#include <iostream>
#include <stdlib.h>
#include <time.h>
using namespace std;
#define VM_PAGE 32 /*假设每个页面可以存放10条指令,则共有32个虚页*/
#define PM_PAGE 4 /*分配给作业的内存块数为4*/
#define TOTAL_INSERT 320
typedef struct
{
int vmn;
int pmn;
int exist;
int time;
int number;
}vpage_item;
vpage_item page_table[VM_PAGE];
vpage_item* ppage_bitmap[PM_PAGE];
int vpage_arr[TOTAL_INSERT];
void init_data() //数据初始化
{
for (int i = 0; i < VM_PAGE; i++)
{
page_table[i].vmn = i + 1; //虚页号
page_table[i].pmn = -1; //实页号
page_table[i].exist = 0;
page_table[i].time = -1;
page_table[i].number = 0;
}
for (int i = 0; i < PM_PAGE; i++) /*最初4个物理块为空*/
{
ppage_bitmap[i] = NULL;
}
}
void FIFO()/*FIFO页面置换算法*/
{
int k = 0;
int i;
int sum = 0;
int missing_page_count = 0;
int current_time = 0;
bool isleft = true; /*当前物理块中是否有剩余*/
while (sum < TOTAL_INSERT)
{
if (page_table[vpage_arr[sum] - 1].exist == 0)
{
missing_page_count++;
if (k < PM_PAGE)
{
if (ppage_bitmap[k] == NULL) /*找到一个空闲物理块*/
{
ppage_bitmap[k] = &page_table[vpage_arr[sum] - 1];
ppage_bitmap[k]->exist = 1;
ppage_bitmap[k]->pmn = k;
ppage_bitmap[k]->time = current_time;
k++;
}
}
else
{
int temp = ppage_bitmap[0]->time; /*记录物理块中作业最早到达时间*/
int j = 0; /*记录应当被替换的物理块号*/
for (i = 0; i < PM_PAGE; i++)
{
if (ppage_bitmap[i]->time < temp)
{
temp = ppage_bitmap[i]->time;
j = i;
}
}
ppage_bitmap[j]->exist = 0;
ppage_bitmap[j] = &page_table[vpage_arr[sum] - 1]; /*更新页表项*/
ppage_bitmap[j]->exist = 1;
ppage_bitmap[j]->pmn = j;
ppage_bitmap[j]->time = current_time;
}
}
current_time++;
sum++;
}
printf("FIFO算法缺页次数为:%d\t缺页率为:%f\t置换次数为:%d\t置换率为:%f\n", missing_page_count, missing_page_count / (float)TOTAL_INSERT, missing_page_count - 4, (missing_page_count - 4) / (float)TOTAL_INSERT);
}
void LRU()
{
int k = 0;
int i;
int sum = 0;
int missing_page_count = 0;
int current_time = 0;
bool isleft = true; /*当前物理块中是否有剩余*/
while (sum < TOTAL_INSERT)
{
if (page_table[vpage_arr[sum] - 1].exist == 0)
{
missing_page_count++;
if (k < PM_PAGE)
{
if (ppage_bitmap[k] == NULL) /*找到一个空闲物理块*/
{
ppage_bitmap[k] = &page_table[vpage_arr[sum] - 1];
ppage_bitmap[k]->exist = 1;
ppage_bitmap[k]->pmn = k;
ppage_bitmap[k]->time = current_time;
k++;
}
}
else
{
int temp = ppage_bitmap[0]->time; /*记录物理块中作业最早到达时间*/
int j = 0; /*记录应当被替换的物理块号*/
for (i = 0; i < PM_PAGE; i++)
{
if (ppage_bitmap[i]->time < temp)
{
temp = ppage_bitmap[i]->time;
j = i;
}
}
ppage_bitmap[j]->exist = 0;
ppage_bitmap[j] = &page_table[vpage_arr[sum] - 1]; /*更新页表项*/
ppage_bitmap[j]->exist = 1;
ppage_bitmap[j]->pmn = j;
ppage_bitmap[j]->time = current_time;
}
}
else
{
page_table[vpage_arr[sum] - 1].time = current_time;
}
current_time++;
sum++;
}
printf("LRU算法缺页次数为:%d\t缺页率为:%f\t置换次数为:%d\t置换率为:%f\n", missing_page_count, missing_page_count / (float)TOTAL_INSERT, missing_page_count - 4, (missing_page_count - 4) / (float)TOTAL_INSERT);
}
void OPT()
{
int k = 0;
int i;
int sum = 0;
int missing_page_count = 0;
int current_time = 0;
while (sum < TOTAL_INSERT)
{
if (page_table[vpage_arr[sum] - 1].exist == 0)
{
missing_page_count++;
if (k < PM_PAGE)
{
if (ppage_bitmap[k] == NULL) /*找到一个空闲物理块*/
{
ppage_bitmap[k] = &page_table[vpage_arr[sum] - 1];
ppage_bitmap[k]->exist = 1;
ppage_bitmap[k]->pmn = k;
ppage_bitmap[k]->time = current_time;
ppage_bitmap[k]->number = vpage_arr[sum];
k++;
}
}
else
{
int i, k;
int j = 0;/*记录应当被替换的物理块号*/
int distance[PM_PAGE] = {0};
int count = 0;
for (i = sum + 1; i < TOTAL_INSERT; i++)
{
for (k = 0; k < PM_PAGE; k++)
{
if (vpage_arr[i] == ppage_bitmap[k]->number&&distance[k] == 0)
{
distance[k] = i - sum;
count++;
break;
}
}
if (count == 3)
{
for (k = 0; k < PM_PAGE; k++)
{
if (distance[k] == 0)
{
j = k;
break;
}
}
break;
}
}
ppage_bitmap[j]->exist = 0;
ppage_bitmap[j] = &page_table[vpage_arr[sum] - 1]; /*更新页表项*/
ppage_bitmap[j]->exist = 1;
ppage_bitmap[j]->pmn = j;
ppage_bitmap[j]->time = current_time;
ppage_bitmap[j]->number = vpage_arr[sum];
}
}
current_time++;
sum++;
}
printf("OPT算法缺页次数为:%d\t缺页率为:%f\t置换次数为:%d\t置换率为:%f\n", missing_page_count, missing_page_count / (float)TOTAL_INSERT, missing_page_count - 4, (missing_page_count - 4) / (float)TOTAL_INSERT);
}
int main()
{
int a, n, m, count = -1;
int live[TOTAL_INSERT] = {0};
srand((unsigned)time(NULL));
while (count < TOTAL_INSERT - 1)
{
//产生随机数n,0至319
n = rand() % 320;
if (live[n] == 0)
{
live[n] == 1;
count++;
}
else
continue;
m = n / 10 + 1;//m为页面号,每10个指令为一个页面
vpage_arr[count] = m;//页面号存入
}
printf("请输入需要选择的页面置换算法:1.FIFO\t2.LRU\t3.OPT\t输入0结束\n");
do
{
scanf_s("%d", &a);
switch (a)
{
case 1:
init_data();
FIFO();
break;
case 2:
init_data();
LRU();
break;
case 3:
init_data();
OPT();
break;
}
} while (a != 0);
return 0;
}
操作系统实验——页面置换模拟程序设计
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