In the wee hours of this morning, I watched Google DeepMind’s AlphaGo programme defeat Lee Se-Dol (9 dan professional) in the first game of a five game match that will continue for the rest of this week. They played on a full-sized (19 by 19) board, AlphaGo played white and Lee Se-Dol paid komi. The field was entirely level, the game entirely fair. This simply wasn’t supposed to happen during my lifetime!
When I first encountered the game in 2007, my friend and fellow programmer promoted it as a game that bots simply couldn’t play. At that time, GNU Go was available but barely stronger than an improving double-digit kyu journeyman like myself – I soon learned to defeat it. A few bots exploited Monte Carlo Tree Search (MCTS) and they could achieve low single-digit kyu strength on a regular desktop computer or amateur dan strength on exceptional hardware but that was about all.
Everyone knew that MCTS was the way forward, that heuristics used in the random Monte Carlo simulations would improve with time, and that the inexorable increase in exploitable computational power would permit an ever-increasing number of simulations to be run. Everyone knew that even the professionals would fall, one day. That day was supposed to be decades away and the DeepMind team proved everyone wrong.
This morning, the outcome of the game was far from the only impressive feat that DeepMind’s programme demonstrated: the human-like nature of its moves and the mature management of the clock were a wonder to behold, as was the calm and steadfast way in which it handled Lee Se-dol’s cunning but unorthodox opening that seemed like an attempt to deviate from more common and well-known openings that would exist in databases and opening books that the artificial intelligence was surely using.
I was strangely sad when I saw Lee throw in a prisoner to indicate his resignation, this morning. In that instant, something ineffable changed in a way that can never be reversed. I will continue to watch in fascination as this match unfolds but, even if Lee wins the four remaining games, history was made this morning and I am very happy to have watched it as it happened.