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

#define NUM_THREADS 4  // Number of threads
#define ARRAY_SIZE 100  // Size of the array

int array[ARRAY_SIZE];
int total_sum = 0;
pthread_mutex_t sum_mutex;
pthread_barrier_t sum_barrier;

// Function for each thread to compute part of the sum
void *partial_sum(void *arg) {
    int thread_part = *(int*)arg;
    int local_sum = 0;

    // Calculate partial sum for this thread's part of the array
    for(int i = thread_part * (ARRAY_SIZE / NUM_THREADS); i < (thread_part + 1) * (ARRAY_SIZE / NUM_THREADS); i++) {
        local_sum += array[i];
    }

    // Wait at the barrier for all threads to finish their part
    pthread_barrier_wait(&sum_barrier);

    // Only one thread at a time updates the total sum
    pthread_mutex_lock(&sum_mutex);
    total_sum += local_sum;
    pthread_mutex_unlock(&sum_mutex);

    pthread_exit(NULL);
}

int main() {
    pthread_t threads[NUM_THREADS];
    int thread_args[NUM_THREADS];
    int status;

    // Initialize array with some values
    for(int i = 0; i < ARRAY_SIZE; i++) {
        array[i] = i + 1;  // Fill the array with numbers 1 to 100
    }

    // Initialize mutex and barrier
    pthread_mutex_init(&sum_mutex, NULL);
    pthread_barrier_init(&sum_barrier, NULL, NUM_THREADS);

    // Create threads
    for(int i = 0; i < NUM_THREADS; i++) {
        thread_args[i] = i;
        status = pthread_create(&threads[i], NULL, partial_sum, (void *)&thread_args[i]);

        if (status != 0) {
            printf("ERROR; return code from pthread_create() is %d\n", status);
            exit(-1);
        }
    }

    // Wait for all threads to complete
    for(int i = 0; i < NUM_THREADS; i++) {
        pthread_join(threads[i], NULL);
    }

    // Print the total sum
    printf("Total sum is: %d\n", total_sum);
    
    // Clean up and exit
    pthread_mutex_destroy(&sum_mutex);
    pthread_barrier_destroy(&sum_barrier);

    return 0;
}