#include 	<pthread.h>
#include	<stdio.h>
#include	<stdlib.h>
#include	<time.h>

//Global variables
const int N=1000000;
const int tNUM = 4;
int array[1000000];
int count; //A shared variable that each thread will access

//The mutex is declared globally
pthread_mutex_t mp;

//function prototypes
int count3s(void);
void *count3s_thread(void *);

int main()
{
    int i, result;
    pthread_mutex_init(&mp, NULL);

//    srand(time(0));

    for (i = 0; i < N; i++)
	array[i] = rand()%100 + 1;
    result = count3s();
    printf("There were %d 3's\n",result);
//  The mutex is no longer needed
    pthread_mutex_destroy(&mp);
    exit(0);
}
// This function creates tNUM threads
int count3s(void)
{
    int i;
    int thr_data[tNUM];
    pthread_t thr[tNUM];
    for (i = 0; i < tNUM; i++) {
	thr_data[i] = i;
	pthread_create(&thr[i], NULL, count3s_thread, (void *)&thr_data[i]);
    }

    /* block until all threads complete */
    for (i = 0; i < tNUM; ++i) {
        pthread_join(thr[i], NULL);
    }

    return count;
}

// The funtion that each will execute
void *count3s_thread(void *id)
{
// Compute the portion of the array that this thread should search
     int myid = *(int *)id, cnt3 = 0, i;
     int private_count = 0;
     int length_per_thread = N/tNUM;
     int start = myid * length_per_thread;

     for ( i = start; i < start + length_per_thread; i++) {
	if(array[i] == 3) 
	   private_count++;
     }
// Acquire the mutex and add the threads count to the global count
     pthread_mutex_lock(&mp);
     count += private_count;
     pthread_mutex_unlock(&mp);
}