Part 8: Review of Game 3: Lee Sedol's opening mistakes due to enormous mental pressure (The historic match of deep learning AlphaGo vs. Lee Sedol)

[NL Versie]

Review of Game  3: Lee Sedol's opening mistakes due to enormous mental pressure

After two successive losses, Lee Sedol is under extremely high pressure not to lose the entire five-game match with AlphaGo. Lee Sedol is heavily touched, very disappointed and feels particular anguish after the shock of his second loss. Both his confusion afterwards about why he had lost the game and the difficulties he had with his team tracing back any mistakes, showed also that AlphaGo played a nearly perfect game.  So, is Lee Sedol able to win from a Go-program that plays virtually perfect?

This match proceeds completely different from what Lee Sedol had expected and hoped. He tries to play with his great sense of responsibility for the hundreds of millions of people worldwide that count on him in this historic match against AI. One way or another he has to turn the tables, but how?

With black 17, a rather complicated opening fight starts in the upper left corner (see Dia. 1). White's invasion inside black's influence is an attempt to reduce the black potential severely, without leaving a weak group that is easy to attack or giving black some advantages otherwise (for instance, to allow for much strength on the outside or territory on the inside). 

Dia. 1:  Game 3, after black 17 (circle, Lee Sedol is black) 

If AlphaGo succeeds in making a solid base with this invasion or a group that easily can extend and escape towards the center, without too many benefits for Lee Sedol, and white's mission proves to be a success, AlphGo can take over the initiative and try to control the game towards victory.

Dia. 2:  Game 3, after white 28 (circle, Lee Sedol is black) 

The opening develops and AlphaGo plays a nice move towards the center meanwhile threatening Lee Sedol's three stones (circle in Dia. 2). As black took the corner and is strong on all sides, everything looks promising for black at this point in the game. However, in this very complicated opening fight in the upper left, Lee Sedol makes a deciding mistake already early in the game. This unfortunate mistake ascertains that the game is pretty much decided shortly after his (at first sight) effective and offensive move (triangle in Dia. 3). 

AlphaGo responds underneath (circle in Dia. 3) to ensure the option to connect later or to be able to attack Lee Sedol later on. This move provides some life-air to the white group as well as possibilities to pressurize black's stones thereabout (triangle in Dia. 3).

Black really had to play first on this point (circle in Dia. 3, instead of triangle) to threaten to connect underneath himself (and keep white weak and separated). And if white then would have responded, black nevertheless would have had (in sente) the opportunity to play the triangle move. In short, a missed opportunity by Lee Sedol which immediately gives AlphaGo the initiative.

Dia. 3:  Game 3, after white 36 (circle, Lee Sedol is black) 

Younggil An (8p) described Lee Sedol's earlier moves as possibly the game-losing moves and Andrew Jackson from the American Go Association considered black 35 (triangle in Dia. 3) as the fatal, losing move. 

Dia. 4:  Game 3, after white 48 (circle, Lee Sedol is black) 

After about fifty moves AlphaGo dictates the game and forces Lee Sedol to continue defending. With 48 (circle in Dia. 4) white also defends his group and at the same time attacks both the black stone left and the black group left (middle).

Obviously, white handles attacking as best defense. Even though white's upper left group is itself still in the danger zone, white is able to escape towards the center. And in case of emergency white can try to make eyes with forcing moves on black's upper left corner. 

Dia. 5:  Game 3, after white 70 (circle, Lee Sedol is black) 

AlphaGo manages to control the fight such that it builds strong influence while attacking, what could the program wish more? Lee Sedol has no other choice since his entire black group on the left, though more or less connected (eventually, later on there is a ko), simply has an inadequate base. With move 69 (triangle in Dia. 5) black escapes to no man's land towards the center where white is waiting for him on every side.

Dia. 6:  Game 3, after white 78 (circle, Lee Sedol is black) 

Lee Sedol creates a base for his 'hanging' group on the left and then starts a counterattack on the right hand side with black 77 (triangle in Dia. 6). By making the position more complex, Lee Sedol might be able to find a solution to deal with AlphaGo's large potential at the lower edge.

Also, white's upper left group is not yet entirely safe and still a significant burden white has to take into account.  AlphaGo's response on Lee Sedol's counterattack is yet effective and cooperates optimally with all white's stones at the right edge. In addition, it's response provides opportunities in case white's group in the upper left later on needs support. 

Dia. 7:  Game 3, after white 90 (circle, Lee Sedol is black) 

To stay in the game Lee Sedol needs to keep AlphaGo from making too many points on the right hand side as well as to prevent getting a half-baked center group whereby his chances for an invasion into white's moyo at the lower edge will become without any prospects.

With 89 (triangle in Dia. 7) black connects more or less the two cutting stones on the right (on P8+9) and at the same time attacks the white group in the upper left. AlphaGo is alert and strengthens it's group immediately with 90 (circle in Dia. 7). It looks like that Lee Sedol should have played here himself first (threatens to cut, makes points and weakens the white group) in sente. However, AlphaGo succeeds in further simplifying the position as the white group in the upper left now has almost sufficient options to live.

Dia. 8:  Game 3, after black 129 (circle, Lee Sedol is black) 

After white lives in the upper left, black in the lower right, and most smoke clouds have disappeared, Lee Sedol's only chance to win the game is to reduce white's huge moyo at the bottom severely (either by living inside or  by dimpling from the outside).

However, AlphaGo stays very calm and plays sophisticated during Lee Sedol's invasion (triangle in Dia. 8). This move gives white a number of opportunities to connect the two white stones either to the left or to the right. Black again complicates the situation to threaten breaking through white's surroundings towards the center,  or to capture the two white stones and try to live. 

