank = (moveKey>>3)&7;
                unsigned int fromSquare = (8 * fromRank) + fromFile,
                             toSquare = (8 * toRank) + toFile;
                std::cout << "Move found: " << createSquareName(fromSquare) << createSquareName(toSquare) << std::endl;
            }
        }
        return move(); //not returning actual move right now
    }

```

But when I for example make my engine play black and I open the game on white with the move *e2e4* then the following is printed upon the engine checking the opening book:

```
Finding moves for board key: 823c9b50fd114196
Move found: c2c4
Move found: e2e4
Move found: c2c3
Move found: e2e3

```

The board key is correct. It is one of the test cases on this site. However, as you can see the moves that are found seem to be for white.

Can someone please help me out? Thanks.

# Answer
> 2 votes
I have found the problem: my board representation was different and while my ranks are also from 0-7, but they are counted from the black side, while in the polyglot encoding, they are counted from the white side (which makes sense).

So I had to invert my ranks like so:

```
unsigned short fromFile = (moveKey>>6)&7,
                          fromRank = 7 - ((moveKey>>9)&7),
                          toFile = (moveKey>>0)&7,
                          toRank = 7 - ((moveKey>>3)&7);

```

Files remain unchanged. I am now getting reasonable output:

```
Finding moves for board key: 823c9b50fd114196
Move found: c7c5
Move found: e7e5
Move found: c7c6
Move found: e7e6

```

---
Tags: engines, programming
---


# Question
Title: A nine pieces opposite color bishop endgame
In the below position, the black pawn in g4 is weak, yet White do not seem profit from the situation. The position is

```
[FEN "8/P1B5/4k3/2Kb4/4p1p1/6P1/4P3/8 b - - 0 0"]

```

with black to move. My modesto Houdini 6.02 give fixed score as far as d=61(three quarters of a hour), but it may be necessary to go as far as d=70, if not even higher, with a tablebases enhanced engine(mine is not) to be completely certain it is actually a draw, or find the win.

# Answer
This position is almost certainly a draw. Black's next move could be Ba8, blocking the a7 pawn and putting the bishop out of harm's way. So how would White proceed from there?

One possible White plan is to promote the a7 pawn. But the promotion square is light-colored, so it cannot be supported by the White bishop. To get support from the king, White needs to get their king to c7 and then b8. (b7 and c6 are guarded by the Black bishop, so the White king cannot use those squares.) But how? If they move the c7 bishop and then play Kb6, Black simply plays Kd7 (or possibly Kd6 or Kd8 if they need to waste a move, depending on the position of White's bishop.)

Another possible White plan is to take the g4 pawn. It's on a light square, so it cannot be taken by the bishop, so that means the king has to do it. But that doesn't work either. White's's king would need to get to f4 (perhaps via e3), but Black can easily move their own king to f5 (or e5 or g5) in time to prevent this.

I don't see any other possible plans. The Black bishop cannot be captured (we've established that the White king cannot get to b8 to threaten it) and the e4 pawn is protected by the Black bishop. Since the White king cannot penetrate into Black's position, the pawns are blocked, and the White bishop cannot make progress on its own, the game is drawn.

```
[FEN "8/P1B5/4k3/2Kb4/4p1p1/6P1/4P3/8 b - - 0 1"]

1... Ba8 2. Kb6 Kd7 3. Be5 Kd8 4. Bb2 Kd7 5. Kc5 Ke6 6. Kd4 Kf5 7. Ke3 Kg5 8. Kd4 Kf5 9. Kc5 Ke6 10. Kb6 Kd7

```
> 1 votes

---
Tags: bishop-endgame
---


# Question
Title: How to think this end game puzzle and play this position
I encountered the following puzzle on Lichess. I instinctively knew I had to play Kc4 and then it would be about counting possible moves since neither king can move with out losing a pawn but I was lost.

How should I approach this position as white?

```
[fen "8/5pp1/3k3p/p1pP4/P7/3K1P2/6PP/8 w - - 0 1"]

```

# Answer
> 7 votes
As you rightly point out Kc4 is forced for white and then whichever king has to move first loses.

It is worth quickly checking if white can abandon the d5 pawn and go for the a5 with the intention of queening the a4 pawn. You do this by counting to see who queens first.

For white it goes Kb5, Kxa5, Kb4 (to threaten the c pawn), a5, a6, a7, a8=Q - 7 moves.

For black it goes Kxd5, c4, Kd4, c3, c2, c1=Q - 6 moves and black will win the white queen after checking on the b and a files.

White can avoid this by going Kb6 instead of Kb4 but then black can miss out the move Kd4 and queen two moves before white instead of just one. Again lost for white. So the kings are locked in place.

We can see that here:

```
[fen "8/5pp1/3k3p/p1pP4/P7/3K1P2/6PP/8 w - - 0 1"]

