Chapter 78

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

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

"Now let's ask CAI to answer."

He blushed and stumbled for a long time: "I'm sorry, I haven't studied this field deeply... Recursive neural network is an artificial neural network with tree hierarchical structure and network nodes recurs the input information according to its connection order. It is one of the deep learning algorithms."

Reluctantly recited some definitions, which really couldn't be fooled. Cai said, "I'm sorry, I don't have a particularly good idea for the time being."

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

He looked up at Zhang Yuan.

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

"Next, please answer Mr. Zhang."

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

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

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

Zhang Yuan thought about it and said, "I haven't studied your research field in depth, just 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, whether the activation function of neurons is monotonic, or whether it is locally monotonic."

"Second, by studying the condition that the energy function becomes a convex function, the operation of Hopfield network is regarded as a constrained convex optimization problem, so as to try to demonstrate whether there is a sufficient condition for the global unique minimum..."

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

This time, when it came to the questioner's heart, he asked several questions about convex optimization and exchanged mathematics on the spot.

Finally, under the guidance of the host, Zhang Yuan had to say: "if necessary, you can talk to me at the back of the stage about the knowledge of convex optimization. I won't explain it in detail here..."

Many things he just talks nonsense according to his usual accumulation. If he can really write a paper according to his own circumstances, he doesn't have to go on stage and just be the "paper God".

There has been a lot of applause from below.

In such a short period of time, the high court made a judgment.

Cai Kun wanted to find a crack in the ground.

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

The host asked again, "666, please say your question."

The questioner is a girl. Her question is relatively pragmatic and less eccentric: "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 period with small data demand, use spare communication resources to place data in each user's cache device. The second is the data distribution stage. It is assumed that during the peak period of data demand, each user randomly requests a complete file from the server. The server comprehensively considers these needs and distributes complete data to meet the needs of all users. "

"My question is, how to design the caching scheme most scientifically?"

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, "well, please think for three minutes."

The microphone was handed over to Zhang Yuan.

He smiled and said, "I think... I'd better give the opportunity to Cai Kun first. I'm afraid he won't say anything after I say it. "

The people at the bottom laughed and whistled again.

Some believe it, others don't.

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

"... I have an idea that each user caches the Mn proportion data of each file respectively, and in the data distribution stage, the server will distribute the data of each (1-mn) part missing by each user one by one. At this time, the value of the transmitted data is r = K (1-mn)..."

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

"You have a point."

Although he said so, the questioner was slightly disappointed. Coding caching can be said to be the most ordinary idea. There have been mature algorithms for a long time, and there is no research significance. If you take this bad idea to start a project, it is estimated that you will be slapped back by your tutor.

Then 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 decode the required part of the information from a single message at the same time, so as to obtain the global cache gain."

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

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

The host was stunned, "yes."

Zhang Yuan drew some pictures on the screen.

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

"Obviously, whether the number of file partitions can be transformed into polynomial level, that is, to reach the level available in industry, depends entirely on whether hypergraph problems satisfying some characteristics can be constructed mathematically. These characteristics are as follows..."

"I think I can write a good paper after converting it into a mathematical problem. As for what the answer is, I certainly can't answer it now. It's just an idea. The student has to think about how to solve this graph theory problem. "

There was a whisper below.

There are still many professionals among the melon eaters here. They naturally have their own way of distinguishing whether they are talking nonsense or not.

make love!

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

Applause thundered below.

Cai Kun had no face to continue to stay. His face flushed and he nodded in a hurry to admit defeat.

He finally knew that he scored 100 points on the same 100 point test paper because of his strength, while others scored 100 points because there were only 100 points on the paper.

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

"Yes..."

"It seems that the loser is not wronged."