..processes[i].remaining_time = processes[i].burst_time; total_burst_time += processes[i].burst_time;是什么意思

这段代码是一个进程调度算法中的一部分，用于初始化进程的剩余执行时间和计算所有进程的总执行时间。

首先，进程调度算法需要知道每个进程的执行时间，这里的 `processes[i].burst_time` 表示第 i 个进程的执行时间。然后，为了方便管理和调度，算法需要知道每个进程还剩下多少时间才能完成，这里的 `processes[i].remaining_time` 初始值设为进程的执行时间。

接下来，`total_burst_time` 变量初始化为所有进程的执行时间之和，用于后续算法的计算和调度。

相关问题

请设计一个程序1、 Simulate the operation of the round-robin algorithm for process scheduling. 2、 Create at least 15 processes and output their scheduling situation under the scheduling algorithm mentioned above and output it to the terminal to check the execution of the algorithm. 3、 The output should include the arrival time of the processes, the end time, and the average execution time.

好的，这是一个实现轮转调度算法的Python程序示例：

class Process:
    def __init__(self, pid, arrival_time, burst_time):
        self.pid = pid
        self.arrival_time = arrival_time
        self.burst_time = burst_time
        self.remaining_time = burst_time

    def execute(self, time_slice):
        if self.remaining_time > time_slice:
            self.remaining_time -= time_slice
            return time_slice
        else:
            time_executed = self.remaining_time
            self.remaining_time = 0
            return time_executed

    def is_finished(self):
        return self.remaining_time == 0


def round_robin(processes, time_slice):
    current_time = 0
    total_waiting_time = 0
    total_turnaround_time = 0
    num_processes = len(processes)

    while True:
        all_finished = True
        for p in processes:
            if p.arrival_time <= current_time and not p.is_finished():
                all_finished = False
                time_executed = p.execute(time_slice)
                current_time += time_executed
                if p.is_finished():
                    p.end_time = current_time
                    p.waiting_time = p.end_time - p.burst_time - p.arrival_time
                    p.turnaround_time = p.end_time - p.arrival_time
                    total_waiting_time += p.waiting_time
                    total_turnaround_time += p.turnaround_time

        if all_finished:
            break

    average_waiting_time = total_waiting_time / num_processes
    average_turnaround_time = total_turnaround_time / num_processes

    return processes, average_waiting_time, average_turnaround_time


if __name__ == '__main__':
    processes = [
        Process(1, 0, 8),
        Process(2, 0, 4),
        Process(3, 0, 9),
        Process(4, 0, 5),
        Process(5, 0, 2),
        Process(6, 0, 4),
        Process(7, 0, 3),
        Process(8, 0, 7),
        Process(9, 0, 6),
        Process(10, 0, 1),
        Process(11, 0, 5),
        Process(12, 0, 3),
        Process(13, 0, 2),
        Process(14, 0, 6),
        Process(15, 0, 4),
    ]

    time_slice = 3

    processes, avg_waiting_time, avg_turnaround_time = round_robin(processes, time_slice)

    print("Process\tArrival Time\tBurst Time\tEnd Time\tWaiting Time\tTurnaround Time")
    for p in processes:
        print(f"{p.pid}\t\t{p.arrival_time}\t\t{p.burst_time}\t\t{p.end_time}\t\t{p.waiting_time}\t\t{p.turnaround_time}")

    print(f"Average waiting time: {avg_waiting_time}")
    print(f"Average turnaround time: {avg_turnaround_time}")

这个程序把15个进程作为参数传入，并且使用了3个时间片进行轮转调度。程序的输出将会包含每个进程的到达时间、结束时间、等待时间和周转时间，以及平均等待时间和周转时间。

注意：这只是一个简单的示例程序，真实的应用程序需要更加复杂的调度算法和更多的进程属性。同时，使用轮转调度算法需要注意时间片大小的选择，如果时间片太小，会增加上下文切换的开销；如果时间片太大，会增加进程等待时间。

round_robin c++实现

Round-robin（轮流调度）是一种常见的 CPU 调度算法，它按照时间片轮流分配 CPU 时间给每个进程。下面是一个简单的 C++ 实现：

#include <iostream>
#include <queue>
using namespace std;

struct Process {
    string name;
    int burst_time;
    int remaining_time;
};

void round_robin(vector<Process>& processes, int time_quantum) {
    int n = processes.size();
    queue<Process> q;
    int current_time = 0;
    int total_waiting_time = 0;
    int total_turnaround_time = 0;
    int completed_processes = 0;

    for (int i = 0; i < n; i++) {
        processes[i].remaining_time = processes[i].burst_time;
    }

    q.push(processes[0]);
    int i = 1;

    while (completed_processes < n) {
        Process p = q.front();
        q.pop();

        if (p.remaining_time > time_quantum) {
            p.remaining_time -= time_quantum;
            current_time += time_quantum;
        } else {
            current_time += p.remaining_time;
            p.remaining_time = 0;
            completed_processes++;
            total_waiting_time += current_time - p.burst_time;
            total_turnaround_time += current_time;
        }

        while (i < n && processes[i].burst_time <= current_time) {
            q.push(processes[i]);
            i++;
        }

        if (p.remaining_time > 0) {
            q.push(p);
        }
    }

    cout << "Average waiting time: " << (double)total_waiting_time / n << endl;
    cout << "Average turnaround time: " << (double)total_turnaround_time / n << endl;
}

int main() {
    vector<Process> processes = {{"P1", 10}, {"P2", 5}, {"P3", 8}, {"P4", 7}};
    int time_quantum = 2;
    round_robin(processes, time_quantum);
    return 0;
}

在上面的代码中，我们定义了一个 Process 结构体来保存进程的名称和执行时间。round_robin 函数接受一个包含所有进程的 vector 和时间片大小 time_quantum 作为输入，并输出平均等待时间和平均周转时间。在函数中，我们首先初始化每个进程的 remaining_time 为其 burst_time。然后，我们将第一个进程加入队列中，并从队列中取出进程进行执行。如果进程的 remaining_time 大于时间片大小，则将其 remaining_time 减去时间片大小并将其放回队列中。否则，我们将进程的 remaining_time 设为 0，记录完成进程数量、等待时间和周转时间，并将其从队列中删除。接着，我们将所有已到达但未执行的进程加入队列中，然后将队列中的下一个进程取出进行执行。最后，我们输出平均等待时间和平均周转时间。