操作系统磁盘移臂调度算法模拟与实现实验代码
一.实验算法
FCFS：按照访问序列的顺序调度
SSTF：每次寻找距离当前磁头位置最近的柱面号进行调度
单向扫描：按照从里到外逐个找到最近，直到扫到最大柱面，再空扫到最小柱面，再进行逐个找最近的进行调度
双向扫描：按当前磁头方向找到逐个找最近的，直到扫到边缘柱面，再反方向扫回去
电梯调度：按照当前磁头方向逐个找最近的，直到这一方向所有需要访问的都访问了，再返回去按逐个找最近的方式进行调度
二.实验代码
#include
#include
#include
#define N 1000
int length;
int sequence[N]; //访问柱面的顺序（从1开始）
int result[N]; //存放最短优先的结果
int now; //当前柱面
int count=0; //记录移动柱面
int border = 199; //最外层柱面
int resultLen = 0; //输出结果的长度
//函数名：input 函数功能:输入访问序列信息
void input() {
printf("请输入访问序列的长度：");
scanf("%d", &length);
printf("请输入访问的柱面顺序：");
for (int i = 0; i < length; i++)
scanf("%d", &sequence[i]);
printf("请输入正在访问的柱面：");
scanf("%d", &now);
count = 0; //初始化移动柱面
resultLen = length+1; //初始化输出长度
}
void printResult()
{
printf("\n移动的顺序为:\n");
for (int i = 0; i < resultLen; i++)
printf("%d ", result[i]);
printf("\n移动柱面为:%d", count);
printf("\n");
}
//函数名：FCFS参数：无
void FCFS() {
//函数功能:调用先来先服务算法
for (int i = 0; i < length; i++)
{
result[i] = now;
count += abs(now - sequence[i]);
now = sequence[i];
}
result[length ] = now;
}
//函数名：SSTF 函数功能:调用短进程优先调度算法
void SSTF() {
int min, nextPos;
for (int i = 0; i < length; i++)
{
result[i] = now;
min = 0x7fffffff;
for (int j = 0; j < length; j++) //寻找下一个位置
{
if (sequence[j] == -1)
continue;
if (abs(now - sequence[j]) < min)
{
min = abs(now - sequence[j]);
nextPos = j;
}
}
now = sequence[nextPos];
count += min;
sequence[nextPos] = -1; //置为-1代表已经访问过
}
result[length] = now;
}
//将sequence数组升序排序
void sort() {//冒泡排序
for (int i = 0; i < length-1; i++) //进行len-1次即可
{
for (int j = 0; j < length-i-1; j++) //下一次遍历减掉已经排好序的元素个数
{
if (sequence[j] > sequence[j+1])
{
int tmp = sequence[j];
sequence[j] = sequence[j + 1];
sequence[j + 1] = tmp;
}
}
}
printf("排序后的序列:");
for (int i = 0; i < length; i++)
printf("%d ", sequence[i]);
printf("\n");
}
//函数名：Oneway_scan 函数功能:调用单向扫描算法
void Oneway_scan() {
sort();
int sum = 0,j; //sum记录逆方向的元素个数
while (sequence[sum] < now)//找到now所在位置,同时i也记录了小于now的个数
sum++;
if (sum == 0) //退化成类似FCFS
{
FCFS();
return;
}
for (j = 0; j < length - sum; j++)//先处理处于移动方向正向的元素
{
result[j] = now;
count += sequence[sum + j] - now; //已经排好序所以不需要取绝对值
now = sequence[sum + j];
}
result[j++] = now;
count += border - now;
result[j++] = border;//处理好边界值
count += border; //处理移动柱面
now = 0;
for (int k = 0; k < sum; k++) //处理剩余的元素
{
result[j++] = now;
count += sequence[k] - now;
now = sequence[k];
}
result[j] = now;
resultLen = length + 3;
}
//函数名：Twoway_scan 函数功能:调用双向扫描算法
void Twoway_scan() {
sort();
int sum = 0,j;
while (sequence[sum] < now)
sum++;
if (sum == 0)
{
FCFS();
return;
}
for (j = 0; j < length - sum; j++)//正向扫一遍
{
result[j] = now;
count += sequence[sum + j] - now;
now = sequence[sum + j];
}
result[j++] = now;
result[j] = border; //调整边界值
count += border - now;
now = border;
for (int k = sum - 1; k >= 0; k--) //反向扫一遍
{
result[j++] = now;
count += now - sequence[k];
now = sequence[k];
}
result[j] = now;
resultLen = length + 2;
}
//函数名：Elevator 函数功能:调用电梯调度算法
void Elevator() {
sort();
int sum = 0,j=0,saveNow=now;
while (sequence[sum] < now)
sum++;
if (sum == 0)//单向,退化成FCFS(排序后)
{
FCFS();
return;
}
printf("\n电梯调度(由里向外)");
for (int k = sum - 1; k >= 0; k--) //反向扫一遍
{
result[j++] = now;
count += now - sequence[k];
now = sequence[k];
}
result[j++] = now;
for (j=sum; j < length; j++)//正向扫一遍
{
result[j] = now;
count += sequence[ j] - now;
now = sequence[j];
}
result[j] = now;
printResult();
now = saveNow;//重新初始化
count = 0;
printf("\n电梯调度(由外向里)");
for (j = 0; j < length-sum; j++)//正向扫一遍,类似FCFS
{
result[j] = now;
count += sequence[sum + j] - now;
now = sequence[sum + j];
}
for (int k = sum - 1; k >= 0; k--) //反向扫一遍
{
result[j++] = now;
count += now - sequence[k];
now = sequence[k];
}
result[j] = now;
printResult();
}
//选择菜单
void choice() {
while (1) {
printf("*************磁盘驱动调度**************\n");
printf(" * 1.FCFS *\n");
printf(" * 2.SSTF *\n");
printf(" * 3.单向扫描 *\n");
printf(" * 4.双向扫描 *\n");
printf(" * 5.电梯调度 *\n");
printf(" * 0.退出 *\n");
printf(" 请输入选项[ ]\b\b");
int op;
scanf("%d", &op);
switch (op) {//选择算法
case 1:
input();
printf("\n*********FCFS磁盘移臂调度过程*********\n");
FCFS();
printResult();
break;
case 2:
input();
printf("\n*********SSTF磁盘移臂调度过程*********\n");
SSTF();
printResult();
break;
case 3:
input();
printf("\n*********单向扫描过程*********\n");
Oneway_scan();
printResult();
break;
case 4:
input();
printf("\n*********双向扫描过程*********\n");
Twoway_scan();
printResult();
break;
case 5:
input();
printf("\n*********电梯调度过程*********\n");
Elevator();
break;
default:printf("\n调度结束！");
return;
}
}
}
//测试用例
//8
//98 183 37 122 14 124 65 67
//53
int main()
{
choice();
return 0;
} 三.实验结果
