Question

Using the following pseudocode write a c program that solves the dining philosophers problem.

#define N 5

#define LEFT (i+N-1)%N

#define RIGHT (i+1)%N

#define THINKING 0

#define HUNGRY 1

#define EATING 2

typedef int semaphore;

int state[N];

semaphore mutex = 1;

semaphore s[N];

void philosopher(int i)

{

while(TRUE) {

think();

take_forks(i);

eat();

put_forks(i);

}

}

void take_forks(int i)

{

down(&mutex);

state[i] = HUNGRY;

test(i);

up(&mutex);

down(&s[i]);

}

void put_forks(i)

{

down(&mutex);

state[i] = THINKING;

test(LEFT);

test(RIGHT);

up(&mutex);

}

void test(i)

{

if(state[i] == HUNGRY && state[LEFT]!= EATING && state[RIGHT] != EATING) {

state[i] = EATING;

up(&s[i];

}

}

Answer 1

File Edit Format View Help #include<stdio.h> #include« semaphore.h> #include«pthread.h> #define N 5 #define THINKING 0 #define HUNGRY ! #define EATING 2 #define LEFT (ph-num-4)SN #define RIGHT (ph-num-1)SN sem_t mutex; sem t S[N]; void * philospher(void *num); void take fork(int); void put fork(int); void test (int); int state[N]; int phil num[N] 0,1,2,3,4; int main) int i; pthread_t thread_id[N]; sem init (&mutex,0,1); for (i-e;i«n;i++) sem init (&S[i],e,0); pthread_create(&thread_id[i],NULL, philospher,&phil_num[i]); printf("Philosopher %d is thinking\n",i+1); for(i-e;i<N;i++) pthread_join(thread id[i],NULL); void *philospher (void *num) while(1) int *i = num; sleep (1); take-fork( *i) ; sleep(0); put fork(*i); void take fork(int ph_num) sem wait (&mutex); state(ph-num] HUNGRY; printf("Philosopher %d is Hungry\n",ph-num-1 ) ;

void take_fork(int ph_num) sem wait (&mutex); state[ph num]HUNGRY printf("Philosopher %d test (ph_num); sem_post (&mutex); sem_wait (&S[ph_num]) sleep (1); is Hungry\n",ph-num-1); void test (int ph_num) if (state[ph-num] HUNGRY && stat e [LEFT] != EATING && stat e [ RIGHT ] != EATING) ー state(ph-num] EATING; sleep (2); printf( "Philosopher %d takes fork %d and %d\n",ph-num-1, LEFT+1 , ph-num-1); printf("Philosopher %d IS Eating\n",ph-num-1); sem post (&Sph numl): void put_fork(int ph_num) sem wait (&mutex); state[ph num]THINKING; printf("Philosopher %d putting fork %d and %d down\n",ph-num-1, LEFT+1,ph-num-1); printf("Philosopher %d Is thinking\n",ph-num-1); test (LEFT); test (RIGHT); sem post (&mutex):