页面置换算法详解
本文详细介绍了几种常见的页面置换算法，包括最佳置换算法、先进先出置换算法、最近最久未使用置换算法、简单Clock置换算法、改进Clock置换算法以及随机置换算法。通过具体的代码实现，展示了每种算法的工作原理及过程。
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<string.h>
#include<math.h>
int Init(int *BlockList,int m,int *PageList,int n); //初始时刻内存块页面的装入
void PrintBlock(int *BlockList); //输出当前内存块的页面
void OptimatAlgorithm(int *BlockList,int m,int *PageList,int n,int fl); //最佳置换算法
void FIFOAlgorithm(int *BlockList,int m,int *PageList,int n,int fl); //先进先出置换算法
void LRUAlgorithm(int *BlockList,int m,int *PageList,int n,int fl,int *FR); //最近最久未使用置换算法
void ClockAlgorithm(int *BlockList,int m,int *PageList,int n,int fl,int *Flag); //简单Clock置换算法
void ClockImproveAlgorithm(int *BlockList,int m,int *PageList,int n,int fl,int *Flag1,int * Flag2); //改进Clock置换算法
void RandomAlgorithm(int *BlockList,int m,int *PageList,int n,int fl); //随机置换算法
void PrintBlock(int *BlockList,int m) //输出当前内存块页面
{
int i = 0;
for(i = 0;i < m;i++)
{
if(i < m-1)
printf("%d ",BlockList[i]);
else
printf("%d",BlockList[i]);
}
printf("\n");
}
int Init(int *BlockList,int m,int *PageList,int n)
{
int i = 0,j = 0,count = 0,flag = 0,r = 0,ran,excount = 0;
for (i = 0;i < n;i++) //初始时
{
if(i == 0)
{
BlockList[count] = PageList[i];
count ++;
}
else
{
for(j = 0;j < m;j++)
{
if(BlockList[j] == PageList[i]) //判断页面是否已在内存中
{
flag = 1;
j = m;
}
}
if(flag == 0)
{
BlockList[count] = PageList[i];
count ++;
}
flag = 0;
}
if(count == m ) //初始内存已满
{
r = i;
i = n;
}
}
printf("当前内存块中的页面：");
PrintBlock(BlockList,m); //输出初始内存页面
return r+1;
}
void OptimatAlgorithm(int *BlockList,int m,int *PageList,int n,int fl)
{
int i = 0,j = 0,k = 0,r = 0;
int flag1 = 0,flag2 = 0,flag = 0;
int count1 = 0,excount = 0;
if(fl == 0)
r = Init(BlockList,m,PageList,n);
else
r = 0;
for(k = r;k<n;k++)
{
flag = 0;
for(j = 0;j < m;j++) //判断内存中是否已有该页面
{
if(PageList[k] == BlockList[j])
{
printf("页面%d,当前内存块中的页面：",PageList[k]);
PrintBlock(BlockList,m);
printf("没有发生置换\n");
flag = 1;
j = m;
}
}
if(flag == 0) //如果没有则置换
{
for(j = 0;j<m;j++)
{
for(i = k;i<n;i++) //寻找被置换的页面
{
if(PageList[i] == BlockList[j])
{
if(i > flag1)
{
flag1 = i; //flag1记录当前被置换的页面
flag2 = j; //flag2记录被置换页面在内存块中的位置
}
i = n;
}
else
{
count1++; //count1用于判断内存中的页面是否在以后出现
}
}
if(count1 == n - k)
{
flag2 = j; //flag2记录被置换页面在内存块中的位置
j = m;
}
count1 = 0;
}
printf("页面%d,当前内存块中的页面：",PageList[k]);
PrintBlock(BlockList,m);
printf("应该被置换的页面：%d\n",BlockList[flag2]);
BlockList[flag2] = PageList[k];
printf("置换后内存块中的页面：");
PrintBlock(BlockList,m);
flag1 = 0;
flag2 = 0;
excount++; //记录置换次数
}
}
printf("最佳置换算法本次置换次数：%d,本次缺页率为：%c%.2f\n",excount,'%',(double)excount/(double)n*100);
}
void RandomAlgorithm(int *BlockList,int m,int *PageList,int n,int fl)
{
int i = 0,j = 0,count = 0,flag = 0,r = 0,ran,excount = 0;
