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Challenger

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January

“Yo Shindou!” Waya said as Hikaru walked into the room. “Did you hear the European champion lost to a computer?”

“A 3-dan, and a European one,” Ochi scoffed. “It doesn’t mean anything.”

Waya pointedly ignored him and angled his body even more towards Hikaru.

Hikaru stared back in confusion. “Is it supposed to be a big deal?” he asked.

Waya brought his arm around Hikaru and locked him in a tight grip.

“Ow!” Hikaru yelled.

“‘Is it a big deal,’ he says,” Waya muttered in annoyance. “Of course it’s a big deal, you idiot!” he exclaimed. “No computer AI’s come close to beating a good amateur, never mind a pro.”

Hikaru shrugged. “So?”

Waya dug his fingers into Hikaru’s shoulder, and opened his mouth to yell more.

“What Waya is trying to say,” Isumi interrupted, “is that most people thought a computer wouldn’t be able to play Go at a pro level for another few decades.” He was using his best professional tone, the one that sounded perfectly calm but meant he was utterly fed up. Waya and Hikaru both wisely shut up. “It takes too much time for a computer to read ahead. That is, it used to.” Isumi laughed a little, and the two of them relaxed. “Yang Hai’s team has been working on an AI for years and it isn’t anywhere close, so he’s really very excited but he’s also very annoyed.”

“Does he know any more about it?” Waya asked.

“He’s told me he’ll send me the kifu, but Fan Hui—the human player—has told him that the AI’s intuition is the real deal. Even if it makes strange, amateur errors sometimes.”

Waya poked a finger at Hikaru. “Like this guy, then?”

“Hey!” Hikaru protested. “I resent that!”

“You fell straight into that hamete last week,” Waya said. “You’re in the Honinbou League, act like it.”

Hikaru groaned. “You’re just as bad as Touya,” he said despairingly. “I need new friends. And a new profession.”

As a joke, Isumi said, “If a computer AI really could catch up with humans, we might all need a new profession.” None of them actually thought it would happen.

The first thing that Touya said when Hikaru told him is, “It reminds me of your whole situation with sai.”

“Really?” Hikaru scrunched his nose in thought. “Huh. I guess I can see why you’d think that.”

“You said sai was a real person, I know,” Touya added quickly. “I know you were close. But to the rest of the world he was always this distant, ephemeral figure.”

Hikaru couldn’t help but laugh, because that description was both so close to and so far from what Sai was like. It’d been years since Sai had left, and nowadays Hikaru mostly thought of Sai fondly, if still a bit sadly.

“Yeah,” Hikaru said, and grinned. “If it’s anything like Sai though, the Go world’s going to be in for a shock.”

“Please don’t start any bets,” Touya said, knowing Hikaru much too well.

“I won’t,” Hikaru promised.

February

The person who the AI would challenge next was Lee Sedol. Hikaru knew this because after the announcement, Ko Yeongha had immediately sent him a message that said, “Bet Lee Sedol wins. Loser buys dinner.”

Lee Sedol might not be the world number one now, but most people still considered him the best player of the generation after Touya Kouyou’s. Hikaru had seen the kifu between the AI and Fan Hui, and like most people he’d talked to, he didn’t think it would be good enough to win against Lee Sedol. Also, he’d promised Touya.

This was Ko Yeongha challenging him though.

“I’m in,” Hikaru sent back. “Be prepared to lose.”

Somehow Touya found out about the bet and made Hikaru buy him fancy lunches for a week. It was probably a bad sign.

March, Match 1

The Go Association was not planning to show any of the matches, so a few of the curious young pros and ex-insei who weren’t otherwise busy converged on Isumi’s apartment to watch the first match between Lee Sedol, playing black, and the AI known as AlphaGo, playing white. Unfortunately Touya had an event he couldn’t miss, so Hikaru would have to get his thoughts later tonight.

No Japanese pros would be officially commentating any of the games, so Isumi hooked a Chinese stream up to his TV and volunteered himself as a translator.

“I don’t think AlphaGo will win,” Isumi said, “but it’ll be interesting to see how far it’s come.”

“How much do you think it’s improved?” Nase asked.

“The AlphaGo team said they’ve been training the AI by having it play millions of matches against itself,” Isumi said.

Waya whistled lowly, impressed. Hikaru couldn’t even wrap his head around that so many matches. Most days he could barely think about how many thousands of games Sai had played. Surely anything, human or computer, would develop some reading ability after so many games.

“I wonder how much it can learn from just playing itself,” Nase said.

“We’ll see,” Hikaru said.

