Answers.Body: <pre><code>1Q2r1k1/P6p/8/8/4q3/7P/6PK/8 w - - 2 6
  </code></pre>
  
  <p>White to move. 1.a8=Q Qxa8 2.Qg3+ may be a perpetual check that is hard to analyze. See the comments in the discussion of this tactics problem at <a href="http://chesstempo.com/chess-problems/103006" rel="nofollow">http://chesstempo.com/chess-problems/103006</a></p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-11-30T10:19:50.990Z
Answers.Text: Really, such a simple looking position? If computer finds this hard to analyze, then this would be one of the best answers for the question.
Answers.UserDisplayName: Cyriac Antony
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-03-06T06:42:53.003Z
Answers.LastActivityDate: 2015-03-06T06:42:53.003Z
Answers.UserDisplayName: MichalRyszardWojcik
Answers.Body: <p><a href="http://chesstempo.com/chess-tactics/90023" rel="noreferrer">http://chesstempo.com/chess-tactics/90023</a>
  The final position of the solution is an ending with queen against two knights with pawns on both sides where the knights can set up a blockade. Looks like a draw but the engine evaluates that the queen side wins.</p>
  
  <pre><code>8/5ppk/7p/3pP3/5P2/5N1P/4NKP1/7q b - - 0 5
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-12-14T08:30:42.000Z
Answers.Text: Can you post the position on here? This link might not be accessible in the future.
Answers.UserDisplayName: SmallChess
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-12-14T08:23:25.947Z
Answers.LastActivityDate: 2014-12-14T15:24:47.327Z
Answers.LastEditDate: 2014-12-14T15:24:47.327Z
Answers.UserDisplayName: MichalRyszardWojcik
Answers.Body: <p>Besides fortresses, another type of position the engines tend to get wrong is when the weaker side is about to promote a pawn but the promotion can be delayed indefinitely. </p>
  
  <pre><code>[FEN "5Q2/8/8/8/2k5/7P/1p4PK/r7 w - - 0 1"]
  [White "Anatoly Karpov"]
  [Black "Anthony Miles"]
  [Event " Biel"]
  [Date "1990  (analysis, white to move)"]
  </code></pre>
  
  <p>For a human player it is easy to see that this is a draw, but the engine has to try all the different checks from all possible squares in all different orders. (I haven't tested this position with the newest engines, perhaps some of them can handle this?)</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-12-14T18:48:27.117Z
Answers.Text: Stockfish 5 takes about 0.02 seconds to recognise this as a draw.
Answers.UserDisplayName: Stephen
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-12-14T18:55:17.733Z
Answers.Text: @Stephen With or without 7-men tablebases?
Answers.UserDisplayName: Dag Oskar Madsen
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-12-14T18:56:25.263Z
Answers.Text: Without any tablebases.
Answers.UserDisplayName: Stephen
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-12-14T19:06:01.723Z
Answers.Text: Good. I just remember looking at this game a few years ago, and the engines at the time didn't see that black should go for this position to save the game.
Answers.UserDisplayName: Dag Oskar Madsen
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-12-14T17:30:24.860Z
Answers.LastActivityDate: 2014-12-14T17:30:24.860Z
Answers.UserDisplayName: Dag Oskar Madsen
Answers.Body: <p>The following two links seem to be exactly what you are looking for (many such positions in each one of them).</p>
  
  <p><a href="http://en.chessbase.com/post/can-we-still-deceive-computers-in-chess">http://en.chessbase.com/post/can-we-still-deceive-computers-in-chess</a></p>
  
  <p><a href="http://www.chess.com/forum/view/general/positions-engines-get-wrong--please-contribute">http://www.chess.com/forum/view/general/positions-engines-get-wrong--please-contribute</a></p>
  
  <p>A cute study, which engines are unable to solve last I checked (white to move and win):</p>
  
