[Retros] Accidental retro

[Noam Elkies]

>>> ... Lajos Szász (1906-1929).



>> 1906-29 -- died at 23!?



> These data are taken from Giffard/Biénabe "Le Guide des Échecs",

> Chapter 'Dictionnaire des Problémistes', so I assume them to be

> correct.


The "!?" was more for "wow" than "this must be an error".

BTW one of his retro problems seems to have a wrong diagram in

  www.softdecc.de/pdb/search.pdb?expression=PROBID='P1012848'

(wKe6 wants to be on e5).


>> It would be nice if the book also listed sources for

>> the various positions so that one could check the original.



> The book lists the sources, but without reference to the problems.


Not very useful when there are thousands of problems :-(


>>> ... "Illegal position. Black has no last move."



>> I wasn't aware that computer programs can now check this.



> I do not claim that my program can do that. The only thing I can

> state, is, that under some circumstances my program is able to

> detect illegal positions.


Naturally.  Even that is more than what the standard solving problems do
(which is at most count Kings and Pawns).


> In #2940, it is easy to see (i.e without deeper analysis,

> simply by the fact, that none of black's pieces has a square,

> from which it could have moved to its current place),

> that black has no last move.


Of course #2940 is simple, though it's still one ply deeper
than the Baird position -- one must also check that wPf7 has no
previous move to support the retraction of Kg8(e8)-f8.


>> Is yours the first such program?



> The first retroanalytical program I'm aware of was mentioned in

> an article in the 'International Journal of Man-Machine Studies',

> 1988, 29, pp.97-112. [...]


Interesting.  I think this is the first time I've seen such a program
mentioned on the retros mailing list, and I have yet to see a published
retro marked C+, but perhaps I'm not looking in the right places.
Perhaps one of these days we'll even see a C+ Illegal Cluster problem.

NDE