novelslam Chapter 51 Lu Feng's European and American Fighting Style
Chapter 51 Lu Feng's European and American Fighting Style
The following evening, in computer room 301 of the computer center.
When Lu Feng pushed open the soundproof door, the six people had already arrived.
Beside the long table, Li Hao was leaning back in his chair scrolling through his phone, while Wang Zhe and Liu Yu were huddled in front of a computer looking at something, occasionally letting out a few low laughs.
Chen Jing and Zhou Xiaoxiao sat at the other end, with several printed copies of past competition questions spread out in front of them, and the two were discussing something in hushed tones.
Hearing the door open, everyone turned around at the same time.
"Your junior is here?" Chen Jing greeted him first. "Have you eaten yet?"
"I've eaten." Lu Feng pulled out a chair, sat down, and stuffed his schoolbag into the drawer.
"All three teachers have something to do tonight and won't be coming." Chen Jing put her phone back in her pocket and patted the competition questions on the table. "Teacher Ye sent a message saying that we should practice as usual, using last year's provincial competition questions."
She took out the top portion and handed it to Lu Feng.
Lu Feng took it and glanced at it.
"A manufacturing company has three production lines. The product qualification rate of each production line is affected by three variables: temperature, humidity, and equipment aging. Production data from the past two years, including daily output, real-time monitoring values of each variable, and quality inspection results, are available. Please build a mathematical model to develop the optimal production scheduling strategy for this company, minimizing the total defect rate while meeting order demands."
A typical hybrid problem of multiple regression and linear programming.
Chen Jing spoke first.
"My idea is to first use principal component analysis to reduce the dimensionality of the three influencing factors, extract the one or two most critical principal components, and then construct a nonlinear programming model with the defect rate as the objective function."
As she spoke, she drew a framework diagram on a draft paper.
"Wait a minute." Zhou Xiaoxiao leaned closer, adjusted her glasses, and said, "Shouldn't we do a multicollinearity test before dimensionality reduction? If there's a high correlation between temperature and humidity, direct dimensionality reduction will lose information."
"Yes, so we need to add a step to calculate the variance inflation factor." Chen Jing nodded and added another branch to the framework diagram.
The two of them talked back and forth for about five minutes, and the framework diagram was already covered with dense arrows and boxes, dragging out the process by seven or eight steps.
Lu Feng remained silent, quietly watching the increasingly complex framework drawing.
Chen Jing noticed his silence and looked up.
"Junior, what do you think of this approach?"
Lu Feng put down the competition questions in his hand and pointed to the colorful flowchart.
"Isn't it unnecessary to make things so complicated?"
Chen Jing's hand froze in mid-air.
"Build a multiple linear regression model to fit the relationship between the pass rate and the three variables, and estimate the parameters using the least squares method." Lu Feng took her pen and wrote a matrix equation on a blank draft paper.
"After the fitting is complete, the regression equation is used as a constraint and put into a standard linear programming model. The objective function is the sum of the weighted defect rates of the three production lines."
"Using the simplex method, you can get the result in three steps."
He spoke casually, as if reciting a takeout menu.
Chen Jing stared at the matrix equation for three seconds, then opened her mouth.
"But...the problem of multicollinearity..."
"With enough data, ridge regression with a regularization term can keep it under control; there's no need for dimensionality reduction." Lu Feng had already started writing down the regression equations on the draft paper.
Zhou Xiaoxiao leaned close to Chen Jing's ear and whispered, "Aren't we making a fool of ourselves?"
Chen Jing gave a wry smile.
What others could solve in three steps, they went around in circles for eight steps and still hadn't gotten to the point.
It's like someone else using a needle to embroider, while he just uses a submachine gun—brutal but effective.
The European and American style of play is simple and direct.
Lu Feng writes very quickly.
The transpose of a matrix, the calculation of its inverse, and the expressions for parameter estimates are laid out line by line.
In less than fifteen minutes, a complete mathematical model was presented on the draft paper.
From the multiple regression equation to the standard form of linear programming, and then to the proof of the existence of the optimal solution, the logic is interconnected, with no unnecessary steps.
