Problem with Dining Philosopher

Semaphore Solution to Dining Philosopher

Each philosopher is represented by the following pseudocode:...

Code

C++ #include #include #include #include #define N 5 #define THINKING 2 #define HUNGRY 1 #define EATING 0 #define LEFT (phnum + 4) % N #define RIGHT (phnum + 1) % N int state[N]; int phil[N] = { 0, 1, 2, 3, 4 }; std::mutex mutex; std::condition_variable S[N]; void test(int phnum) { if (state[phnum] == HUNGRY && state[LEFT] != EATING && state[RIGHT] != EATING) { // state that eating state[phnum] = EATING; std::this_thread::sleep_for(std::chrono::milliseconds(2000)); std::cout << "Philosopher " << phnum + 1 << " takes fork " << LEFT + 1 << " and " << phnum + 1 << std::endl; std::cout << "Philosopher " << phnum + 1 << " is Eating" << std::endl; // notify the philosopher that he can start eating S[phnum].notify_all(); } } // take up chopsticks void take_fork(int phnum) { std::unique_lock lock(mutex); // state that hungry state[phnum] = HUNGRY; std::cout << "Philosopher " << phnum + 1 << " is Hungry" << std::endl; // eat if neighbours are not eating test(phnum); // if unable to eat wait to be signalled S[phnum].wait(lock); std::this_thread::sleep_for(std::chrono::milliseconds(1000)); } // put down chopsticks void put_fork(int phnum) { std::unique_lock lock(mutex); // state that thinking state[phnum] = THINKING; std::cout << "Philosopher " << phnum + 1 << " putting fork " << LEFT + 1 << " and " << phnum + 1 << " down" << std::endl; std::cout << "Philosopher " << phnum + 1 << " is thinking" << std::endl; test(LEFT); test(RIGHT); } void philosopher(int num) { while (true) { take_fork(num); put_fork(num); } } int main() { std::thread threads[N]; for (int i = 0; i < N; i++) { threads[i] = std::thread(philosopher, i); std::cout << "Philosopher " << i + 1 << " is thinking" << std::endl; } for (int i = 0; i < N; i++) threads[i].join(); return 0; } C #include #include #include #define N 5 #define THINKING 2 #define HUNGRY 1 #define EATING 0 #define LEFT (phnum + 4) % N #define RIGHT (phnum + 1) % N int state[N]; int phil[N] = { 0, 1, 2, 3, 4 }; sem_t mutex; sem_t S[N]; void test(int phnum) { if (state[phnum] == HUNGRY && state[LEFT] != EATING && state[RIGHT] != EATING) { // state that eating state[phnum] = EATING; sleep(2); printf("Philosopher %d takes fork %d and %d\n", phnum + 1, LEFT + 1, phnum + 1); printf("Philosopher %d is Eating\n", phnum + 1); // sem_post(&S[phnum]) has no effect // during takefork // used to wake up hungry philosophers // during putfork sem_post(&S[phnum]); } } // take up chopsticks void take_fork(int phnum) { sem_wait(&mutex); // state that hungry state[phnum] = HUNGRY; printf("Philosopher %d is Hungry\n", phnum + 1); // eat if neighbours are not eating test(phnum); sem_post(&mutex); // if unable to eat wait to be signalled sem_wait(&S[phnum]); sleep(1); } // put down chopsticks void put_fork(int phnum) { sem_wait(&mutex); // state that thinking state[phnum] = THINKING; printf("Philosopher %d putting fork %d and %d down\n", phnum + 1, LEFT + 1, phnum + 1); printf("Philosopher %d is thinking\n", phnum + 1); test(LEFT); test(RIGHT); sem_post(&mutex); } void* philosopher(void* num) { while (1) { int* i = num; sleep(1); take_fork(*i); sleep(0); put_fork(*i); } } int main() { int i; pthread_t thread_id[N]; // initialize the semaphores sem_init(&mutex, 0, 1); for (i = 0; i < N; i++) sem_init(&S[i], 0, 0); for (i = 0; i < N; i++) { // create philosopher processes pthread_create(&thread_id[i], NULL, philosopher, &phil[i]); printf("Philosopher %d is thinking\n", i + 1); } for (i = 0; i < N; i++) pthread_join(thread_id[i], NULL); }...

Problem with Dining Philosopher

We have demonstrated that no two nearby philosophers can eat at the same time from the aforementioned solution to the dining philosopher problem. The problem with the above solution is that it might result in a deadlock situation. If every philosopher picks their left chopstick simultaneously, a deadlock results, and no philosopher can eat. This situation occurs when this happens....

FAQs on Dining Philosopher Problem Using Semaphores

Q.1: What is the main challenge in the dining philosophers problem?...