After being compelled to flex its muscles for a short time and gaining the upper hand, AlphaGo began to play leisurely moves. By now, most observers know that this is a feature of the ruthlessly efficient algorithm which guides AlphaGo’s play. Unlike humans, AlphaGo doesn’t try to maximize its advantage. Its only concern is its probability of winning.
The machine is content to win by half a point, as long as it is following the most certain path to success. So when AlphaGo plays a slack looking move, we may regard it as a mistake, but perhaps it is more accurately viewed as a declaration of victory?
Lee soldiered on with commendable fighting spirit, probing the computer’s weaknesses here and there. He tried a clever indirect attack against White’s center dragon with Black 77, but AlphaGo’s responses made it feel like it knew exactly what Lee’s plan was.
Next he tried a cunning probe inside White’s territory, with move 115, attempting to break a ladder in sente or live inside White’s territory, but White responded firmly. He attempted to make good of his probe by living inside White’s territory with sharp tactics, but White was unperturbed. Finally, he even tried forcing a complicated ko. At this point, AlphaGo once again showed just how strong and detached its play is by ignoring the ko fight to play honte at White 148.
This move also removed any possibility of a double ko after Black at 148 (which may have been what Lee was planning). Having answered many questions about AlphaGo’s strengths and weakness, and exhausting every reasonable possibility of reversing the game, Lee was tired and defeated.
He resigned after 176 moves.