Chen Jing picked up the draft paper, looked at it twice, and her expression changed from surprise to resignation.
She turned to look at Zhou Xiaoxiao, who was equally stunned, and the two locked eyes.
"How about... we both take turns being his assistants from now on?" Chen Jing's voice carried a sense of relief after being crushed by reality.
Zhou Xiaoxiao nodded vigorously.
Lu Feng ignored their self-abandonment, organized the formulas and algorithm ideas he had written, tore off the few pages of draft paper, and got up to walk over to the programming group.
"Senior Li Hao, this is the result of the modeling. The regression parameters and the planning model are all on it. You can write the code based on this."
Li Hao took the draft paper and huddled together with Wang Zhe and Liu Yu to study it.
Lu Feng returned to his seat and had just sat down.
"Junior, sir~"
Chen Jing had moved to his left at some point, holding a copy of last year's national competition questions.
"How should the boundary conditions be set for the differential equations in this SIR model of infectious diseases? I feel that the method for estimating the initial number of infections is not quite right."
Just as Lu Feng was about to speak, another head popped out from the right.
"Junior, junior, I also have a question!" Zhou Xiaoxiao held up her draft paper. "How do you determine the sign of the Lagrange multipliers in this convex optimization KKT condition?"
The two people stood on either side of each other, like two woodpeckers, pecking here and there.
Lu Feng's lips twitched.
You two are quite talkative.
He took a deep breath, answered Chen Jing's question first, and then turned to deal with Zhou Xiaoxiao's question.
Just after she finished speaking, Chen Jing asked another question about the details of parameter sensitivity analysis.
Lu Feng felt like he wasn't in a training camp, but rather in a Q&A session.
While the two were engrossed in processing what he had just said, Lu Feng took out his phone to clear his messages.
The moment the screen lit up, a bank text message popped up.
"Your account ending in 3847 received a transfer of 5000.00 yuan on October XX, leaving a balance of 6247.32 yuan."
The prize money has arrived.
He scrolled down to the next one.
"Your account ending in 3847 received a transfer of 600.00 yuan on October XX, leaving a balance of 6847.32 yuan."
The stipends for Li Hongde's group were also transferred over.
Lu Feng switched to QQ, and the group chat for Lab 302 was flooded with messages.
Li Hongde: "Have you all received the money?"
Zhou Mingyuan posted a meme of a tough guy crying.
Zhao Pengfei: "Received it, teacher!"
Sun Hao simply posted a screenshot of his bank balance with the caption: "Finally, I don't have to eat steamed buns for a month anymore."
Zhou Mingyuan sent another dog emoji: "Teacher's kindness is immense, I will never forget it."
Seeing the lively chatter in the group, Lu Feng casually added a thank-you emoji to his message to the boss.
Six thousand eight.
Six thousand eight hundred yuan in 2012.
He silently calculated that he would keep two thousand yuan for living expenses and books this month, and transfer the rest to his parents.
Four thousand eight hundred yuan is enough to make the old couple happy for a while.
Lu Feng exited QQ, opened his mobile banking app, and entered his mother's bank card number.
Transfer amount: 4800 yuan.
Note: Mom, it's getting cold. Dad and I should buy two thick coats.
Click to confirm.
Before the notification sound of a successful transfer had even faded, a commotion suddenly broke out in the programming group.
"Another error!" Wang Zhe slammed his hand on the table.
"Which module?" Li Hao leaned closer.
"After substituting the regression parameters, the dimensions of the constraint matrix of the planning model did not match, and the program crashed directly."
Liu Yu pushed up his glasses, his forehead covered in sweat as he stared at the glaring red error message on the screen.
Three third-year computer science students, the main programmers, sat around a computer, their faces increasingly grim.
Lu Feng shifted his gaze from his phone screen to the three disheveled figures on the other side.
He didn't go over immediately.
Instead, he leaned back in his chair and watched quietly for five seconds.
Then he stood up, put his phone back in his pocket, and walked towards the programming group.
"let me see."