Questions tagged [retrograde-analysis]
Retrograde analysis is the method of deducing information by working backwards from a given position or outcome. This information can be about past positions of the same game, or may contain forward content, such as optimal play.
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What is the correct retro protocol for this problem? PRA or RS?
[Title "#1 - W. Keym. Die Schwalbe, 1969. Ded. K. Fabel"]
[FEN "qrbR4/rP1P1pp1/pQ1pp3/pPp5/6P1/1P3BB1/3PP2P/R3K1k1 w - - 0 1"]
The solution to the problem is simple. Black has ...
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Is the RS method actually a convention? If so, what can be written in it that is not in 16.1 and 16.2?
The RS Agreement is mentioned in paragraph 16.3 of the Code. But in such a context that I want to cry.
... then the Retro-Strategy (RS) convention should be applied: whichever castling is executed ...
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What conditions must/should be added to this fairy selfmate stipulation?
[Title "s#2 (?) Maximummer - Anatolii Vasylenko Die Schwalbe 132 12/1991 4. Lob"]
[FEN "1K2k2r/r4R2/8/QPp4p/8/8/8/8 w - - 0 1"]
1. bxc6ep Rxf7 2. Qxh5 0-0#
1. ...
...
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Does the AP Convention and Rule 16.2 allow E.P. to be performed without justification?
Rule 16.2
En-passant convention. An en-passant capture on the first move is permitted only if it can be proved that the last move was the double step of the pawn which is to be captured
The AP ...
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What are the castling & e.p. conventions, and how are they used?
Castling & en passant are often called "conditional moves". In the chess problem world, we frequently hear about the castling & e.p. conventions. What are these exactly, and how are ...
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Position where last x halfmoves are determined
What is the largest integer x such that there exists a position such that:
That position can occur in a legal chess game
It is possible to prove at least x halfmoves have been played
It is possible ...
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What is A Posteriori (AP)?
A number of problem-related questions recently mention AP by which they mean “A Posteriori”.
What are they talking about?
It seems as if the guys talking about it don’t have a common understanding. Is ...
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Can a unique position be deduced if pieces are replaced by checkers (can see piece color but not type)
Inspired by a video where top players guess which famous game a position is from, except pieces in the position are replaced by checker pieces (so they can see the piece color but not type). Of course ...
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Show an AP Type Keym #n, where Black's castling illegality with WTM drives both basic White mate & AP?
Let me explain with an example what is meant.
[Title "#2 - Lord Dunsany. Fairy Chess Review, 1943"]
[FEN "r3k3/ppp5/2p2P2/3PpK2/8/NP1R4/p1P3P1/1b3N1R w - - 0 1"]
1. Ke6 (0-0? ...
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Why is the abbreviated retronotation not used?
When playing forward, both full and abbreviated notation are used with equal success. Decoding the abbreviated notation does not cause any problems for the user.
Why can't you do the same in retro ...
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Can the problem condition "A Posteriori Type Keym", which flips the player to move, also flip the player that delivers mate?
Again, I composed the task, but doubts crept in. Is everything really as I think it is?
4k2r/4p3/4P3/7N/8/P7/rP1PP1P1/5KQR w - - 1 13
2b1k2r/1p1pp1p1/4P3/p6N/6P1/2P5/1PrPP1P1/1B3KQR w - - 1 13
...
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Is Retro Zugzwang possible?
What is just a zugzwang is clear. This is when, in a normal good position, a side is forced to make a move, and any move made leads to a loss.
Accordingly, in Retro moves are made not forward, but ...
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Have problems similar to this recent composition of mine been done before?
N1Nrk2r/n1ppp1p1/1pQ5/1P6/5R1P/3P3B/3PPBPp/R3K3 w - - 1 13
Checkmate in two moves.
AP (Type Keym + Type 3)
The AP Convention (A Posteriori) states: "If the player needs castling rights in order ...
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How many moves needed to reach this position?
"Homebase" is where all the surviving pieces are apparently on their starting squares. Here is a very easy new example proof game: can you find the unique shortest game that leads to this ...
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Lower bound on the number of moves to reach given position
I'm trying to analyze opening positions using the Lichess evaluations database. Loading the entire database into memory is somewhat costly, so I'd like to filter out positions that occur after, say, ...
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