Review of Game 1: Lee Sedol underestimates AlphaGo's incredible fighting power
Both sides will thus be scanning each other for the very first time, finding out the strategies, way of thinking, patterns, playing strength of the opponent and exploit any possible weaknesses. While AlphaGo originally trained on 130,000 amateur games (up to 8-9 dan = ~1-2p) and further improved from millions of self-play games, Lee Sedol played several thousands of top-tournament games in the almost 25 years of his professional Go-life.
The opening moves of the first game in this historic match between mankind and AI are played while it is early in the morning 5 AM in the Netherlands. Here the match is watched under extremely high-voltage excitement in the European Go Cultural Center (EGCC) by more than 60 people that have come from all corners of The Netherlands with or without sleeping bag, to experience this once-in-a-lifetime event together real-time and to live through the game as conscious as possible.
Two big screens are placed on the wall from which the online game commentary and playing room of the match are displayed. Huge posters, a demonstration board and many laptops with all-sides discussions of the match worldwide. Meanwhile the game is discussed by the strongest European players we have: Merlijn Kuin (6d), Peter Brouwer (6d), and Guo Juan (5p, inactive as pro player).
After Lee Sedol's move with black 7 (see Dia. 1) Merlijn Kuin (6d) kicks off immediately: “this is a rather unique move and very aggressive of black. According to me, this is a position which appeared never before on the board. I am convinced that Lee Sedol uses a preconceived strategy that fits his style". Lee Sedol makes a bad decision by choosing an unusual opening of which he is sure it is absent in AlphaGo's database. However, Lee Sedol himself is also unfamiliar with such a rare and less optimal opening pattern.
Dia. 1: Game 1, after white 14 (lowest triangle, Lee Sedol is black).
Black's move 7 is marked with a green dot.
Dia. 2: Game 1, after black 23 (circle, Lee Sedol is black)
After barely 25 moves (Dia. 3), there are seven groups fighting each other. Peter Brouwer (6d) remarks that the shapes and patterns in this game are not particularly beautiful. And Michael Redmond (9p) comments: "in reaction to a slightly less optimal move by AlphaGo, it appears that Lee Sedol comes at once with an overplay. This human reaction is well understandable and makes AlphaGo at least one stone stronger".
Dia. 3: Game 1, after white 50 (circle, Lee Sedol is black)
Dia. 4: Game 1, after white 80 (white stone with square)
With AlphaGo's strategy Lee Sedol gets huge influence in the center. But at the expense of a much weaker corner at the bottom right. After black neutralizes most of the aji of the two white cutting stones in the center (triangle in Dia. 4), white strikes and invades (circle in Dia. 4). Evidently, AlphaGo wants to use the force of the white wall and to transform that into fighting power.
Lee Sedol plays tenuki and attacks the white stone in the bottom left corner while expanding his center moyo (blakc stone with square in Dia. 4). In turn, AlphaGo plays tenuki as well and captures two black stones, thereby removing most dangers (aji) around the center position (white stone with square in Dia. 4).
However, since removing black's aji is not urgent right now and with this move AlphaGo makes an important error in positional judgement. After the program's blunder, top prof Gu Li (9p) stated: "Lee has now a chance of 90% to win this game". And Michael Redmond comments: "AlphaGo is very accurate and profound in computing moves and very balanced in influence and territory. After an earlier better position for AlphaGo, Lee Sedol has brought the game in balance again".
Dia. 5: Game 1, after white 102 (circle, Lee Sedol is black)
A top Go-prof who thoughtfully suggested this move was laughed at in his face: initially many Go-profs are rather negative and demand proof for this move. AlphaGo just plays it as nothing special. In second thought, however, profs worldwide admire this wonderful effective invasion. Others are heavily disconcerted by this remarkable move of the AI program as it shows it's incredible strength and profound 'understanding' of the concepts the game (including aji). This clearly shows how different this version of AlphaGo is compared to that during the Fan Hui match.
With this invasion AlphaGo attempts to blow up entirely Lee Sedol's position at the right side of the board in a terrifying fight (circle Dia. 5) while using the great influence it has built earlier. At the same time, this invasion gives opportunities to make a base for white's group by exploiting the weaknesses in black's position on the right-hand side (note how the white group extends over the full length of the board, see Dia. 6).
Dia. 6: Game 1, after white 116 (circle, Lee Sedol is black)
Dia. 7: Game 1, after black 127 (circle, Lee Sedol is black)
Dia. 8: Game 1, after white 136 (circle, Lee Sedol is black)
Dia. 9: Game 1, final position after white 186 (circle, Lee Sedol is black)
Despite his loss in this opening game, Lee Sedol stated he did not regret accepting the challenge: "I had a lot of fun playing Go this game and I'm looking forward to the future games".
And AlphaGo has played at least one incredibly wonderful move that achieved so many goals at the same time that it is hard to apprehend (Dia. 5). During the fight that followed, the program succeeded in getting enough advantage so that it was confident to secure the upper left corner with an all-telling move and claiming the victory of the game (Dia. 6).
Although Lee Sedol controlled the majority of the game, AlphaGo managed to rebuild itself in a phenomenal way and secured a clear advantage during the last 20 minutes of the game after which Lee Sedol resigned.
With all his hubris and self-assurance prior to this match, his underestimation of the startling, mind-boggling, fabulous, and wonderful play and strength of AlphaGo, his expectations on the basis of the games during the Fan Hui match, his immense concentration and involvement with this first game of the match, and the enormous media attention and psychological pressure by all eyes of the world, this extremely surprising and unexpected loss must have felt particular anguish for Lee Sedol.