操作系統實習--模擬哲學家進餐

vc6.0，dev-cpp均可運行

#include<stdio.h>
#include<windows.h>
#include<process.h>

#define N 5                          //哲學家個數
#define LEFT(i) ((i) + N - 1) % N    //左邊哲學家編號
#define RIGHT(i) ((i) + 1) % N       //右邊哲學家編號
#define THINKING 0                   //思考狀態
#define HUNGRY 1                     //飢餓狀態
#define EATING 2                     //就餐狀態

int state[N];                        //哲學家狀態數組
HANDLE mutex;                        //狀態訪問互斥量，保證任一時刻，只有一個哲學家線程在檢查左右兩邊狀態
HANDLE semaphore[N];                 //哲學家線程信號量，標識哲學家是否獲取了筷子，否則線程阻塞
HANDLE semPar;                       //線程同步信號量，

void thinking(int i);  //思考
void eating(int i);   //吃飯
void take_chopsticks(int i);  
void put_chopsticks(int i);    
void test(int i);        //判斷左右是否有空筷子

unsigned int __stdcall philosopher(void *pM)
{
    int i,cnt =20;
    i = *(int*)pM;
    //線程編號，同步
    ReleaseSemaphore(semPar, 1, NULL);
    while(cnt--)// 規定每位哲學家用用餐20次後結束 
    {
        thinking(i);
        take_chopsticks(i);
        eating(i);
        put_chopsticks(i);
    }
    return 0;
}

void take_chopsticks(int i)
{
    //互斥修改及檢查哲學家狀態
    WaitForSingleObject(mutex, INFINITE);
    state[i] = HUNGRY;
    test(i);
    ReleaseSemaphore(mutex, 1, NULL);
    //若獲得了兩隻筷子，則繼續執行，否則阻塞在此處，等待鄰居放下筷子
    WaitForSingleObject(semaphore[i], INFINITE);
}

void put_chopsticks(int i)
{
    WaitForSingleObject(mutex, INFINITE);
    state[i] = THINKING;
    test(LEFT(i));                         //檢查左邊哲學家是否可以就餐
    test(RIGHT(i));                        //檢查右邊哲學家是否可以就餐
    ReleaseSemaphore(mutex, 1, NULL);
}

void test(int i)
{
    if(state[i] == HUNGRY && state[LEFT(i)] != EATING && state[RIGHT(i)] != EATING)
    {
        state[i] = EATING;
        ReleaseSemaphore(semaphore[i], 1, NULL);
    }
}

void eating(int i)
{
    printf("哲學家[%d]正在吃飯\n", i);
    Sleep(3000);
    printf("哲學家[%d]已經吃完 放下筷子\n\n", i);
}

void thinking(int i)
{   printf("哲學家[%d]正在思考\n", i);
    Sleep(3000);
	printf("哲學家[%d]思考完餓了\n\n", i);
 }


int main()
{
    int i;
    HANDLE thread[N];
	printf("--------------------------------\n");
	printf("-         模擬哲學家進餐       -\n");
	printf("********************************\n");
    mutex = CreateSemaphore(NULL, 1, 1, NULL);  //設定每個哲學家在思考
    for(i = 0;i < N;i++)
    {
        semaphore[i] = CreateSemaphore(NULL, 0, 1, NULL);    //將每個信號量賦值
    }

    semPar = CreateSemaphore(NULL, 0, 1, NULL);

    for(i = 0;i <N;i++)
    {
        thread[i] = (HANDLE)_beginthreadex(NULL, 0,philosopher, &i, 0, NULL);
        WaitForSingleObject(semPar, INFINITE);
    }
    WaitForMultipleObjects(N, thread, TRUE, INFINITE);
	return 0;
}