圍棋人機大戰-官方解說 15 分鐘覆盤【全五集】::Match 4 15 Minute Summary - Google DeepMind Challenge Match 2016

Hello and welcome to the game highlights for Game 4 in the Google DeepMind Challenge. Today, Lee Sedol was looking for the weakness in AlphaGo, which he had not been able to find in the first three games. Today, he found it. Michael, show us how. Yeah, well, shall we begin with the game? Absolutely. AlphaGo is black. Yes. At this point, it's exactly the same opening as it played in the second game. And at this point, Lee Sedol changed tactics in the second game he played here, and AlphaGo actually left that. So this was actually kind of a surprise, because just about everyone was expecting AlphaGo to be sort of orthodox in its opening. And so in that game, AlphaGo left it and played on this side here. So Lee Sedol apparently didn't like that, and so he changed his move here. Top players also, people tend to like to change their moves just to avoid the same game, for one thing. And maybe he thought that it was important for him to keep AlphaGo on the defensive a little bit, because this sort of threatens to attack these stones. So black sort of needs to play that extension. And gives Lee Sedol the chance to play the kakari. Very common position here. Locally, there's a lot of moves that white can choose from. Basically, any move directly protecting this one stone will allow black to play towards the right side here, and make a framework here while letting white live. That would be also a joseki. But since black does have this weak stone here, it sort of makes sense for white to switch to the side here. And allow black to take the corner. And create a weak black group. And now black played once here. This is really big in helping black's framework. And white played the final, you could call that the final big point, the final oba. This was an interesting move. Interesting move. It's not unheard of. It's a move that has been played before. If white had played here, black would have been satisfied to play forcing moves from outside. Sort of forcing white to put a lot of stones in that corner. So this was the plan. So white says, no, you can't do that. Now black's aim is to try to get some maji in the corner. There's moves like this, which can cause some trouble in the corner. But it's interesting that before black does that, alphaGo plays once here in an attempt to sort of erase the side first and then go back there later. And I don't really know why. I think Lee Sedol might have been worried that at this point in time, now alphaGo would be trying something in the corner. I'm not really clear as to how that would turn out. But normally I think white should have been playing one push at least. And hopefully if black plays here, then it would be a different story when white plays here. There would be more space for this white. And the actual game white played here immediately. And this does sort of make white a bit cramped. So this is something that I didn't really like for white. And I thought it was a bit difficult. In this fight, both the black group and the white group are actually weak groups. And if you look at the positions on the side, we can see that it looks like, for instance, if white plays here, if we just look at this position, black's group is the weaker one. But there is the fact that now it's black's move. So black gets to play the key move here. That's kind of a vital point in white's shape. And so because of that, the strength of the two groups is maybe about the same. There's also the fact that if black can curl around on the top here, there's going to be a big moyo in this area. So white decided to play the safe move. We can see alphaGo playing very aggressively here. And just closing off the center. And then connecting. This is sort of a vital point in white's shape. With this move, white has a living shape. And so far, white has taken territory here, here, here. And a framework here, which is not really so big. Black, this is not really territory. Black has territory in the corner maybe here. And then this framework. So what happens to this framework is really important in this game. It's white's turn. White played here. And so white started by invading the side here. But decided that it was a bit heavy to actually be moving out with these stones. So he played a very light move here. This is sort of moving out. Not really trying to save all of the stones. But also looking at the cut here. This cut came later in the game. But this is always something that white is sort of hoping to play at some point. This is similar to the magic move in game 2. Although that of course was... This is more of a normal shoulder hit. It's a more normal shoulder hit. In this case actually, black is trying to cover up on the top and surround these stones. Depending on how white handles it. So in that way, it also resembles a move that Lee Sedol played in game number 3. In which case he was attaching against a white structure in the lower right actually. In an attempt to attack white's center group. This is basically an oblique attack against white's stones here. And instead of trying to take territory over the side which would sort of fall into black's trap. White does have to push through here and try to make a connection with these two groups. Again, just like here, AlphaGo is playing very strongly. It's quite a similar shape actually. At this point, white does have a kind of a connection. If white had for instance played something like this, it would have been much more peaceful. Black would probably just take the one stone. And black would have some thickness towards here. Would still have the torn territory and this territory. And would later have a move here to cut this off. So white would need to put one more stone in for instance here. And the kind of clumsy shape here is what Lee Sedol didn't like. Because he also has a weak point here. So the whole group here, although it's connected and saved now, it's still not a very happy shape. And the fact that black is thick here means that black is going to get some extra points instead. So that's why Lee Sedol just didn't like that I suppose. And since the latter is good for white, so he escaped here. The drawback is that this move is attacking white here. It turns into a kind of a trade. Now at this point, you were feeling pretty good for AlphaGo. I think AlphaGo should have a lead