MTL - The Science Fiction World of Xueba-Chapter 445 One man

Lunch was served in Warwick's canteen.

Although Warwick is not large in scale, the treatment of employees is really nothing.

Especially in this era, Warwick's cafeteria is full of meat, eggs, milk, fruits and vegetables, although the taste is not particularly good, but the nutrition is absolutely balanced.

After dinner, everyone rested for another hour, and then returned to the conference room to continue the explanation.

With the preparation in the morning, the explanation in the afternoon is even more familiar.

"Next, let's talk about the design of the program-controlled switching software for 2,000 digital program-controlled switches and some algorithmic features."

"The basic task of the program-controlled switch exchange software is to control the operation of the switch, that is, to complete the call processing. The characteristics of the program-controlled switch are large business volume, high real-time and reliability requirements, so it also requires high implementation efficiency for the running software. To be able to handle a large number of calls, the uninterrupted nature of communication services must be guaranteed. "

"Because of this, the switching software must have three characteristics, real-time performance, multi-tasking concurrent execution, and high reliability."

"In a sense, the software system of a program-controlled switch is a collection of operating system and application software. The operating system is the interface between computer hardware and application software. It is a real-time multi-tasking operating system. Such an operating system requires Respond to and deal with random external occurrences in a timely manner. Although the time of occurrence cannot be predicted, it must be able to respond within a strict time limit when it occurs, even under heavy loads. "

"In addition, the operating system must support multi-tasking concurrent processing. Due to the multi-tasking concurrency, it will inevitably cause problems such as the mutual exclusion of tasks, communication, and resource sharing. Due to the control system of program-controlled switches, distributed Multi-processor architecture, so its operating system must also have the characteristics of network operating systems and distributed operating systems. "

"Because of the above reasons, the operating system of the program-controlled switch generally uses the priority-based preemptive scheduling algorithm for task scheduling."

"That is, every task in the system has a priority. At any time, the system kernel allocates CPU to the task with the highest priority in the waiting queue. Preemptive means that if the system kernel finds that the priority is higher than the currently running one, If the task has a higher priority, the current task exits the CPU, enters the waiting queue, and immediately switches to the execution of the task with a higher priority. When processing tasks of the same priority, a first-come-first-served or round-robin scheduling algorithm is used. "

"Of course, in the program-controlled exchange system, we can divide the different tasks into three types according to the urgency and real-time requirements, fault-level tasks, cycles and tasks and basic tasks."

"The fault-level task processing function has the highest priority. Periodic tasks refer to tasks that are started and executed periodically by a clock interrupt. The priority of a periodic-level task is lower than that of a fault-level task. Programs, user scan programs with a period of 100 milliseconds, etc. "

"As for the last basic-level task, because the real-time requirements for starting are not high, and the task can be appropriately delayed, the priority is the lowest."

"With regard to the scheduling and processing of tasks at different levels, we can set an interrupt to occur every 10 milliseconds. During the first 10 millisecond period, the processor has completed the periodic and basic tasks, and paused and waited for the arrival of the next terminal. In the second is a 10 millisecond cycle, the periodic task is executed first, and then the basic task is executed, but the basic task is interrupted as soon as it has not been completed. The third 10 millisecond cycle is entered. In the third is a millisecond cycle, Due to the failure, the periodic task is interrupted, and the fault record is transferred to process. After the fault record is processed, the periodic task can be executed ... "

Pang Xuelin's tone was unhurried, but the whole conference room scene was quiet and audible.

Xu Wenwei and Zheng Bao both showed shocking expressions on their faces.

Although while talking with Pang Xuelin about technology that day, Pang Xuelin had already demonstrated his ability in software algorithms, but Xu Wenwei was still a bit unbelievable.

This is not to say how profound Pang Xuelin said, but Xu Wei found that Pang Xuelin is explaining the design principle of the program-controlled switch software from a theoretical level.

If you want to do this, you must have a thorough understanding of the entire R & D process of the program-controlled switchboard, as well as the software and hardware systems.

At present, the R & D team of Huawei's program-controlled switches is actually a grass-roots team. Many people have no experience in the research and development of program-controlled switches at all. Many of them are based on foreign product instruction manuals.

