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