@Mendelfist said in #8:
> Consider game A and B. In game A you have castling right but can't use it because your king would be in check.
The problem in the Martinez - Sarana game is not the check as check only means temporary loss of castling rights. The problem is that after 15. Bxf7+, the only legal move of black is 15... Kd8 which removes the castling rights permanently (for the rest of the game) therefore there is no legal way black could possibly castle after 15. Bxf7+, whatever the game would continue like. In other words, the set of possible continuations after 15. Bxf7+ and after 19. Bf7+ is exactly the same.
@Panagrellus said in #7:
> Maybe the players were just confused what was going on at that moment, and what exactly the issue was. As far as I know they get penalized on the clock for incorrect claims
The penalization would be adding 2 minutes to the other player; at the moment white had 28 minutes and black 72 minutes so I doubt that was an issue. I rather suspect that white had this line prepared and knew there was a repetition after Bf7+ so that when the claim was rejected, he simply made one more cycle (and claimed with 21. Bf7+ only written in the scoresheet) and didn't check if he could not claim earlier. (I'm aware that the position was winning for white according to the engine but he won the first game so that a draw was perfectly fine for him while playing for a win could be a risk.)
@mkubecek said in #11:
> . In other words, the set of possible continuations after 15. Bxf7+ and after 19. Bf7+ is exactly the same.
Yes, this makes this specific example quite absurd. On the other hand I can understand why castling rights and e.p. rights are considered as making positions different under the 3-fold repetition rule - in many cases there ARE different paths ahead if castling or e.p. is an option.
And adding another "special case rule" on top of this already rather esoteric rule to cover cases where the paths are identical arguably makes it even more confusing - so better to have a few rather strange edge cases like this one for the sake of (relative) clarity and simplicity.
Easy rule of thumb:
If the FEN's are equal, then the positions are equal.
@sheckley666 said in #13:
> Easy rule of thumb:
> If the FEN's are equal, then the positions are equal.
This is not how three-fold repetition works, since moves since last capture or pawn move is part of the FEN, and is not a factor in claiming three-fold repetition.
Well, if the king was in check during the initial position, that means it didn ́t have the right to castle at the moment, yes? And after 15... Kd8 it didn ́t have them either, yes? So i don ́t really see the practical difference in the positions. Very confusing indeed, and to my simple (chess)mind the position(s) are the same afterwards, if not for the permanent vs. temporary losing of the right to castle.
Maybe that ́s where the beef is, i don ́t know.
@chesseater78
You are right, *in this case* there is no practical difference, as the king had no choice , castling rights will be lost as soon he moves, and he must move because there's no way to block the check.
But just before he moved, he still had castling rights, and that's what counts to determine if the position is identical.
So you could say it was a pedantic application of the rule, and I hear you. But on the other hand, rules are rules, and as I said in #12, adding another "special case rule" on top of this already rather esoteric rule would not make it any clearer imo.
In short: it‘s always about the rights. Rule of thumb: same fen or not.
There are positions where you never be able to castle but you have the „right“. Random example: a black pawn e2 protected by a light-squared bishop, White Ke1, Rh1, and a dark-squared bishop.