Fortunately, the hardware part says that when opening similar products, there is always an intuitive reference.

The real problem is the software system. For the program-controlled switches of Alcatel and Ericsson, their software is strictly encrypted. There is no way to extract the source code without destroying their data structure.

Therefore, Huawei engineers can only design software step by step based on the hardware design plan and their own understanding of the program-controlled switch.

This makes it easy to step on mines throughout the development process.

Often this problem is solved and new problems arise.

From the establishment of the 2,000 digital program-controlled switches in the second half of 1991 to the present, the entire R & D team has a feeling of hard work.

Pang Xuelin just explained Gao Wujian's explanation, which solved the problem of the entire program-controlled switch software design system systematically from a theoretical level, so that those software engineers have a sense of seeing the cloud and having a clear mind.

Pang Xuelin didn't pay attention to everyone's reaction, smiled, and continued: "This is about the design of the operating system. Let's talk about the application software of the program-controlled switch."

"The application software of the program-controlled switch is mainly divided into the following three categories, first, call processing software, second OMA (operation and maintenance management) software, and third, database system."

"Call processing software is mainly responsible for the establishment and release of call links and the control of business processes. It specifically completes the following functions: detection and identification of various input signals on subscriber lines and trunks, management of call-related resources, call status of user data, and Numbers, etc. for analysis, routing, controlling call state transitions, controlling timing, tone delivery, and switching network connections. "

"OMA software is software for operation, maintenance, and management of program-controlled switches, which is used to ensure efficient, flexible, and reliable operation of the system. The main functions must include user data and local data operation and management tests, alarms, fault diagnosis and processing, and dynamic monitoring. , Traffic statistics, billing, overload control, and more. "

"As for the database system, the program-controlled switch will use and generate a large amount of data in the process of call processing and operation maintenance management. These data include system data, user data and office data. The system data is related to the hardware architecture and software programs of the switch. Does not change with the application environment of the exchange office. If different telephone exchanges use the same type of exchange system, their data is the same. The difference is user data and office data. The user data reflects the specific situation of the user. There are static users. The difference between data and dynamic user data ... "

...

After spending an entire afternoon, Pang Xuelin explained the overall design ideas of the entire program-controlled switch software to everyone.

It was not until six o'clock in the evening that the whole day's lecture was finished.

"Well, today's relevant content about the hardware design and software design of the program-controlled switch, the details of the latter will take some time to understand slowly, everyone has written down."

"Have it down."

The engineers in the conference room answered in succession.

Pang Xuelin laughed and said, "Okay, then tomorrow we will start the formal R & D process. But I have issued a military order with Ren Zongli. I completed the R & D of 2,000 program-controlled switches in one week and 10,000 program controls in one month. R & D of switches. So starting tomorrow, I hope that everyone can officially enter the R & D process, modify the design of our previous product from scratch, and strive to get 2,000 program-controlled switches in a week! "

"okay!"

"Mr. Pang, we are confident that we can complete the task with you."

"Rest assured, Mr. Pang, we will definitely let President Ren obediently spend this money!"

...

Everyone couldn't help laughing.

At this time, Ren Zhengfei brought Zheng Baoyong, Xu Wenwei, and Sun Yafang over.

"Mr. Pang, I didn't expect it. In one day, you let our research and development team come alive!"

Zheng Baoyong also exclaimed: "Yeah, this lecture today really made us feel like we're going to the cloud, and even myself, I have a lot of ideas out of thin air."

You should know that before that, because of the continuous twists and turns in the research and development process and the pressure of the company's capital chain, everyone was struggling, but there was nowhere to vent.

The arrival of Pang Xuelin was a timely rain, so that Warwick's R & D team saw hope for success.

Pang Xuelin smiled and was about to speak. At this moment, Li Yinan came over and was a little embarrassed. "Mr. Pang, can I ask you a question?"

In the afternoon, Li Yinan had clearly felt the gap between himself and Pang Xuelin. Therefore, when facing Pang Xuelin, his arrogance suddenly converged.

Pang Xuelin laughed: "What's wrong?"

