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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Do endgame tablebases only handle legal positions?

The title is my question for now. I also wonder if similar legality concerns may reduce the number of input FENs as checkmates used as input to the retrograde proofing or construction process. In ...
dbdb's user avatar
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3 votes
2 answers
141 views

Max number of promoted units on the board in a monochromatic game

A whimsical question just occurred to me. I think I have an answer, but I thought I would share it here as a puzzle. What is the maximum number of promoted units that can appear simultaneously on the ...
Laska's user avatar
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6 votes
2 answers
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What are "monochromatic" retrograde analysis problems?

What does it mean when a retrograde analysis problem is qualified as being "monochromatic" ?
Brian Towers's user avatar
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4 votes
2 answers
167 views

Missing move in a chess match due to lousy annotation

I am a beginner in championships (well, and in chess in general). The other day I played a match that I can't analyze because there is an error in the annotation sheet. [FEN ""] 1. e4 e5 2. ...
Ramiro Rego Álvarez's user avatar
1 vote
1 answer
102 views

Could castling ever be proven to be legally allowed for sure if the first move is required to be a pawn move?

In retrograde analysis problems, castling is assumed to be allowed unless it could be proven that either the king or the rook has previously moved. It is well known, of course, that one could never be ...
Geoffrey Trang's user avatar
2 votes
2 answers
128 views

How would I detect dead position in a tablebase?

I am programming a tablebase for fairy chess, and would like to conclude the game if mate cannot be reached in any way. I guess this has to be detected when the evaluation (win in... / loss in... / ...
Ferazhu's user avatar
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6 votes
4 answers
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When can you tell which pieces are 'White' from a position where the pieces are colored red and green and you know whose move it is? [duplicate]

Suppose you come across a chessboard where the pieces are colored red and green and there are no labels on the squares. You don't know which move number it is. What are the positions where, by only ...
michaelc35's user avatar
4 votes
1 answer
117 views

Term to distinguish between two categories of illegal positions

Consider these two categories of illegal positions. First, e.g.: Not having exactly one King of each color Both Kings being in check Pawns on the first or eighth ranks Second, e.g.: Having more ...
Joseph Sible-Reinstate Monica's user avatar
7 votes
2 answers
1k views

Legal positions with one color to move only?

Most positions in chess can be reached with both black or white to move. Some positions are only legal with one color to move. One such position is the starting position, which famously can't be ...
SE - stop firing the good guys's user avatar
7 votes
1 answer
279 views

Do any unique proof games feature an en-passant capture?

Most positions that could be reached, in a specified number of moves, after an en passant capture could be reached just as well without one, suggesting that such positions could not occur in unique ...
supercat's user avatar
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11 votes
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Open problems in chess involving maximum material imbalances

I am posting the present question since here Very unbalanced Chess Positions I have introduced three open problems (i.e., the third one, the fourth one, and the sixth one from the above), regarding ...
Marco Ripà's user avatar
5 votes
2 answers
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How many more squares can you attack?

(Inspired by this cool problem) Let’s say it’s White to move. Let A = the number of squares currently attacked by White, and B = the number of squares attacked by White after White’s next move. What ...
Benjamin Wang's user avatar
5 votes
2 answers
172 views

Which piece was captured last - knowing that this position was reached in the minimum number of moves possible?

This is a puzzle that I made a while ago, but never really published anywhere before (although I posted it on an obscure Dutch telegram channel). The question is simple: what was the piece that was ...
Carlo Wood's user avatar
15 votes
2 answers
4k views

Which methods can be used to prove that a position is illegal?

Given a board position, there are programs that try to find a series of legal moves that lead to it. Are there algorithms that can do the opposite - prove that the position is not reachable by a ...
2080's user avatar
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12 votes
1 answer
2k views

How to solve proof games?

The following question deserves to be asked! "I see a lot of proof game problems, where I am given a diagram and have to find the unique way to reach that position in the specified number of ...
Laska's user avatar
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3 votes
2 answers
170 views

Generate an entire chess game up to a position

I recently found a chess problem YouTube video with this position. [FEN "r4rq1/5p1p/p5kn/R1B1Q1b1/6p1/5p2/PNP2P2/1K6 w - - 0 1"] I want to turn this position into an entire game of chess. ...
SteepAtticStairs's user avatar
0 votes
1 answer
157 views

Reach this position in four moves [duplicate]

I recently came across this chess problem. The requirement is to reach this position (starting from a basic board set up board) in 4 moves. How do you do it? [FEN "rnbqkbnr/pp3ppp/2p1p3/8/4P3/8/...
Harry Iguana's user avatar
4 votes
1 answer
868 views

Mate in 1, then No Mate in 1, then Mate in 1

Anand and Bobby both are members of their school's chess club. And while cleaning up the games room at the end of the day, they saw a board with the following position: [FEN "rbR1B1Q1/k1n1nN1p/...
justhalf's user avatar
  • 192
20 votes
2 answers
5k views

Is the position in this trick question reachable?

