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

#define THREADS 32
#define START 0
#define END 100000

/* the function called for each thread */
float sum_part() {
    /* get our thread id */
    int id = omp_get_thread_num();

    /* calculate the start and end points by evenly dividing the range */
    unsigned long start = ((END - START) / THREADS) * id;
    unsigned long end = start + ((END - START) / THREADS) - 1;

    /* the last thread needs to do all remaining ones */
    if (id == (THREADS - 1)) {
        end = END;
    }

    /* do the calculation */
    unsigned long i;
    float sum = 0;
    for (i = start; i <= end; i++) {
        sum += i;
    }

    return sum;
}

int main() {
    float global_sum = 0;
#pragma omp parallel num_threads(THREADS) reduction(+:global_sum)
    global_sum += sum_part();

    /* now all results are in */
    printf("Final answer = %f.\n", global_sum);
    return 0;
}