[computer-go] When is Pass the best move?

[Erik van der Werf]

Well at least we can be sure that for any two person game, if a position
occurs 3 times, at least 2 will have the same player to move ;-)

Erik


On 11/8/06, John Tromp <john.tromp at gmail.com> wrote:
>
> The difference between PSK and SSK also comes up in chess.
> Witness these events taking place yesterday in the Tal Memorial
> chess festival in Moscow:
>
> Morozevich-Carlsen was interesting for a technical reason. White had
> some advantages but Carlsen locked up the position in sound defence.
> There was some shuffling around with the pieces, and at one stage
> Magnus Carlsen approached the deputy arbiter Eduard Dubov to announce
> that he intended to play the move 46...Qc7 and produce the same
> position for a third time on the board. The chief arbiter Geurt
> Gijssen was summoned and he started to check the game with Carlsen in
> the analysis room. Gijssen also informed Morozevich about Carlsen's
> claim and invited him to join in the checking. But Morozevich refused.
> Carlsen and Gijssen replayed the game and came to the conclusion that
> indeed the final position had occurred for a third time. A draw was
> given and both players signed the scoresheets. Afterwards Gijssen had
> some doubts and again checked the game. It was then that he discovered
> that while the position had appeared three times on the board, it was
> not with the same player having the move. "It means that the claim was
> wrong and my decision was wrong as well," writes Gijssen in his
> report. He informed Carlsen about this and the young Norwegian was
> immediately ready to continue the game. The organizers tried to reach
> Morozevich, but he was nowhere to be found. In the end his coach
> Kuzmin informed the organizers that, in his opinion, the draw should
> stand. And so it did.
> [http://www.chessbase.com/newsdetail.asp?newsid=3476]
>
> This is not the first occurrance of such confusion:
>
> In the twentieth game of the 1972 Bobby Fischer-Boris Spassky match
> (the Match of the Century), Fischer claimed a draw because of
> threefold repetition. Spassky did not dispute it and the arbiter
> agreed. After the draw had been agreed, it was pointed out that the
> position had occurred after White's forty-eighth and fiftieth moves,
> and again after Black's fifty-fourth move (the final position). So the
> claim was actually invalid because it was not the same player's turn
> to move in all three instances (Alexander 1972:137-38).
> [http://en.wikipedia.org/wiki/Threefold_repetition]
>
> Perhaps positions are more easily recognized than situations...
>
> regards,
> -John
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