# [Retros] Die Schwalbe 222 nr 13237

Rol, Guus G.A.Rol at umcutrecht.nl
Mon Jan 22 10:05:21 EST 2007

I think a few restrictions should be in place to make the stipulation somewhat sensible:

1. No pawns on 1st and 8th rank
2. Exactly one king of each colour

It is questionable that this is sufficient. Since 11 squares can be filled with 2 kings and 9 white pawns, 10 squares would be an upper limit for compliance. If that is undesitrable, add another restriction "no more than 8 pawns of one colour" and next in line are the promotions. With the further restriction of "no more than the maximum number of pieces of one type including promotions"? you have to deal with 10 white bishops on 10 black squares. Then with combined promotions of different type, then with promotions + pawns, the sum of black + white promotions .... Gets very confusing unless the restrictions are precisely stated.

The basic problem with this stipulation is that you must decide somehow that having 6 black kings is "illegally illegal" whereas 4 white pawns + 7 white bishops are merely "legally illegal". Since there are no obvious differentiators for these categories, the composer 'd better tell us how exactly!

Guus.

-----Oorspronkelijk bericht-----
Van: retros-bounces at janko.at [mailto:retros-bounces at janko.at] Namens Otto Janko
Verzonden: zondag 21 januari 2007 13:18
Aan: 'The Retrograde Analysis Mailing List'
Onderwerp: [Retros] Die Schwalbe 222 nr 13237

My interpretation:

A set of marked squares is not compliant if there is at least one setup of pieces on these squares which forms an illegal position. What is the largest compliant set of squares?

Thus, for example, two adjacent squares are not allowed in any compliant set of squares because you can put the two kings on it yielding an illegal position.

~ÔttÔ~

________________________________

From: retros-bounces at janko.at [mailto:retros-bounces at janko.at] On Behalf Of peter.fayers at virgin.net
Sent: Sunday, January 21, 2007 1:05 PM
To: retros at janko.at
Subject: [Retros] Die Schwalbe 222 nr 13237

What have I missed here? why is e1 g3 h1 legal - put wP on e1!

Rgds,

Peter.

13237 - Gerald Irsigler

How many squares can you mark at most on a chess board so that every
possible position with pieces on those squares (including wK and bK) is
legal?

(e.g.: mark e1 g2 h1 isn't valid, since wKe1, wBh1 wKg2 isn't legal. e1
g3 h1
is valid though)

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