Answers.Body: <p>A good example is the following position from a study by William Rudolph (which is also in the posting linked to by ASTA):</p>
  <pre><code>3B4/1r2p3/r2p1p2/bkp1P1p1/1p1P1PPp/p1P4P/PPB1K3/8 w - - 0 1
  
  1. Ba4+! Kxa4 2. b3+ Kb5 3. c4+ Kc6 4. d5+ Kd7 5. e6+ Kxd8 6. f5
  </code></pre>
  <p>The problem here is that White seems to be completely lost no matter what they do, but it is in fact possible for them to lock up the position by giving up even more material.</p>
  <p>In general, fortresses are still difficult for standard top engines. It is not hard to come up with positions that current top engines do not understand. It is, however, very difficult to achieve such positions in real games with any reliability.</p>
  <p>It is also worth noting that there are engines that have specialised fortress-detection code. For instance, the Stockfish fork <em>Crystal</em> solves the position given above in a matter of seconds. However, these engines are weaker than the top engines in normal positions.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-03-23T16:52:12.917Z
Answers.Text: +1 but why can’t fortress detection code be added to usual Stockfish, making it stronger?
Answers.UserDisplayName: Vivaan Daga
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-03-24T10:03:04.243Z
Answers.Text: Fortresses are rare. Even if it was free to handle of them completely correctly (it is likely an unattainable goal to handle them correctly even at high cost, because there are fortresses that are not obvious even to humans), the Elo gain from doing so would in all likelihood be very small. As it stands, additional fortress heuristics would simply take up computing cycles that Stockfish can use to find better moves in normal positions.
Answers.UserDisplayName: Polytropos
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-03-21T10:30:07.250Z
Answers.LastActivityDate: 2023-03-21T23:42:15.110Z
Answers.LastEditDate: 2023-03-21T23:42:15.110Z
Answers.UserDisplayName: Polytropos
Body: <p>Are there any positions where computers would play a bad move, but we humans know of the existence of a better move?</p>
  <p>By “computer” I mean standard engines such as Stockfish, at full power.</p>
  <p><strong>Edit:</strong> By a “bad” move I mean a move that changes the &quot;shape&quot; of the game.</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-03-12T07:07:51.987Z
Comments.Text: By bad I mean something that can change the "shape" of a game @user30536
Comments.UserDisplayName: Vivaan Daga
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-03-13T01:13:04.657Z
Comments.Text: Example: https://chess.stackexchange.com/questions/19107/kasparov-said-humancomputer-beats-just-computer-what-does-human-bring-to-the-t/27680#27680 You can find lots of others on the site.
Comments.UserDisplayName: Allure
Tags: <engines>
Title: Examples of Computers failing
ThreadText: # Examples of Computers failing
  
  (Asked by: username_0 on 2023-03-12)
  
  Are there any positions where computers would play a bad move, but we humans know of the existence of a better move?
  
  By “computer” I mean standard engines such as Stockfish, at full power.
  
  **Edit:** By a “bad” move I mean a move that changes the "shape" of the game.
  
  **Tags:** engines
  
  > **Comments:**
  > **username_0**: By bad I mean something that can change the "shape" of a game @user30536  
  > **username_1**: Example: https://chess.stackexchange.com/questions/19107/kasparov-said-humancomputer-beats-just-computer-what-does-human-bring-to-the-t/27680#27680 You can find lots of others on the site.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_2 on 2023-03-21. Score: 8 | Accepted answer
  
  A good example is the following position from a study by William Rudolph (which is also in the posting linked to by ASTA):
  
  ```
  3B4/1r2p3/r2p1p2/bkp1P1p1/1p1P1PPp/p1P4P/PPB1K3/8 w - - 0 1
  
  1. Ba4+! Kxa4 2. b3+ Kb5 3. c4+ Kc6 4. d5+ Kd7 5. e6+ Kxd8 6. f5
  
  ```
  
  The problem here is that White seems to be completely lost no matter what they do, but it is in fact possible for them to lock up the position by giving up even more material.
  
  In general, fortresses are still difficult for standard top engines. It is not hard to come up with positions that current top engines do not understand. It is, however, very difficult to achieve such positions in real games with any reliability.
  
  It is also worth noting that there are engines that have specialised fortress-detection code. For instance, the Stockfish fork *Crystal* solves the position given above in a matter of seconds. However, these engines are weaker than the top engines in normal positions.
  
  > **Comments:**
  > **username_0**: +1 but why can’t fortress detection code be added to usual Stockfish, making it stronger?  
  > **username_2**: Fortresses are rare. Even if it was free to handle of them completely correctly (it is likely an unattainable goal to handle them correctly even at high cost, because there are fortresses that are not obvious even to humans), the Elo gain from doing so would in all likelihood be very small. As it stands, additional fortress heuristics would simply take up computing cycles that Stockfish can use to find better moves in normal positions.  
  
  ---
  
  