Part 7: Review of Game 2: AlphaGo's new move and devastating aggression (The historic match of deep learning AlphaGo vs. Lee Sedol)

[NL Versie]

Review of Game 2: AlphaGo's new move and devastating aggression

At the press conference after the first game, Lee Sedol estimated himself to have a 50% chance of winning the second game. The main question is whether AlphaGo will play (now with black) as aggressive and offensive as in the first game.

You can imagine that Lee Sedol has adapted severely his playing style in multiple ways after losing the first game. In contrast, in the basis AlphaGo is unable to adapt in any way as training a new version of the program takes about 4 - 6 weeks. So it is not possible (and also not desirable) to apply important changes in AlphaGo's algorithms during this seven-day match (except in case serious bugs would occur).

Lee Sedol concentrates before the start of the second game.
Referee Fan Hui (left) watches. 

Lee Sedol plays the first moves in any case more conservative and calm. According to commentator Michael Redmond (9p): "Lee Sedol perhaps has considered a slightly more careful way of playing considering how well AlphaGo has performed in the first game. However, in this game AlphaGo not only plays even more aggressive but it seems that the program also makes less mistakes".

Dia. 1:  Game 2, after black 37 (circle, AlphaGo is black) 

AlphaGo's 19th move (circle in Dia. 1) is an equally astonishing as powerful move. Lee Sedol appears to be as surprised as everyone: he leaves the match table immediately, takes a (allowed) break while his clock remains ticking. Michael Redmond: "This is a creative move. It is a move which I believe I have never seen before in a top professional game". Virtually all AlphaGo's stones are cooperating together effectively with this creative 'shoulder hit'. 

When Lee Sedol returns at the match table, he takes an unusually long time to answer and after only just forty moves in the game, he is already 20 minutes behind in thinking time compared to AlphaGo. Redmond: "He has clearly difficulties to handle such a strong move that he has never seen before. It is a new and unique move and Lee Sedol has to think about it. This is the reason why people become professionals". 

Dia. 2:  Game 2, after black 41 (circle, AlphaGo is black) 

After this well balanced move AlphaGo evidently is the attacker. Younggil An (8p) mentioned AlphaGo's move (see Dia. 1) "a rare and intriguing shoulder hit but Lee Sedol's answer (see Dia. 2) was excellent and beautiful".  

Lee Sedol prevents AlphaGo to build up a moyo at the upper center and leaves the option open to make some territory himself at the right side. However, AlphaGo keeps the initiative and with black 41 (circle in Dia. 2) the program creates possibilities to play on one of the triangles (Dia. 2). Thereby Alphago can try to attack the white stones while making territory at the lower side. In addition, this move of AlphaGo helps to build the center moyo and prevents a white extension at the bottom side. 

Dia. 3:  Game 2, after black 61 (circle, AlphaGo is black) 

With AlphaGo's move 61 (circle in Dia. 3) it builds influence in the upper left center, provides some extension air to it's group in the center left (preventing white's attack), and threatens to invase white's group at the lefthand side (and to cut off a white stone). It is crystal clear that AlphaGo keeps putting pressure and controls the initiative.

Dia. 4:  Game 2, after black 81 (triangle, AlphaGo is black) 

AlphaGo seems not to worry about Lee Sedol's previous strengthening of his groups to prepare a fight at the upper edge. AlphaGo just continues building up it's own framework and, while doing so, exhibits an incredible flexibility.

In response to white's invasion (square in Dia. 4) black doesn't respond with obvious moves either on top or to the left of the invading stone, but instead plays a very solid move at the outside (triangle in Dia. 4), removing any weaknesses there so that black will have all his hands free to attack the invading stone much more heavily and aggressively later on.

AlphaGo still maintains the initiave and forces too choose between: a) extending to the center to make there a living group and neutralize black's strong influence in the center, and b) to make a small living basis in the upper left corner with the great risk that black will become rock-solid at the outside and with that strength can try to cash in the built center moyo (Dia. 4).

Dia. 5:  Game 2, after black 97 (circle, AlphaGo is black) 

Lee Sedol makes the choice to attempt to neutralize the center but remains with a small heavy group without a base while AlphaGo takes points at both sides, strengthens it territory and tightens the pressure on the white group (Dia. 5).

Dia. 6:  Game 2, after black 101 (circle, AlphaGo is black)

White has no choice other than to persevere consequently but black keeps heavily attacking. And during this offense AlphaGo every time profits. With a next beautifully balanced attacking move (circle in Dia. 6) black prevents white from making eyes easily or can connect to the white group at the right hand side. And meanwhile black substantiates the center (which will be of benefit later on during the fight).

