parallel programming : pi calculation.

main.c

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

double piCalculation() {
    static int num_total_steps = 100000;
    int num_steps = (num_total_steps / omp_get_num_threads());
    double step;
    double sum = 0.0;
    double execution_time = omp_get_wtime();
    step = 1.0 / (double)  num_total_steps;
    #pragma omp parallel num_threads(1)
    {
        int i;
        double x;
        double localSum = 0.0;
        for (i = omp_get_thread_num() * num_steps; i < num_steps; i++) {
            x = (i + 0.5) * step;
            localSum += 4.0 / (1.0 + x * x);
        }

        #pragma omp critical
        sum += localSum;
    };

    printf("Execution time : %f\n",  omp_get_wtime() - execution_time);

    return step * sum;
}

int main() {
    omp_set_num_threads(4);
    printf("Result : %f\n", piCalculation());
}

sum_execution_time += execution_time; this statement may cause raise condition. The sum operation should be atomic.

I used the mutex to sync sum_execution_time and sum shared variables with using #pragma omp critical directive. Could you check this again @muatik