Answers.Body: <p><strong>EDIT</strong>: Now that I look closely, I have solved a different variant than what was asked. Probably this is interesting anyway :) The variant's rules are described here: <a href="http://www.chesscorner.com/tutorial/basic/pawngame/pawngame.htm" rel="noreferrer">http://www.chesscorner.com/tutorial/basic/pawngame/pawngame.htm</a></p>
  
  <p>I have written a piece of software to solve this. Contrary to my and other people's expectations, and barring bugs, it shows that the game is actually a win for white. Without en passant it was a draw.</p>
  
  <p>The only winning opening moves for white are <strong>1. b4</strong> and <strong>1. c4</strong> (and the symmetric <strong>1. f4</strong> and <strong>1. g4</strong>).</p>
  
  <p>Curiously, all other white opening moves are a win for black. <strong>1. d4</strong> is refuted by <strong>1. ... b5 0-1</strong>; all other black responses are wins for white.</p>
  
  <p>I put the code here: <a href="https://github.com/sliedes/pawnsonly" rel="noreferrer">https://github.com/sliedes/pawnsonly</a>. With the default setup it uses 25 gigabytes of memory for the transposition table and I seem to remember it takes a few hours to solve the 8x8 case. I have not tested how slow it is with less memory.</p>
  
  <p>Here are some results of the first two or three moves:</p>
  
  <ul>
  <li><a href="http://sliedes.kapsi.fi/pawnsonly/pawnsonly-moves-d4.txt" rel="noreferrer">First two full moves (small text file)</a></li>
  <li><a href="http://sliedes.kapsi.fi/pawnsonly/pawnsonly-moves-d6.txt.gz" rel="noreferrer">First three full moves (5 megabytes gzip compressed, 75 megabytes decompressed)</a></li>
  </ul>
  
  <p>Some of the lines end with "1/2-1/2+" or "1/2-1/2-". "1/2-1/2+" means that white can force at least a draw, and no further search was done because this information was enough for perfect play from the starting position (so it might also be a white win). Correspondingly, "1/2-1/2-" means that black is able to force at least a draw.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-05T09:18:30.647Z
Answers.Text: Great work! Do you have some sample games? What's the key idea for W's breakthrough? What was the depth of the search?
Answers.UserDisplayName: Aravind
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-05T22:26:25.973Z
Answers.Text: I don't currently have any sample games. I've been thinking about how easy it would be to make it somehow queriable; the transposition table could presumably be used to speed up queries. The search was exhaustive, i.e. it continued until the game was over, and therefore the result is exact (barring bugs). It would be interesting to know how many moves it takes for white to win, but unfortunately even that is nontrivial with alpha-beta and the very compact transposition table I use.
Answers.UserDisplayName: Sami Liedes
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-07-27T22:53:43.263Z
Answers.Text: To be clear, this is **without the kings**. First to reach back rank wins.
Answers.UserDisplayName: deep thought
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-03-31T19:22:51.283Z
Answers.LastActivityDate: 2016-03-31T19:22:51.283Z
Answers.UserDisplayName: Sami Liedes
Answers.Body: <p>I setup the position using this FEN String</p>
  
  <pre><code>4k3/pppppppp/8/8/8/8/PPPPPPPP/4K3 w - - 0 1
  </code></pre>
  
  <p>Using a grid engine cluster with 24 nodes, each node having 16 cores at 3.2 Ghz with 60gb of ram</p>
  
  <p>The engine used was Houdini 4 pro (allowing multiple cores)</p>
  
  <p>After analyzing for several days ( 4 days 12 hours 2 minutes and 15 seconds to be precise)
  the engine scored the position 0.00 flat with the suggested move line</p>
  
  <pre><code>1.d4 d5 2.Kd2 Kd7 3.Kd3 Kd6
  </code></pre>
  
  <p>Of course this is not nearly a bruteforce method, but i believe it is safe to say this is a draw. Of course @Rauan Sagit is correct. Correct play comes with intimate knowledge of pawn endings and will be even harder to achieve correct play against a skilled opponent</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-06-19T08:31:38.540Z
Answers.Text: That's some powerful computer analysis!
Answers.UserDisplayName: Aravind
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-04-23T15:32:50.483Z
Answers.LastActivityDate: 2014-04-23T15:32:50.483Z
Answers.UserDisplayName: Yusuf Ali
Body: <p>In the pawns-only variant of chess, each side starts with 8 pawns and a king on the usual squares, no pieces,
  with other rules being the same as in regular chess, including promotion.</p>
  
  <p>While general consensus is that chess is a theoretical draw, with best play by both sides, this is not proved because of
  its complexity.</p>
  
  <p>The pawns-only variant looks more amenable to computer analysis.</p>
  
  <p>In the pawns-only variant, is it possible for Black to imitate White or otherwise create a blockade?
  Is the pawns-only variant a theoretical draw? </p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2016-04-01T10:25:44.243Z
Comments.Text: See also this question and its answers: http://chess.stackexchange.com/questions/8755/is-the-result-in-mini-chess-known-with-perfect-play/8945#8945
Comments.UserDisplayName: Sir Cornflakes
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-02-22T23:51:43.197Z
Comments.Text: Not directly relevant, but Euwe showed that the pawn-only version of the exchange Ruy Lopez is a forced win for white.  http://en.m.wikipedia.org/wiki/Ruy_Lopez,_Exchange_Variation
Comments.UserDisplayName: Noah Snyder
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-03-03T11:18:31.557Z
Comments.Text: How is this pawns-only variant won, do you get a queen and play on as normal on promotion, or does the first to promote win?
Comments.UserDisplayName: RemcoGerlich
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-04-03T16:55:27.913Z
Comments.Text: @Rauan Sagit, no more info on this. I am not accepting your answer because I am looking for a "proof", not an intuitive guess.
Comments.UserDisplayName: Aravind
Tags: <theory><pawns><draw><chess-variants><pawn-endgame>
Title: Is the pawns only variant a draw?
ThreadText: # Is the pawns only variant a draw?
  