if(fl == 0)
r = Init(BlockList,m,PageList,n);
else
r = 0;
srand((unsigned)time(NULL));
for(i = r;i<n;i++)
{
ran = rand()%m; //应该被淘汰出内存的页面
flag = 0;
for(j = 0;j < m;j++)
{
if(PageList[i] == BlockList[j])
{
printf("页面%d,当前内存块中的页面：",PageList[i]);
PrintBlock(BlockList,m);
printf("没有发生置换\n");
flag = 1;
j = m;
}
}
if(flag == 0)
{
printf("页面%d，当前内存块中的页面：",PageList[i]);
PrintBlock(BlockList,m);
printf("应该被置换的页面：%d\n",BlockList[ran]);
BlockList[ran] = PageList[i];
printf("置换后内存块中的页面：");
PrintBlock(BlockList,m);
excount++;
}
}
printf("随机置换算法本次置换次数：%d,本次缺页率为：%c%.2f\n",excount,'%',(double)excount/(double)n*100);
}
void FIFOAlgorithm(int *BlockList,int m,int *PageList,int n,int fl)
{
int i = 0,j = 0,count = 0,flag = 0,r = 0,excount = 0,k = 0,co = 0;;
if(fl == 0)
r = Init(BlockList,m,PageList,n);
else
r = 0;
for(k = r;k<n;k++)
{
flag = 0;
for(j = 0;j < m;j++) //判断内存中是否已有该页面
{
if(PageList[k] == BlockList[j])
{
printf("页面%d,当前内存块中的页面：",PageList[k]);
PrintBlock(BlockList,m);
printf("没有发生置换\n");
flag = 1;
j = m;
}
}
if(flag == 0) //如果没有则置换
{
printf("页面%d，当前内存块中的页面：",PageList[k]);
PrintBlock(BlockList,m);
printf("应该被置换的页面：%d\n",BlockList[co]);
BlockList[co] = PageList[k];
printf("置换后内存块中的页面：");
PrintBlock(BlockList,m);
co = (co + 1)%m;
excount++;
}
}
printf("先进先出页面置换算法本次置换次数：%d,本次缺页率为：%c%.2f\n",excount,'%',(double)excount/(double)n*100);
}
void LRUAlgorithm(int *BlockList,int m,int *PageList,int n,int fl,int *FR) //FR为寄存器
{
int i = 0,j = 0,k = 0,count = 0,excount = 0;
for(i = 0; i < n; i++)
{
if(count < m && fl == 0) //初始时直接装入内存
{
for(j = 0;j <= count;j++)
{
if(PageList[i] == FR[j])
{
for(k = j;k <= count - 1;k++)
{
FR[k] = FR[k+1];
}
FR[count - 1] = PageList[i];
j = m;
}
else if(j == count)
{
FR[count] = PageList[i];
BlockList[count] = PageList[i];
count++;
j = m;
}
}
if(count == m)
{
printf("当前栈中页面顺序FR: ");
PrintBlock(FR,m);
printf("当前内存块中的页面：");
PrintBlock(BlockList,m);
}
}
else
{
for(j = 0;j < m;j++)
{
if(PageList[i] == FR[j])
{
for(k = j;k <= m - 1;k++)
{
FR[k] = FR[k+1];
}
FR[m - 1] = PageList[i];
printf("当前栈中页面顺序FR: ");
PrintBlock(FR,m);
j = m;
}
else if(j == m - 1)
{
for(k = 0;k < m;k++)
{
if(BlockList[k] == FR[0])
{
printf("页面%d，当前内存块中的页面：",PageList[i]);
PrintBlock(BlockList,m);
printf("应该被置换的页面：%d\n",BlockList[k]);
BlockList[k] = PageList[i];
printf("置换后内存块中的页面：");
PrintBlock(BlockList,m);
excount++;
k = m;
}
}
for(k = 0;k < m - 1;k++)
{
FR[k] = FR[k+1];
}
FR[m - 1] = PageList[i];
printf("当前栈中页面顺序FR: ");
PrintBlock(FR,m);
j = m;
}
}
}
}
printf("最近最久置换算法本次置换次数：%d,本次缺页率为：%c%.2f\n",excount,'%',(double)excount/(double)n*100);
}
void ClockAlgorithm(int *BlockList,int m,int *PageList,int n,int fl,int *Flag)
{
int i = 0,j = 0,k = 0,r = 0,flag = 0,count = 0,excount = 0;
