[Retros] Accidental retro

Noam Elkies elkies at math.harvard.edu
Wed Feb 8 10:59:37 EST 2006

>>> ... 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


(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.


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