# [Retros] Cooking a famous AP-problem?

Rol, Guus G.A.Rol at umcutrecht.nl
Thu Jun 28 14:57:56 EDT 2007

Dear retro-friends,

Another chapter in my discussion of retro-strategic principles is this
famous problem by Gert Rinder. Now, I haven't voiced my concerns on the
foundations of AP-logic here (yet) and I won't be doing so at this
point. I'd rather focus on 2 aspects of this composition:

(1) the post factum principle in the move choice for "AP after Keym"
(2) how can the automatic repetition rule cook this problem - to create
an even better one!

Author: Gert Rinder
Position: r2bk3/p1Rpp3/P1p2p2/KpP2P2/1P2p3/1P6/P7/8
Author stipulation: Draw (AP after Keym)
My stipulation: Black wins!

Starting from the second aspect I suggest this solution: 1.cxb6 e.p.
(requiring justification) axb6+ 2.Kxb6 Pa1R 3.Kb7 R1xa6 4.Rc8 (first
time) R8a7+!! 5.Kb8 Ra8+ 6.Kb7 (second time) R8a7+ 7.Kb8 Ra8+ 8.Kb7
(third time!); if you know PB-R309, you know what comes next. The
position can't be considered a draw since there is no proof that the
"same" position occurred thrice! Continuing play however - by whatever
move, e.g. R6a7 mate - proves prior black castling right absolutely, and
thereby proves the e.p. right a posteriori.

Now there are several ways to argue against this approach - we don't
want this automatic draw convention, it didn't exist at the time, this
is a strange mix of AP and PF (not a good objection), etc - but all
objections overlook the angle of having just created a beautiful new
solution to a famous AP-problem. Not only does it contain all of the
content of the previous one - the original solution becoming the try -
but it adds a new element as well which is not readily available in most
AP-compositions. I couldn't find another existing AP-problem cooked
through this procedure, but I could find some that will be easily cooked
by the 50-moves rule if it ever became automatic. It is a characteristic
trait of AP-problems that short AP-solutions can be refuted by long
"virtual" variants.

Now back to point (1). In one of my previous posts I introduced the
(rather arbitrary) concept of "game enforcers". This is a good case for
demontrating what I mean by that. The principle behind game enforcement
is that "a PF-solution continues under most conditions unless can be
shown that it stops". One of the reasons is that PF implies that all
choices from all "acceptable pasts" are available simultaneously. White
may castle long if he can, he may castle short if he can - his choice is
arbitrary even if the castlings are mutually exclusive. In Gert Rinders
problem the question is the choice between 2 pasts: (I) a past in which
white is stalemated in the diagram (II) a past in which e.p. is legal
and can be justified a posteriori. PF logic says he can chose either one
of them and therefore must chose the one that will leave him a move.
Stalemate is the absence of even a single option to move. PF-logic shows
that "AP after Keym" need not necessarily be addressed as of the
retro-variant type. So indeed, with PF-logic white starts and black wins
in this composition.

Note: I use the common descriptor PF here, but I'd rather use PA (Post
Actum) for its major component. Left for another post.

Guus Rol.
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