"Why do you want to simulate the human brain?"

As if there was no omen, Mitsuki Haihara asked.

"Huh?"

After hearing her son's question, Mrs. Kaihara let out a surprised voice. Strangely, she didn't seem to expect her son to ask such a question.

Even Dome couldn't help but be a little stunned, she also didn't quite understand why her brother suddenly asked such a question.

"Didn't you just say that simulating the human brain was done at the beginning of this century? As a supercomputer ahead of its time, why did the treemap designers do what they had already done at the beginning of this century? ”

Mitsuki Umihara added.

(Is that so?) ）

After a little thought, Dome finally reflected on the significance of his brother's question. Come to think of it, there is something that doesn't make sense.

Imagine if a famous car company built the world's most advanced supercar, what would they do? Will it be a test run on a normal road at a normal speed?

No, of course not. If there is a car like this, it is the right thing to do if it can run enough records on the world's most advanced racing track.

Mrs. Kaihara smiled a little embarrassed and scratched her cheek. She sighed softly and spoke slowly.

"It's my fault, my words are too easy to misunderstand."

With that, she smiled gently as usual. Seeing her reaction, for some reason, Mitsuki Kaihara closed his lips tightly and looked at his mother intently.

"Your question, in fact, is not so easy to answer. Do you know why the tree designer made it? ”

"Analyze the weather data, right? ...... on the bright side"

Dome replied.

Although it is true that there is such a name. But in fact, inside and outside the school city,No one really thinks so.。

Treemap designers are responsible for a large number of scientific research calculations and analysis tasks, not only the analysis of meteorological data published on the surface. Just as meteorological satellites often undertake some military tasks, nominally and in reality do not exactly coincide, and this is a game that humans often like to play.

In fact, it's also an open secret.

"Well, let's just analyze the meteorological data, how long does the tree diagram designer calculate the meteorological changes at a time?"

Mrs. Kaihara continued to ask.

"I heard, it seems like a month? Calculate motion at the molecular scale to calculate weather changes. ”

"Actually, there should be more computing power, right? One month may be a theoretical upper limit, otherwise wouldn't it be possible to keep counting? ”

The brother and sister guessed separately.

Mrs. Kaihara spread her hand between the siblings and shook her head slowly as if in the negative.

"Do you think it's possible?"

Hearing her mother say this, Dome frowned. If nothing else, it's hard for her to believe that it's achievable.

"Impossible."

Chaos effects undoubtedly cause errors to accumulate, and the accumulation and amplification of errors are undoubtedly nonlinear, which in principle should make calculations impossible. It's just that she doesn't know much about computer theory, so it's difficult to make a definite conclusion.

"So this is originally a lie, but in fact, it can only deceive ordinary people. This is not how treebuilders calculate the weather. ”

"The tree diagram designer should be a quantum computer, right?"

Mitsuki Umihara interjected.

"If that's not the case, then there's nothing to say. But if that's all there is to it, it's not enough, it's not enough. This needs to be explored mathematically, as it is related to the origin of the name 'tree designer'. In fact, the name 'tree designer' has at least 5 different meanings. From a physical Feynman diagram to a DNA hotspot tree and so on. However, most of these reasons are speculated from the perspective of 'what it wants it to achieve'. What is related to our topic should not be a goal, but a problem. Let me say so, well......" Mrs. Uehara tapped her cheek, then dipped her fingers in the water in her glass and nodded seven points on the table, "Suppose there is a salesman who needs to go to several cities to sell his wares, and he must pass through each of them, and return to the city from which he departed at the end. I now ask, how can he take the shortest route to achieve this? (Note 1)

"If there aren't many cities, it's not difficult to solve. However, even if it is just one more city, the difficulty of solving it will increase significantly. With a computer, it is difficult to find a solution under the premise of multiple cities...... Uh-"

But in the middle of his words, he suddenly showed a confused expression. She was very good at math and immediately realized why her mother was asking such a question.

Isn't it quite similar in nature to the so-called "calculating the weather for a month"?

