多级反馈队列调度算法C++
时间: 2023-07-10 20:35:29 浏览: 42
以下是多级反馈队列调度算法的C++实现:
```cpp
#include<iostream>
#include<queue>
using namespace std;
struct Process {
int pid;
int arrival_time;
int burst_time;
int priority;
int remaining_time;
};
int main() {
int n;
cout << "Enter the number of processes: ";
cin >> n;
queue<Process> q1, q2, q3;
// Input the process details
for(int i=0; i<n; i++) {
Process p;
cout << "Enter the arrival time for process " << i+1 << ": ";
cin >> p.arrival_time;
cout << "Enter the burst time for process " << i+1 << ": ";
cin >> p.burst_time;
cout << "Enter the priority for process " << i+1 << ": ";
cin >> p.priority;
p.pid = i+1;
p.remaining_time = p.burst_time;
q1.push(p);
}
int time = 0;
queue<int> completed_processes;
while(true) {
if(q1.empty() && q2.empty() && q3.empty()) break;
// Check if any process in queue 1 can be executed
if(!q1.empty()) {
Process p = q1.front();
if(p.arrival_time <= time) {
cout << "Process " << p.pid << " executing in queue 1 at time " << time << endl;
p.remaining_time--;
time++;
if(p.remaining_time == 0) {
completed_processes.push(p.pid);
q1.pop();
}
else q2.push(p);
}
else time++;
}
// Check if any process in queue 2 can be executed
else if(!q2.empty()) {
Process p = q2.front();
cout << "Process " << p.pid << " executing in queue 2 at time " << time << endl;
p.remaining_time--;
time++;
if(p.remaining_time == 0) {
completed_processes.push(p.pid);
q2.pop();
}
else q3.push(p);
}
// Check if any process in queue 3 can be executed
else {
Process p = q3.front();
cout << "Process " << p.pid << " executing in queue 3 at time " << time << endl;
p.remaining_time--;
time++;
if(p.remaining_time == 0) {
completed_processes.push(p.pid);
q3.pop();
}
// Demote the process to queue 2 after 5 time units
else if(time-p.arrival_time >= 5) {
q3.pop();
p.priority++;
p.remaining_time = p.burst_time;
q2.push(p);
}
}
}
cout << endl << "The order of process execution is: ";
while(!completed_processes.empty()) {
cout << completed_processes.front() << " ";
completed_processes.pop();
}
cout << endl;
return 0;
}
```
在此实现中,有三个队列,分别代表三个级别的优先级。当一个新进程到达时,它会被插入到队列1中。进程从队列1开始执行,如果它的剩余时间为0,则从队列中删除。否则,它被移到队列2中。在队列2中,进程以相同的方式执行,但是如果它在队列2中等待超过5个时间单位,则它会被降级到队列3中。在队列3中,进程以相同的方式执行,但是如果它在队列3中等待超过5个时间单位,则它会被再次降级到队列2中。当所有进程都完成执行时,它们的顺序将被打印出来。
注意:此实现中没有考虑上下文切换开销和时间片大小等因素,这些因素可能对算法的性能产生影响。
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