Timeline for Undecidable Checkmate
Current License: CC BY-SA 4.0
17 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| 13 hours ago | comment | added | Zizy Archer | @TimSeifert Yeah you are right, I forgot about this corner case of a dead game. But yeah it doesn't help here because you can only prove one casting move keeps the game going (or checkmates) - you can't prove castling is possible when you have another option to checkmate. | |
| 17 hours ago | comment | added | Tim Seifert | @ZizyArcher Remarkably, you sometimes can tell that castling rights must still remain! For instance, consider 8/8/8/8/7N/5QP1/3PPPBp/R3K1kN. If White has the move, they must be able to castle since otherwise the position is dead and the game would be already over. (Unfortunately, this doesn't help much with this puzzle as it's not possible that both castling moves would give checkmate in the same position.) | |
| 18 hours ago | comment | added | Zizy Archer | @AJM You cannot prove castling is possible when you are only given piece placement and nothing else, as in any case there could have been two extra king/rook moves (and two extra knight moves from the other player). And because we are looking for a mate in one, it doesn't matter if black can castle or not (a mate in 2 could be tricky in this way where eg black could be shown to be able to castle one way or the other but not in both, or combining castling + en passant like Smullyan's problem) | |
| yesterday | comment | added | AJM | My guess is that White cannot tell if they have already castled or not. If they haven't, the act of castling will check Black's king with the rook and mate. If they have... yeah, that's where I'm out of ideas. | |
| yesterday | comment | added | Miguel Ambrona | Rather than knowing "the current position", it would be more precise to say "the board configuration of pieces" or similar. Note that a "position" carries information about castling rights and e.p. too. | |
| yesterday | vote | accept | fblundun | ||
| yesterday | comment | added | fblundun | @Cheshire_the_Maomao it's referring to the list of information that White knew given in the first paragraph. | |
| yesterday | comment | added | Cheshire_the_Maomao | I feel confusedand can't understand the question...what does "this information" in "This information was enough to deduce that there existed a legal move" refer to? | |
| 2 days ago | answer | added | xnor | timeline score: 12 | |
| 2 days ago | history | became hot network question | |||
| 2 days ago | comment | added | fblundun | @GentlePurpleRain White can tell that there exists a mate in one. | |
| 2 days ago | answer | added | noedne | timeline score: 12 | |
| 2 days ago | comment | added | GentlePurpleRain | Are you saying that white's next move will checkmate the opponent, or just that white will be able to checkmate the opponent (say, in the next 2 or 3 moves)? | |
| 2 days ago | answer | added | mathperson314 | timeline score: 2 | |
| 2 days ago | comment | added | fblundun | Yes - there isn't a unique solution. | |
| 2 days ago | comment | added | z100 | I believe the solution is not unique and is related to en passant or castling. | |
| 2 days ago | history | asked | fblundun | CC BY-SA 4.0 |