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Apr-12-06
 | | OhioChessFan: <Why not 1. Ke6?>
<Yourang>
1. Ke6 0-0-0 |
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| Apr-12-06 | | RolandTesh: <OhioChessFan>
<By George, you're getting there.> Why am I not already there? After d5xe6 (en passant), all Black replies allow Qh8#, and 0-0-0 allows Qa8#. |
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| Apr-12-06 | | YouRang: Oh yeah. (duh). ...Er, I was trying to solve it with one eye closed. Then it's got to be en passant. |
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Apr-12-06
| | OhioChessFan: <Why am I not already there? After d5xe6 (en passant), all Black replies allow Qh8#, and 0-0-0 allows Qa8#. > <Oh yeah. (duh). ...Er, I was trying to solve it with one eye closed.
Then it's got to be en passant.>
If I'm not mistaken, Ke6 is a possibility for White's first move. |
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| Apr-12-06 | | RolandTesh: <OhioChessFan>
This is a clever puzzle (yours?), what with two "tricky things," one for each side. However, I believe that for such you puzzle to be "elegant" it must be the nature of the puzzle that Black's last move must have been e5-e7. Since it is possible that Black moved either his king or rook to reach this position, then both "tricky things" are just theoretical. Still, very clever. :-) |
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Apr-12-06
| | OhioChessFan: Clever trumps elegant in my book every time! I consider it a little elegant that if e5 wasn't Black's last move, he has forfeited his option of castling. |
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Apr-12-06
| | OhioChessFan: I have only a last name for the puzzle author-Moravec. |
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| Apr-12-06 | | RolandTesh: <OhioChessFan>
<Clever trumps elegant in my book every time! I consider it a little elegant that if e5 wasn't Black's last move, he has forfeited his option of castling.> Okay, now I get the elegance. If e5 was not Black's last move, then Ke6 would also mate in 2 since 0-0-0 is not possible (king or rook must have previously moved). A minor point is that this only proves that there are not two solutions. For example, after Ke6, how do you prove that Black has never moved the king or rook previously in the game? Still, everything else is clever enough to qualify as elegant. :-) Is this your creation?
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Apr-12-06
| | OhioChessFan: <A minor point is that this only proves that there are not two solutions. For example, after Ke6, how do you prove that Black has never moved the king or rook previously in the game?> There are only 3 possibile moves for Black to reach the puzzle position. A. Ra8
B. Ke8
C. e7-5.
To solve the puzzle, you must know that Black's last was either A/B or C. If it was A/B, then White's first move is Ke6, and Qh8 mates in 2.
If it was C, then White's first move is the en passant capture, and Qa8 or h8 mates in 2. The retrograde analysis is the point of the puzzle. |
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| Apr-12-06 | | RolandTesh: I know there must be something I'm missing, but aren't you proving that there are two possible solutions? If Black's last move was A or B -- then Ke6 is the first move of the puzzle. If Black's last move was C -- then e6 (en passant) is the first move of the puzzle. Don't we need to know what Black's last move was before knowing whether Ke6 or e6 (en passant) is the solution? |
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| Apr-12-06 | | YouRang: I believe it is problem etiquette to assume that castling is possible unless stated otherwise. With this being the case, we must assume that O-O-O is possible, meaning that the last move could not have been the rook or king, but MUST have been e7-e5. In other words, etiquette dictates that en passant capture must be possible. That's why this puzzle is both clever and elegant. Very nice. :-) |
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| Apr-12-06 | | RolandTesh: It has been my understanding with "problem etiquette" that nothing is to be assumed -- that everything must be provable. Why are you assuming the 0-0-0 is allowable -- just because the Black king is on e8 and the rook on a8? For all we know, the a8 rook started out on h8. I think I'm getting the point that this problem does have two solutions, both work, but only if we make assumptions as to what Black's previous move was. |
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| Apr-12-06 | | YouRang: To make sure I'm not crazy, I did some research.
If the British Chess Problem Society is an authority on the matter, then my point about castling is correct.