  <pre><code>6r1/p1p1p1pP/P1PpP1P1/8/2P1B3/2K3pp/3P2rq/R5bk w - - 1 0
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-03-06T19:52:55.530Z
Answers.Text: I think the study might be cooked. The mainline goes **1.hxg8=N d5 2.Bf3 d4+ 3.Kb4 d3 4.Nh6 gxh6 5.g7 h5 6.g8=N h4 7.Nf6 exf6 8.e7 f5 9.e8=N f4 10.Nd6 cxd6 11.c7 d5 12.c8=N d4 13.Nb6 axb6 14.a7 b5 15.a8=B bxc4 16.Bae4 c3 17.Bxd3 c2 18.Bf1 d3 19.Kb3 c1=Q 20.Rxc1 Bd4 21.B1xg2# 1-0**. But 12... dxc4 poses problems. The intended solution continues 13.Nb6 c3 14.Kc4 cxd2 15.Kxd3, but 14... axb6 seems to throw a spanner in the works. See for example [this discussion in Dutch](http://schaaksite.nl/page.php?al=timman-weerlegd).
Answers.UserDisplayName: kahen
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-03-06T19:53:31.460Z
Answers.Text: [Google translate link](https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fschaaksite.nl%2Fpage.php%3Fal%3Dtimman-weerlegd&edit-text=) (for the Dutch-impaired - such as me).
Answers.UserDisplayName: kahen
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-13T17:43:46.023Z
Answers.LastActivityDate: 2014-09-13T18:03:39.810Z
Answers.LastEditDate: 2014-09-13T18:03:39.810Z
Answers.UserDisplayName: GloriaVictis
Body: <p>Basically, I would like to ask people to share their knowledge on famous and/or particularly instructive examples of chess positions, which chess engines do not understand well (i.e. do not evaluate correctly).</p>
  
  <p>A good example of the kind of positions I am interested in is the <a href="http://en.wikipedia.org/wiki/Rook_and_pawn_versus_rook_endgame#Van.C4.8Dura_position">Vančura Position-Wiki</a> (cf. also <a href="http://en.chessbase.com/post/karsten-mueller-understanding-the-vancura-draw">Vančura Position-Chessbase</a>), which occurred very recently (at the Sinquefield Cup 2014) in the game <a href="http://www.chessgames.com/perl/chessgame?gid=1772860">Carlsen-Aronian</a>. Although the engine was saying white is completely winning, the game was a theoretical draw after black's 48th move.</p>
  
  <p>Thanks in advance!</p>
  
  <p>P.S. I should stress that I am looking for realistic examples, i.e. those which are likely to happen in a real game. Positions of the following type,</p>
  
  <pre><code>[fen "4k3/4p3/3pPp2/2pP1Pp1/1pP3Pp/pP1K3P/P2RRR2/8 w - - 0 1"]
  </code></pre>
  
  <p>and similar artificial positions is <strong>not</strong> the kind of thing I am looking for.</p>
  
