[Retros] Illegal moves by grandmasters

[tregeryefim at aol.com]

About "illegal moves".

The whole idea of the iilegal move (from the games below) is at least strange (dubious, wrong). IMO: an illegal move is a move, which breaks fundamental rules of chess (piece movement, etc.). Mathematically: Imagine the tree of all positions (including dead ones, etc.). Each position is a vertex,  edges between them are the legal moves. The Illegal moves do not correspond to any edges.
Yefim Treger










-----Original Message-----
From: Francois Labelle <flab at wismuth.com>
To: retros at janko.at
Sent: Tue, May 10, 2011 1:05 am
Subject: [Retros] Illegal moves by grandmasters


In June 2007, Noam Elkies posted to this list about an illegal move (due
o Article 1.3 of the Laws of Chess) in the game
Shakhriyar Mamedyarov (2757) vs Viswanathan Anand (2786), Dortmund, 2007
ttp://www.chessgames.com/perl/chessgame?gid=1464708
Noam's post is here:
ttp://www.pairlist.net/pipermail/retros/2007-June/002059.html
How common or rare is this? To find out, I used my chess engine (which
mplements A1.3) to analyze 2.3M games from the ICOfY game database. The
esults:
- 0.023% of games have at least one illegal move
- 0.00036% of plies are illegal
- I found 19 more examples of illegal moves played by 2700+ rated
layers since 1998, including one by the current world champion,
iswanathan Anand. Most examples are due to insufficient material (like
n the Mamedyarov-Anand game), but I found one example of "forced
nsufficient material"
Loek Van Wely (2625) vs Leinier Dominguez (2717), Wijk aan Zee, 2009
ttp://www.chessgames.com/perl/chessgame?gid=1531105
and two examples of "forced stalemate", such as
lexander Grischuk (2720) vs Boris Avrukh (2652), Saint Vincent, 2005
ttp://www.chessgames.com/perl/chessgame?gid=1363625
- there is a game with a sequence of 18 illegal plies
ikhail Glukhov (2205) vs Ilia Shkurikhin (2417), Tomsk, 2009
There are more details on my website at
ttp://wismuth.com/chess/illegal-moves.html
    Francois
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