编写C程序模拟实现单处理机系统中的进程调度算法,实现对多个进程的调度模拟,要求采用短作业优先算法,进行模拟调度。
时间: 2023-09-24 11:11:27 浏览: 94
好的,短作业优先(SJF)算法是一种基于作业执行时间的调度算法,它优先选择执行时间最短的作业进行调度。下面是一个简单的短作业优先算法的实现样例:
```c
#include <stdio.h>
#include <stdlib.h>
#define MAX_PROCESSES 10
typedef struct Process {
int pid; // 进程ID
int priority; // 优先级
int burst; // 执行时间
int remaining; // 剩余执行时间
int arrival; // 到达时间
int waiting; // 等待时间
int turnaround; // 周转时间
} Process;
void sjf_schedule(Process processes[], int n) {
int current_time = 0;
int completed = 0;
int shortest_job = 0;
int shortest_job_remaining = 0;
int waiting_time = 0;
while (completed < n) {
// 选择执行时间最短的作业
shortest_job = -1;
shortest_job_remaining = INT_MAX;
for (int i = 0; i < n; i++) {
if (processes[i].arrival <= current_time && processes[i].remaining < shortest_job_remaining && processes[i].remaining > 0) {
shortest_job = i;
shortest_job_remaining = processes[i].remaining;
}
}
if (shortest_job == -1) {
current_time++;
}
else {
processes[shortest_job].remaining--;
current_time++;
if (processes[shortest_job].remaining == 0) {
completed++;
processes[shortest_job].turnaround = current_time - processes[shortest_job].arrival;
processes[shortest_job].waiting = processes[shortest_job].turnaround - processes[shortest_job].burst;
printf("Process %d: turnaround=%d, waiting=%d\n", processes[shortest_job].pid, processes[shortest_job].turnaround, processes[shortest_job].waiting);
waiting_time += processes[shortest_job].turnaround - processes[shortest_job].burst;
}
}
}
printf("Average waiting time: %f\n", (float)waiting_time / n);
}
int main() {
Process processes[] = {
{ .pid = 1, .priority = 3, .burst = 24, .remaining = 24, .arrival = 0 },
{ .pid = 2, .priority = 1, .burst = 3, .remaining = 3, .arrival = 0 },
{ .pid = 3, .priority = 2, .burst = 3, .remaining = 3, .arrival = 0 },
{ .pid = 4, .priority = 4, .burst = 5, .remaining = 5, .arrival = 0 },
};
int n = sizeof(processes) / sizeof(processes[0]);
sjf_schedule(processes, n);
return 0;
}
```
上面的代码实现了一个简单的短作业优先(SJF)算法,可以按照作业执行时间从短到长的顺序选择作业进行调度,并计算出其周转时间和等待时间。在实际的操作系统中,还需要考虑诸如进程切换、时间片等因素,您可以根据需要进行扩展。
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