Dining Philosophers Problem between Processes

This is a solution to Dining Philosophers Problem between Processes. It starts 5 processes that runs infinitely, so require at least Intel i3 processor.

Platform : Linux

#include<iostream>
#include<stdlib.h>
#include<sys/ipc.h>
#include<sys/types.h>
#include<sys/shm.h>
#include<sys/mman.h>
#include<fcntl.h>
#include<unistd.h>
#include<semaphore.h>
using namespace std;
#define FORKS 5
#define PHIL_NUM 5
#define SNAME "SEM"
key_t key = 5678;
class philosopher {
 sem_t *lock;
 int shmid, *s, *shm, n, left_fork, right_fork;
 void open_sem();
 void open_shm(int);
 void think (void);
 void eat (void);
 void take_forks ();
 void put_forks ();
 public:
 const static int INIT = 0, NORMAL = 1;
 philosopher(int );
 void init_shm();
 void start();
};
/* initialises shared memory all positions to 0*/
void philosopher :: init_shm () {
 open_shm (INIT);
}
/** opens shared memory for a process at normal mode **/
void philosopher :: open_shm(int mode) {
 if ((shmid = shmget(key, FORKS * sizeof(int), IPC_CREAT | 0666)) < 0) {
 cout<<"shmget";
 exit(1);
 }
 if ( * (shm = (int *)shmat(shmid, NULL, 0)) == -1) {
 cout<<"shmat";
 exit(1);
 }
 s = shm;
 if (mode == INIT) {
 for(int i = 0; i < PHIL_NUM; i++) {
 *s++ = 0;
 }
 }
}
/** opening shared semaphores **/
void philosopher :: open_sem() {
lock = sem_open(SNAME, O_CREAT, 0644);
 sem_init(lock, 1, 1);
}
void philosopher::think() {
 cout<<"Philosopher "<<n<<" Starts thinking.\n";
 sleep(2);
 take_forks();
}
void philosopher::eat() {
 cout<<"Philosopher "<<n<<" Starts eating.\n";
 sleep(2);
 put_forks();
}
void philosopher::take_forks() {
 sem_wait(lock);
 while(!(s[left_fork] == 0 && s[right_fork] == 0)) {
 }
 s[right_fork] = 1;
 s[left_fork] = 1;
 sem_post(lock);
 eat();
}
void philosopher::put_forks() {
 s[right_fork] = 0;
 s[left_fork] = 0;
 think();
}
philosopher::philosopher(int num) {
 this->n = num;
 this->left_fork = num;
 this->right_fork = (num + 1) % PHIL_NUM;
 open_shm(NORMAL);
 open_sem();
}
void philosopher :: start() {
 take_forks();
}
int main() {
 /** Initialize the shared memories to 0 - means forks free **/
 philosopher p(2);
 p.init_shm();
 /** Create dynamic philosophers **/
 for(int i = 0; i < PHIL_NUM; i++)
 if(fork() == 0) {
 philosopher *p = new philosopher(i);
 p -> start();
 exit(0);
 }
sleep(10);
return 0;
 }