I found this trick question on r/Anarchy chess: White to move, mate in two. [FEN "2R2RK/6PP/5P/3PN/P/1pQ3p/n1p1qbp/5brk w - - 0 1"] [StartFlipped "1"] The trick is that But is ...
SQB's user avatar
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13 votes
1 answer
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Harry Potter Chess Analysis

So, I've been reading Harry Potter and The Philosopher's Stone. If you haven't read the book yet, or watched the movie, and you don't want any spoilers, stop reading this question. Continuing, there ...
Anonymus 25's user avatar
4 votes
1 answer
87 views

Coordinates probem

[FEN "8/8/8/8/8/4R3/2N2R2/3N1k1K w - - 0 1"] Given that this position could be reached in a legal game of chess, and that no piece was captured on the last move, are we seeing the board ...
dr.vlad lup's user avatar
4 votes
2 answers
690 views

Where does the black king stand in this specific position?

[FEN "7r/pppppKpP/6P1/8/8/8/n7/8 w - - 0 1"] Assume that the following position was reached in a legal game of chess. In the last 5 moves, no pawn has moved and no pieces were captured. The ...
dr.vlad lup's user avatar
6 votes
1 answer
508 views

Brainteaser puzzle

So... initial position is [FEN "7k/8/6KB/8/p7/8/Q7/8 w - - 0 1"] Now... Neither white's king nor queen has moved in the previous five moves. In addition, no pieces have been captured by ...
dr.vlad lup's user avatar
9 votes
1 answer
661 views

Find color of the pieces

Given the following position, what colour are the pieces and what was the last move played? [FEN "B1KRN3/PP6/2QK1R2/8/8/8/8/8 w - - 0 1"]
dr.vlad lup's user avatar
5 votes
1 answer
724 views

Do you know this proof game?

I'm not familiar with this proof game. [FEN "r2qk1nr/ppp1pp1p/2n1p2p/8/8/1P6/NPPPPPPP/R3K2R w KQkq - 0 1"] What square was the white queen captured and how?
dr.vlad lup's user avatar
3 votes
1 answer
366 views

Retrograde analysis problem

Given that this position is legal, and could be reached in a legal game of chess, what were the two last half-movess, or one move for White and one for Black? [FEN "5K2/8/6Pk/8/5Q1R/8/8/8 w - - 0 ...
dr.vlad lup's user avatar
25 votes
3 answers
7k views

Given a legal chess position, is there an algorithm that generates a series of moves that lead to it?

Given a FEN board position, is there an algorithm that can return a PGN move list that evaluates to it from the standard initial position?
2080's user avatar
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2 votes
1 answer
77 views

Help needed with a problem

On an empty board, how can you place a White king, two White, rooks, and a Black king so that White can give mate in 4 ways from that position?
dr.vlad lup's user avatar
2 votes
2 answers
157 views

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 ...
Laska's user avatar
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9 votes
1 answer
1k views

From Mate-in-3 to Mate-in-1

Here is my new problem in 3 steps - the key designates here the piece that moves first in the solution. An other way to reach a mate in one I hope you'll enjoy... [Title "From Mate in 3 to ...
Xavier Labouze's user avatar
10 votes
2 answers
605 views

Mate in One the Missing King

The post "A mysterious mate in one" made me think of one of my last problems which is also a Mate-in-One with no black King: [Title "White to move and mate in one"] [FEN &...
Xavier Labouze's user avatar
37 votes
3 answers
6k views

A mysterious mate in one

Here's a question that's a little off the usual format, but problem questions like this have been done before and are on topic, so here we go! Question: Can you find the mysterious mate in one? The ...
Rewan Demontay's user avatar
3 votes
3 answers
268 views

Retrograde problem websites

I am looking for a good chess website about retrograde analysis problems, but after a few searches, I haven't found anything. Are there any websites that you can recommend?
user avatar
4 votes
1 answer
210 views

Where are the non captured Black pieces?

[FEN "8/8/8/8/8/PP4PP/2PPPP2/NNBQKBRR w - - 0 1"] Here is a problem from my blog once more. This is the position after White's 14th move. Seven Black pieces were captured during the game ...
Eric ANGELINI's user avatar
4 votes
1 answer
154 views

Which White piece moved only once?