Dia. 9:  Game 3, after white 148 (circle, Lee Sedol is black) 

During this complex fight, Lee Sedol manages to get the maximum out of the position by creating, in an ingenious and beautiful manner, a game-winning ko (triangle in Dia. 9). However, AlphaGo again plays calm and efficient: apparently the program has already computed that it will win this ko anyhow. Then white just ignores the ko for now and occupies the largest endgame move on the board (circle in Dia. 9) while threatening to enter black's territory at the upper side. 

Dia. 10:  Game 3, end stand after white 176 (circle, Lee Sedol is black) 

It is for the first time that AlphaGo is forced into a complex and big ko-fight. Despite earlier expectations that the program herewith would suffer from severe problems, AlphaGo plays superb and shows it assesses, computes, and latches ko-fights excellently.  

Unfortunately, Lee Sedol is unable to force AlphaGo into any error, not even a single one. Using internal ko threats, AlphaGo triumphs (as the program already 30 moves ago had evaluated or computed). And after white 176 (circle in Dia. 10) there is no other option for Lee Sedol than to resign. 

Kwon Kay-Yong, one of Lee Sedol's former coaches, told a news agency: "AlphaGo played consistent and well balanced from start to finish while Lee, as he is only human, showed some mental vulnerability". Thereby, Lee Sedol's great feeling of responsibility --towards all people that were watching over his shoulder and had such a great faith in him-- inevitably began to work against him. 

According to Younggil An (8p) and David Ormerod, this third game demonstrated that "AlphaGo is simply stronger than any known human Go player. AlphaGo was seen to capably navigate tricky situations known as ko-fights that did not come up in the previous two matches". Ormerod added: "in the middle of a complex, all-or-nothing ko fight, AlphaGo displayed sufficient 'confidence' that it was winning the fight and simply ignored the ko and played a large move elsewhere". 

During the post-game press conference, where hundreds of photographers exposed Lee Sedol to minutes-long dazzling flashlight, while the loss of the Google DeepMind challenging match was still hammering his mind with this third successive defeat by AlphaGo, Lee Sedol was visibly touched and deeply saddened: "I don't know how to start or what to say today but I think I would have to express my apologies first: I should have shown a better result and better outcome and better contents of the game played. I apologize about not being able to satisfy a lot of people's expectations. I felt powerless. If I would redo the match I probably would not have been able to win".

And: "In the first game I  have lost because I bad judged the capabilities of AG. The second game would be the mental break of you but at the beginning of the 2nd game, the game did flow the way I intended and there were a number of opportunities which I admittedly missed. Looking at the third game: I do have extensive experience in the playing the game of Go but there was never a case or game where I experienced this amount of pressure. I was unable overcoming the amount of pressure I was experiencing. Sure I lost the match, AlphaGo is now a clear winner. However, when when it comes to human beings, there comes in this psychological aspect. If I play the fourth and fifth game of the match, I do ask you to continue keep following the match and keep your interest in the games and follow what happens".

Michael Redmond (9p) commented: "At first, I sort of doubted the capabilities of AlphaGo but after three straight wins these were canned now. Lee Sedol played a very powerful fighting game. In this third game, he played to do his style and showed us an exciting match and I believe that Lee Sedol would have been difficult to beat today by any other top human professional. I think that Lee did his very best and showed us a very good game. Nevertheless, AlphaGo played excellent this fighting game and played the ko's everybody was afraid that it might have a weakness in, played all of the complicated fighting". 

To continue: "I think it is fair to say that it beat Lee Sedol at his own game. What I see in AlphaGo is the potential when it plays new moves as it did in the 2nd game, it's potential to inspire Go players to perhaps study a different type of opening moves. I think we could have a revolution of the years coming up with AlphaGo helping us, giving us a boost to start it. I like to characterize today by my believe that the AlphaGo team created a true work of art".

Hassabis described AlphaGo's victories on Lee Sedol as: "hard to believe" and said the games had been 'mega-tense': "while AlphaGo computes tens of thousands positions per second, Lee Sedol incredibly can compete with that in periods of high pressure. His ingenuity and extraordinary talent have stressed AlphaGo to it's limits during these first three games.  We came here to challenge Lee Sedol as we wanted to learn from him and see what AlphaGo is capable of. And his amazing genius and creative skills have done that". 

And answering a journalist's question, Lee Sedol said: "Although AlphaGo is a strong program, I would not be able to say AlphaGo is a perfect program (not at the level of so called divine Gods). Yes, compared to humans it's moves are different and from time to time are superior but I do feel that there are weaknesses in AlphaGo's way of playing. Today was Lee Sedol's defeat but not a defeat of human beings". 

Google and the Korean Baduk Association, who both organized this match, already agreed earlier on that the match would continue up to and including the fifth game in case the winner of the match would be known after three wins in a row.  

[Deep Learning AlphaGo vs Lee Sedol Overview]

[Part 1: Details of the Match of the 21st century]

[Part 2: AlphaGo under a Magnifying Glass]

[Part 3: Lee Sedol about the Go board in his head]

[Part 4: AI versus Human: Expectations and Predictions] 

[Part 5: Google's biggest press conference ever: opening of the match AI vs. Mankind]

[Part 6: Review of Game 1: Lee Sedol underestimates AlphaGo's incredible fighting power]

[Part 7: Review of Game 2: AlphaGo's new move and devastating aggression]

[Part 9: Review of Game 4: Lee Sedol's brilliant move reveals weaknesses AlphaGo]