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 _______________________________________________ computer-go mailing list [email protected] http://www.computer-go.org/mailman/listinfo/computer-go/