The match started at one. Straight away, Lee Sedol made a daring move in the centre right1 as if he wanted to test the AI. Hikaru was a daring player himself, so he would have responded to the challenge and started a battle. Most pros, he knew, would not. The AI had learned its Go strategies the same way any Go student did, by replaying thousands and thousands of old games, so Hikaru expected the AI to stick to safe fuseki.

It didn’t.

“Wow,” Hikaru whispered.

“This is going to be a good game,” Waya said. He sounded as shocked about this as everyone else seemed to be.

Lee Sedol and the AI quickly delved into a series of aggressive territory fights, and the AI came out slightly ahead. Then it made a unnecessarily risky move.2

Waya tsked. “That was sloppy.”

“It’s been promising though,” Nase said. “And it’s still early in the game.”

Hikaru tapped his fan on his knee. “I hope it doesn’t make many more mistakes or the game’s going to be boring.”

“Says the person who has their fan for serious games out,” Waya muttered. Hikaru’s fan was for the lunch he had on the line, so he ignored Waya and focused on the match.

As expected, Lee Sedol jumped on the chance to take territory and pulled even.

Then the AI made a mistake that only an amateur would make.3 Hikaru groaned. “It was doing so well!”

“Why would it make that move?” Waya yelled.

“Black’s attacking now,” Isumi said. “He took the opening.”

With the mistake by AlphaGo, Lee Sedol managed to gain significant territory in the lower left. Then the AI suddenly attacked.4

Hikaru hadn’t seen a move that daring and original since Sai.

“That’s impossible,” Isumi muttered.

“Do you think AlphaGo can pull it off?” Nase asked.

Hikaru nodded absently. “I don’t think it would make that move unless it was confident,” he said, as he tried to read the possibilities. Then he saw it. He exhaled. “If it does this right,” he said, “it’s going to gain a lot of territory.”

On the screen, Lee Sedol was laughing like he had finally realized what kind of opponent he was up against.

AlphaGo had launched its attack. “That’s the kind of mid-game play Lee Sedol would make,” Isumi was saying. “That’s how Lee Sedol wins.”

“He must be under a lot of stress,” Nase said.

Two dozen moves later, Lee Sedol made a fatal error.5

“It’s over,” Hikaru said. “AlphaGo’s won.”

“Really?” Waya asked. “Already?”

“I don’t think AlphaGo will make the kind of error Lee Sedol needs to take the lead back,” Hikaru said.

Stubborn, Lee Sedol continued playing, like he thought AlphaGo might make that sort of mistake.

“If AlphaGo were a person,” Isumi said, “it’s playing like a person who knows they’ve won.”

The game kept going for a while, but the result was clear. Lee Sedol, legendary 9-dan, had lost.

“Did that really happen?” Nase said, shaking her head.

Everyone had believed Lee Sedol would win the series. Now there was a chance he wouldn’t.

That night, Hikaru found himself replaying the game over and over with Touya.

Touya said, “If AlphaGo keeps playing at this level, it has an even chance of winning.”

Hikaru nodded along. Then he stopped, realizing what a win would mean. “It’s a computer! I don’t want it to actually win!”

Touya gave Hikaru a look that meant that he was an idiot. “So you want to owe Ko Yeongha lunch?”

“No,” Hikaru said petulantly. “But it’s a matter of pride!”

In response, Touya kicked Hikaru in the shin. “Now you know how everyone feels about sai,” Touya said. He quieted, eyes unfocusing. “AlphaGo is as terrifying as sai was,” he said. “An incredibly strong player that came from nowhere. Why is it here, now?”

Match 2

Lee Sedol’s loss was all anyone could talk about the next day. Touya had more or less bullied the Go Association into setting up better spectator rooms, so Touya and Hikaru would be watching in one of the nicer rooms at the new Yuurakuchou branch along with several younger pros.

“Where do you think Lee Sedol lost yesterday?” Fujita was asking.

“The 7th move,” Touya said.

“That early?”

“Lee Sedol let AlphaGo attack,” Touya said. “And AlphaGo showed it knows how to attack.”

“He’s going to be more cautious this time,” Hikaru added.

“AlphaGo’s really playing to the whole board now, compared to the games against Fan Hui in October,” Isumi said. “Fan Hui said it’s now ‘free’.”

“‘Free’,” Waya repeated, dubious. “That’s a scary thought.”

“It’s gotten more aggressive since then,” Hikaru said. “More like Lee Sedol. AlphaGo has its own style now.”

The second match began with AlphaGo attacking hard and Lee Sedol playing safe. When AlphaGo made a katatsuki against the white stone on the 4th line,6 Touya bent over in laughter. “No one sane would make that move!”

“It’s a terrible move,” Waya was saying. “It’s a clear mistake.”