"Yes, a normal computer can't solve this problem. At each moment, according to the state and input at the time, they can only make a unique definite action, which is the 'sequential control logic method'. Every step of it is linked to each other, determined. They are a kind of 'deterministic automaton'. Or, in the language of the computer world, they are 'deterministic Turing machines'. Just like my Theseus, although they have the ability to memorize, trial and error, etc., they have one thing missing, that is, they don't 'guess'. If you want to use them to solve the problem of salespeople, I am afraid that you can only start with exhaustive methods, which is obviously a dead end. Therefore, it is impossible to calculate the weather with a deterministic Turing machine. Do you understand? From the beginning of the design and construction, the tree diagram designer did not use the deterministic general Turing machine as a sample, it was a 'non-deterministic Turing machine'. Depending on the current state and input, there are a variety of possible actions. Just as the solution space of the salesperson path is a tree, so its computation on the input string is a tree, with different branches corresponding to different possibilities for each step of the calculation. You see, from this point of view, every time you use this computer, isn't it just designing a 'tree diagram'? While the name 'Tree Designer' doesn't have more than just that, this is what I like the most. Why simulate the brain? If you simulate the brain with a deterministic Turing machine, it's really nothing special. But what if such a thing was done with a non-deterministic Turing machine? The non-deterministic Turing machine has a special ability to 'guess'. This ability allows it to move from the 'sequential control logic method' of the deterministic Turing machine to the 'cognitive logic method'. Until then, it had been a no-go zone for humans. Not to mention computers, even other creatures in nature do not have this kind of thinking skills. Isn't it curious to use it to simulate what the human brain would be? Isn't it worth the attempt to consider that the human learning process is the same as Claude Shannon's definition of communication, and that the process of thinking will eventually converge on Hilbert's three questions? ”

Is it worth it? In many cases, this question is difficult to answer.

What would you do when you had the means to theoretically solve all the codeable problems that exist in the world?

I'm afraid most people's answer would be "write a program that solves all the problems that can be coded".

The people who used the tree diagram designers back then (and maybe weren't at the time) just thought the same way.

Mitsuki Umihara stood up abruptly.

"Sorry, I'll go to the bathroom."

He said so.

_

At the same time, there is something going on in the Ninth School District.

It was a very ordinary sight, a schoolgirl from the Fog Hill was sitting under the umbrella of an open-air coffee shop with another schoolgirl who had been on the plane for a long time. The schoolgirl in the foggy hill sucks on a drink with a cup, while the schoolgirl who gets on the computer for a long time ignores her and plays with her laptop by herself.

At least it seems,It's really an ordinary daily drama in the evening in the school city.。

After a while, the female student who got on the computer for a long time closed the notebook with a "snap".

"Done?"

For some reason, although it was an inquiring tone, it sounded like the Kirigaoka student who was asking the question was not interested. Anyone could tell that she didn't care at all about the answer to that question.

"Don't underestimate me." The student who got on the plane for a long time glanced at the gray-white suitcase placed next to the student seat in the foggy hill, "With this thing, I'm afraid there are not many people who can catch me." ”

"That's good."

The students of Kirigaoka finished their drinks in two sips and prepared to get up and leave. At this time—

"Wait a minute."

The student who got on the plane stopped her.

"What else?"

"You're asking me what else is going on?" The student who got on the computer shook his head incredulously, "Suddenly appeared in front of me and told me that I could temporarily lend enough equipment to crack the top secret of the school city for me to use, on the condition that I use it to hack into a family restaurant, and I don't have to do anything." If someone takes such a cheap deal for granted and takes it for granted, it is probably incredible. ”

Indeed, she was right in what she said. In this world, there is never anything to take advantage of, and some are just the price paid whether they know it or not.

"To tell you the truth, I don't know."

However, the students of the foggy hill exhaled listlessly.

"If I want to lie to you, I don't need to use words like 'I don't know.'"

Although it sounds hard to believe, the credibility of this statement is very high. It's better to say that if it's the truth, it's harder to believe.

The schoolgirl who got on the plane took a breath and glared at the person in front of her.

To say that there is no hostility towards this person is obviously an out-and-out lie. His enemy is the entire school city.,The woman in front of me who maintains the school city in the shadows is not only her enemy.,And I'm afraid it's one of the biggest enemies.。

But for now, at least, there is no idea of wanting to do anything with her. Maybe this day will be inevitable in the future, but at least not now.

If you know this, the other party should know the same. But why, she appeared in front of her eyes uncharacteristically today? And promised yourself such a benefit? Doesn't she know what it means with her hacking skills?

"Okay, okay. If you don't make it clear, you probably won't be satisfied. But your questions are probably piling up a long time ago, so I'll just answer two. The schoolgirl in the foggy hill sighed softly, like **, "I really don't know why I made this deal with you, because I was just asked by the teacher." And if you doubt the purpose of my meeting with you, the answer is simple - it's just that people are dying, and their words are good. ”

“……”

If it's a joke, it's really not laughing at all.

