[Retros] Illegal moves by grandmasters

tregeryefim at aol.com tregeryefim at aol.com
Tue May 10 10:51:29 EDT 2011

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
Noam's post is here:
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
- 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
and two examples of "forced stalemate", such as
lexander Grischuk (2720) vs Boris Avrukh (2652), Saint Vincent, 2005
- 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
etros mailing list
etros at janko.at

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