哲学家进餐问题奇偶方法代码c++

以下是哲学家进餐问题的奇偶方法的 C++ 代码实现：

#include <iostream>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <chrono>

using namespace std;

// 定义哲学家数量
const int kPhilosopherCount = 5;

// 定义叉子数量
const int kForkCount = 5;

// 定义哲学家和叉子的状态
enum class State {
    kThinking,
    kHungry,
    kEating
};

// 定义互斥锁和条件变量
mutex gForkMutex[kForkCount];
mutex gPrintMutex;
condition_variable gForkCV[kForkCount];
State gPhilosopherState[kPhilosopherCount];

// 左右叉子的编号
int LeftFork(int philosopher_id) {
    return philosopher_id;
}

int RightFork(int philosopher_id) {
    return (philosopher_id + 1) % kForkCount;
}

// 哲学家进餐
void Eat(int philosopher_id) {
    unique_lock<mutex> lock(gPrintMutex);
    cout << "Philosopher " << philosopher_id << " is Eating!" << endl;
    lock.unlock();
    // 模拟吃饭
    this_thread::sleep_for(chrono::seconds(1));
}

// 哲学家思考
void Think(int philosopher_id) {
    unique_lock<mutex> lock(gPrintMutex);
    cout << "Philosopher " << philosopher_id << " is Thinking!" << endl;
    lock.unlock();
    // 模拟思考
    this_thread::sleep_for(chrono::seconds(1));
}

// 获取叉子
void GetForks(int philosopher_id) {
    unique_lock<mutex> lock(gPrintMutex);
    cout << "Philosopher " << philosopher_id << " is Hungry!" << endl;
    lock.unlock();
    // 尝试获取左右叉子
    gForkMutex[LeftFork(philosopher_id)].lock();
    gForkMutex[RightFork(philosopher_id)].lock();
    // 修改哲学家状态为就餐状态
    gPhilosopherState[philosopher_id] = State::kEating;
    lock.lock();
    cout << "Philosopher " << philosopher_id << " gets forks and begins to eat!" << endl;
    lock.unlock();
}

// 放下叉子
void PutForks(int philosopher_id) {
    unique_lock<mutex> lock(gPrintMutex);
    cout << "Philosopher " << philosopher_id << " puts forks down!" << endl;
    // 修改哲学家状态为思考状态
    gPhilosopherState[philosopher_id] = State::kThinking;
    lock.unlock();
    gForkMutex[LeftFork(philosopher_id)].unlock();
    gForkMutex[RightFork(philosopher_id)].unlock();
    // 唤醒左右邻居，通知他们可以获取叉子了
    gForkCV[LeftFork(philosopher_id)].notify_all();
    gForkCV[RightFork(philosopher_id)].notify_all();
}

// 哲学家线程函数
void PhilosopherThread(int philosopher_id) {
    while (true) {
        // 哲学家思考
        Think(philosopher_id);
        // 哲学家变为饥饿状态
        gPhilosopherState[philosopher_id] = State::kHungry;
        // 尝试获取叉子
        GetForks(philosopher_id);
        // 哲学家进餐
        Eat(philosopher_id);
        // 放下叉子
        PutForks(philosopher_id);
    }
}

int main() {
    // 初始化哲学家状态为思考状态
    for (int i = 0; i < kPhilosopherCount; ++i) {
        gPhilosopherState[i] = State::kThinking;
    }
    // 创建哲学家线程
    thread philosopher_threads[kPhilosopherCount];
    for (int i = 0; i < kPhilosopherCount; ++i) {
        philosopher_threads[i] = thread(PhilosopherThread, i);
    }
    // 等待所有哲学家线程执行完毕
    for (int i = 0; i < kPhilosopherCount; ++i) {
        philosopher_threads[i].join();
    }
    return 0;
}

此代码实现了哲学家进餐问题的奇偶方法，通过奇偶编号的哲学家获取叉子的顺序不同，避免了死锁的问题。其中，`GetForks()` 函数中使用了条件变量，当左右叉子都被占用时，当前哲学家线程会等待左右邻居线程放下叉子并通知它可以获取叉子了。