  <p>I should also say that endgame tablebase examples are OK. The only requirement is that engines (run on an average computer) are not able to evaluate the position correctly after given, say, 10-15 minutes time to "think".</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-08-03T23:26:55.027Z
Comments.Text: The position is illegal: White has 3 rooks so at least one must be promoted. But white has 8 pawns.
Comments.UserDisplayName: Lucenaposition
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-09-13T11:40:43.700Z
Comments.Text: Maybe "engine" is a bit too vague. I keep wondering why "machines" are often believed to have one unique chess style.
Comments.UserDisplayName: Pierre Arlaud
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-09-13T12:22:40.393Z
Comments.Text: @Pierre Arlaud: Specifically, when I used the word "engine", I had for example Stockfish or Houdini in mind (the chess engines most often used in live broadcasts of chess events, and considered to be the the best widely used chess engines). The purpose of my question was to pinpoint the most important situations, in which these, most commonly used and trusted, tools fail to provide a satisfactory or correct answer. And also, because the positions which engines do not evaluate well are often very instructive and interesting to analyze (when they are realistic).
Comments.UserDisplayName: Zvonimir
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-09-13T13:21:50.720Z
Comments.Text: @Ricky Demer: Not necessarily. The examples can include fortresses, but since there are many types of fortresses and most of them are a problem for engines to evaluate correctly, I am searching for particularly aesthetic and instructive examples of fortresses; the ones that really catch your eye when you see them. Also, an example of a famous game featuring some nice fortress ideas would also be appreciated. The stress is on aesthetics and theoretical or historical importance of the examples.
Comments.UserDisplayName: Zvonimir
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-09-13T16:14:34.437Z
Comments.Text: @Ricky Demer: Brilliant, thank you! Btw, I think I am going to remove the word "list" from the title of the question, since it seems to discourage people from answering the question :)
Comments.UserDisplayName: Zvonimir
Tags: <engines><endgame>
Title: Instructive chess positions (and famous games/studies containing these) that engines do not understand well
ThreadText: # Instructive chess positions (and famous games/studies containing these) that engines do not understand well
  
  (Asked by: username_0 on 2014-09-13)
  
  Basically, I would like to ask people to share their knowledge on famous and/or particularly instructive examples of chess positions, which chess engines do not understand well (i.e. do not evaluate correctly).
  
  A good example of the kind of positions I am interested in is the [Vančura Position-Wiki](http://en.wikipedia.org/wiki/Rook_and_pawn_versus_rook_endgame#Van.C4.8Dura_position) (cf. also [Vančura Position-Chessbase](http://en.chessbase.com/post/karsten-mueller-understanding-the-vancura-draw)), which occurred very recently (at the Sinquefield Cup 2014) in the game [Carlsen-Aronian](http://www.chessgames.com/perl/chessgame?gid=1772860). Although the engine was saying white is completely winning, the game was a theoretical draw after black's 48th move.
  
  Thanks in advance!
  
  P.S. I should stress that I am looking for realistic examples, i.e. those which are likely to happen in a real game. Positions of the following type,
  
  ```
  [fen "4k3/4p3/3pPp2/2pP1Pp1/1pP3Pp/pP1K3P/P2RRR2/8 w - - 0 1"]
  
  ```
  
  and similar artificial positions is **not** the kind of thing I am looking for.
  
  I should also say that endgame tablebase examples are OK. The only requirement is that engines (run on an average computer) are not able to evaluate the position correctly after given, say, 10-15 minutes time to "think".
  
  **Tags:** engines, endgame
  
  > **Comments:**
  > **username_2**: Maybe "engine" is a bit too vague. I keep wondering why "machines" are often believed to have one unique chess style.  
  > **username_0**: @username_2: Specifically, when I used the word "engine", I had for example Stockfish or Houdini in mind (the chess engines most often used in live broadcasts of chess events, and considered to be the the best widely used chess engines). The purpose of my question was to pinpoint the most important situations, in which these, most commonly used and trusted, tools fail to provide a satisfactory or correct answer. And also, because the positions which engines do not evaluate well are often very instructive and interesting to analyze (when they are realistic).  
  > **username_0**: @Ricky Demer: Not necessarily. The examples can include fortresses, but since there are many types of fortresses and most of them are a problem for engines to evaluate correctly, I am searching for particularly aesthetic and instructive examples of fortresses; the ones that really catch your eye when you see them. Also, an example of a famous game featuring some nice fortress ideas would also be appreciated. The stress is on aesthetics and theoretical or historical importance of the examples.  
  > **username_0**: @Ricky Demer: Brilliant, thank you! Btw, I think I am going to remove the word "list" from the title of the question, since it seems to discourage people from answering the question :)  
  > **username_1**: The position is illegal: White has 3 rooks so at least one must be promoted. But white has 8 pawns.  
  