Dia. 7:  Game 2, after black 127 (triangle, AlphaGo is black)

With determination Lee Sedol tries to solidify his center group and to prevent AlphaGo from making a mountain of points in the center but the white group remains shaky and stays a heavy burden to Lee Sedol (Dia. 7). While white takes points at the lower edge (square in Dia. 7), black calmly makes territory in the center (triangle in Dia. 7). 

Redmond: "the control of the flow of the game has been alternated between the players several times. However, while fighting in the center AlphaGo played brilliant moves which forced Lee Sedol into immediate actions and choices". And while Lee Sedol seriously threatened the territory at the upper side, AlphaGo doesn't seem to worry and just cashes in points in the center: "points are points and it is completely irrelevant where on the board these points are taken" Redmond continues.

Dia. 8:  Game 2, after black 139 (triangle, AlphaGo is black)

While attacking AlphaGo takes already a tank of points in the center by cutting off a part of Lee Sedol's group. White just has no choice: otherwise his whole group will die. 

But even after white's big move in the upper right (square in Dia. 8) which threatens black's territory at the upper right edge, black plays calmly in the center. Thereby threatening to cut off another little tasty trail from white (triangle in Dia. 8).

Dia. 9:  Game 2, after black 151 (circle, AlphaGo is black)

Unfortunately, also in this situation Lee Sedol has to take eggs for his money and after another substantial bleeding is the white center group, meanwhile strongly shrunk, still not yet connected. AlphaGo keeps up the pressure and with black 11 the program plays a nice move that achieves many results simultaneously (circle in Dia. 9).

Dia. 10:  Game 2, after black 163 (circle, AlphaGo is black)

Again Lee Sedol has no other choice than to try connecting his stones without AlphaGo playfully kicking in even more points in the mean time.  Yet white looses once more some points. With black's forcing move (circle in Dia. 10) to cut again (triangle in Dia. 10), or even to catch the left over group in it's entirety (with a cut on O11 in Dia. 10) it is trying to empty the ocean with a thimble for white.  

At this point in the game Lee Sedol is behind about five points (komi included) so if black is able to cut yet more stones from white's meanwhile disintegrated center group it is definitively end of story. And this is exactly what ultimately happens: white is cut off once more. 

Dia. 11:  Game 2, end position after black 211 (circle, AlphaGo is black)

With this cut the game is over and Lee Sedol resigns about 50 moves later (see final position in Dia. 11), at that time he is about 10 points behind. AlphaGo did not relinquish control of the initiative at any moment in this game: Lee Sedol was defeated by the program in a rather straightforward and very impressive manner.

While Lee Sedol played some obvious overplays (a move that is too greedy to make more points than the opponent, more than could be considered as reasonable on the basis of your opponent's strength) in the first match, this game it is a completely other story: Lee Sedol didn't play any overplays and showed the very best of his Go play while seriously considering AlphaGo as one of his strongest opponents until now.  

Several new and interesting moves have been conjured effortlessly on the board by a very aggressively playing AlphaGo. Some of which initially were regarded as unreasonable, incorrect, or simply not working. 

In an exceptionally big fight during the second half of the middle game, Lee Sedol was put under enormous pressure (Dia. 6 en 7).With clearly much too little time to calculate accurately all favorable variations and outcomes in this extremely complex, never before occurring Go position. 

Regrettably Lee Sedol didn't succeed in finding a better alternative in this ultra complicated, misleading, unclear and confusing position. On that account he made the decisive mistake that gave AlphaGo a lead of about 5 points. At the deciding moment in the game (Dia. 6) Redmond suggested that Lee Sedol possibly was already somewhat behind. 

In the end, Lee Sedol quits while being defeated more or less with his own weapon: starting ultra complex, all-or-nothing fights and then to try getting decisive advantage during that battle. For many top professionals it remained unclear until the last part of the middle game what would be the outcome of this second game. 

Demis Hassabis mentioned that from the second half of the game on, AlphaGo became more and more confident in victory from the midway point of the game (as is continuously monitored by it's probability theory of winning). Even though the professional commentators could not tell who was ahead at that stage in the game. 

Lee Sedol explained afterwards: "Today, AlphaGo played a nearly perfect game: from the very beginning of the game I did not feel like there was a point that I was leading. While during the first game I was overwhelmed and surprised by AlphaGo's way of play, today I was startled and speechless about the extremely strong moves AlphaGo generated, some of which were unexpectedly well working out. Furthermore, AlphaGo, unlike yesterday, did not make any unreasonable or incorrect moves from the second part of the middle game until the end of the game". 

