Ending the exchange with Gao Fei, Ye Fei read other people's posts again.

By night, the mission progress will reach 60%.

Ye Fei thought to himself: "Is my task set up simply?" In most of the day, the mission progress reaches 60%. ”

"Do you want to set the task to enter the SCI Zone 1?"

"......" Ye Fei was taken aback by this terrible thought, what do you want, enter the SCI area 1?

With his current ability, he will have to go through a long period of study before he can enter the second district.

Zhuang Nanshou left the computer and said with a gossipy face: "Ye Fei, do you know why the tutor let your paper enter the CSCDA area?" ”

"Why?"

"Do you still remember my supervisor's opponent, Professor Li Jiguo, I heard that one of his first-year students had a paper that entered the CSCDA area not long ago."

Professor Li Jiguo is also from the Department of Mathematics, and he and Professor Lu Yishan once competed for the provincial scientific research fund, both of them wanted to do scientific research and needed scientific research funds.

However, Professor Li Jiguo's competition failed, which led to the postponement of Professor Li Jiguo's scientific research, and later competed with Professor Lu Yishan for full professorship.

Because of the delay in scientific research, his scientific research was not completed at that time, which led to the failure of the competition for full professorship.

This came and went, and the two of them were married.

"In addition, you are the only one of us who has come up from the research institute, and the mentor usually has high requirements for you, so naturally this glorious task will be handed over to you." Zhuang Nan said with a smile.

"I said why did the tutor make my thesis enter Area A!" Ye Fei shook his head and said.

Ye Fei didn't doubt Zhuang Nan's intelligence, Zhuang Nan was known as a little intelligence expert, and he could inquire about the big and small things in the school, as long as he was given half a day.

"Isn't it sad?" Zhuang Nan smiled: "It is a disaster that falls into the unjustified." ”

"Not really." Ye Fei said: "Area A is Area A, let's not be unable to enter." ”

Zhou Lin and Xu Tian walked in together with smiles on their faces and talked to each other about their girlfriends.

Zhou Lin said: "Women, spending money is not just beckoning." ”

"Cut ......" Xu Tiandao: "Are those women the ones who have a crush on you, are they fancys to your money, do you have to be careful about getting a girlfriend, women care about the details." ”

Zhou Lin said disdainfully: "Are you going to be distracted, you are going to be kidneys." ”

Ye Fei and Zhuang Nan looked at the two people who walked in together, and scolded in their hearts: "Two scumbags, I don't know how many girlfriends to play." ”

Ye Fei is very strange sometimes, he looks very good-looking, but he is still a novice, 100% new.

In terms of appearance, the entire dormitory itself is the highest.

Forget about Zhou Lin, the rich second generation is like a fish in water in the love field.

But Xu Tian, an ordinary family, is not tall or handsome, and is a little dark, but with a mouth that can tell the dead to live, his ex-girlfriend has a row.

In the end, Ye Fei concluded, no wonder there are few girls in science, women are too irrational, and they can't find the southeast and northwest if they are sweetly talked.

The next day, more than 30 people were in class.

A professor in his forties was speaking from the podium about the scalability of linear functional functions in Banach space in the Hahn-Banach theorem of functional analysis.

This also belongs to set theory, which is the axiom of choice among the five axioms of set theory.

If the continuum hypothesis is proven, then there are six axioms.

This is a very profound science.

Although everyone had a preview in advance, no one in the class could understand 100% of the time, so everyone was painstakingly jot down what the professor said on the computer.

Wait until after class to review, if you still can't learn, you can find materials to study on your own, or ask your own tutor, or ask the seniors who have already learned.

There are more than 30 people in this class, but they are not graduate students under one supervisor, but graduate students under multiple supervisors gather together to take classes.

There are some things that are very different between graduate and undergraduate students.

Graduate students no longer say so-and-so class, but follow so-and-so tutor.

A tutor can bring one or two graduate students at least every year, and three or four at most, and in three years, he can bring three to twelve students.

The four of Ye Fei's dormitory followed the same tutor.

Zhuang Nan, who was sitting next to Ye Fei, asked quietly: "Ye Fei, seeing that you listen so carefully, how much do you understand?" ”

"I understand it all." Ye Feitou didn't reply.

In math class, you can't talk casually, you can't bow your head, you may say something, bow your head, and then look up to listen to the teacher's class, and you will be dumbfounded.

What is the teacher talking about?

How to solve it here?

...... I don't understand.

Zhuang Nan pouted and said, "You just blow it!" ”

Although Ye Fei came up from Baoyan, they have been together for nearly a year, and he still knows what level Ye Fei is.

Baoyan is only good at the undergraduate level, but not necessarily at the graduate level.

And with such a difficult course, can you understand them all?

A smile appeared at the corner of Ye Fei's mouth, he may not have understood it before, but with the blessing of the system, he really understood.

And the level of understanding is not 66.8%, nor 99.8%, but 100%.

The professor on the podium coughed lightly when he saw Ye Fei and Zhuang Nan talking.

College is not as strict as junior high school and high school, and as long as the influence in the classroom is not great, the professor will turn a blind eye.

But Zhuang Nan didn't seem to notice it, and said to Zhou Lin and Xu Tian beside him that Ye Fei could understand everything, and both of them showed disbelieving eyes.