at this point. And it all depends on how much white can get out of the Aji here. Because there's a lot of Aji or potential. Especially for this stone. And this stone and the weakness in the cut. And the Hane here. I'm just putting a lot of stones down. This really puts these stones into... So there's a little bit of potential here. And even professionals when playing will not be really sure whether this stone is completely dead or not. But for the time being, covering here is a very strong move for black. White can't really allow that to happen. So white had to put a stone in here. Black played here. This is large scale. Now if this move happened to be... It turned out that white managed to destroy this black center territory. With a brilliant sequence. And if that is true. If that worked actually. Maybe black should have been a bit more cautious here. This would be maybe a bit over cautious. But at least something like this. To avoid that kind of thing. But my theory here is that the moves that Lee Sedol did to break up this center. They took me by surprise. I wouldn't be surprised if they were outside the tree of variations that AlphaGo was creating. Because it was a brilliant sequence. Which is really amazing though. And we'll see this shortly. But AlphaGo performed virtually flawlessly in the first three games. Yes and in this game also. I think AlphaGo was playing a good game. So suddenly. The moment Lee Sedol sort of... It's a pretty standard move. This is normal. There's nothing special here. This is another. Well there's a choice here. Between this move and this move. They both have their drawbacks. The whole situation here. This black group has some dummies Murray. A lack of liberties. There's weak points in black all over the place. So it is a kind of a worrying situation. However black plays. This looked like it was a safe move to me. Absolutely. When black played it. Black. White cuts here. Again. Playing Atari. And allowing white to get some stones lined up here. Would set up this move. And that would be a disaster. Coming this side. Would allow this to be sente. And white would be again. Would be able to use this kind of aji. To run out with a fairly good shape. And that would put these stones in trouble. So this is the move that comes to mind. It's a really nice move. It's a nice move. Now white plays here. And this is forcing. White. Black has to answer this. And in order to make this cut work. White really needs. He needs this move. This is a forcing move. That obviously will work. White. Black is going to answer it. White needs this forcing move. And it still doesn't work. Because white cuts. Black comes out. Here. And black can come here. To capture the two stones. Right. So white needs one more forcing move here. Now if we do this in order. It's just not going to work. Because. White. Black can answer the final forcing move. With this. This move. Right. And white cannot get out here. It just doesn't work. So the move that Lee Sedol played. Was just brilliant. And it was. He wouldn't have been playing this way. To start with. If he hadn't. Been sort of. Feeling. The potential for this move. Already. I don't know if he had it. Completely read out. Or maybe just was sort of. Smelling something that happened. And he was. Being very modest about it. In the press conference. But all of this stuff he's doing. Would be sort of meaningless. If he hadn't. Had something like this in mind. When he did. This was a brilliant move. I think it got a wow out of me. While I was doing the commentary. Basically it's. If black plays here. It means that white will get that. Extra forcing move here. And this would set up. The capture here. Of the two black stones. Not really paying very much for it. Capturing these two stones. Would give white a victory. In actuality. Black played here. White pushed through here. Black covered. And white cut. Now at this point. It's still not clear what's going to happen. If black takes the one stone. White can force with this. And force with this. And again white's got the three. Forcing moves that he needed. So white can cut here. And capture the two stones. So it's these three points. That white needs to make this cut work. So that's relatively simple. In the actual game. AlphaGo stopped playing. In this vicinity at this point. Now the move that I was looking at. Was this one. And if white plays here. It's not going to work. Because white cannot capture this stone. On the ladder. So this looks bad for white. But there is potential on this side. For instance if white plays here. And black plays here. White can push through here. Black covers. White cuts. And now white plays here. After this. The throw in here which kills these stones. And the cut there. This is bad too. So this would capture these stones. So this would be a disaster. I'm not really clear what happens. If black plays this move on this side. In which case it doesn't really seem to work. But in actuality. AlphaGo apparently decided it didn't work. To play here. And so AlphaGo started doing stuff like this. And just didn't work. After this actually the game sort of. Deteriorated for AlphaGo. Because AlphaGo was just doing all sorts of things. That did not work. And now took here. And then played down here. And white just took. Black played the key point. But black was already losing the semi here. This whole sequence. It didn't. Black gained some back on here. But it increased white's territory here. Really wasted the black potential there. And in the center again. This point in cutting off the two stones. It's Miyai. So at this point the game is already looking good for white. It's an amazing turnaround for Lee Sedol. Who had basically. We had counted. 80, 90, 100 points. Without anything like this. The game would have been hopeless for white. And this was really a brilliant move. That was led up to by a sequence here. In which Lee Sedol was certainly. Sensing something there. In the middle of black's territory. Thank you for. It was so long. It seemed like a really long commentary. Again another long complicated game. Thanks for leading us through it. Congratulations to Lee Sedol. For finally finding. A weakness. In a program that up until now. Has been virtually. Seemed invincible. But it's got a bit of a flaw. We will look forward to game five. The final game. With great anticipation. Thank you again Michael. Thank you.