if(fl == 0)
{
r = Init(BlockList,m,PageList,n);
for(i = 0;i < m;i++)
Flag[i] = 0;
}
else
r = 0;
for(i = r;i < n ;i++)
{
flag = 0;
for(j = 0;j < m;j++) //判断内存中是否已有该页面
{
if(PageList[i] == BlockList[j])
{
Flag[j] = 1; //访问位置1
printf("当前页面与内存中页面相等Flag: ");
PrintBlock(Flag,m);
flag = 1;
j = m;
}
}
if(flag == 0) //没有，需要置换
{
for(j = 0;j < m;j++)
{
if(Flag[count] == 0)
{
printf("置换前访问位Flag: ");
PrintBlock(Flag,m);
printf("页面%d，当前内存块中的页面：",PageList[i]);
PrintBlock(BlockList,m);
printf("应该被置换的页面：%d\n",BlockList[count]);
BlockList[count] = PageList[i];
printf("置换后内存块中的页面：");
PrintBlock(BlockList,m);
Flag[count] = 1; //访问位置1
count =(count + 1)%m;
printf("置换后访问位Flag: ");
PrintBlock(Flag,m);
excount++;
j = m;
}
else
{
printf("当前访问位Flag: ");
PrintBlock(Flag,m);
Flag[count] = 0;
printf("修改当前访问位后Flag: ");
PrintBlock(Flag,m);
count = (count + 1)%m;
if(j == m-1)
j = 0;
}
}
}
}
printf("Clock置换算法的本次置换次数为：%d,本次缺页率为：%c%.2f\n",excount,'%',(double)excount/(double)n*100);
}
void ClockImproveAlgorithm(int *BlockList,int m,int *PageList,int n,int fl,int *Flag1,int *Flag2)
{
int i = 0,j = 0,k = 0,r = 0,flag = 0,count = 0,flag1 = 0,flag2 = 0,excount = 0;
if(fl == 0)
{
r = Init(BlockList,m,PageList,n);
for(i = 0;i < m;i++)
{
Flag1[i] = 0;
Flag2[i] = 0;
}
}
else
r = 0;
for(i = r;i < n ;i++)
{
flag = 0;
for(j = 0;j < m;j++) //判断内存中是否已有该页面
{
if(PageList[i] == BlockList[j])
{
Flag1[j] = 1; //访问位置1
printf("当前页面与内存中页面相等Flag1: ");
PrintBlock(Flag1,m);
flag = 1;
j = m;
}
}
if(flag == 0) //没有，需要置换
{
while(flag1 == 0 && flag2 == 0)
{
for(j = 0;j < m;j++)
{
if(Flag1[count] == 0 && Flag2[count] == 0)
{
printf("置换前访问位Flag1: ");
PrintBlock(Flag1,m);
BlockList[count] = PageList[i];
printf("置换前修改位Flag2: ");
PrintBlock(Flag2,m);
Flag2[count] = 1; //修改位置1
count =(count + 1)%m;
flag1 = 1;
printf("第一步置换后内存页面：");
PrintBlock(BlockList,m);
printf("置换后访问位Flag1: ");
PrintBlock(Flag1,m);
printf("置换后修改位Flag2: ");
PrintBlock(Flag2,m);
excount++;
j = m;
}
count = (count+1)%m;
}
if(flag1 == 0)
{
for(j = 0;j < m;j++)
{
if(Flag1[count] == 0 && Flag2[count] == 1)
{
BlockList[count] = PageList[i];
Flag2[count] = 1; //修改位置1
count =(count + 1)%m;
flag1 = 1;
flag2 = 1;
printf("第二步置换后内存页面：");
PrintBlock(BlockList,m);
printf("置换后访问位Flag1: ");
PrintBlock(Flag1,m);
printf("置换后修改位Flag2: ");
PrintBlock(Flag2,m);
excount++;
j = m;
}
Flag1[count] = 0; //访问位置0
printf("第二步扫描后访问位Flag1: ");
PrintBlock(Flag1,m);
printf("第二步扫描后修改位Flag2: ");
PrintBlock(Flag2,m);
count =(count + 1)%m;
}
}
}
count = (count + m -1)%m;
flag1 = 0;
flag2 = 0;
}
}
printf("改进Clock置换算法的本次置换次数为：%d,本次缺页率为：%c%.2f\n",excount,'%',(double)excount/(double)n*100);
}
转载于:https://blog.51cto.com/592669550/1161832
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