From http://www.bcps.knightsfield.co.uk/... : "Castling
Castling during the solution of a problem is considered legal unless it can be proved, by retrograde analysis, that it is illegal." |
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| Apr-12-06 | | YouRang: Also from Wikipedia
http://en.wikipedia.org/wiki/Chess_... :
"In all the above types of problem, castling is assumed to be allowed unless it can be proved by retrograde analysis (see below) that the rook in question or king must have previously moved. En passant captures, on the other hand, are assumed not to be allowed, unless it can be proved that the pawn in question must have moved two squares on the previous move." |
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| Apr-12-06 | | RolandTesh: <YouRang>
I was slow on the up-take and get it now. The problem is perfectly elegant. As <OCF> pointed out, this is a retrograde problem. The point being to demonstrate a mate in 2 against all possible previous Black moves. As you say, very nice. |
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| Apr-12-06 | | YouRang: <RolandTesh> I think I erred in my earlier comment, <I believe it is problem etiquette to assume that castling is possible unless stated otherwise>. But "stated" is the wrong word. I should have said "proven". Therefore: Since we cannot prove that castling is illegal, we must assume that it's legal. But this assumption, in turn, forces us to assume that en passant is in effect. Hence, the solution is unique. :-) |
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| Apr-12-06 | | YouRang: Along similar lines of thought, <acirce> posted this mate-in-2 problem a while back (so you might have already seen it).
click for larger view |
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| Apr-12-06 | | RolandTesh: <YouRang>
<Castling during the solution of a problem is considered legal unless it can be proved, by retrograde analysis, that it is illegal."> Interesting, I did not know this. I was about to ask if the same was true for en passant, but you covered this as well. |
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| Apr-13-06 | | YouRang: The more I think about <OhioChessFan>'s puzzle, the more I think that perhaps it's intent is to reveal a logical flaw in the 2 problem rules: #1 <"In all the above types of problem, castling is assumed to be allowed unless it can be proved by retrograde analysis (see below) that the rook in question or king must have previously moved.> #2 <En passant captures, on the other hand, are assumed not to be allowed, unless it can be proved that the pawn in question must have moved two squares on the previous move.> This puzzle seems to demonstrate that these rules allow for a logical contradiction: By rule #1, we *assume* that Black can play O-O-O (because we can't prove that the rook or king moved). But does this assumption constitute *proof* that White can play dxe6 e.p.? By rule #2, we *assume* that Black cannot play dxe6 e.p. (because we can't prove that Black just played e7-e5). But does this assumption constitute *proof* that Black cannot play O-O-O? The fiendish problem from <acirce> (shown above) also stretches the rules in ways that I'm sure the rule makers never imagined. |
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Apr-13-06
| | OhioChessFan: <I know there must be something I'm missing, but aren't you proving that there are two possible solutions?
If Black's last move was A or B -- then Ke6 is the first move of the puzzle. If Black's last move was C -- then e6 (en passant) is the first move of the puzzle. Don't we need to know what Black's last move was before knowing whether Ke6 or e6 (en passant) is the solution??> <RolandTesh> It seems to me that when solving a puzzle, you must consider all possible moves by the losing side. In this puzzle, you must determine the move made before the puzzle position. As there are 2 possibilities, you must find the subsequent solution for each possibility. I don't see it as any different than mate in 2 puzzles where Black has 2 options on his first move and you must find the corresponding second move for each of those. |
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Apr-13-06
| | OhioChessFan: I have now learned more about puzzle rules than I'd ever expected. I just liked the retrograde analysis involved. |
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| Apr-13-06 | | themadhair: If you like retrograde analysis try this one.
click for larger view
The question I am sure you are wondering is "Where is the white king?"
That is for you to find out. |
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| Apr-13-06 | | RolandTesh: <themadhair>
<"Where is the white king?"> Why can't it be in either of two places -- either a3 or c3? First, I assume it is Black to move (and that White just moved his king to reveal a discovered check)? So, if you take the position back two moves -- putting the White king on b3, and the Black rook on d5 -- then the game progresses -- Rb5+, followed by either Ka3 or Kc3. I must be missing something since there would then be two possible solutions. But why doesn't this work? |
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| Apr-13-06 | | YouRang: <themadhair><RolandTesh> I think I've seen this puzzle before; except the bishop should be on d5, not e6.
click for larger view
This makes the puzzle not so trivial. :) |
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| Apr-14-06 | | themadhair: <YouRang>
Sorry - you are indeed correct. The bishop should indeed be at d5. My bad. |
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