C++ 实现的 FCFS、SSTF、SCAN 和 CSCAN 四种磁盘调度算法。
/**磁盘调度算法**/
/**by Darius**/
#include <iostream>
#include <algorithm>
#include <cstdio>
#define MAX 1000
using namespace std;
//求平均寻道长度
double average(int *length, int n){
double sum=0;
int i;
for(i=0;i<n;i++)
sum+=length[i];
return sum/n;
}
//先来先服务寻道算法
void First_come_first_server(int *a, int n, int now) {
int i, k=0;
int t = n;
int next[MAX], length[MAX];
int visit[MAX] = {0};
while(t--)
{
for(i = 0;i < n;i++) {
if(visit[i])
continue;
else {
length[k] = abs(a[i] - now);
next[k++] = a[i];
visit[i] = 1;
now = a[i];
}
}
}
cout << endl << "下一个磁道 " << "移动距离" << endl;
for (i = 0; i < n; i++)
cout << next[i] << " " << length[i] << endl;
cout << "平均寻道长度:";
printf("%.2f
", average(length, n));
}
//最短寻道时间优先算法
void Shortest_seek_time_first(int *a, int n, int now) {
int i, min, k = 0;
int flag;//最短路径的下标
int t = n;
int next[MAX], length[MAX];
int visit[MAX] = {0};//访问数组，已经访问过的为1
//寻道n次
while (t--) {
min = 999999;
//找没有访问过的中最近的
for (i = 0; i < n; i++) {
if (visit[i])
continue;
if (abs(a[i] - now) < min) {
flag = i;
min = abs(a[i] - now);
}
}
length[k] = min;//移动的距离
next[k++] = a[flag];//下一个被访问的磁道号
visit[flag] = 1;//访问过的置1
now = a[flag];//磁道移动到当前位置
}
cout << endl << "下一个磁道 " << "移动距离" << endl;
for (i = 0; i < n; i++)
cout << next[i] << " " << length[i] << endl;
cout << "平均寻道长度:";
printf("%.2f
", average(length, n));
}
//扫描算法
void Scan(int *a, int n, int now){
int i,flag=0,k=0;
int next[MAX],length[MAX];
sort(a,a+n);//从小到大排序
//寻找开始磁道
for(i=0;i<n;i++){
if(a[i]>=now){
flag=i;
break;
}
}
//往递增方向访问
for(i=flag;i<n;i++){
next[k]=a[i];
length[k++]=abs(a[i]-now);
now=a[i];
}
//回来往递减方向访问
for(i=flag-1;i>=0;i--){
next[k]=a[i];
length[k++]=abs(a[i]-now);
now=a[i];
}
cout<<endl<<"下一个磁道 "<<"移动距离"<<endl;
for(i=0;i<n;i++)
cout<<next[i]<<" "<<length[i]<<endl;
cout<<"平均寻道长度:";
printf("%.2f
", average(length, n));
}
void Circle_scan(int *a, int n, int now){
int i,flag=0,k=0;
int next[MAX],length[MAX];
sort(a,a+n);//从小到大排序
for(i=0;i<n;i++){
if(a[i]>=now){
flag=i;
break;
}
}
//往递增方向访问
for(i=flag;i<n;i++){
next[k]=a[i];
length[k++]=abs(a[i]-now);
now=a[i];
}
//循环往递增方向访问
for(i=0;i<flag;i++){
next[k]=a[i];
length[k++]=abs(a[i]-now);
now=a[i];
}
cout<<endl<<"下一个磁道 "<<"移动距离"<<endl;
for(i=0;i<n;i++)
cout<<next[i]<<" "<<length[i]<<endl;
cout<<"平均寻道长度:";
printf("%.2f
", average(length, n));
}
int main(){
int a[MAX];//存放要用到的磁道号
int start;//开始的磁道
int n,i,flag=1;
cout<<"一共要用到的磁道数："<<endl;
cin>>n;
cout<<"随机的磁道："<<endl;
srand((int)time(0));
for(i=0;i<n;i++) {
a[i] = rand()%100;
cout<<a[i]<<" ";
}
cout<<endl<<"开始的磁道："<<endl;
cin>>start;
//磁盘调度目录
while(flag){
cout<<"请选一种磁盘调度算法："<<endl;;
cout<<"1.先来先服务寻道算法"<<endl;
cout<<"2.最短寻道时间优先"<<endl;
cout<<"3.扫描算法"<<endl;
cout<<"4.循环扫描算法"<<endl;
cout<<"0.退出"<<endl;
cin>>flag;
switch(flag){
case 1:
First_come_first_server(a,n,start);
break;
case 2:
Shortest_seek_time_first(a, n, start);break;
case 3:
Scan(a, n, start);break;
case 4:
Circle_scan(a, n, start);break;
case 0:
break;
}
}
return 0;
}