IMPLEMENTING DINING PHILOSOPHER PROBLEM

C PROGRAM THAT IMPLEMENTS A  DINING PHILOSOPHER PROBLEM

#include<stdio.h>
#include<stdlib.h>
#include<semaphore.h>
#include<pthread.h>
#include<unistd.h>
#include<string.h>
#include<sys/types.h>
#include<sys/wait.h>
#define N 5
#define LEFT (i+4)%N

#define RIGHT (i+1)%N

#define THINKING 0
#define HUNGRY 1
#define EATING 2
sem_t spoon;
sem_t phil[N];
int state[N];
int phil_num[N]={0,1,2,3,4};
int fd[N][2];// file descriptors for pipes
pid_t pid, pids[N];// process ids
int i;int num;
void philosopher(int i);
void test(int i);
void take_spoon(int i);
void put_spoon(int i);
char buffer[100];
int main(void)
{
for(i=0;i<N;++i)
{

pipe(fd[i]);
pids[i]= fork();

printf("i=%d\n",i);

printf("pids[i]=%d\n",pids[i]);
if(pids[i]==0)
{// child

dup2(fd[i][1],1);

close(fd[i][0]);

close(fd[i][1]);

philosopher(i);

exit(0);
}
else
if(pids[i]>0)
{
// parent

dup2(fd[i][0],0);

close(fd[i][0]);

close(fd[i][1]);
}
}// wait for child processes to end
for(i=0;i<N;++i) 
waitpid(pids[i],NULL,0);
return 0;
}
void philosopher(int i)
{
while(1)
{

sleep(1);

take_spoon(i);

sleep(2);

put_spoon(i);

sleep(1);
}
}
void take_spoon(int i)
{

sem_wait(&spoon);

state[i]= HUNGRY;

printf("philosopher %d is hungry\n",i+1);

test(i);

sem_post(&spoon);

sem_wait(&phil[i]);
}
void put_spoon(int i)
{

sem_wait(&spoon);

state[i]= THINKING;

printf("philosopher %d puts down spoon %d and %d hin\n",i+1,LEFT+1,i+1);

printf("philosopher %d thinks\n",i+1);

test(LEFT);

test(RIGHT);

sem_post(&spoon);
}
void test(int i)
{
if( state[i]== HUNGRY && state[LEFT]!= EATING && state[RIGHT]!= EATING)
{

state[i]= EATING;

printf("philosopher %d takes spoon %d and %d\n",i+1,LEFT+1,i+1);

printf("philosopher %d eats\n",i+1);

sem_post(&phil[i]);
}
}

output:-