Here is a chess problem that uses retrograde analysis. I’ve also posted it on the “France-Echecs” chess forum, which is in French of course, and on my blog. [FEN "3qk3/3pp3/8/8/8/3PP3/1PP2PP1/...
Eric ANGELINI's user avatar
1 vote
1 answer
146 views

What’s the difference between Partial Retrograde Analysis and Retro Strategy?

What’s the difference between Partial Retrograde Analysis (PRA) and Retro Strategy (RS) which are different ways of interpreting retrograde analysis chess problems?
Laska's user avatar
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7 votes
3 answers
671 views

Challenge: Create the longest game determined only by the final diagram and move number

The challenge is to create the longest list of half moves whereby an AI could re-create that list of moves perfectly, only given the ending board state and the number of moves. As example I will first ...
jbernard3396's user avatar
5 votes
2 answers
380 views

Seeking a particular problem

I recall seeing a problem in Games magazine, probably in the early 1990s, that required the solver to deduce that a capture en passant was possible (not just because that's the only way to get a ...
msh210's user avatar
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17 votes
9 answers
4k views

Could a chess engine do retro analysis?

If I took a legal chess position, to what extent could an engine work out the previous moves? [in some other board games such as Othello such game reconstruction is done easily with an engine.]
Snack_Food_Termite's user avatar
9 votes
2 answers
711 views

Pal Benko's final problem

EDIT: Link added One of my chess heroes, Hungarian GM Pal Benko, is no longer with us. He overcame many difficulties in his early life to live one which was rich and full, and reached the age of 91 ...
Laska's user avatar
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12 votes
2 answers
3k views

Identify a problem where a potentially winning move draws because of the 50 move rule

I'm trying to recall a particular chess problem. It's related to retrograde analysis. All what I can remember is this: it's an endgame where there is only one way to reach the position, and during ...
dveim's user avatar
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2 votes
2 answers
326 views

Attempting to create a retraction problem

I am trying to create a retraction problem, but I am unsure if it is sound, and I do not know where to find resources on them. I have two questions. Is my problem correct? I am not giving a solution ...
Rewan Demontay's user avatar
3 votes
2 answers
370 views

Where can I find these mentioned chess problems?

In his article “The Horse Concoction", Tim Krabbe mentions retrograde analysis problems that involve placing 10 rooks, knights, or bishops on the board for a mate in 1. The 10 rooks problem shown ...
Rewan Demontay's user avatar
2 votes
2 answers
466 views

A question regarding "The Horse Concoction"

Long ago in 2000, Tim Krabbe presented, a now classic, problem by Harry Goldsteen in his article “The Horse Concoction” on his site. It has blossomed across the Internet, as some of us know. The task'...
Rewan Demontay's user avatar
4 votes
1 answer
821 views

Searching for a "where is the black king" problem

Sometime ago, a friend showed me a position where he had the Black king removed. The goal was to find where is the Black king using some pretty weird reasoning. There were only a few pieces on the ...
ghilesZ's user avatar
  • 265
4 votes
2 answers
429 views

Can we say for sure that Black's king has not moved?

The following position appears as the 7th puzzle of Raymond Smullyan's Arabian Knights, a book about retrograde analysis. [FEN "3qk2r/p2pp1bp/bpp2n2/8/3N3Q/1PN1P1P1/P1PPP2P/3K1n2 w - - 0 50"]...
shabbychef's user avatar
14 votes
5 answers
2k views

What is the result? (Rules + puzzle)

[EDITED to include followup - EDIT 2 to include definition of position] This is in part a genuine question on the FIDE Laws of Chess, and in part a small puzzle to solve. Suppose that during a long ...
Remellion's user avatar
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15 votes
2 answers
3k views

Can white win in this almost 20 year old puzzle?

It's White to move-can they force a win?. The left bottom is a1 as usual. [FEN "4k2r/6p1/p4pKb/p2N3p/p7/p5Q1/p1n5/qrn5 w - - 9 9"] Note for people who saw an earlier version: the position ...
Albert Hendriks's user avatar
10 votes
4 answers
957 views

Can you mate with each of your 16 pieces on its original square?

An opinion poll conducted by problem composer Roberto Osorio over 10 master-level chess players in the Argentine Chess Club produced 100% wrong answers! :-) When the right answer is posted here, I ...
Laska's user avatar
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3 votes
1 answer
361 views

Are there any legal positions known to be impossible to come to in a normal game? [duplicate]

There are some fairly obvious ways to set up a chess board that cannot possibly happen: both kings simultaneously in check would be one. There are some positions that seem impossible in a normal ...
user1833028's user avatar