philosem2.c

word count information using message queues

/*
  check fifth fork...output is oppikable

*/

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#include<sys/shm.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/sem.h>

#define N  5
#define THINKING 1
#define HUNGRY 2
#define EATING 3
#define uniqkey ftok("." , 'A')
 
union semun 
	{
	int val;
	struct semid_ds *buf;
	ushort *array;
	};
int state[N];
int semid,ret=0;
  static struct sembuf acquire={0,-1,SEM_UNDO};
  static struct sembuf release={0,1, SEM_UNDO};
 
static ushort initial[6]={6,5,4,3,2,1};	//its giving some error other way
union semun arg;
 

void initialize (void)
{
	int ky=0;
	for(ky;ky<N;ky++)
		{
		state[ky]=THINKING;
		}
}

int left (int k)
	{
	return ((k+N-1)%N);
	}

int right (int k)
	{
	return ((k+1)%N);
	}

int randomizeme (int d)				//not used
{
	int lret;
	ret=(ret +1)%5;
	lret=ret*d - (ret+d);
	if(lret<=0)
		return 5;
	else
		return lret;
}

void printstate (void)
{
	int ku=0;
	for(ku;ku<5;ku++)
		{
		printf(" P%d --",ku);
		switch (state[ku])
			{
			case 1 :
				printf("THINKING ## ");break;
			case 2 :
				printf("HUNGRY ## ");break;
			case 3 :
				printf("EATING ## ");break;
			default :
				printf("invalid choice \n");
			}
		printf("\n");
		}

}

int test (int ph)
{
	if( (state[left(ph)]!=EATING) && (state[right(ph)]!=EATING) &&  (state[ph]==HUNGRY)  )
		{
			if(ph==0)
			{
			acquire.sem_num=5;
			if(semop(semid,&acquire,1)==-1)
				{
				printf("error in acquiring %d \n",5);
				}
			}
			else
			{
			acquire.sem_num=ph;
			if(semop(semid,&acquire,1)==-1)
				{
				printf("error in acquiring %d \n",ph);
				}
			}
			acquire.sem_num=(ph+1)%N;
			if(semop(semid,&acquire,1)==-1)
				{
				printf("error in acquiring %d \n",(ph+1));
				}
			state[ph]=EATING;
		return 1;
		}
	else
		{return 0;}
}

void takeforks (int p)
{
	int t;
	if((p%2)==0)
		{
		state[p]=HUNGRY;
		if(test(p))
			{	//left right
			
			sleep(2); //eating time
		
			}
		else
			{
			sleep(2);
			takeforks(p);
			}
		}
	else
		{
		state[p]=HUNGRY;
		//sleep(1); 	 //randomness urapppilla
		if(test(p))
			{	//right left
// 			acquire.sem_num=right(p);
// 			if(semop(semid,&acquire,1)==-1)
// 				{
// 				printf("error in acquiring %d \n",right(p));
// 				}
// 			acquire.sem_num=left(p);
// 			if(semop(semid,&acquire,1)==-1)
// 				{
// 				printf("error in acquiring %d \n",left(p));
// 				}
// 			state[p]=EATING;
			sleep(2); //eating time
		
			}
		else
			{
			sleep(3);
			takeforks(p);
			}
		}
	//putdownforks(p);
}

void putdownforks (int r)
{
	if(r==0)
	{
	release.sem_num=(5);
	if(semop(semid,&release,1)==-1)
				{
				//printf("error in releasing %d \n",5);
				}
	}
	else
	{
	release.sem_num=(r);
	if(semop(semid,&release,1)==-1)
				{
				printf("error in releasing %d \n",r);
				}
	}
	release.sem_num=(r+1);
	if(semop(semid,&release,1)==-1)
				{
				printf("error in releasing %d \n",(r+1));
				}
	state[r]=THINKING;
// 	if (test(r))
// 	{
// 	takeforks(left(r));putdownforks(r);
// 	takeforks(right(r));putdownforks(r);
// 	}
}


void * philosopher (void *num)
{
	int n,ch=6;
	n=(int) num;
	printf("***%d \n",n);
	if(n!=N)
		{
		if(semget(uniqkey,6,0)==-1)		//diff process should first access semaphore(no need 4 creation)
			{
			printf("error in accessing semaphores \n");
			}	

			
		if((n%2)!=0)
			{sleep(1);}
			
		while(ch)
			{
// 			printf("[ %d #### %d ] \n",n,state[n]);
			ch--;
 			//printf()
			takeforks(n);
			putdownforks(n);
			sleep(4);
			}

		

		}
	else
		{//for printing
		ch=25;
		while(ch)
			{
			printf("=====================================================\n");
			sleep(1);
			printstate();
			ch--;
			}
		}
	pthread_exit(NULL);
}

int main()
{
printf("ok\n");
printf(" eshwara ithu work cheyyane \n");
//printf("$$%d$$",left(0));
//printf("$%d$",right(0));
initialize();			//all philosophers are made to think

arg.array=initial;		//not able to do globally! :(

semid=semget(uniqkey,6,IPC_CREAT|IPC_EXCL|0666); //6 bcz i am using from 1 to 5...5 is enough
if(semid==-1)
	{
	printf("error in making semaphore \n");
	}
if(semctl(semid,0,SETALL,arg) == -1)
	{
	printf("error in initialization \n");
	}

//int po=555;
pthread_t  phil ;
int thread;
int i=0;
for(i;i<=N;i++)
	{
	thread=pthread_create(&phil,NULL,philosopher,(void *) i);
	if(thread)
		{
		printf("error in creating threads \n");
		}
	}
for(i=0;i<=N;i++)
	{
	pthread_join(phil,NULL);
	}

if(semctl(semid,0,IPC_RMID,0) ==-1)
	{
	printf("error in removing semaphores \n");
	}
 printf("=======================THE END======================\n");
 
return 0;
}