1. Kc4 h5 2. Kb5 Kxd5 3. Kxa5 c4 4. Kb4 (4. Kb6 c3 5. a5 c2 6. a6 c1=Q 7. a7 Qb2+) 4...Kd4 5. a5 c3 6. a6 c2 7. a7 c1=Q 8. a8=Q Qb2+ 9. Ka4 Qa1+ 10. Kb4 Qxa8

```

Then it becomes a case of counting "reserve moves". Basically the number of reserve moves each side has in this position is the number pawn moves before losing something. Black has two problems here. First they have to move first and second the symmetry in the position suggests that the number of reserve moves for each side is the same.

Obviously, unless you have a tactical possibility, then you only ever want to move a pawn one square forward and never two. That would be a blunder and just lose a precious reserve move. Also, if you can move an opposed pawn past the halfway line between your pawn and your opponent's pawn you can maybe gain a move / deprive your opponent of a move.

Checking that is relatively easy. Here is what it could look like:

```
[fen "8/5pp1/3k3p/p1pP4/P7/3K1P2/6PP/8 w - - 0 1"]

1. Kc4 h5 2. f4 g6 3. g3 f6 4.h3 g5 5. f5 g4 6. h4

```

and black, as predicted, has run out of reserve moves first and so loses.

---
Tags: endgame, puzzles, pawn-endgame
---


# Question
Title: Is the position in this trick question reachable?
I found this trick question on r/Anarchy chess: White to move, mate in two.

```
[FEN "2R2RK/6PP/5P/3PN/P/1pQ3p/n1p1qbp/5brk w - - 0 1"]
[StartFlipped "1"]

```

The trick is that

> you're looking from Black's side, so the white pawn on the H file can promote to a Queen or a Rook, with the only option left for Black to throw their Queen in between.

But is this position actually reachable?

The black and white pawns must've passed eachother, which is not impossible but not trivial either.

# Answer
> 40 votes
Even though the board is upside down, the position is still easily legal.

```
[FEN ""]
[startply "86"]
[StartFlipped "1"]

1. a4 h5 2. g4 h4 3. Bg2 Rh5 4. gxh5 h3 5. h6 e5 6. Nf3 Bc5 7. Nxe5 hxg2 8. h4 Ne7 9. h5 g5 10. Rh4 Ng6 11. Rf4 g4 12. Rxf7 Qh4 13. e3 Bxe3 14. Ke2 a5 15. f4 Qf2+ 16. Kd3 Nc6 17. b4 b5 18. bxa5 Rxa5 19. Rf8+ Ke7 20. f5 b4 21. f6+ Ke6 22. hxg6 Rc5 23. g7 Rxc2 24. h7 Rxc1 25. Ra3 Rxb1 26. Qc2 Rg1 27. Rc3 Kf5 28. Rc5 Kf4 29. Rd5 Kg3 30. Ke4 Ba6 31. Rxd7 Bf1 32. Rdd8 Qe2 33. Kf5 Bf2 34. Kg6 Kh2 35. Kf7 Kh1 36. Kg8 b3 37. Qc3 Nb4 38. d4 Na2 39. d5 c5 40. Rc8 c4 41. Qd2 c3 42. Qd3 c2 43. Qc3 g3

```

# Answer
> 8 votes
A rule of thumb for these kind of positions that capturing an officer will allow a pair of pawns to pass one another and potentially promote. Capturing a pawn will allow three other pawns to become passed. So you can see that there is easily enough missing pieces to have created this position.

If the issue is that pawns have moved sideways, then the arithmetic is different. Or there may be parity concerns sometimes, particularly if the colour of bishop promotions is important. Neither case applies here however.

---
Tags: checkmate, problems, retrograde-analysis
---


# Question
Title: limit stockfish 9 to a specific range of ELO rating
I am using stockfish 9 for our chess game project, and I want to limit the ELO rating of the engine to a range. I saw attributes like `movetime` and `depth` are used to limit the engine skill level, but I am not sure about how to match these attributes to a specific ELO rating.

# Answer
https://github.com/official-stockfish/Stockfish. Check `UCI_LimitStrength`. One of the UCI options.
> 2 votes

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


# Question
Title: Looking for a simple GUI for variants of chess
I am currently coding an engine for a variant of chess called Monster Chess. I was wondering if there a GUI existed that would simply take pieces from a square to another (eg e4 to e5) without considering the legality of the move or whose turn it was, since in Monster Chess white gets two plies for every ply black gets, and white can temporarily move into check.

# Answer
> 1 votes
The chessboard editor at https://www.apronus.com/chess/pgnviewer/ has two modes selected by radio buttons: "position setup" and "legal moves only". In position setup you can do anything on the board including adding or removing chessmen.

---
Tags: engines, chess-variants, programming
---


title: What to do with space?

text:
# Question
Title: What to do with space?
I sometimes find that after an opening, I have created "space" for myself, and control most of the board. But then I'm not sure what to do next.

For instance (0 6 time control on Lichess, me 1560 vs 1400):

```
[FEN ""]
[StartPly "25"]