Asked about any possible weaknesses of AlphaGo, Lee Sedol passed over the question to Demis Hassabis after first stating that "today I lost because I was unable to find and detect any weaknesses in the play of AlphaGo". Hassabis answered the question by stating that one of the goals of the match of AlphaGo vs. Lee Sedol is to find out if AlphaGo has any such weaknesses and to try to learn from them. 

Go-prof Hong Minpyo (9p) confirmed that Lee Sedol and he afterwards have analysed every move of the second game for five hours. After the game, Lee Sedol was very confused about why he had lost this game. This post-game analysis and research  probably helped Lee Sedol to recover somewhat. 

Today, AlphaGo apparently has beaten Lee Sedol with unprecedented accurate force power and incredibly profound computations during the most complex phase of the game. Reaching the point at which many human top professional Go players, including Lee Sedol, were unable to confidently calculate and reliably assess the outcome of the complex variations possible. 

Lee Sedol remarked that in the upcoming third game of the match he will have to focus and concentrate on the opening and first part of the game, to seek and exploit any weaknesses of AlphaGo in order to build a lead early in the game.

So now, after two incredibly fascinating and thrilling games of the match --despite their totally different type in nature both have been won by AlphaGo-- the real strength of the AI program becomes more and more apparent. 

The chances of winning this match by Lee Sedol against such a magnificent and superbly playing deep learning AlphaGo seem to decrease rapidly (down to very improbable) after considering this astonishing, fascinating and breathtaking second game of the match. Today, again history has been written, both by Lee Sedol and the team of AlphaGo in many, irreversible, indelible, and unimaginable ways.

This must feel for Lee Sedol like he was hit by a relentless gravitational wave. Struck, overwhelmed, greatly saddened, almost destroyed. What would be in his mind after this second consecutive loss? At this stage in the match Lee Sedol deserves more than the very, very best and the deepest respect, support and admiration to overcome his great disappointment. 

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

Part 6: Review of Game 1: Lee Sedol underestimates AlphaGo's incredible fighting power (The historic match of deep learning AlphaGo vs. Lee Sedol)

[NL Versie]

Review of Game 1: Lee Sedol underestimates AlphaGo's incredible fighting power

The first game of the Google DeepMind challenging match  between deep learning AlphaGo and top Go professional Lee Sedol (9p) is the most important game of this match as this is the first time an AI program plays without handicap against one of the strongest human Go-players of the world.

AlphaGo has not learned from professional games and therefore, as repeatedly stated and emphasized by Demis Hassabis, has not a single game of Lee Sedol in it's database. Lee Sedol doesn't know much more about the program than what he has seen from AlphaGo's match against Fan Hui (2p) last October: a strong but now and then malfunctioning program, sometimes making obvious mistakes in complex situations, without too much whole-board understanding. And that against a substantially weaker Go-player who made many overplays Lee Sedol probably never would make. 

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).

It is no secret that Lee Sedol consulted several Go-players and programmers in preparation to this match. This may be also one of the reasons why Lee Sedol will test in specific manners how AlphaGo will treat and react on moves that the program never has seen (or learned) before. Besides, Lee Sedol is assisted by a team of psychologists and coaches to deal with the enormous mental pressure and media attention worldwide. And to let himself not being brought out-of-balance by the non-ability to assess the emotional state and mental stability of his opponent (in this case, the biggest challenge is actually to win from himself in particular). 

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. 

When seeing the first moves played by AlphaGo, Guo Juan (5p) shakes her head in a clearly disapproving manner (Dia. 1): "this program really needs a good teacher who will knock and bestow upon the head when playing such a bad move, every just knows that this move isn't good at all ... these first white moves are obviously not optimal and look like beginner's mistakes". The order in which the white moves are played (marked with a triangle in Dia. 1), provide black with the opportunity to answer as in the game. Therefore, the result is somewhat less for AlphaGo (see Dia. 1).

Dia. 2:  Game 1, after black 23 (circle, Lee Sedol is black) 

With Lee Sedol's move 23 (circle in Dia. 2) the game is going up in flames immediately. Guo Juan (5p) comments almost instantly: "this move by Lee Sedol is much too compulsory and forcing" and she indicates that black's tsuke (touching move) is a huge overplay. The tone of the game has been set as the rest of the game flow will be determined by Lee Sedol's huge underestimation of the program. AlphaGo cuts at once and takes the initiative by putting Lee Sedol under high pressure.

