OPT, LRU, FIFO页面调度算法的模拟

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <deque>
#include <map>
#include <algorithm>

using namespace std;
int findLRU(map<int, int> managedMap);
deque<int> fifo;
map<int, int> lru;
map<int, int>opt;

const int LEN = 1000;		//要访问的页面总数
const int BLOCKNO = 3;  //物理块数
const int INF = 999999; //用于opt算法中在后续找不到该元素所用

int main() {
//初始化测试以数据
srand((unsigned)time(NULL));
int testData[LEN];
//int testData[LEN] = {2,3,2,1,5,2,4,5,3,2,5,2};
for (int i = 0; i < LEN; i++) {
testData[i] = rand() % 5 + 1;
}

//初始化测试数据完毕

int success=0;	//命中次数
int fail = 0;	//缺页次数 + 物理块数

//FIFO算法
for (int i = 0; i < LEN; i++) {
auto pos = find(fifo.cbegin(), fifo.cend(), testData[i]);
if (pos != fifo.cend())
success++;
else {
fail++;
if (fifo.size() < BLOCKNO) {
fifo.push_back(testData[i]);
}
else {
fifo.pop_front();
fifo.push_back(testData[i]);
}
}
}
cout << "测试数据：[" << testData[0];
for (int i = 1; i <= LEN-1; i++) {
cout << ", " << testData[i];
}
cout << "]" << endl<<endl;
cout << "使用"<<BLOCKNO<<"个物理块"<<endl;
cout << "FIFO算法" << endl;
cout << "\t缺页数：" << fail - BLOCKNO;
cout << "\t缺页率" << (double)fail / LEN;
cout << "\t命中率" << (double)success / LEN<<endl<<endl;

success = 0;
fail = 0;

//LRU算法 lru的map，map->first代表页面值，每过一个循环map->second全部都会+1，那么越久没用到的它的second就越大，那么替换的时候
//就把second最大的替换出去
for (int i = 0; i < LEN; i++) {
auto pos = lru.find(testData[i]);
if (pos != lru.end()) {
success++;
lru[testData[i]] = 0;
}
else {
fail++;
if (!(lru.size() < BLOCKNO)) {
lru.erase(findLRU(lru));

}

lru[testData[i]] = 0;

}
map<int, int>::iterator it=lru.begin();
for (; it != lru.end(); it++) {
it->second++;
}

}

cout << "LRU算法" << endl;
cout << "\t缺页数：" << fail - BLOCKNO;
cout << "\t缺页率" << (double)fail / LEN;
cout << "\t命中率" << (double)success / LEN<<endl<<endl;

success = 0;
fail = 0;

//OPT算法   与lru相同这个也用map实现，first含义与lru相同，second代表的是下一个相同的页面出现的位置，这个位置越远那么他越先被
//替换，这个算法是命中率最高的，但在实际情况中是无法实现的。我们只能假装模拟一下
for (int i = 0; i < LEN; i++) {
auto pos = opt.find(testData[i]);
if (pos != opt.end()) {
success++;
}
else {
fail++;
if (!(opt.size() < BLOCKNO)) {
opt.erase(findLRU(opt));
}
}
//更新second数据
int nextPos = -1;
for (int j = i + 1; j < LEN; j++) {
if (testData[j] == testData[i]) {
nextPos = j;
break;
}
}
if (nextPos == -1)
nextPos = INF;
opt[testData[i]] = nextPos;

}

cout << "OPT算法" << endl;
cout << "\t缺页数：" << fail - BLOCKNO;
cout << "\t缺页率" << (double)fail / LEN;
cout << "\t命中率" << (double)success / LEN;

return 0;
}

int findLRU(map<int, int> managedMap) {
int max = -1;
int index;
map<int, int> ::iterator it=managedMap.begin();
for (; it != managedMap.end(); it++) {
if (it->second > max) {
max = it->second;
index = it->first;
}
}
return index;
}