1. d4 e6 2. c4 c6 3. Nc3 d5 { D31 Semi-Slav Defense: Accelerated Move Order } 4. c5 Bd7 5. Nf3 Nf6 6. Bg5 Be7 7. Bxf6 Bxf6 8. e4 dxe4 9. Nxe4 Be7 10. Bd3 b6 11. b4 bxc5 12. bxc5 Bc8 13. Qd2 Ba6 14. Bxa6 Nxa6 15. O-O Qc7 16. Qd3 Nb8 17. Nfg5 Nd7 18. Nf3 Rb8 19. Neg5 h6 20. Ne4 O-O 21. Rab1 Rxb1 22. Rxb1 Rb8 23. Rxb8+ Qxb8 24. Qc2 Qb5 25. h3 Nf6 26. Nd6 Bxd6 27. cxd6 Qd5 28. Qc5 Qxc5 29. dxc5 Nd7 30. Nd4 Kf8 31. Nxc6 Nxc5 32. Nxa7 Ke8 33. Nb5 Kd7 34. Kf1 Nb7 35. Ke2 Nxd6 36. Nxd6 Kxd6 37. Kd3 Kc5 38. Kc3 Kb5 39. Kb3 f6 40. a4+ Ka5 41. f3 g6 42. Kc4 Kxa4 43. Kc5 e5 44. Kd5 Kb4 45. Ke6 f5 46. Kxe5 Kc5 47. Kf6 g5 48. Kxf5 Kd5 49. Kg6 Ke5 50. Kxh6 Kf4 51. Kh5 Kg3 52. Kxg5 Kxg2 53. f4 Kxh3 54. f5 { Black resigns. } 1-0

```

I'm equal on material, ahead on development, and I control much more of the board.

How do I convert these advantages into something concrete?

# Answer
Having a space advantage means you have more room to navigate your pieces.

Space may allow you to attack on both sides of the board, or attack on one side then switch to the other; the cramped defender simple can't navigate as well.

You may be able to dominate an open file as it is easier for you to double or triple heavy pieces.

In late middlegame to endgame situations your king can get further up the board.

In your specific game black has a lot of weak squares and is behind in development as well as space disadvantaged. Your play needs to consider other fundamental elements. First after 13...Ba6 you shouldn't waste **time** with 14.Bxa6 which after Nxa6 allows Nc7-d5 with occupation of an **outpost**. But rather just continue development with 14.0-0

In the game black continued to play horribly with 15...Qc7 and after 16.Qd3 Nb8 you have various options. Doubling rooks on the b-file and penetrating the 7th rank will be crushing. Consider the rook lift Rb1-b3 -- if Black castles trying to get his h8 rook in the fight, the b3 rook can swing to the kingside.

You can also think about occupying d6 with a knight (Ne5-c4-d6).

Wasting time with Ng5 and back like you did is not because you don't know what to do with space, but rather you don't know what to do with your pieces in general.

Target weak squares, coordinate, and invade!
> 2 votes

---
Tags: strategy, middlegame, space
---


title: What is black's idea in this puzzle?

text:
# Question
Title: What is black's idea in this puzzle?
This is one of Lichess's puzzles, taken from a real game. Black is on the move.

```
[FEN "1r1q1rk1/5pbp/3pbnp1/1p1Np1B1/1p1nP3/P1N2P2/2P1B1PP/R2Q1RK1 b - - 0 1"]

1... Nxe4 2. Bxd8

```

The suggested move is Nxe4. However, I don't see how Black gains an advantage after White plays Bxd8.

Correction: The suggested move is Nxd5

# Answer
You are quite right Nxe4 makes no sense. However Nxd5 does because then Qxd8 ends up losing 4 pieces for a queen:

```
[fen "1r1q1rk1/5pbp/3pbnp1/1p1Np1B1/1p1nP3/P1N2P2/2P1B1PP/R2Q1RK1 b - - 0 1"]

1...Nxd5 2. Bxd8 Nxc3 3. Qd2 Ncxe2+ 4. Kh1 Rfxd8

```

However if white doesn't take the queen and instead plays the next most obvious move, taking the knight with the e pawn, white still ends up losing a piece:

```
[fen "1r1q1rk1/5pbp/3pbnp1/1p1Np1B1/1p1nP3/P1N2P2/2P1B1PP/R2Q1RK1 b - - 0 1"]

1...Nxd5 2. exd5 Qxg5 3. dxe6 bxc3 4. exf7+ Rxf7 5.

```
> 8 votes

---
Tags: puzzles, lichess
---


title: Lichess summary analyzer tool

text:
# Question
Title: Lichess summary analyzer tool
I'm trying to find an online tool that I had once used to analyze my games. It allowed me to import thousands of my games from Lichess and showed what my most common opening mistakes were. The only thing it needed was my Lichess user name.

I had learned about that tool from an Eric Rosen twitch stream. I used it only once on that day. It's been a while since then and I've forgotten the name of the website. I tried searching for various keywords but I'm unable to find it. Maybe it's not visible to search engines?

I would like to know what website it is.

# Answer
> 6 votes
I suspect you are looking for OpeningTree

---
Tags: opening, analysis, lichess
---