c++实现银行家算法
时间: 2023-11-13 12:57:01 浏览: 67
银行家算法是一种避免死锁的算法,它通过动态地分配资源来避免进程因争夺资源而发生死锁。下面是C++实现银行家算法的基本思路:
1. 定义资源数量和进程数量
2. 定义可用资源向量、最大需求矩阵、已分配矩阵和需求矩阵
3. 初始化可用资源向量、最大需求矩阵、已分配矩阵和需求矩阵
4. 判断当前状态是否安全,如果安全则分配资源,否则等待
5. 释放资源
下面是一个简单的C++实现:
```c++
#include <iostream>
#include <vector>
using namespace std;
const int MAX_PROCESS = 10;
const int MAX_RESOURCE = 10;
int available[MAX_RESOURCE];
int max_need[MAX_PROCESS][MAX_RESOURCE];
int allocation[MAX_PROCESS][MAX_RESOURCE];
int need[MAX_PROCESS][MAX_RESOURCE];
bool finish[MAX_PROCESS];
int n_process, n_resource;
bool is_safe() {
vector<int> work(available, available + n_resource);
vector<bool> finish(n_process, false);
int count = 0;
while (count < n_process) {
bool found = false;
for (int i = 0; i < n_process; i++) {
if (!finish[i]) {
bool can_allocate = true;
for (int j = 0; j < n_resource; j++) {
if (need[i][j] > work[j]) {
can_allocate = false;
break;
}
}
if (can_allocate) {
for (int j = 0; j < n_resource; j++) {
work[j] += allocation[i][j];
}
finish[i] = true;
found = true;
count++;
}
}
}
if (!found) {
return false;
}
}
return true;
}
bool request_resources(int pid, int request[]) {
for (int i = 0; i < n_resource; i++) {
if (request[i] > need[pid][i] || request[i] > available[i]) {
return false; }
}
for (int i = 0; i < n_resource; i++) {
available[i] -= request[i];
allocation[pid][i] += request[i];
need[pid][i] -= request[i];
}
if (is_safe()) {
return true;
} else {
for (int i = 0; i < n_resource; i++) {
available[i] += request[i];
allocation[pid][i] -= request[i];
need[pid][i] += request[i];
}
return false;
}
}
void release_resources(int pid, int release[]) {
for (int i = 0; i < n_resource; i++) {
available[i] += release[i];
allocation[pid][i] -= release[i];
need[pid][i] += release[i];
}
}
int main() {
cout << "Enter the number of processes: ";
cin >> n_process;
cout << "Enter the number of resources: ";
cin >> n_resource;
cout << "Enter the available resources: ";
for (int i = 0; i < n_resource; i++) {
cin >> available[i];
}
cout << "Enter the maximum need matrix: ";
for (int i = 0; i < n_process; i++) {
for (int j = 0; j < n_resource; j++) {
cin >> max_need[i][j];
}
}
cout << "Enter the allocation matrix: ";
for (int i = 0; i < n_process; i++) {
for (int j = 0; j < n_resource; j++) {
cin >> allocation[i][j];
need[i][j] = max_need[i][j] - allocation[i][j];
}
}
if (is_safe()) {
cout << "The system is safe." << endl;
} else {
cout << "The system is not safe." << endl;
}
int pid;
int request[MAX_RESOURCE];
int release[MAX_RESOURCE];
while (true) {
cout << "Enter the process id (or -1 to exit): ";
cin >> pid;
if (pid == -1) {
break;
}
cout << "Enter the request vector: ";
for (int i = 0; i < n_resource; i++) {
cin >> request[i];
}
if (request_resources(pid, request)) {
cout << "The request is granted." << endl;
} else {
cout << "The request is denied." << endl;
}
cout << "Enter the release vector: ";
for (int i = 0; i < n_resource; i++) {
cin >> release[i];
}
release_resources(pid, release);
}
return 0;
}
```