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Subject: Romulan cloaking device

Author: Steven Edwards

Date: 21:24:12 04/14/05


A while back I was playing against Richard Lang's PDA chess program on my Palm
Tungsten T and I managed to make it well past a hundred moves.  I had a losing
position with just a few men left on the board, but I kept on playing to see how
the program would handle the ending.  To my surprise, the program played a
wholly unexpected double move: it advanced a knight and at the same time its
king disappeared!  I wish I had coded this little tactic into my program, but
somehow I missed the section in the Laws Of Chess that allows for such a
stunning play.

I had seen something like this before.  In a similarly long game against the
Chess Champion Mark V (or maybe it was the Mark VI), a piece vanished without
being captured -- what a concept!

Then again, in my early 1980s program Oracle, the restrictions on available
memory would force a diagnostic output after the 200th move: Game Over/Too Many
Moves.  Not the best solution to be sure, yet at least the overflow was detected
without crashing, hanging, or sending some of the chess pieces into the Twilight
Zone.

And not just pieces can disappear.  Moves can, too.  Back at the 1994 ACM
tournament my progarm Spector was on the black side of a Sicilian and played
9... Nbd7, right out of the book if I recall correctly.  The opponent program,
perhaps marginally stronger I admit, decided somehow to have that move vanish
from its list of acceptable inputs.  I saw this myself on the opponent's monitor
and I believe that its operator was as surprised as I was.  It may have been due
to a failure to accept file letter disambiguation, maybe it was something else;
I'm not sure.  Anyway, all attempts to convince the program to accept 9... Nbd7
were in vain and its operator had to save the game, manually edit the game file,
restart the program, reload the game, and then start the search.  Perhaps I
should have made a claim to the TD for a forfeit win, but I didn't because of
the long heritage in CC tournaments of allowing screw-ups in the greater
interests of science.  Anyway, Spector lost the game; it never made any pieces
or moves invisible, only the victory point.



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