4 ms·
The position nearly plays itself - none of the black pieces except the bishops have any legal moves, so if white moves his king around, without capturing anythi
by yaakov34 10y ago
The position nearly plays itself - none of the black pieces except the bishops have any legal moves, so if white moves his king around, without capturing anything, a draw will result by the 50 move rule (the bishops can't mate the king, since they won't control any light squares). For black, the play is even more automatic, since moving the bishops back and forth on the dark squares is the only legal option.
I do think that a computer will play this correctly for both black and white; for white, a capture will result in a checkmate within a few moves, which the computer will be able to see. So this may result in incorrect computer evaluation, but not in incorrect play.
- Jtsummers 10y agoThanks for pointing out that those were bishops in the diagram. I found it difficult to parse the drawing for some reason.
- dsp1234 10y agonone of the black pieces except the bishops have any legal moves, Why couldn't black move the topmost pawn forward?
- ianpurton 10y agoBlack is moving down the board.
- yaakov34 10y agoForward for black pawns is down, in a standard chess diagram; white's side of the board is at the bottom. So black pawns have no legal moves, while the white pawns could move (the topmost pawn) or capture either of the black rooks, although this would be disastrous for white, as the black pieces would then be able to leave their position and would checkmate white in a few moves.
- fosco 10y agoKing is in way, only pieces black can move are bishops. The orientation of board is white started on bottom and black on top. Quick thing to also remember is that the bottom right square should always be white.
- nthcolumn 10y agoHe cannot move his king out of its way first due to check from the white pawn if that is what you mean. The article makes it sound like a difficult problem with some super prize. I can't believe that a chess program can't figure out it doesn't have any meaningful moves left.
- jonwachob91 10y agoHow does this account for the black pawns playing in the same rank? To me it looks like a board transformation occurs, resulting in a left-to-right movement as opposed to a up-to-down movement.
- dmichulke 10y agoBlack abc pawns are in their original file. d and e pawns captured pieces to get to a and b. Two of the three remaining pawns promoted to a bishop.
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- grondilu 10y agoAgreed. An example where a human easily finds a win while a computer fails would be much more convincing of the point Penrose is trying to make. Anyway this position reminds me of the fact that if there is any kind of situation where computers struggle it's exactly these kinds : where everything is closed apart from a few pieces. IIRC that was exploited by grandmaster Hikaru Nakamura few years ago for his handicap match against chess engine Komodo.
- ouid 10y agoyes, but the question isn't if a computer will play correctly given the position, it's "will the computer force this position as white, if it's the best move?" which relies on it's evaluation of the position.
- yaakov34 10y agoIt's not really a position you can force from further away than one move, since it would require complete cooperation between the players to create such a position. But yes, given a chance to get into this position, sure it will - e.g. given https://en.lichess.org/analysis/8/p7/kpP5/qrp1b3/rpP2b2/p5b1/PP2K3/8_w_-_- https://en.lichess.org/analysis/8/p7/kpP5/qrp1b3/rpP2b2/p5b1..., it will correctly play b3 and force the original position, since everything else results in a mate that it can see. All it needs for correct play is to rank the alternatives in the right order, and mate ranks below playing on with a material disadvantage.
- ouid 10y agohttps://en.lichess.org/analysis/8/p7/kpn5/qrpPb3/rpP2b2/pP4Q1/P3K2b/8_w_-_- https://en.lichess.org/analysis/8/p7/kpn5/qrpPb3/rpP2b2/pP4Q... here's a preceding position which stockfish completely fails to play correctly.
- yaakov34 10y agoYeah, that's a great enhancement to the original - having the queen around lets the computer avoid mate for longer than its horizon, so it prefers keeping the queen. Then again, I am not sure the computer will lose in even this scenario - it has so many queen checks that my evaluation of this position after 10 minutes of playing with it is "screw it", although I feel there has to be some way of punishing it.
- ouid 10y agowell you're playing against a computer that doesn't understand the position, black should simply disentangle his pieces, he can sacrifice almost everything he has and still win in this position, even if white is allowed to keep the queen. He can sacrifice a queen and a rook to this end, easily. how I play the position as black is Ne7 followed by Bd6. if white plays Qh4, I can play nd4+ followed by nf5 and nd6, and my king is safe. and I can slowly, safely, extricate myself and win.
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- 33W 10y agoThere's the white win if black blunders. If white moves the forwardmost pawn ahead and black does not capture it with the bishop (the blunder), then promoting the pawn to a queen or bishop is checkmate.