The professor saw that Zhuang Nan was still talking, and everyone in the classroom was listening quietly, he was talking, and he was still smiling, and the nearby students were affected, which was unforgivable.

He pointed to Zhuang Nan and said, "This classmate, you stand up." ”

The classroom was silent for a moment, and everyone looked at Zhuang Nan.

Zhuang Nan looked around blankly, and when he saw everyone looking at him, he knew that he had angered the professor by speaking something, and he was a little panicked.

He stood up in a panic.

The professor asked, "What did you just say?" So excited. ”

Zhuang Nan lowered his head and said guiltily: "Professor, I'm sorry. ”

"Tell me, what you just said." The professor said.

"......" Zhuang Nan was silent, it didn't matter if he was punished himself, it would be bad if he affected the other three roommates, so he was silent.

Seeing that he didn't speak, the professor pointed at Ye Fei and said, "This classmate on the right, he was the first to talk to you, what did you say?" ”

Ye Fei stood up and said, "Professor, he asked me how much I understood, and I said I understood everything." ”

"You understand it all?" The professor asked, surprised.

He knows the difficulty of this course, and few of them can understand all of them after the first year of study, and they all learn it slowly after carefully reviewing and checking the information after the class.

Many people looked at Ye Fei in surprise.

Do you understand them all?

Don't brag about whether it's good or not.

The professor said amusedly: "Since you said that you understand everything, then you can tell me how to solve linear equations using the Krylov subspace method." ”

The professor felt that this was too difficult for a graduate student, and said, "Don't seek all the solutions, just give the general idea." ”

Ye Fei said: "Professor, can I go up?" It's hard to say, you have to write it. ”

Everyone looked at him in surprise, big brother, you are really on!

It's easy to go up, but it's hard to get down!

No one believed that Ye Fei could solve the professor's problem.

"Yes!" The professor nodded.

He didn't want to embarrass Ye Fei, but Ye Fei said that he understood everything, and he wanted to test it.

It's a good time to relieve the fatigue of long hours of class, and use it as a pastime!

It doesn't matter if you can't solve it, it's normal that you can't solve it, and if you solve it, it proves that the student really understands everything.

Ye Fei stepped forward, picked up the chalk, and faced everyone: "If you want to use the Krylov subspace to solve linear equations, you can first borrow the Hilbert space to preprocess the Krylov subspace and its convergence. ”

"Consider linear algebraic systems."

He took a chalk and wrote a set of equations on the blackboard.

【Ax=b】

“……”

"b∈R are known column vectors."

"That's the general idea I had in mind."

"Good!" The professor nodded with satisfaction: "It seems that you have indeed understood everything, and the idea of solving the problem is very correct." ”

Everyone was surprised, this really understood everything, don't blind the cat and run into a dead mouse, you just happen to know where the professor said!

Ye Feidao: "In fact, if you want to solve a linear algebra system, you can solve it like this. ”

Ye Fei found that he had just come up to solve the problem, and the progress of the task had improved a little.

In that case, let's solve some more problems and improve the progress of the task.

"Do you still have a way?" The professor was stunned.

"Yes!" Ye Fei nodded: "For solving linear algebra systems, you can also use the projection algorithm of the Krylov subspace method. ”

"Do you know the projection algorithm?" The professor was surprised.

This method is considered over-the-top, and he has not taught it in class.

Moreover, projection algorithms are not something that you learn in the first year of study, and you can only learn it in the third year of research.

"I've read it in a paper before." Ye Fei said: "So I learned it." ”

"Then you use the projection algorithm to see."

Ye Fei turned around and wrote on the blackboard.

[Let the initial solution be x, then the corresponding initial residual is r=b-ax, which we call the formula.]

K(A，r)=span{r，ArA^2r，... Ar}

……

Here L is another m-latitude subspace, which is called the constrained subspace. 】

The classroom looked at what Ye Fei wrote happily and said approvingly: "Very good, very good, completely correct." ”

"Classmate, what's your name? Which professor's graduate students? ”

There are so many people in class, and such a class is only once every half a month, so the professor doesn't know all the students present.

"My name is Ye Fei, and my tutor is Professor Lu Yishan."

"It turned out to be a student of Professor Lu Yishan, no wonder." The professor nodded and said, "Ye Fei, I remember you." ”

The students below looked at what Ye Fei wrote and were dumbfounded.

...... I don't understand.

When did we have such a great person in basic mathematics major?

Aren't you a researcher?

Are we in the same graduate school?

Zhuang Nan and the two roommates looked at each other in surprise, Ye Fei, when did you become so powerful?

"Okay, you can go down." The professor said, "Sit down and stop talking, or I'll tell you to stand up." ”

"You also study with the classmate next to you, study hard."

Zhuang Nan listened very heartily, who didn't study hard? I studied hard, but Ye Fei didn't know how today, it seemed to be open.

After class, Zhuang Nan and the three of them surrounded Ye Fei, looked at him with fierce eyes, and said, "Ye Fei, say, did you study secretly?" ”

"Not really!" Ye Fei shook his head: "I just read the literature that my tutor usually asks me to read, and he also recommends you to read it, you don't blame anyone." ”

"Really?" Zhuang Nan and the three of them were suspicious, glanced at each other, and said in their hearts: "No, I will also have to read the literature recommended by my mentor from today." ”

"Let's go!" Ye Fei walked forward: "There is still a class below!" ”