[Retros] A retro in the fairy tournament, Messigny 2010

Noam Elkies elkies at math.harvard.edu
Mon Jun 14 00:50:41 EDT 2010

I wrote:

>> I had found what I think is the intended solution [...]

Nicolas.Dupont at math.univ-lille1.fr replies:

> The intended solution is: [...]

Yes, that's what I had too.

> This possibility is avoided in the following :

>>> rnbkakb1r/pppppppp/3n4/8/8/6N1/PPPPPPPP/RNBKaKB1R

>>> PG 6.5

>>> 2 solutions


> The intended solution is: [...]

As it happens that's the first one I found; but the second,
which you describe as "clearly non-human", wasn't much harder.

> As it is one move less than the previous cooked problem,

> we tried Popeye (with huge memory).

I was going to ask if you could then try it also on my attempted setting
(r1bkakbnr/pppppppp/2n5/8/3N4/8/PPPPPPPP/RNBKaKB1R) which has the same
length, but now I see that the move order of the intended solution
is not unique :-(

> We were surprised but pleased to see appear the following

> curious second solution

That's happened to me a couple of times too...

>> You've found a neat new corner of fairy PG-land (Ka's instead of both Q's,

>> no captures or P/B moves); it seems to be sufficiently circumscribed

>> that -- even allowing for K and R moves -- Francois Labelle should be

>> able to quickly carry out an exhaustive analysis and find all the

>> interesting proof games that it supports.

> Indeed this is an interesting possibility.

I should also have added the possibility of pawns moves to h3, a3, h6, a6
which would retain the parity puzzle.


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