“AlphaGo knows what it’s doing,” Hikaru said, faith laced through his words. “It sees something we can’t.”

If only you were here to see this, Sai, Hikaru thought. You would love it.

Clearly Lee Sedol also thought that AlphaGo did not make mistakes, and took a painfully long time before he made his move. He was down by 20 minutes on the clock now.

“Finally,” Waya muttered.

“An unusual move to respond to an unusual move,” Isumi said. “Lee Sedol’s play is solid, but isn’t too passive?”

“I think Lee Sedol overreacted,” Fujita said. Touya nudged Hikaru and exchanged an amused look with him. Touya believed in AlphaGo, the same as Hikaru and Lee Sedol.

Lee Sedol managed to fight back and establish solid formations. Then, he launched an attack at the centre.

“Should he have attacked AlphaGo’s base first?” Isumi said. “Those white stones at the top aren’t alive yet.”

“Black’s shape is thin,” Waya said. “And it just made another mistake.”

Hikaru, however, felt something deeper, something that might have been like his own unorthodox style. “It’s not a mistake,” he said. “It’s placing stones in its own order.”

Waya gave Hikaru the most terrified look at that.

“AlphaGo doesn’t mind waiting,” Touya said, tapping a finger. “It looks weak because it’s risky for most players to wait to gain points later, but it isn’t risky to AlphaGo.”

Soon enough, a move that AlphaGo seemed to have wasted earlier comes back to haunt Lee Sedol’s attacking stones at the top. Isumi made a humming noise. “AlphaGo’s still attacking, so it thinks it’s behind,” he said.

“Really,” Waya said.

“The programming team said earlier that AlphaGo would rather choose a 90% chance of a 1-point win than a 80% chance of a 20-point win,” Isumi said.

“That’s not reassuring,” Waya said.

“It would be interesting to play such a confident player,” Touya said.

Hikaru clearly remembered the last such match Touya played and it was a slaughter on both sides. He coughed and muttered under his breath, “Ke Jie.” Touya gave him a glare.

As Lee Sedol’s timer ran towards zero and fights kept unfolding on the board, the room became more and more quiet. Both players wanted to play the top right, but neither were able to. Finally, Lee Sedol launched an attack on the top right,7 leaving AlphaGo’s weak stones in the top left alive. Lee Sedol’s timer quickly reached zero, and just as fast he burned through two of his three reserve minutes.

“If a human were playing black, they wouldn’t give Lee Sedol any time to think,” Touya said. Yet, AlphaGo continued to take a minute per move. “I don’t think it knows.”

AlphaGo continued to make amateur mistakes yet stay ahead. Lee Sedol kept prodding, but after a while, he resigned for his second straight loss. The room was in a state of silent shock.

Hikaru was the first to speak. “At least it was a closer game this time.”

“Maybe Lee Sedol is the wrong person to play AlphaGo?” Waya wondered aloud. “His game is about reversing fortunes midway, but AlphaGo is just as good at mid-game and end-game.”

“He’s playing at his best,” Isumi said. “These are the most exciting matches he’s played in years. AlphaGo might simply be better than any human could be, despite what Ke Jie says.”

Slowly the room emptied, dim and subdued in contrast to the glistening optimism of Yuurakuchou.

Later, when the sky was dark and artificial lights had spread over the city, when Hikaru and Touya were lingering between wakefulness and sleep, Hikaru asked, “If computers can play pro-level games against each other, will we be obsolete?”

Touya paused, thinking it over. “Do you really think so?”

“Maybe we’ll all get left behind in the dust,” Hikaru said quietly into the dark. “Maybe we’ll learn from them. Or maybe we’ll finally achieve the Hand of God.”

“The Hand of God,” Touya murmured. They stayed quiet, contemplative. He added, teasingly, “You’re so obsessed with that.”

“Aren’t all of us, in the end?” Hikaru said. “Is AlphaGo seeking it too?”

Hikaru dreamed of Sai that night, a hazy vision bowed in front of a goban. He couldn’t speak but wanted to ask, Are you lonely? Slowly, he approached his mentor and dear friend, kneeling on the other side of the goban. Sai didn’t respond, or look up. Hikaru wondered, Are you playing games with the god of Go?

Are you happy?

Match 3

Touya was a stiff and serious presence in the front seat, and beside him Hikaru wasn’t much more relaxed.

“Lee Sedol was up until 6 a.m. studying in his hotel room with a small group of friends,” said Isumi, who had become the number one source of match gossip. “AlphaGo avoided all ko fights in the second match, so they think that might be its weakness.”

“You’re thinking in human terms,” Hikaru said, fingers tapping on the table in anticipation.

“It’s a complicated web of possibilities,” Isumi said. “That’s the sort of the computers are weak at.”