"Why is this expression? You shouldn't have to worry about me. It's better for you—"

Just as she said this with a feeble shrug of her shoulders, suddenly her eyebrows raised slightly.

The reason is simple, her phone rang suddenly.

She took out her phone slowly, and just glanced at it, and couldn't help but widen her eyes at the overly unexpected number.

Turning her head to the girl who was on the plane at the long point, she made a gesture to let her leave quickly, and the other party also picked up the suitcase and left quite interestingly.

"How is this going on?" Holding her jaw inexplicably, she pressed the answer button and put the phone to her ear, "Yo, boy." Although I gave you the necessary contact information, I also said that you should not bother me if you are fine, and I hope you will not make me angry this time. ”

Just now, he seemed weak, but suddenly changed to an old-fashioned tone. If anyone hears this, they will probably be dumbfounded by this strange speed of changing faces.

"Let's get straight to the point." The voice coming from the earpiece didn't even say hello, "Do you have some papers here?" I don't know what the author's full name is, but it's probably Alice. ”

“……”

For a moment, the girl in the fog hill fell silent. Soon, though, she reverted to her tone.

"What the hell are you talking about? Juvenile. I'm going to be angry if I bother me for such an inexplicable reason. ”

"If I'm not mistaken, you're a student of Fog Hill and a classmate of Senior Sister Bi, right? As long as you think about the strange things that happened to the senior sister, it is not difficult to make this kind of guess. I'm going to ask now, are you sure you want me to keep guessing? ”

“……”

She swallowed instinctively and shook her head silently.

"It's really a defeat to you, I didn't expect to provoke such a famous detective, I knew that I should have let someone else take over."

"It's a great honor to be complimented. The answer is yes? ”

"I'm sorry, but you're looking for the wrong person. I did keep the papers, but I destroyed them a long time ago. ”

"Why?"

"No big deal for a reason. It's just that the change in the storage media means that I don't have to keep the original text anymore. Although there are not many papers in that batch, the number of relevant documents is not small. If it is stored in crystal, it is undoubtedly much more convenient than the original text. So after saving them on the crystal, I destroyed the original text. ”

"So, is that crystal with you?"

"That's why I said, you're really looking for the wrong person."

She sighed,

"For the past few months, that memory crystal has been in the hands of Mr. Yan."

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Note 1: The picture drawn by Mrs. Kaihara looks like this:

_[[[CP|W:300|H:250|A:L|U:http://file1./chapters/201410/10/2125880635485714325305000751748.jpg]]]

_

This is one of the world-famous seven major mathematical problems of the millennium, "P/NP problem", related to the popular example of the NP problem - the traveling salesman problem.

The Seven Mathematical Problems of the Millennium, which are listed in the Hilbert Problem Set at the beginning of the last century, are special in that the selection criteria for the Seven Mathematical Problems of the Millennium are not purely mathematical, but have a significant impact on the development of mankind in this century. While none of these mathematical puzzles have a great reputation (at least not compared to Goldbach's conjecture), each of them is significant because they are very "useful".

Take, for example, the P/NP issue mentioned in this chapter. Computer theory has not changed fundamentally since Alan Turing began to develop to the present day. The quantum computer, which has been completed in theory, is a leap forward (in Feynman's words, just about actually building it), but it is still not a fundamental change. The real qualitative change in computer technology is the non-deterministic Turing machine, which must be solved on the basis of the P/NP problem.

A similar situation also appears in the Poincaré conjecture for quantum gravity, in the NS equation for fluid mechanics, and in the mathematical proof of the Yang-Mills gap in existence and mass (by the way, this problem is the only one of the seven mathematical problems that basically no one dares to touch, and the difficulty is terrible).

When the Hilbert Problem Set was published in the last century, some people felt that if they wanted to know the extent of the development of mathematics, they only needed to look at the progress of solving the Hilbert problem. The seven mathematical problems of this century are not as numerical as the Hilbert problem, but they are no less significant – they are, to a large extent, a representation of how far humanity has come and how far it can go.

PS: Part of this chapter was added for a reader who seems to have some misunderstandings. The Turing machine is a mathematical concept that has nothing to do with the human brain, and it is not based on the human brain for a computer to simulate the human brain, which is another content that is purely based on mathematical concepts. Hopefully, the explanations in this chapter will make this reader somewhat comprehensible.