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Date: 08 Nov 2007 20:30:31
From: Amarande
Subject: Castles, mate (Helpmate problem)
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This occurred to me today on FICS, when someone needed an example of O-O
mate.
Premise: Starting from the initial position, construct the shortest
possible game so that the final move is a mate delivered by castling.
I could quickly come up with a solution in 9:
1 f4 f5 2 e4 fxe4 3 b3 Kf7 4 Bb2 Kg6 5 Bc4 Kf5 6 h4 Kxf4 7 h5 Kf5 8 h3
Nc6* 9 O-O#
This is easily shortened to 8 by sacrificing the pawn at f5:
1 f4 f5 2 e4 fxe4 3 f5 Kf7 4 h4 Kf6 5 d4 Kxf5 6 Bc4 g6 7 Nh3 Nf6* 8 O-O#
(* A number of other moves are possible also)
and after a short little additional finagling I managed to remove a
couple of wasted moves, producing a 7-move solution:
1 f4 f5 2 e4 fxe4 3 f5 Kf7 4 Nh3 Kf6 5 Bc4 Kxf5 6 d4 g6 7 O-O#
Which looks pretty nice, really :) I'm not sure if a pure-mate version
is possible (we have redundant coverage of g5 here); d4 is needed to
cover e5 (which otherwise takes two moves to guard, as in the 9-mover),
and the Knight can only go to h3 (f3 blocks the mate, and e2 results in
an extra move being wasted to cover g4). It doesn't look that I can
lower this below 7 moves, though someone else might be able to figure
out a way to do so (castling itself involves 4 moves, plus it looks that
White has to move the f-pawn once or twice in order to get it out of the
way ...)
Can it be done in 4 or 5 or 6?
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Date: 13 Nov 2007 14:12:54
From: David Richerby
Subject: Re: Castles, mate (Helpmate problem)
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Aande <[email protected] > wrote:
> Can it be done in 4 or 5 or 6?
It can't be done in four. To play 4.O-O#, White must move his e-pawn
or g-pawn, move his bishop, move his knight somewhere other than f3
and somehow lose his f-pawn. There's no time to move the f-pawn
before it is captured and it must be captured by a black piece, not by
a pawn because the capturing piece must move out of the way, because
White doesn't have time to capture it. However, capturing the Pf2
with a black piece takes at least three moves. After these three
moves, 4.O-O cannot give mate (if it's even legal) because the black
king's still on e8.
Similarly, to play 4... O-O#, Black must move his e/g pawn, move his
bishop, move his knight somewhere other than f6 and lose his f-pawn
without moving it. It takes White at least three moves to capture the
Pf7 but, after those three moves, his king's still on e1, White has a
piece of some kind on f7 and a pawn on f2 so 4... O-O cannot be check.
I think similar reasoning should show that it can't be done in five,
either, but it's more complicated because there's a bit more freedom
in the moves. A useful trick is likely to be that, if the losing side
captures the winner's unmoved f-pawn on move three, on move four, he
must move the capturing piece out of the way but, on move five, he can
move it back to f2/f7 so any check cannot be mate. But we also need
to consider cases where the loser captures the f-pawn after it has
been moved or places a piece on his opponent's K3 or KN3, which the
winner captures with his f-pawn to open the file.
I'll let somebody else think about that.
Dave.
--
David Richerby Hilarious Sushi (TM): it's like a raw
www.chiark.greenend.org.uk/~davidr/ fish but it's a bundle of laughs!
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Date: 10 Nov 2007 19:27:05
From: SBD
Subject: Re: Castles, mate (Helpmate problem)
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On Nov 9, 6:32 am, David Richerby <[email protected] >
wrote:
> SBD <[email protected]> wrote:
> > Sounds interesting, but I don't think a pure mate is possible since
> > you have nightwatchmen sitting at the homebase; if pieces are
> > unused, the mate is not pure, or?
>
> `Pure' just means that each of the king's possible escape squares is
> covered by exactly one piece, doesn't it? It's not a problem if there
> are any number of pieces doing nothing, so long as they're not
> contributing to the checkmate, either.
That is not true from a problemist's perspective, pure or ideal means
each square is covered only once, and that there are no superfluous
pieces at all. In a model mate, you can have idle king or pawns,
nothing else. There is a magazine devoted to ideal or pure mate
problems: Ideal Mate Review.
I would think this would hold OTB as well since pure as a mating
designation must be aesthetic in nature.
One thing I was playing with was the shortest h# from the start with
long castling. Its pretty neat, I find it hard not because of the
longer time to long castling, but proper coverage of each piece; I
always leave a square open.
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Date: 09 Nov 2007 03:07:50
From: Stephan Bird
Subject: Re: Castles, mate (Helpmate problem)
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On Thu, 08 Nov 2007 20:30:31 -0500 in [email protected],
Aande <[email protected] > wrote:
> This occurred to me today on FICS, when someone needed an example of O-O
> mate.
...
> Can it be done in 4 or 5 or 6?
Well, there are examples of proof games - where the move order is
uniquely determined and *Black* can mate in 6 from the initial position.
See e.g. <URL:http://www.janko.at/Retros/Records/ShortestMate/
Geissler.htm >
1.e4 e5 2.Ke2 Ne7 3.Kf3 Nec6 4.Kg4 f5+ 5.Kxf5 Bc5 6.Qg4 0-0#
Stephan
--
Stephan Bird MChem(Hons) AMRSC
Currently in Caernarfon, Wales
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Date: 09 Nov 2007 07:04:55
From: SBD
Subject: Re: Castles, mate (Helpmate problem)
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Sounds interesting, but I don't think a pure mate is possible since
you have nightwatchmen sitting at the homebase; if pieces are unused,
the mate is not pure, or?
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Date: 09 Nov 2007 12:32:37
From: David Richerby
Subject: Re: Castles, mate (Helpmate problem)
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SBD <[email protected] > wrote:
> Sounds interesting, but I don't think a pure mate is possible since
> you have nightwatchmen sitting at the homebase; if pieces are
> unused, the mate is not pure, or?
`Pure' just means that each of the king's possible escape squares is
covered by exactly one piece, doesn't it? It's not a problem if there
are any number of pieces doing nothing, so long as they're not
contributing to the checkmate, either.
Dave.
--
David Richerby Incredible Flower (TM): it's like a
www.chiark.greenend.org.uk/~davidr/ flower but it'll blow your mind!
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