LRU

LRU.cpp

#define MAXSIZE    20
#include <iostream.h>

void main()
{
    int input=0;                                   //用于输入作业号
    int worknum=0;                                 //输入的作业个数
    int storesize=0;                               //系统分配的存储区块数
    int interrupt=0;                               //缺页中断次数
    int stack[MAXSIZE];                            //栈，LRU算法的主要数据结构
    int workstep[MAXSIZE];                         //记录作业走向
    /*初始化*/
    for(int i=0;i<MAXSIZE;i++)
    {
        stack[i]=0;
        workstep[i]=0;
    }
    cout<<"请输入存储区块数：";
    cin>>storesize;
    cout<<"请输入作业的页面走向（输入0结束）：\n";
    for(int j=0;j<MAXSIZE;j++)
    {
        cout<<"页面号 "<<j+1<<” :”;
        cin>>input;     
        workstep[j]=input;
        if(input==0)
        {
            cout<<"输入结束！\n";
            break;
        }
        worknum++;
    }
    if(workstep[0]==0)
    {
        cout<<"未输入任何作业，系统将退出！\n";
        return;
    }
    cout<<"置换情况如下：\n";
    for(int k=0;k<worknum;k++)
    {
        /*在栈中找相等的页号或空位置*/
        for(int l=0;l<storesize;l++)
        {
            /*是否有相等的页号*/
            if(stack[l]==workstep[k])
            {
                cout<<"内存中有"<<workstep[k]<<"号页面，无须中断！\n"; 
                goto step1;
            }
            /*找栈中是否有空位置*/
            if(stack[l]==0)
            {
                stack[l]=workstep[k];
                cout<<"发生中断，但内存中有空闲区，"<<workstep[k]<<"号页面直接调入！\n";
                interrupt++;
                goto step1;
            }
        }
        /*上述情况都不成立则调出栈顶，将调入页面插入栈顶*/
        cout<<"发生中断，将"<<stack[0]<<"号页面调出，"<<workstep[k]<<"号装入！\n";
        interrupt++;
        /*新掉入的页面放栈顶*/
step1:  for(int m=0;m<storesize;m++)
        {
            stack[m]=stack[m+1];
        }
        stack[storesize-1]=workstep[k];

    }
    cout<<"作业"<<worknum<<"个，"<<"中断"<<interrupt<<"次，"<<"缺页率："<<float(interrupt)/float(worknum)*100<<"%\n";
}

LRU.java

public class LRU {

    public static void main(String[] args){
        int worknum = 10;
        int work[] = {1,2,3,4,5,7,7,7,7,7};
        int memory[] = new int[3];
        int intterp = 0;
        boolean flag;
        for(int i=0;i<worknum;i++){
            flag = true;
            for(int j=0;j<memory.length;j++){
                if(memory[j]==work[i]){
                    System.out.println("内存中有"+work[i]+"无需中断");
                    swapmemroy(memory,work[i]);
                    flag = false;
                }
                else if(memory[j]==0){
                    System.out.println("发生中断，但内存中有空闲区，"+work[i]+"直接调入");
                    intterp++;
                    swapmemroy(memory,work[i]);
                    flag = false;
                }
            }
            if(flag){
                System.out.println("发生中断，，"+memory[0]+"调出"+work[i]+"调入");
                swapmemroy(memory, work[i]);
                intterp++;
            }
        }
        System.out.println("中断次数"+intterp+"缺页率"+(double)intterp/(double)worknum*100);
    }

    static public void swapmemroy(int[] memory,int worknum){
            for(int i=0;i<memory.length-1;i++){
                memory[i] = memory[i+1];
            }
            memory[memory.length-1] = worknum;
    }

}