Answers.Body: <p>Revised stockfish to skip searching double pawn push. Each engine is using 2 threads at TC 1m+1s. It got 4 draws in 20 games.</p>
  <h3>Test 1</h3>
  <p><code>sf_no_pawnpush4</code> is not aware that its opponent can play a double step pawn push and <code>sf_normal</code> is not aware that its opponent can only play a single step pawn push.</p>
  <pre><code>Score of sf_no_pawnpush4 vs sf_normal: 0 - 16 - 4 [0.100]
  ...      sf_no_pawnpush4 playing White: 0 - 7 - 3  [0.150] 10
  ...      sf_no_pawnpush4 playing Black: 0 - 9 - 1  [0.050] 10
  ...      White vs Black: 9 - 7 - 4  [0.550] 20
  Elo difference: -381.7 +/- 252.4, LOS: 0.0 %, DrawRatio: 20.0 %
  20 of 20 games finished.
  </code></pre>
  <p>Sample games:<br />
  <a href="https://lichess.org/UVMYm3Tf#6" rel="nofollow noreferrer">https://lichess.org/UVMYm3Tf#6</a><br />
  <a href="https://lichess.org/sBp98pXn#84" rel="nofollow noreferrer">https://lichess.org/sBp98pXn#84</a></p>
  <h3>Test 2</h3>
  <p>Each engine is aware of its opponent's capabilities.</p>
  <pre><code>Score of sf_no_pawnpush4_aware vs sf_normal_aware: 0 - 19 - 1 [0.025]
  ...      sf_no_pawnpush4_aware playing White: 0 - 10 - 0  [0.000] 10
  ...      sf_no_pawnpush4_aware playing Black: 0 - 9 - 1  [0.050] 10
  ...      White vs Black: 9 - 10 - 1  [0.475] 20
  Elo difference: -636.4 +/- nan, LOS: 0.0 %, DrawRatio: 5.0 %
  20 of 20 games finished.
  </code></pre>
  <p>Sample games:<br />
  <a href="https://lichess.org/l86RNFcn" rel="nofollow noreferrer">https://lichess.org/l86RNFcn</a><br />
  <a href="https://lichess.org/A67hMP3i" rel="nofollow noreferrer">https://lichess.org/A67hMP3i</a></p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T07:02:29.333Z
Answers.Text: Surprised to see such a drastic difference in performance.
Answers.UserDisplayName: shoonya
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T07:40:55.503Z
Answers.Text: Although this is perhaps one of the most direct way of calculating the difference, I don't think this is a very good estimate. Chess engines study openings, and limiting pawn movement simply changes the whole thing. The most accurate comparison would be training an engine with only 1 square pawn movement, and the same engine with 2 squares pawn movement, then compare the results.
Answers.UserDisplayName: Sinan Yaman
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T08:54:53.457Z
Answers.Text: The space advantage is too much.
Answers.UserDisplayName: ferdy
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T09:15:12.353Z
Answers.Text: By second move - the evaluation is already +1
Answers.UserDisplayName: shoonya
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T12:37:04.520Z
Answers.Text: I imagine a Indian chess player would understand that the opponent may play e2-e4 even if they don't play it themselves. What happens if Stockfish-Indian is aware that the opponent may play double pawn moves?
Answers.UserDisplayName: Mateen Ulhaq
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T12:53:09.973Z
Answers.Text: I interpret the question as "you can't move pawns 2 squares, but you know your opponent can". Not searching double pawn push is a significantly stronger handicap.
Answers.UserDisplayName: Allure
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T13:17:52.807Z
Answers.Text: @MateenUlhaq In addition, it may be added that Stockfish-Indian is aware that the opponent is aware that Stockfish-Indian is not able to play double pawn move.
Answers.UserDisplayName: Durmus
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T20:05:44.103Z
Answers.Text: @Durmus I don't see how you could know that, given that ferdy hasn't even yet disclosed whether the evaluation/search is symmetric or asymmetric. The awareness you speak of also wouldn't make any difference as Stockfish doesn't use an opponent model. (So Stockfish-Indian's beliefs about its opponent don't factor in beyond that opponent's move choices.)
Answers.UserDisplayName: Mobeus Zoom
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T20:08:16.897Z
Answers.Text: @Allure You're presumably right. What I wonder is whether the opponent (Stockfish pure) also has an asymmetric search i.e. knows that handicapped Stockfish cannot play double pawn pushes.
Answers.UserDisplayName: Mobeus Zoom
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-19T07:20:02.283Z
Answers.Text: The question was about someone who has less experience with double pawn move yet both players are allowed to play double pawn moves. And it asked whether forbidding Stockfish from playing that move would be a good metric or not (I guess it wouldn't). Yet this answer just tested that constraint, which is not really an answer to whether it's a good metric for the original question. Yet, strangely, it was accepted, so maybe the question was a bit ambiguous?
Answers.UserDisplayName: vsz
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-19T10:53:38.740Z
Answers.Text: How would this hypothesis be formulated? Opening book not have any 2 pawn move? @vsz you can edit the question
Answers.UserDisplayName: shoonya
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-01-18T06:33:12.017Z
Answers.LastActivityDate: 2022-01-19T00:11:20.697Z
Answers.LastEditDate: 2022-01-19T00:11:20.697Z
Answers.UserDisplayName: ferdy
Body: <p>In Indian chess, the pawn doesn't move two squares, however in the western chess, pawn can move two squares. Now, since the pawn can't move 2 in the Indian style, the fianchetto is a natural square to develop your bishops.</p>
  <p>So for a player like Sultan Khan playing against other chess players from West, what kind of an Elo disadvantage would that put him? How does one estimate such a number?</p>
  <p>Suppose one puts a constraint like this in Stockfish and lets it play against another Stockfish and observe how it does in a million games - would that be an acceptable way to estimate disadvantage?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2022-01-18T12:29:20.413Z
Comments.Text: Sultan Khan did push pawns two squares
Comments.UserDisplayName: Michael West
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2022-01-18T13:38:13.487Z
Comments.Text: When Indian chess has different rules for pawn movement, then it isn't really the same game. That makes ELO score not really comparable. That would be like comparing American Football players with Rugby players. Sure, they are similar and *some* skills are transferable, but they are still two different games. Which means people who practice both games would need a separate score for each.
Comments.UserDisplayName: Philipp
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2022-01-18T18:11:26.160Z
Comments.Text: @Philipp I think the question is phrased a bit awkwardly, but is really "If a chess player self-imposed the handicap to never move a pawn two squares, how much ELO would that player lose?"
Comments.UserDisplayName: Stef
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2022-01-19T02:03:52.670Z
Comments.Text: ELO is a rock band. Elo is the name of the man who devised a rating system.
Comments.UserDisplayName: bof
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2022-01-19T03:25:58.917Z
Comments.Text: @stef well the thought came like that only - if sultan khan had always been playing indian version - how much of an opening disadvantage he have against western players.
Comments.UserDisplayName: shoonya
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2022-01-19T12:44:09.557Z
Comments.Text: @shoona could be an advantage in some cases.  His opponents may be surprised when he wins by stalemate in a king and pawn ending.
Comments.UserDisplayName: Michael West
Tags: <opening><history><tactics><chess-variants><elo>
Title: Elo disadvantage due to one pawn move in Indian Chess
ThreadText: # Elo disadvantage due to one pawn move in Indian Chess
  
