Chapter 74

"Ask the two players to think for three minutes."

Soon, three minutes later, the host handed the microphone to Cai Kun.

"Next, let's invite CAI to answer."

He blushed and stuttered for a long time: "I'm sorry, I haven't studied this field in depth Recurrent neural network (RNN) is an artificial neural network with tree hierarchical structure and its nodes recurse the input information according to their connection order. It is one of the deep learning algorithms

After reluctantly reciting some definitions, Cai said, "I'm sorry, I don't have any special ideas for the time being."

A burst of boos came from below. Although Cai blushed, he still stood on the stage with a stiff head.

He looked up at Zhang Yuan.

It depends on what you can answer. If you can't answer anything, why do you have higher interview scores than me?

"Next, let's welcome Mr. Zhang to answer."

"I have a question." Zhang Yuan raised his hand, "I've heard of Hopfield network, but what is network stability?"

The questioner laughed: "if some weights of the network can converge to the equilibrium point, which is called weight convergence, then the output can fit the expected output, which is called system stability. Therefore, convergence is for variables and stability is for systems."

"The stability of the system can not be guaranteed, the control system is unstable, and the convergence of the network has lost its foundation."

Zhang Yuan pondered for a while and said, "I have not studied your research field in depth, but I have read some papers. But I have some simple ideas that you can listen to. "

“…… The first is the monotonicity problem. In the Hopfield network model of discrete-time continuous state, when the activation function of neurons is monotone or locally monotone, we find that the activation function of neurons is monotone

"The second is to study the condition that the energy function becomes convex function, and regard the operation of Hopfield network as a constrained convex optimization problem, so as to try to prove whether there is a sufficient condition for a globally unique minimum..."

"Convex optimization, you are right! Convex optimization is exactly what I'm doing. I have another problem... "

This time, he talked about the heart of the questioner. He also asked some questions about convex optimization, and exchanged mathematics on the spot.

Finally, under the direction of the host, Zhang Yuan had no choice but to say: "if you need the knowledge about convex optimization, you can ask me to discuss it behind the stage, but I won't explain it in detail here..."

A lot of things he just talks nonsense according to his usual accumulation. If he can write a thesis according to circumstances, he doesn't have to go on stage to be the "thesis God".

There has been a round of applause from below.

In such a short period of time, the Supreme Court ruled.

Cai Kun wanted to find a crack in the ground.

He can only blush and cheer himself up secretly. Maybe it's because of the difference caused by too few samples. He just meets the problem that he won't and the other party will.

The host asked, "666, please tell me your question."

The questioner is a girl, her question is relatively pragmatic, not so partial: "I want to ask a question about caching in the server."

"Caching is divided into two stages: one is the data placement stage. In the idle time when the data demand is small, the spare communication resources are used to place data in each user's caching device. The second is the data distribution stage. It is assumed that in the peak period of data demand, each user randomly requests a complete file from the server. The server considers these needs comprehensively and distributes complete data to meet the needs of all users. "

"My question is, how to design caching scheme in the most scientific way?"

The questioner even sent a PPT to the screen.

This question is very professional, but everyone can understand what is being asked.

The host said, "OK, everyone, please think for three minutes."

The microphone was handed to Zhang Yuan.

He said with a smile, "I think Let's give Cai Kun the chance first. I'm afraid after I say it, he won't be able to say it. "

There was another burst of laughter and whistles from the people below.

Some believe it, others don't.

Cai Kun was stunned. This time, he still had some ideas, but Zhang Yuan, who was opposite, seemed unable to say anything. He needed more time to think.

“…… I have such an idea that each user caches the M / N ratio data of each file separately, and in the data distribution stage, the server releases the data of each (1-m / N) part missing by each user one by one. At this time, the value of the transmitted data is r = K (1-m / N)... "

"I don't know if you've ever heard of a scheme called encoding cache. The specific algorithm is like this..."

"You have a point."

Although the questioner was slightly disappointed by what he said, coding cache is the most common idea. There has been a mature algorithm for a long time, and there is no research significance. If you take this bad idea to start a project, you will be slapped back by the tutor.Next it was Zhang Yuan's turn. He cleared his throat.

"Cai Kun's idea is very good. In the distribution stage, we use the relationship between the existing cache information to design a certain coding combination of the required broadcast content, so that multiple users can simultaneously decode the required information from a single message, so as to obtain the global cache gain."

"However, the limitation is that each file should be divided into a parameter that increases exponentially with the number of users K. as we all know, it is difficult to realize the partition of exponential level in algorithm..."

"May I borrow your digital pen and the big screen?"

Host Leng for a while, "can."

Zhang Yuan drew some pictures on the screen.

“…… In essence, it is a combinatorial graph theory problem. What we want to get is a cache scheme when f is a polynomial level of K and R is a constant level. Or to prove the existence of such a scheme. "

"Obviously, whether the file partition number can be transformed into polynomial level, that is, to reach the industrial level, depends entirely on whether the hypergraph problem satisfying some characteristics can be constructed mathematically. These characteristics are like this..."

"I think I can write a good paper after turning it into a mathematical problem. As for the answer, I can't answer it now. It's just an idea. How to solve the problem of graph theory, this student has to think about it by himself

There was a whisper below.

There are still many professionals among the melon eaters here. Naturally, they have their own opinions on whether they are talking nonsense or not.

Pa Pa!

A few minutes later, the questioner took the lead in clapping.

There was a lot of applause.

Cai Kun has no face to continue to stay. He blushes and nods in a hurry to admit defeat.

He finally knew that he got 100 points because of his strength, while others got 100 points because there was only 100 points on the paper.

"Lao Cai, you've met a real pervert!"

"Yes..."

"It doesn't seem to be wrong to lose."