Li Yinan said, "When you explained the common scheduling strategies of successful switches in the afternoon, you mentioned fixed-priority algorithms, circular selection methods, the lowest-priority method for recent trials, and first-come-served methods. There are some inherent disadvantages, such as Because high-priority tasks are executed first, when too many high-priority tasks need to be processed, low-priority tasks cannot be processed within the tolerance time, which affects the overall performance of the system. Therefore, a scheduling algorithm is needed. You can quickly change the task scheduling as the traffic volume fluctuates, so that the overall performance of the system is optimal and the service quality of the switch is the best. Do you already have an idea for this algorithm? "

"Oh, why do you think I already have ideas?"

Pang Xuelin smiled and looked at Li Yidao.

Li Yinan said: "Fixed priority algorithms, circular selection, etc. are sufficient when developing 2,000-gate program-controlled switches, but if you want to develop 10,000-gate program-controlled switches, you need a new algorithm. Since you Mr. Ren has been assured that the research and development of 10,000-gate program-controlled switches will be completed within one month, so I guess you must have a solution. "

Pang Xuelin, Ren Zhengfei and Xu Wenwei looked at each other and said with a smile: "General Ren, you Warwick are really talented."

He only showed Xu Wenwei and Ren Zhengfei the dispatching algorithm of the Wanmen switch, but he did not expect that Li Yinan had inferred that he had the scheduling algorithm of the Wanmen program-controlled switch based on his explanation in the afternoon.

At this time, Zheng Bao laughed: "Mr. Pang, this is Li Yinan, a new engineer in our company's R & D department. He previously had an internship at our Warwick. The young man has a solid technical foundation. I am preparing to entrust him with a heavy task."

Pang Xuelin nodded, and asked with a smile: "Li Gong, I do have some research and development ideas for the 10,000-gate program-controlled switch, but this must be based on our 2,000-door program-controlled switch development, so I hope you can I fully understood what I said about the 2,000-gate program-controlled switchboard in the afternoon, and then I will consider the development of the 10,000-gate program-controlled switchboard. "

Li Yinan said: "Mr. Pang, you can just call me Xiao Li. In addition, you have fully understood the technical route of the 2,000-gate program-controlled switchboard."

"Comprehensively understood?"

Pang Xuelin couldn't help but look at Li Yinan up and down.

Li Yinan seemed to be somewhat proud of Pang Xuelin's surprise, and said with a smile: "In fact, I had some ideas about the design of the 2,000-gate program-controlled switch, but your solution is much more mature and complete than my solution, but maybe With the previous foundation, it is not difficult for me to understand your ideas, but there are many places that give me a sense of complete realization. "

"Oh?!"

Pang Xuelin laughed and said, "Can you tell me some ideas about group processing in program-controlled exchange software technology?"

Li Yinan nodded and said, "In order to improve efficiency, in a software design, a group of objects should be logically processed and processed at the same time. We can call this method group reading at UU Kanshu www.uukanshu.com. Below I will use As an example, the user line on-hook scan is used to explain the basic method of group processing. Set the word length of the processor to 16 bits. Since each user can pick up the on-hook scan status, it can be represented by only one binary bit, so we can simultaneously A group of 16 users performs off-hook detection. During the group processing, checking the off-hook and on-hook users bit by bit is actually a bit-by-bit check. Which one of the calculation results is 1 ... "

Li Yinan is not ill, and he talks about what Pang Xuelin explained.

Pang Xuelin's expression of approval appeared on his face, and he smiled and said, "Yes, then you can talk about it, what is the sequential expansion method?"

Li Yinan thought for a while and said, "Serial expansion method, based on the organizational expansion analysis table, the table is a multi-level search table with a tree structure. Each level table corresponds to a number, that is, the first number is received. First level table, receive the second digit number, check the second level table, etc. Each cell in the table is composed of two parts: indicator bit and address field. The indicator bit is used to indicate that the address field stores the next level search. The first address of the table is also the address of the conclusion table. The former indicates that the analysis of the number of heads has not yet been performed, and the analysis of the number of heads must be continued. The latter indicates that the analysis of the number of heads is complete. , Receivable number length and routing information ... "

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