Answers.Body: <p>I actually did the experiment and will answer now. Three main factors go into the evaluation (as king safety doesn't play the slightest role): material, space, and movability.</p>
  <p>The effect of space is rather high at +1.4.</p>
  <pre><code>[FEN &quot;4k3/p1p1p1p1/P1P1P1P1/8/8/8/8/4K3 w - - 0 1&quot;]
  </code></pre>
  <p>Any useless doubled pawn is about +0.7, giving +4.2.</p>
  <pre><code>[FEN &quot;4k3/p1p1p1p1/P1P1P1P1/P1P1P1P1/8/8/8/4K3 w - - 0 1&quot;]
  </code></pre>
  <p>Don't underestimate agility, we're already at +5.9.</p>
  <pre><code>[FEN &quot;4k3/p1p1p1p1/P1P1P1P1/8/8/8/P1P1P1P1/4K3 w - - 0 1&quot;]
  </code></pre>
  <p>You can give White a useless bishop and scratch the 10.0 but I stop here, although it would be a fun challenge for the highest evaluation in a dead drawn position But +99.0 seems to be Lichess/Stockfish cutoff. :-)</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-02-12T21:04:23.193Z
Answers.Text: You could also replace a pawn for another bishop (a promoted one) if you wanted to further pump up the eval
Answers.UserDisplayName: pulsar512b
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-02-13T10:25:55.130Z
Answers.Text: @pulsar512b - Been there, done that, Lichess doesn't even complain against 32 bishops :-) Likewise, a walled in Q or R works wonders. An engine is hopelessly optimistic: Maybe it can break out somewhere over the horizon...
Answers.UserDisplayName: Hauke Reddmann
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-02-12T20:22:25.633Z
Answers.LastActivityDate: 2021-02-12T20:51:45.283Z
Answers.LastEditDate: 2021-02-12T20:51:45.283Z
Answers.UserDisplayName: Hauke Reddmann
Body: <p>Let us look at this position.</p>
  <pre><code>[FEN &quot;4k3/8/8/p1p1p1p1/P1P1P1P1/8/8/4K3 w - - 0 1&quot;]
  </code></pre>
  <p>This is obviously a draw. Analyzing this with the Stockfish engine says that it is a balanced position. However, Stockfish does not recognize that it is a draw.</p>
  <p>Slightly rearranging the pawns, we receive a similar position that is an obvious draw.</p>
  <pre><code>[FEN &quot;4k3/3p4/p1pPp3/P1P1P1p1/6P1/8/8/4K3 w - - 0 1&quot;]
  </code></pre>
  <p>Here, Stockfish says that white has an advantage of +0.7.</p>
  <p>Where does this miscalculation come from? I understand that draws in these positions cannot be detected from tablebases, as there are still too many pieces on the board. It seems that these special positions are called <a href="https://www.chessprogramming.org/Pawn_Rams_(Bitboards)" rel="nofollow noreferrer">Pawn Rams</a> or <a href="https://www.chessprogramming.org/Blockage_Detection" rel="nofollow noreferrer">Blockages</a>.</p>
  <p>The chess programming article about <a href="https://www.chessprogramming.org/Blockage_Detection" rel="nofollow noreferrer">Blockage Detection</a> provides code for detecting blockages, but I do not understand how it works.</p>
  <p>What are the underlying factors that make draw detection so hard from a computational point of view?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-09T18:12:25.677Z
Comments.Text: Are you interested in theoretical draws or only dead positions?
Comments.UserDisplayName: Brian McCutchon
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-09T18:16:23.363Z
Comments.Text: @BrianMcCutchon What is the difference?
Comments.UserDisplayName: banana_bunny
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-09T18:22:06.297Z
Comments.Text: A theoretical draw is a draw if both players play perfectly. For example, the starting position might be a theoretical draw (we don't know yet, and maybe never will). A dead position is a draw no matter what you play. Your examples are dead positions.
Comments.UserDisplayName: Brian McCutchon
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-11T01:58:25.903Z
Comments.Text: You might be interested: https://chess.stackexchange.com/questions/32270/lichess-endgame-evaluation
Comments.UserDisplayName: Allure
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-11T01:58:57.220Z
Comments.Text: I do believe the question is answerable, but it is very broad, since there are four questions asked and some of them aren't related to the others (e.g. 4 and 3)
Comments.UserDisplayName: Allure
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-11T15:34:05.513Z
Comments.Text: I think the answer to the main question is obvious: Spaaaaace. Suggested experiment: Place all black pawns on their original square. If I'm right, Whites plus will go further up. Also, blockades are *notorically* difficult to detect by engines. Experiment 2: Give White another useless double pawn, what happens? What has more effect?
Comments.UserDisplayName: Hauke Reddmann
Tags: <engines><programming><draw><50-move-rule><dead-position>
Title: A question about draw detection in chess engines
ThreadText: # A question about draw detection in chess engines
  
