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2/24/2016 – Over Christmas we showed you an interesting problem: say you have found some moves somewhere, in coordinate notation without piece names – is it possible to reconstruct the original supposedly meaningful position to which they apply? The author, who has a Ph.D. in artificial intelligence, tried to do it, but with modest success. A reader presented a more plausible solution and won a valuable prize

Recomposition Contest Result

By Azlan Iqbal, Ph.D.

As part of the ChessBase Christmas puzzle series at the end of 2015, I submitted a new type of puzzle called, ‘recompositions’. The idea here is to ‘recompose’ the original starting position given just fragments of information such as the moves (in coordinate notation) and perhaps an engine evaluation score of that line. ChessBase readers were tasked with some detective work in finding the original starting position that made the most sense.

From all the submissions I received, none actually solved the problem satisfactorily, but one came quite close such that even I used it as a different starting point to experiment with a viable solution. Alas, that solution still remains elusive, and perhaps always will. In any case, the submission in question is therefore in my view still worthy of the featured prize. Here it is, compared to my own original solution (which admittedly did not work).

My original proposed solution The winner’s solution, by Koen Eeman



As you can see, the position has been altered considerably. Notably, the black king has moved a great distance to the other side of the board, and the bishop on d8 has been replaced with a queen. The pair of white rooks, however, remains the same as is probably also in the actual starting position (whatever that may be). The winner apparently used the Stockfish 6 engine and his solution corresponds to the original variation I provided until about move 3 of the line. Instead of 3. ... Nh4, the main line shown for his position is 3. ... Nc3 and it differs totally from there. Also, it appears to be a forced mate for Black! So the solution only goes so far.

[Event "Forensic Chess"] [Site "?"] [Date "2016.01.28"] [Round "?"] [White "Eeman, Koen"] [Black "Recomposition problem"] [Result "0-1"] [SetUp "1"] [FEN "3q4/7N/8/1R1p1nr1/n7/bR3K2/2P5/3k4 w - - 0 1"] [PlyCount "20"] [EventDate "2016.??.??"] [SourceDate "2016.01.28"] {Recomposition from the move sequence: 1. h7g5 d8g5 2. b5d5 d1c2 3. b3a3 f5h4 4. f3e4 g5e7 5. e4f4 e7a3 6. d5b5 a3d6 7. f4g5 a4c3 8. g5h4 c3b5 9. h4g5 d6e5 10. g5g6 c2d3} 1. Nxg5 Qxg5 2. Rxd5+ Kxc2 3. Rxa3 Nh4+ 4. Ke4 Qe7+ 5. Kf4 Qxa3 6. Rb5 Qd6+ 7. Kg5 Nc3 8. Kxh4 Nxb5 9. Kg5 Qe5+ 10. Kg6 Kd3 0-1

The winner, from what I understood, also posited the idea that the line I provided (with a score of +8) may have been an incomplete evaluation at the time it was cut off (assuming it was cut off). This is possible but yet a far cry from Black forcing mate. In any case, congratulations to our winner! I played around with the pieces and Stockfish 6 myself and could not make further progress from his solution so it remains the closest one thus far.

Nevertheless, here is a new challenge where I actually know the original position, so potential solutions can be compared against it for accuracy. The engine analysis for this line is +9.99. Good luck!

1. h2e5 e3c5

2. h1g2 f5g5

3. d5d6 g5g6

4. d6d7 g6g8

5. f6f7 g8f8

6. d7d8 f8d8

7. c6d8 e2c4

8. g2c6 b5a5

9. d2d3 c4f7

10. d8f7 a5b6

You can send your solutions to my official email address with a c.c. to my private address, just in case our spam filter here at the university gets too fussy.

Koen Eeman wins this copy of Fritz 13, signed by Garry Kasparov.

A similar prize awaits the winner of the new problem.

Previous ChessBase articles by Prof. Azlan Iqbal