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MatPlus.Net Forum Internet and Computing popeye and piece attribute "uncapturable"

popeye and piece attribute "uncapturable"

Does anybody know, what the piece attribute 'uncapturable' can be used for?

(2) Posted by Joost de Heer [Saturday, Jun 12, 2010 21:57]; edited by Joost de Heer [10-06-12]

Ghost chess and haunted chess.

And Gobble Chess. :-)

Sounds like it could be used for old conditional problems, in which
'white undertakes to mate in 14 moves, without capturing any of
the opponent's pawns'.

If there was an 'unmoveable' still further of such old problems
might be tested: '... and without moving any if his own rooks'.

QUOTE

And Gobble Chess. :-)

No. Uncapturable means that a piece can't be captured, not that a piece can only make capturing moves.

It was introduced in Popeye for the implementation of ghost- and haunted chess (the reborn pieces in those fairy conditions can't be captured anymore), but it can be implemented in standalone compositions too of course (search e.g. in Winchloe for 'Pièce Tabou').

But apparently it doesn't work:
pie whi ka1
bla uncap pa2
stip ~1
end

Only legal move is Ka1-b2, but Popeye also shows Ka1*a2.

Bug has been filed

QUOTE
Sounds like it could be used for old conditional problems, in which
'white undertakes to mate in 14 moves, without capturing any of
the opponent's pawns'.

I first thought, that this is exactly the meaning of 'uncapturable', but as the following experiment shows, this assumption is wrong:

begin
pieces
white uncapturable Pa2 Kh1
Black uncapturable Pb7 Kh8
stip exact-h~2
option WhiteToPlay
end

1...uPa2-a4 2.uPb7-b5 uPa4-a5
1...uPa2-a4 2.uPb7-b5 uPa4*b5

QUOTE
If there was an 'unmoveable' still further of such old problems
might be tested

Not only conditional problems, but also for testing 'normal' problems such an attribute might be useful, e.g.
Bosko Miloseski + Zlatko Mihajloski
Novi Temi 1974
(= 2+5 )

ser-h=21
(s. http://web.iol.cz/vaclav.kotesovec/shp.htm)
If one could specify that black pawns g2 and h2 are unmoveable (or immobile, as I call it), this would speed up the investigation time considerably (in this special case it can be simulated by using "cond hole g2 h2" instead of the 2 pawns).
And perhaps popeye already has such an attribute which it uses internally (e.g. for proof games and A=>B stips), so it would be easy to offer it as a new attribute?

Declaring g2 and h2 unmovable could lead to cooks where g1 and/or h1 are unoccupied (with a fairy stalemate). You'd need something like 'option nomovesduringsolution g2h2'.

@Joost: I suggested "Gobble Chess" to which you replied "no".

Example: wRa1 bBa2 Gobble Chess

If the wR moves, it must capture bBa2. But... if bBa2 is declared "uncapturable", then surely the wR is free to move along the 1st rank, yes?

@Dan,
Re: Gobble Chess + popeye's uncapturable attribute...

>Example: wRa1 bBa2 Gobble Chess
>If the wR moves, it must capture bBa2. But... if bBa2 is declared "uncapturable", then surely the wR is free to move along the 1st rank, yes?

The parameters of your question are not entirely clear... I can only guess your meaning might be one of the following:
a) popeye has implemented gobble chess, and must consider how the condition is impacted by the "uncapturable" attribute, or
b) popeye may someday implement gobble chess, and must consider how the "uncapturable" attribute is impacted by the condition, or
c) you are attempting to use the uncapturable attribute to solve a specific gobble chess problem.

I am not necessarily arguing that any of these scenarios alters your question's boolean return value...
However, if you meant c), then I fail to understand how you intend to use this attribute to solve a specific gobble problem.

Moreover, if you meant a) or b), then I fail to appreciate why the alternate interpretation would be any less valid, as the default combination of these two fairy elements.
That is to say, if wRa1 is restricted to one capturing move by the gobble condition, yet is unable to perform this capturing move because the fairy attribute of bBa2 prevents it, it [is ambiguous] whether wRa1 is completely free or completely immobilized, no?

Much depends upon the precise definitions for "Gobble Chess" and the word "uncapturable."
I presume neither element has been so carefully defined that the resolution in combination is inherently unambiguous.
It happens -- even the most rigorous attempts [at clarity still may] produce ambiguities when fairy elements are used in combination.
In such cases, the burden must rest upon each composer to provide a definition which avoids cooks and busts...

d) to constrain programmers as to what their default implementation should be for a special case rule born of two fairy elements (which might never officially unite).

Why bother?
It is unreasonable to burden programmers to meet every permutation of conjoined fairy elements.
Furthermore, you could easily define a surrogate attribute (e.g., "non-capturable"), if all default programming happens to go against your particular expectation...

@Kev: "...it [is ambiguous] whether wRa1 is completely free or completely immobilized, no?"

OK, but whether the wR is free to move, or completely immobilized, that is still an EFFECT. The original post asked what "uncapturable" could be used for. Clearly, 'uncapturable' has some impact when coupled with Gobble Chess. I'm just not sure what that impact is.

@Dan,

>Clearly, 'uncapturable' has some impact when coupled with Gobble Chess. I'm just not sure what that impact is.

Thanks for the clarification.
I completely agree, there will be some impact.
Depending upon the implementation, this should (fingers crossed) only affect whether the Rook defaults to mobilized / immobilized.
I'm not sure it matters what the default shakes out to be... though it certainly is an interesting case for programmers to predict & test.

If your aim here is to encourage a consistent interpretation -- the noble effort toward a grand unification -- I fear the whole conversation may already have spiraled beyond the event horizon.
Fairy Chess is not a set of islands on a chess problem planet; rather, it is a set of singularities in a simulated multiverse.
Establishing "the law of everything" (read: a fairy codex) would require a CERN-like collaboration (problemists, programmers, and variant enthusiasts).
Presently, any such consistency is, by default, attributed to be "uncapturable."

"If your aim here is to encourage a consistent interpretation..."

Nope, just offering a hypothetical. No GC/uncapturable masterpieces in the works, I'm afraid!

QUOTE
It was introduced in Popeye for the implementation of ghost- and haunted chess (the reborn pieces in those fairy conditions can't be captured anymore)

Are you sure about this for Haunted Chess? Check, for example, http://www.sah-zveza.si/rez/0208/probl/sake.pdf—in quite a few award-winning problems the same piece is captured and uncaptured many times.

BTW, the 1st prize from the tourney mentioned above is cooked:

1.g8=Q! R*e4 2.Qe6 Rd4[+wQe4] 3.Rc7 R*e4 4.Qd7 Rd4[+wQe4] 5.Bb3+ K*b3 6.Qb1+ Ka3[+wBb3] 7.Qb2+ K*b2 8.Sd3+ R*d3#