基于优先级的时间片轮转调度算法

1. PCB结构（Block）

pcb

由此定义如下结构体：

typedef struct Block
{int processID; // 进程号int priority; // 优先级int status; // 状态double arrivalTime; // 到达时间double serviceTime; // 服务时间double runTime; // 已运行时间struct Block *next; // Next Block
} Block;

2. 数据结构（队列）

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typedef struct Link
{struct Block *first;  // 指向队头struct Block *last;   // 指向队尾
} Link;

队列操作函数：

initLink：初始化队列

void initLink(Link *l)
{// 分配空间并检测是否成功l->first = l->last = (Block *)malloc(sizeof(Block));if (!l->first){fprintf(stderr, "Malloc Error!\n");exit(-1);}// 空队列l->first->next = NULL;l->last->next = NULL;
}

isEmpty：判断队列是否为空

int isEmpty(Link *l)
{return l->first->next == NULL? 1: 0;
}

printLInk：输出队列中所有元素的信息

void printLink(Link *l)
{Block *p = l->first->next;// 遍历队列并输出printf ("\nProcess ID\tPriority\tArrival Time\tService Time\tRun Time\tStatus\n");while (p != NULL){printf("\t%d\t%d\t\t%.2lf\t\t%.2lf\t\t%.2lf\t\t%s\n", \p->processID, p->priority, p->arrivalTime, \p->serviceTime, p->runTime, p->status == 0? "ready": "finished");p = p->next;}
}

removeFirst：将队列中第一个元素中的数据复制到给定参数中（用于返回），并删除

void removeFirst(Link *l, Block *b)
{Block *t;// 空队列则直接返回if (isEmpty(l)){return ;}// t指向第二个Block，用于之后将队列接上t = l->first->next->next;// 将第一个Block中的内容复制到b中，用于返回b->processID = l->first->next->processID;b->priority = l->first->next->priority;b->arrivalTime = l->first->next->arrivalTime;b->serviceTime = l->first->next->serviceTime;b->runTime = l->first->next->runTime;b->status = l->first->next->status;// 释放第一个Block，并把队列接上free (l->first->next);l->first->next = t;
}

append：将新的元素添加到队尾

void append(Link *l, Block *b)
{Block *t;// 分配空间，并检测是否成功t = (Block *)malloc(sizeof(Block));if (t == NULL){fprintf(stderr, "Malloc Error!\n");exit(-1);}// 将b中的内容复制到t中t->processID = b->processID;t->priority = b->priority;t->arrivalTime = b->arrivalTime;t->serviceTime = b->serviceTime;t->runTime = b->runTime;t->status = b->status;// 将t接到队尾t->next = NULL;l->last->next = t;l->last = t;
}

deleteLinkItem：删除队列中指定的元素

void deleteLinkItem(Link *l, Block *target)
{Block *p, *t;// 遍历队列，寻找目标Blockp = l->first;while (p != NULL && p != target){t = p;p = p->next;}// 若存在，则释放if (p != NULL){t->next = p->next;free(p);}
}

sortByArrivalTime：根据进程到达时间将队列排序（从小到大）

void sortByArrivalTime(Link *l, int order)
{Block *p, *q, *tp, *tq;Block *temp, *min, *tmin;int minArrivalTime;// 这里使用了选择排序tp = tq = l->first;p = q = l->first->next;while (p != NULL){// 这个数字可以修改的大一点。。。minArrivalTime = 9999;while (q != NULL){// 寻找最小到达时间的Blockif (q->arrivalTime < minArrivalTime){minArrivalTime = q->arrivalTime;tmin = tq;min = q;}tq = q;q = q->next;}// 若寻找的Block与当前Block不是同一个则交换if (p != min){tp->next = min;tmin->next = p;temp = min->next;min->next = p->next;p->next = temp;}tp = tq = p;p = q = p->next;}
}

3. 基于优先级的时间片轮转调度算法

流程图

流程图

算法

void RR(Link *l, Link *r)
{Block *p, *t;double maxPriority;double currentTime = 0;int selected, timeSlice;// 种下随机种子srand((unsigned)time(NULL));// 遍历队列t = p = l->first->next;while (p != NULL){// 输出在当前时间已到达的进程Block信息printf ("\nProcess ID\tPriority\tArrival Time\tService Time\tRun Time\tStatus\n");selected = 0;maxPriority = 9999;while (p != NULL && currentTime >= p->arrivalTime){selected = 1;printf("\t%d\t%d\t\t%.2lf\t\t%.2lf\t\t%.2lf\t\t%s\n", \p->processID, p->priority, p->arrivalTime, \p->serviceTime, p->runTime, p->status == 0? "ready": "finished");// 寻找优先级最高的进程if (p->priority < maxPriority){maxPriority = p->priority;t = p;}p = p->next;}// 生成随机时间片timeSlice = rand() % 10;if (selected){// 运行进程（模拟）printf("Current time: %.0lf, Selected process: %d\n", currentTime, t->processID);t->runTime += timeSlice;t->priority += 2;// 若进程已经结束，则将该进程添加到完成队列，并从当前队列中删除if (t->runTime >= t->serviceTime){t->status = 1;currentTime += t->serviceTime - (t->runTime - timeSlice);t->runTime = t->serviceTime;append(r, t);deleteLinkItem(l, t);}}else{currentTime += timeSlice;}// 打印完成队列printLink(r);t = p = l->first->next;}
}