Dining_Philosopher.c

//
// Created by Sumit on 26/09/22.
//

#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
#include <dirent.h>
#include <sys/types.h>
#include <stdlib.h>
#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 sleep(int i);

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]);
    }
}

void sleep(int i) {

}

// 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);
}