Notes

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

#include <pthread.h>

// size of array
#define MAX 16

// maximum number of threads
#define MAX_THREAD 4


int a[] = { 1, 5, 7, 10, 12, 14, 15, 18, 20, 22, 25, 27, 30, 64, 110, 220 };
int sum[4] = { 0 };
int part = 0;

void* sum_array(void* arg)
{

// Each thread computes sum of 1/4th of array
int thread_part = part++;

for (int i = thread_part * (MAX / 4); i < (thread_part + 1) * (MAX / 4); i++)
sum[thread_part] += a[i];
}

// Driver Code
int main()
{

pthread_t threads[MAX_THREAD];

// Creating 4 threads
for (int i = 0; i < MAX_THREAD; i++)
pthread_create(&threads[i], NULL, sum_array, (void*)NULL);

// joining 4 threads i.e. waiting for all 4 threads to complete
for (int i = 0; i < MAX_THREAD; i++)
pthread_join(threads[i], NULL);

// adding sum of all 4 parts
int total_sum = 0;
for (int i = 0; i < MAX_THREAD; i++)
total_sum += sum[i];

printf("n sum is %i ", total_sum) ;

return 0;
}