Chess 960: The back row setup is selected randomly but the King must be between the two Rooks, and Bishops must be of opposite colour. White setup mirrors Black’s.
The rules of castling in Chess 960:
After a-side castling (queen-side castling in standard chess), the king finishes on the c-file (c1 for White; c8 for Black) and the a-side rook finishes on the d-file (d1 for White; d8 for Black). The move is notated 0-0-0 as in standard chess.
After h-side castling (king-side castling in standard chess), the king finishes on the g-file and the h-side rook finishes on the f-file. The move is notated 0-0 as in standard chess.
Castling has the same prerequisites as castling under standard chess rules, namely:
The king and the castling rook must not have previously moved.
No square from the king’s initial square to the king’s final square may be under attack by an enemy piece.
All the squares between the king’s initial and final squares (including the final square), and all the squares between the rook’s initial and final squares (including the final square), must be vacant except for the king and rook.
Annan Chess (Southern Chess): A unit (incl.King) one square in front of a friendly unit moves in the manner of the rear unit, not as itself. For White, affected units are on the same file and one rank higher, for Black they are one rank lower. Transference of powers is only to the next unit: with 3 friendly units adjacent in a file, the 3rd moves as the 2nd, the 2nd moves as the 1st and the 1st is unaffected. A white Pawn on the first rank is immobile.
Thanks. That is what I understood too. What I meant was why the starting position is not mentioned in the solution and why there is no explanation in the solution how that starting position was arrived eliminating other positions.
The first rank of the starting position was given just before the first move of the solution, you probably missed it. As for your other point, in an ordinary PG the move sequence of the solution is arrived at by eliminating other potential move sequences, but in the comment section of other PGs I don’t see you commenting that there is no explanation in the solution how the move sequence was arrived at. Why should it be different here, replacing “move sequence” with “starting position”?
Much better! Now I wonder about the relevance of the alternate moves (5. …) discussed in the solution, because they don’t even obey the diagram with undefined pieces. They would make sense if the stipulation were “PG 4.5 & #1”, but not when it’s “PG 5 white is checkmate”, right?
A demolished version of this enigma took part in the Quartz TT10. Only after Jacobi was launched was it possible to get it sound. Thank you, Francois! And thank you for all the comments that help to understand this puzzle. The alternative moves B5 makes sense, indeed, if the stipulation were PG4.5 then #1. I wanted to show only that the mating move is unique, for the giving position.
Nikola Predrag
February 25, 2018 22:15
Well François, looking for possible n-moves and possible n-moves x 960 is not the same thing (unless n=0 -:)).
They’re not, but the difference is the same as adding one extra move. Chess960 could be defined as a fairy condition that starts orthodox, followed by “move 0” which is a special move where we shuffle the pieces to one of the allowed 960 start positions, followed by ordinary chess moves. With that point of view the entire solution is a sequence of moves, and so there is no reason to worry about move 0 and not about move 1 or move 2. The written solution even looks like that interpretation.
Georgy Evseev
February 26, 2018 11:35
Does Jacobi+ means that all 960 possible initial positions were checked and there is no solution in other 959 cases?
No.1279
hm… so, what was the starting position? How is it arrived at?
In a Chess960 PG, the starting position is part of the mystery. It must be found through retrograde analysis (or through trial and error).
This particular problem seems to be missing the condition “Checkmate position”, though. The are many cooks without it.
Thanks. That is what I understood too. What I meant was why the starting position is not mentioned in the solution and why there is no explanation in the solution how that starting position was arrived eliminating other positions.
The first rank of the starting position was given just before the first move of the solution, you probably missed it. As for your other point, in an ordinary PG the move sequence of the solution is arrived at by eliminating other potential move sequences, but in the comment section of other PGs I don’t see you commenting that there is no explanation in the solution how the move sequence was arrived at. Why should it be different here, replacing “move sequence” with “starting position”?
Sorry I missed that the starting position is mentioned in the solution.
My mistake, the stipulation is corrected to “PG 5 White is checkmate”. I’m sorry!
Much better! Now I wonder about the relevance of the alternate moves (5. …) discussed in the solution, because they don’t even obey the diagram with undefined pieces. They would make sense if the stipulation were “PG 4.5 & #1”, but not when it’s “PG 5 white is checkmate”, right?
A demolished version of this enigma took part in the Quartz TT10. Only after Jacobi was launched was it possible to get it sound. Thank you, Francois! And thank you for all the comments that help to understand this puzzle. The alternative moves B5 makes sense, indeed, if the stipulation were PG4.5 then #1. I wanted to show only that the mating move is unique, for the giving position.
Well François, looking for possible n-moves and possible n-moves x 960 is not the same thing (unless n=0 -:)).
They’re not, but the difference is the same as adding one extra move. Chess960 could be defined as a fairy condition that starts orthodox, followed by “move 0” which is a special move where we shuffle the pieces to one of the allowed 960 start positions, followed by ordinary chess moves. With that point of view the entire solution is a sequence of moves, and so there is no reason to worry about move 0 and not about move 1 or move 2. The written solution even looks like that interpretation.
Does Jacobi+ means that all 960 possible initial positions were checked and there is no solution in other 959 cases?
Yes, of course.
Bravo: undefined pieces is combo with Chess960!