  ---
  
  ## 4 answers
  
  ### Answer by username_8 on 2014-09-13. Score: 10 | Accepted answer
  
  The following two links seem to be exactly what you are looking for (many such positions in each one of them).
  
  <http://en.chessbase.com/post/can-we-still-deceive-computers-in-chess>
  
  <http://www.chess.com/forum/view/general/positions-engines-get-wrong--please-contribute>
  
  A cute study, which engines are unable to solve last I checked (white to move and win):
  
  ```
  6r1/p1p1p1pP/P1PpP1P1/8/2P1B3/2K3pp/3P2rq/R5bk w - - 1 0
  
  ```
  
  > **Comments:**
  > **username_9**: I think the study might be cooked. The mainline goes **1.hxg8=N d5 2.Bf3 d4+ 3.Kb4 d3 4.Nh6 gxh6 5.g7 h5 6.g8=N h4 7.Nf6 exf6 8.e7 f5 9.e8=N f4 10.Nd6 cxd6 11.c7 d5 12.c8=N d4 13.Nb6 axb6 14.a7 b5 15.a8=B bxc4 16.Bae4 c3 17.Bxd3 c2 18.Bf1 d3 19.Kb3 c1=Q 20.Rxc1 Bd4 21.B1xg2# 1-0**. But 12... dxc4 poses problems. The intended solution continues 13.Nb6 c3 14.Kc4 cxd2 15.Kxd3, but 14... axb6 seems to throw a spanner in the works. See for example [this discussion in Dutch](http://schaaksite.nl/page.php?al=timman-weerlegd).  
  > **username_9**: [Google translate link](https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fschaaksite.nl%2Fpage.php%3Fal%3Dtimman-weerlegd&edit-text=) (for the Dutch-impaired - such as me).  
  
  ---
  
  ### Answer by username_3 on 2014-12-14. Score: 5
  
  <http://chesstempo.com/chess-tactics/90023>
  The final position of the solution is an ending with queen against two knights with pawns on both sides where the knights can set up a blockade. Looks like a draw but the engine evaluates that the queen side wins.
  
  ```
  8/5ppk/7p/3pP3/5P2/5N1P/4NKP1/7q b - - 0 5
  
  ```
  
  > **Comments:**
  > **username_5**: Can you post the position on here? This link might not be accessible in the future.  
  
  ---
  
  ### Answer by username_3 on 2015-03-06. Score: 4
  
  ```
  1Q2r1k1/P6p/8/8/4q3/7P/6PK/8 w - - 2 6
  
  ```
  
  White to move. 1.a8=Q Qxa8 2.Qg3+ may be a perpetual check that is hard to analyze. See the comments in the discussion of this tactics problem at <http://chesstempo.com/chess-problems/103006>
  
  > **Comments:**
  > **username_4**: Really, such a simple looking position? If computer finds this hard to analyze, then this would be one of the best answers for the question.  
  
  ---
  
  ### Answer by username_6 on 2014-12-14. Score: 3
  
  Besides fortresses, another type of position the engines tend to get wrong is when the weaker side is about to promote a pawn but the promotion can be delayed indefinitely.
  
  ```
  [FEN "5Q2/8/8/8/2k5/7P/1p4PK/r7 w - - 0 1"]
  [White "Anatoly Karpov"]
  [Black "Anthony Miles"]
  [Event " Biel"]
  [Date "1990  (analysis, white to move)"]
  
  ```
  
  For a human player it is easy to see that this is a draw, but the engine has to try all the different checks from all possible squares in all different orders. (I haven't tested this position with the newest engines, perhaps some of them can handle this?)
  
  > **Comments:**
  > **username_7**: Stockfish 5 takes about 0.02 seconds to recognise this as a draw.  
  > **username_6**: @username_7 With or without 7-men tablebases?  
  > **username_7**: Without any tablebases.  
  > **username_6**: Good. I just remember looking at this game a few years ago, and the engines at the time didn't see that black should go for this position to save the game.  
  
  ---
  
  