LRU算法
#include <stdio.h>
#include <stdlib.h> #define mSIZE 3
#define pSIZE 8 static int memery[mSIZE] = {0};
static int process[pSIZE] = {0};
//static int process[pSIZE] = {2,3,2,1,5,2,4,5,3,2,5,2};
//static int process[pSIZE] = {7,10,1,2,10,3,10,4,2,3,10,3,2,1,2,10,1,7,10,1};
void build(); //生成一个随机数序列
void LRU(); //最近最久未使用(LRU)置换算法 int main(int argc, char *argv[])
{
printf("产生随机序列如下：\n");
build();
printf("最近最久未使用(LRU)置换算法 \n");
LRU();
system("PAUSE");
return 0;
}void build()
{
int i = 0;
for(i=0; i<pSIZE; i++)
{
process[i] = (int)(10.0*rand()/(RAND_MAX+1.0) + 1);
printf("%d ",process[i]);
}
printf("\n");
}void LRU()
{
int flag[mSIZE] = {0};
int i = 0, j = 0;
int m = -1, n = -1;
int max = -1,maxflag = 0;
int count = 0;
for(i = 0; i<pSIZE; i++)
{
//找第一个空闲的物理块
for(j=0; j<mSIZE; j++)
{
if(memery[j] == 0)
{
m = j;
break;
}
}
//找与进程相同的标号
for(j = 0; j < mSIZE; j++)
{
if(memery[j] == process[i])
{
n = j;
}
}
//找flag值最大的
for(j = 0; j < mSIZE;j++)
{
if(flag[j]>maxflag)
{
maxflag = flag[j];
max = j;
}
}
if(n == -1) //不存在相同进程
{
if(m != -1) //存在空闲物理块
{
memery[m] = process[i];
flag[m] = 0;
for(j = 0;j <= m; j++)
{
flag[j]++;
}
m = -1;
}
else //不存在空闲物理块
{
memery[max] = process[i];
flag[max] = 0;
for(j = 0;j < mSIZE; j++)
{
flag[j]++;
}
max = -1;
maxflag = 0;
count++;
}
}
else //存在相同的进程
{
memery[n] = process[i];
flag[n] = 0;
if(m != -1) //若存在空闲物理块
{
flag[m] = 0;
}
for(j = 0;j < mSIZE; j++)
{
flag[j]++;
}
max = -1;
maxflag = 0;
n = -1;
}
for(j = 0 ;j < mSIZE; j++)
{
printf("%d ",memery[j]);
}
printf("\n");
}
printf("页面换算次数为：%d\n",count);
}