  (Asked by: username_0 on 2022-01-18)
  
  In Indian chess, the pawn doesn't move two squares, however in the western chess, pawn can move two squares. Now, since the pawn can't move 2 in the Indian style, the fianchetto is a natural square to develop your bishops.
  
  So for a player like Sultan Khan playing against other chess players from username_1, what kind of an Elo disadvantage would that put him? How does one estimate such a number?
  
  Suppose one puts a constraint like this in Stockfish and lets it play against another Stockfish and observe how it does in a million games - would that be an acceptable way to estimate disadvantage?
  
  **Tags:** opening, history, tactics, chess-variants, elo
  
  > **Comments:**
  > **username_1**: Sultan Khan did push pawns two squares  
  > **username_2**: When Indian chess has different rules for pawn movement, then it isn't really the same game. That makes ELO score not really comparable. That would be like comparing American Football players with Rugby players. Sure, they are similar and *some* skills are transferable, but they are still two different games. Which means people who practice both games would need a separate score for each.  
  > **username_3**: @username_2 I think the question is phrased a bit awkwardly, but is really "If a chess player self-imposed the handicap to never move a pawn two squares, how much ELO would that player lose?"  
  > **username_4**: ELO is a rock band. Elo is the name of the man who devised a rating system.  
  > **username_0**: @username_3 well the thought came like that only - if sultan khan had always been playing indian version - how much of an opening disadvantage he have against western players.  
  > **username_1**: @shoona could be an advantage in some cases.  His opponents may be surprised when he wins by stalemate in a king and pawn ending.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_5 on 2022-01-18. Score: 12 | Accepted answer
  
  Revised stockfish to skip searching double pawn push. Each engine is using 2 threads at TC 1m+1s. It got 4 draws in 20 games.
  