  (Asked by: username_0 on 2014-02-22)
  
  In the pawns-only variant of chess, each side starts with 8 pawns and a king on the usual squares, no pieces,
  with other rules being the same as in regular chess, including promotion.
  
  While general consensus is that chess is a theoretical draw, with best play by both sides, this is not proved because of
  its complexity.
  
  The pawns-only variant looks more amenable to computer analysis.
  
  In the pawns-only variant, is it possible for Black to imitate White or otherwise create a blockade?
  Is the pawns-only variant a theoretical draw?
  
  **Tags:** theory, pawns, draw, chess-variants, pawn-endgame
  
  > **Comments:**
  > **username_2**: Not directly relevant, but Euwe showed that the pawn-only version of the exchange Ruy Lopez is a forced win for white.  http://en.m.wikipedia.org/wiki/Ruy_Lopez,_Exchange_Variation  
  > **username_3**: How is this pawns-only variant won, do you get a queen and play on as normal on promotion, or does the first to promote win?  
  > **username_0**: @Rauan Sagit, no more info on this. I am not accepting your answer because I am looking for a "proof", not an intuitive guess.  
  > **username_1**: See also this question and its answers: http://chess.stackexchange.com/questions/8755/is-the-result-in-mini-chess-known-with-perfect-play/8945#8945  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_6 on 2014-04-23. Score: 11 | Accepted answer
  
  I setup the position using this FEN String
  4k3/pppppppp/8/8/8/8/PPPPPPPP/4K3 w - - 0 1
  
  Using a grid engine cluster with 24 nodes, each node having 16 cores at 3.2 Ghz with 60gb of ram
  The engine used was Houdini 4 pro (allowing multiple cores)
  After analyzing for several days ( 4 days 12 hours 2 minutes and 15 seconds to be precise)
  the engine scored the position 0.00 flat with the suggested move line
  1.d4 d5 2.Kd2 Kd7 3.Kd3 Kd6
  
  Of course this is not nearly a bruteforce method, but i believe it is safe to say this is a draw. Of course @Rauan Sagit is correct. Correct play comes with intimate knowledge of pawn endings and will be even harder to achieve correct play against a skilled opponent
  
  > **Comments:**
  > **username_0**: That's some powerful computer analysis!  
  
  ---
  
  ### Answer by username_4 on 2016-03-31. Score: 9
  
  **EDIT**: Now that I look closely, I have solved a different variant than what was asked. Probably this is interesting anyway :) The variant's rules are described here: <http://www.chesscorner.com/tutorial/basic/pawngame/pawngame.htm>
  
  I have written a piece of software to solve this. Contrary to my and other people's expectations, and barring bugs, it shows that the game is actually a win for white. Without en passant it was a draw.
  
  The only winning opening moves for white are **1. b4** and **1. c4** (and the symmetric **1. f4** and **1. g4**).
  
  Curiously, all other white opening moves are a win for black. **1. d4** is refuted by **1. ... b5 0-1**; all other black responses are wins for white.
  
  I put the code here: <https://github.com/sliedes/pawnsonly>. With the default setup it uses 25 gigabytes of memory for the transposition table and I seem to remember it takes a few hours to solve the 8x8 case. I have not tested how slow it is with less memory.
  
  Here are some results of the first two or three moves:
  
  * [First two full moves (small text file)](http://sliedes.kapsi.fi/pawnsonly/pawnsonly-moves-d4.txt)
  * [First three full moves (5 megabytes gzip compressed, 75 megabytes decompressed)](http://sliedes.kapsi.fi/pawnsonly/pawnsonly-moves-d6.txt.gz)
  
  Some of the lines end with "1/2-1/2+" or "1/2-1/2-". "1/2-1/2+" means that white can force at least a draw, and no further search was done because this information was enough for perfect play from the starting position (so it might also be a white win). Correspondingly, "1/2-1/2-" means that black is able to force at least a draw.
  
  > **Comments:**
  > **username_0**: Great work! Do you have some sample games? What's the key idea for W's breakthrough? What was the depth of the search?  
  > **username_4**: I don't currently have any sample games. I've been thinking about how easy it would be to make it somehow queriable; the transposition table could presumably be used to speed up queries. The search was exhaustive, i.e. it continued until the game was over, and therefore the result is exact (barring bugs). It would be interesting to know how many moves it takes for white to win, but unfortunately even that is nontrivial with alpha-beta and the very compact transposition table I use.  
  > **username_5**: To be clear, this is **without the kings**. First to reach back rank wins.  
  
  ---
  
  