  (Asked by: username_0 on 2021-02-09)
  
  Let us look at this position.
  
  ```
  [FEN "4k3/8/8/p1p1p1p1/P1P1P1P1/8/8/4K3 w - - 0 1"]
  
  ```
  
  This is obviously a draw. Analyzing this with the Stockfish engine says that it is a balanced position. However, Stockfish does not recognize that it is a draw.
  
  Slightly rearranging the pawns, we receive a similar position that is an obvious draw.
  
  ```
  [FEN "4k3/3p4/p1pPp3/P1P1P1p1/6P1/8/8/4K3 w - - 0 1"]
  
  ```
  
  Here, Stockfish says that white has an advantage of +0.7.
  
  Where does this miscalculation come from? I understand that draws in these positions cannot be detected from tablebases, as there are still too many pieces on the board. It seems that these special positions are called [Pawn Rams](https://www.chessprogramming.org/Pawn_Rams_(Bitboards)) or [Blockages](https://www.chessprogramming.org/Blockage_Detection).
  
  The chess programming article about [Blockage Detection](https://www.chessprogramming.org/Blockage_Detection) provides code for detecting blockages, but I do not understand how it works.
  
  What are the underlying factors that make draw detection so hard from a computational point of view?
  
  **Tags:** engines, programming, draw, 50-move-rule, dead-position
  
  > **Comments:**
  > **username_1**: Are you interested in theoretical draws or only dead positions?  
  > **username_0**: @username_1 What is the difference?  
  > **username_1**: A theoretical draw is a draw if both players play perfectly. For example, the starting position might be a theoretical draw (we don't know yet, and maybe never will). A dead position is a draw no matter what you play. Your examples are dead positions.  
  > **username_2**: You might be interested: https://chess.stackexchange.com/questions/32270/lichess-endgame-evaluation  
  > **username_2**: I do believe the question is answerable, but it is very broad, since there are four questions asked and some of them aren't related to the others (e.g. 4 and 3)  
  > **username_3**: I think the answer to the main question is obvious: Spaaaaace. Suggested experiment: Place all black pawns on their original square. If I'm right, Whites plus will go further up. Also, blockades are *notorically* difficult to detect by engines. Experiment 2: Give White another useless double pawn, what happens? What has more effect?  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_3 on 2021-02-12. Score: 3
  
  I actually did the experiment and will answer now. Three main factors go into the evaluation (as king safety doesn't play the slightest role): material, space, and movability.
  
  The effect of space is rather high at +1.4.
  
  ```
  [FEN "4k3/p1p1p1p1/P1P1P1P1/8/8/8/8/4K3 w - - 0 1"]
  
  ```
  
  Any useless doubled pawn is about +0.7, giving +4.2.
  
  ```
  [FEN "4k3/p1p1p1p1/P1P1P1P1/P1P1P1P1/8/8/8/4K3 w - - 0 1"]
  
  ```
  
  Don't underestimate agility, we're already at +5.9.
  
  ```
  [FEN "4k3/p1p1p1p1/P1P1P1P1/8/8/8/P1P1P1P1/4K3 w - - 0 1"]
  
  ```
  
  You can give White a useless bishop and scratch the 10.0 but I stop here, although it would be a fun challenge for the highest evaluation in a dead drawn position But +99.0 seems to be Lichess/Stockfish cutoff. :-)
  
  > **Comments:**
  > **username_4**: You could also replace a pawn for another bishop (a promoted one) if you wanted to further pump up the eval  
  > **username_3**: @username_4 - Been there, done that, Lichess doesn't even complain against 32 bishops :-) Likewise, a walled in Q or R works wonders. An engine is hopelessly optimistic: Maybe it can break out somewhere over the horizon...  
  
  ---
  
  