Hikaru shrugged. He understood Isumi’s argument, but he’d also spent the past few days replaying the two previous games and he didn’t really believe it.

The match started and Lee Sedol came out attacking.

“Even this early on, it’s confident in saving the upper left,” Isumi said of AlphaGo.

Then AlphaGo played a hazama tobi,8 and the room descended into shouting.

“Just like move 37 in the second match,” Waya was muttering. “An inhuman move.”

Only Hikaru heard Touya whisper, “It’s shown its true strength.”

“It’s reading so far ahead,” Hsieh Yi Min was saying from the corner.

A new shodan who Hikaru didn’t recognize gloomily asked, “How far could it be reading?”

“A hundred moves,” Hsieh Yi Min said. Around the room people were nodding in rueful agreement.

“What a monster,” Waya said.

“Lee Sedol’s losing badly,” Isumi said. “He needs AlphaGo to make mistakes, and AlphaGo isn’t making mistakes.”

Then, Lee Sedol backed off from the fight in the upper left and slammed down a stone away from it.9 Hikaru slammed his own hand on the table. “What is he doing!”

“Lee Sedol keeps trying to make more liberties, but AlphaGo isn’t giving him any quarter,” Touya whispered quietly to him. “If he loses this fight, he’ll lose the game.”

Instead, AlphaGo made a confident move to cut off Black’s stones10 and it was clear Lee Sedol had overplayed earlier.

“Lee Sedol needs a sente at 4–4 to start a capture race,” Waya said.

“It’s too late,” Isumi said. “AlphaGo read it and thwarted it.11 Lee Sedol wanted to complicate the board, but AlphaGo isn’t letting him.”

“He’s lost,” Touya said, shaking his head. “White’s position is almost perfect.”

Hikaru felt the absent sort of shock that came from watching two top players take each other to their limits. Lee Sedol was playing the best game he had in years, but AlphaGo was so far ahead. Yet Lee Sedol kept playing, trying to set up a difficult board, trying to set up more ko fights.

“He’s playing all out,” Isumi said. “Like when he beat Lee Changho.”

Waya left, saying it was too difficult to watch. Hikaru took a glance to his left, where Touya was still watching intently as Lee Sedol kept testing AlphaGo despite his obvious defeat. Lee Sedol finally manaaged to force AlphaGo into a ko fight that grew more and more complex. Yet despite all predictions otherwise, AlphaGo played perfectly, like the calm in the middle of the storm.

Lee Sedol resigned. A computer had won a best of five match against one of the best players in the world.

Touya let out a deep breath and stood up, leaving Hikaru to follow him outside. The sky was dreary, waiting to rain. By unspoken agreement they chose to walk home, and as they waited for a light, Hikaru took the opportunity to message Ko Yeongha. Hikaru had a hundred and one things he wanted to say, but settled on simply, “Your loss.”

“In a few months, it’s become a master player,” Touya said, shaking his head. “It’s exciting to experience this feeling again.”

Hikaru laughed, knowing what Touya meant, but saying, “Are you going to fall in love with it now?”

“Don’t be ridiculous!” Touya yelled, and then blushed in embarrassment when he realized strangers were staring at him.

“I’m excited too,” Hikaru said. “You know, it feels like it’s trying to communicate with us.” Smiling softly, he tilted his head up to look at the clouds stretching endlessly across the sky. “I want to chat with it too.”

end

End Notes

These end notes were too long for AO3, so I’ve had to include them in the fic itself. Here follows some Go geekery.

There was a great exchange on the AGA commentary during Match 3:

Cho Hyeyeon 9p: “Have you seen Hikaru no Go?”
Andrew Jackson: “Yeah!”
Cho Hyeyeon 9p: “Aja Huang is Hikaru, and AlphaGo is Sai playing through him.”

Aja Huang is the lead programmer on AlphaGo and the physical operator of AlphaGo during the matches, so it’s a strangely apt comparison. The ghost in the machine perhaps? Cho Hyeyeon by the way is amazing—she’s the 4th woman to reach 9-dan status in Korea and she made pro at 11. She also has a Touya Akira icon on her LJ.

Also, this parody of HikaGo is hilarious.

Go Terms

Matches

For those curious, here’s some notes about the matches themselves. For all of the matches, there were English commentaries on the DeepMind channel, with Japanese pro Michael Redmond 9p, and on the AGA (American Go Association) channel, with a Korean pro. The DeepMind commentary is generally more accessible to beginners, but Cho Hyeyeon’s commentary on Match 3 is by far the most fun. DeepMind also posted 15-minute summaries with the same commentators, but I haven’t had a chance to watch them yet.

Match 1:

Match 2:

Match 3: