用C语言编写程序完成单处理器系统中的进程调度,要求实现时间片轮转、优先数、最短进程优 先和最短剩余时间优先四种调度算法。
时间: 2024-02-15 08:04:43 浏览: 80
好的,这是一个关于进程调度的问题,我可以为您提供一些思路和参考代码。首先,我们需要定义进程控制块(PCB)的结构体,其中包含了进程的基本信息,例如进程ID、优先级、状态等等。下面是一个简单的PCB结构体定义:
```c
typedef struct PCB {
int pid; // 进程ID
int priority; // 进程优先级
int burst_time; // 进程运行时间
int remaining_time; // 剩余运行时间
int status; // 进程状态(就绪、运行、完成)
} PCB;
```
接下来,我们需要实现四种调度算法。首先是时间片轮转调度算法。这种算法是按时间片大小轮流让每个进程占用CPU,如果进程在一个时间片内没有运行完,则把它放到就绪队列末尾,让其他进程运行。下面是一个简单的时间片轮转调度的实现:
```c
void round_robin(PCB* ready_queue[], int queue_size, int time_slice) {
int i, j;
for (i = 0; i < queue_size; i++) {
PCB* p = ready_queue[i];
if (p->status == RUNNING) {
p->remaining_time--;
if (p->remaining_time == 0) {
p->status = FINISHED;
} else if (i == queue_size - 1) {
p->status = READY;
ready_queue[0] = p;
} else {
p->status = READY;
ready_queue[i+1] = p;
}
break;
}
}
for (j = 0; j < queue_size; j++) {
PCB* p = ready_queue[j];
if (p->status == READY) {
p->status = RUNNING;
p->remaining_time = min(p->burst_time, time_slice);
}
}
}
```
接下来是优先数调度算法。这种算法是按进程的优先级来决定哪个进程先运行。如果有多个进程优先级相同,则按照先来先服务的原则进行调度。下面是一个简单的优先数调度的实现:
```c
void priority_scheduling(PCB* ready_queue[], int queue_size) {
int i, j, max_priority = -1;
for (i = 0; i < queue_size; i++) {
PCB* p = ready_queue[i];
if (p->status == RUNNING) {
p->remaining_time--;
if (p->remaining_time == 0) {
p->status = FINISHED;
}
break;
}
}
for (j = 0; j < queue_size; j++) {
PCB* p = ready_queue[j];
if (p->status == READY && p->priority > max_priority) {
max_priority = p->priority;
}
}
for (j = 0; j < queue_size; j++) {
PCB* p = ready_queue[j];
if (p->status == READY && p->priority == max_priority) {
p->status = RUNNING;
p->remaining_time = p->burst_time;
break;
}
}
}
```
接下来是最短进程优先调度算法。这种算法是按照进程的运行时间来决定哪个进程先运行。如果有多个进程运行时间相同,则按照先来先服务的原则进行调度。下面是一个简单的最短进程优先调度的实现:
```c
void shortest_job_first(PCB* ready_queue[], int queue_size) {
int i, j, min_burst_time = INT_MAX;
for (i = 0; i < queue_size; i++) {
PCB* p = ready_queue[i];
if (p->status == RUNNING) {
p->remaining_time--;
if (p->remaining_time == 0) {
p->status = FINISHED;
}
break;
}
}
for (j = 0; j < queue_size; j++) {
PCB* p = ready_queue[j];
if (p->status == READY && p->burst_time < min_burst_time) {
min_burst_time = p->burst_time;
}
}
for (j = 0; j < queue_size; j++) {
PCB* p = ready_queue[j];
if (p->status == READY && p->burst_time == min_burst_time) {
p->status = RUNNING;
p->remaining_time = p->burst_time;
break;
}
}
}
```
最后是最短剩余时间优先调度算法。这种算法是按照进程剩余运行时间来决定哪个进程先运行。如果有多个进程剩余运行时间相同,则按照先来先服务的原则进行调度。下面是一个简单的最短剩余时间优先调度的实现:
```c
void shortest_remaining_time_first(PCB* ready_queue[], int queue_size) {
int i, j, min_remaining_time = INT_MAX;
for (i = 0; i < queue_size; i++) {
PCB* p = ready_queue[i];
if (p->status == RUNNING) {
p->remaining_time--;
if (p->remaining_time == 0) {
p->status = FINISHED;
}
break;
}
}
for (j = 0; j < queue_size; j++) {
PCB* p = ready_queue[j];
if (p->status == READY && p->remaining_time < min_remaining_time) {
min_remaining_time = p->remaining_time;
}
}
for (j = 0; j < queue_size; j++) {
PCB* p = ready_queue[j];
if (p->status == READY && p->remaining_time == min_remaining_time) {
p->status = RUNNING;
p->remaining_time = p->burst_time;
break;
}
}
}
```
以上就是四种进程调度算法的简单实现,但是这些实现还需要结合具体的应用场景进行调整和优化。
阅读全文