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) 

With move 48 (triangle in Dia. 3), white attacks the black group in the upper right-hand side. Black answers (square in Dia. 3) and adds some strength to his group by creating additional eye potential. In case of emergency, black can connect underneath with the three black stones at the top right side (e.g. by black R18). However, since it is far too early for black to play himself on 48 (triangle in Dia. 3), white's move 48 is seen by top profs as a mistake by AlphaGo (even though it is sente).

Dia. 4:  Game 1, after white 80 (white stone with square)  

After AlphaGo pushes from behind on the seventh line in Dia. 4, it becomes clear that the program does not respect widely accepted Go-proverbs ('in the far east a child gets a smacking or a hit with a japanese fan on his hands"). 

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)

And then suddenly in a calmly developing game, a dramatic upheaval happens: "AlphaGo's move 102 (Dia. 5) really is a superhuman move" according to Michael Redmond. It looks like white has carefully prepared this invasion with moves in the upper right and with the corner approach --25 moves earlier-- at the bottom right (white 78, circle in Dia. 4). 

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)

With AlphaGo's impressively strong and fabulous move, Lee Sedol has no choice other than to give up is three stones in the upper right (see Dia. 6). In exchange, he gets three white stones but black's potential at the right side has disappeared like frost under the morning sun (in gote). Then, AlphaGo plays a rather slow (and a bit cowardly as it seems unnecessary right now and is not optimal according to the commentators) but surely effective move which secures the white corner in the upper left (circle in Dia. 6).

To play this move right now in the game (while there are several other, larger moves) indicates that the program believes it is ahead and has taken a sufficient lead to win the game. AlphaGo is absolutely not interested in playing the most optimal, largest or most efficient moves: the program only plays moves that provide the highest probability of winning the game.

Dia. 7:  Game 1, after black 127 (circle, Lee Sedol is black)

Anyhow, Lee Sedol starts a fight in the bottom right corner in an attempt to put AlphaGo under pressure (Dia. 7). Due to some mistakes by black,  white succeeds in making a living group that is much larger than what black should have allowed. Lee Sedol seems already too much behind to catch up in the rest of the game.

Dia. 8:  Game 1, after white 136 (circle, Lee Sedol is black) 

Nonetheless, Lee Sedol checks AlphaGo's whole-board awareness (triangle in Dia. 8): does white notice that his long, elongated group is not yet alive? With the effective defense by AlphaGo it becomes clear that the program has excellent whole-board understanding (circle in Dia. 8).

Dia. 9: Game 1, final position after white 186 (circle, Lee Sedol is black)

After about 50 endgame moves, Lee Sedol resigns. With AlphaGo's move 186 (circle in Dia. 9), Lee Sedol is more than 5 points behind. No doubt, Lee Sedol is greatly saddened by his severe underestimation of the mind-blowing strength and amazing fighting of this version of AlphaGo (as opposed to that during the Fan Hui match about half year ago).

This is the first time in history that an AI program defeats a top Go-prof in a formal game without handicap. Go-profs worldwide are speechless and all agree that this has been a fabulous and historical game. And of course, there is a lot more to say in detail about the firm attacks, remarkable, aggressive and deliberate moves, tactics and strategies of both sides in this game. 

The era in which a human could wipe an AI program (without handicap) from the board is past and once and for all closed. This magnificent and superbly profound way of playing Go is never shown before on our planet. And will leave behind incredibly deep imprints and heavy tracks on the hundreds of millions of people worldwide who were following this game online.

Lee Sedol loses this first game against AlphaGo and reacts deeply saddened, disappointed and very touched: "I was very surprised because I did not think that I would lose the game. I am shocked by how well AlphaGo played, I can admit that. I didn't think that AlphaGo would play the game in such a perfect manner. A notable mistake from my side at the beginning of the game kept continuing during the game and lasted until the very last. AlphaGo's early strategy was excellent and I was stunned by one unconventional move Alphago made (see Dia. 5) that a human never would have played. I am in shock, but what's done is done".

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". 

Michael Redmond (9p): "In this first game of the series, AlphaGo triumphed by a very narrow margin. While Lee Sedol had led for most of the match, AlphaGo managed to build up a strong lead in the closing stages of the game. AlphaGo played profound and solid moves with which it secured victory and ultimately has punished Lee Sedol severely and consequent for his lesser opening move (move 7) and aggressive overplay (move 23)". 

In this first game, AlphaGo has shown evidently  that it has a taste for aggressive and offensive play, something the program not necessarily demonstrated during the Fan Hui match. In this game AlphaGo has exhibited surprisingly accurate, profound, and versatile judging of the position.

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.

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