Chapter 102 (1/2)

It's not only Hao Yun's parents who are watching CCTV interview, but also Hao Yun's three sons in the 401 bedroom, plus a little fat man Zhou Xuan who always comes to the 401 side to sleep.

”Brother Yun, Niupi! This has to break the Guinness world record for the fastest time to hand in papers in the hope cup competition? ” Looking at Hao Yun coming out of the gymnasium, Zhou Xuan couldn't help shouting.

”And the record?” Asked Liang Ziyuan.

”Hey, hey, we can apply for one for him.” Zhou Xuan is embarrassed to say with a smile.

”But what the moderator said... The main examination committee is in a meeting. What are you going to discuss?” Zheng Xueqian felt his chin and frowned.

”I don't know. Maybe I wrote some wonderful answers.” Zhou Xuan shrugged his shoulders, but said.

Amazing answer?

What's the answer?

Including Zhou Xuan himself who threw out this sentence, the people around the computer were all curious.

At the same time, Professor Li Xuesong, who was reading his paper in the office of several colleges of Jiangcheng University, suddenly received a call from Xia Guo Institute of mathematics.

The caller is Professor Liu Shoufeng, a big bull in the field of number theory in China. He is also the author of the last big question in the previous undergraduate mathematics competition.

Professor Li Xuesong was too lazy to answer the caller ID on his mobile phone, but he thought that the old man was not so careful, so he patiently pressed the connect button.

”Hello? What's the matter, Lao Liu? ”

”Did you see the email I sent you?”

”Mail?”

”Just sent it to you!”

I don't know what medicine is buried in the old man's stomach. Professor Li Xuesong opened his mailbox full of doubts and saw an unread email.

Good guy, one minute ago?

It's not that wechat has a message to remind you that ghost can't see your email!

He rolled his eyes and opened the e-mail, but Professor Li Xuesong, who saw the contents, was stunned.

The text has only a string of characters with unknown meaning -- 0x5f375a86

”Is this a hexadecimal number?” Touching his chin, Professor Li Xuesong's face was filled with expressions of interest, ”is there any mystery about this number?”

Every time Liu Shoufeng, an old man, calls him, there are only two things, either to show off or to share the latest discovery. As usual, he could see some clues, but after watching this number for a long time, he even quietly changed the decimal system and binary system in his heart, and didn't feel anything different.

Professor Liu Shoufeng on the other end of the phone laughed: ”sure enough, even you can't see what's special about this number!”

”You old man, don't be so fussy. If you have a fart, let it go at once. If it's OK, I'll hang up!” Professor Li Xuesong said with a smile.

”Hang up? Then you will regret it! I'm not bullshit with you. Do you remember the Newton Raphson method? ”

”Nonsense, who can't remember that!”

Newton Raphson method, which was put forward by Newton in the 17th century, is a method of approximate solving equations in real number field and complex number field. Although these people who study pure mathematics rarely use this method, this method is widely used in the field of computer.

For example, if you want to calculate the value of √ 2, you can guess a number casually, for example, 4. There is no doubt that √ 2 cannot be equal to 4, but as long as you use Newton's iterative method to iterate continuously, after n steps of iterative operation, you can always calculate 1.414. And if you use 2 as a guess, because 2 is close enough to 1.414, you only need two iterations to figure it out.

Li Xuesong remembers that he seemed to have talked about this piece of knowledge more than once in class with computer majors, but he really didn't know what to dig into.

Professor Liu Shoufeng: ”I just sent you an email. There is an algorithm that has been translated into mathematical language. You can see why I am so surprised at this number after reading it.”

Hearing this, Professor Li Xuesong couldn't help rolling his eyes, but he couldn't resist his curiosity and opened the next email as he said.

The whole algorithm itself is not difficult, but just find the reciprocal of the square root. Professor Li Xuesong even felt that even if he did not translate it into the language of mathematics, he could fully understand it.

In short, the 0x5f375a86 is a constant used to calculate the guess value.

Because using Newton iterative algorithm to find the reciprocal of square root first needs a guess value, which is usually determined by a series of calculations according to the user's input value.