  ### Test 1
  
  `sf_no_pawnpush4` is not aware that its opponent can play a double step pawn push and `sf_normal` is not aware that its opponent can only play a single step pawn push.
  
  ```
  Score of sf_no_pawnpush4 vs sf_normal: 0 - 16 - 4 [0.100]
  ...      sf_no_pawnpush4 playing White: 0 - 7 - 3  [0.150] 10
  ...      sf_no_pawnpush4 playing Black: 0 - 9 - 1  [0.050] 10
  ...      White vs Black: 9 - 7 - 4  [0.550] 20
  Elo difference: -381.7 +/- 252.4, LOS: 0.0 %, DrawRatio: 20.0 %
  20 of 20 games finished.
  
  ```
  
  Sample games:  
  <https://lichess.org/UVMYm3Tf#6>  
  <https://lichess.org/sBp98pXn#84>
  
  ### Test 2
  
  Each engine is aware of its opponent's capabilities.
  
  ```
  Score of sf_no_pawnpush4_aware vs sf_normal_aware: 0 - 19 - 1 [0.025]
  ...      sf_no_pawnpush4_aware playing White: 0 - 10 - 0  [0.000] 10
  ...      sf_no_pawnpush4_aware playing Black: 0 - 9 - 1  [0.050] 10
  ...      White vs Black: 9 - 10 - 1  [0.475] 20
  Elo difference: -636.4 +/- nan, LOS: 0.0 %, DrawRatio: 5.0 %
  20 of 20 games finished.
  
  ```
  
  Sample games:  
  <https://lichess.org/l86RNFcn>  
  <https://lichess.org/A67hMP3i>
  
  > **Comments:**
  > **username_0**: Surprised to see such a drastic difference in performance.  
  > **username_6**: Although this is perhaps one of the most direct way of calculating the difference, I don't think this is a very good estimate. Chess engines study openings, and limiting pawn movement simply changes the whole thing. The most accurate comparison would be training an engine with only 1 square pawn movement, and the same engine with 2 squares pawn movement, then compare the results.  
  > **username_5**: The space advantage is too much.  
  > **username_0**: By second move - the evaluation is already +1  
  > **username_7**: I imagine a Indian chess player would understand that the opponent may play e2-e4 even if they don't play it themselves. What happens if Stockfish-Indian is aware that the opponent may play double pawn moves?  
  > **username_8**: I interpret the question as "you can't move pawns 2 squares, but you know your opponent can". Not searching double pawn push is a significantly stronger handicap.  
  > **username_9**: @username_7 In addition, it may be added that Stockfish-Indian is aware that the opponent is aware that Stockfish-Indian is not able to play double pawn move.  
  > **username_10**: @username_9 I don't see how you could know that, given that username_5 hasn't even yet disclosed whether the evaluation/search is symmetric or asymmetric. The awareness you speak of also wouldn't make any difference as Stockfish doesn't use an opponent model. (So Stockfish-Indian's beliefs about its opponent don't factor in beyond that opponent's move choices.)  
  > **username_10**: @username_8 You're presumably right. What I wonder is whether the opponent (Stockfish pure) also has an asymmetric search i.e. knows that handicapped Stockfish cannot play double pawn pushes.  
  > **username_11**: The question was about someone who has less experience with double pawn move yet both players are allowed to play double pawn moves. And it asked whether forbidding Stockfish from playing that move would be a good metric or not (I guess it wouldn't). Yet this answer just tested that constraint, which is not really an answer to whether it's a good metric for the original question. Yet, strangely, it was accepted, so maybe the question was a bit ambiguous?  
  > **username_0**: How would this hypothesis be formulated? Opening book not have any 2 pawn move? @username_11 you can edit the question  
  
  ---
  
  