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

#define TOSSES 100000000

/* estimate Pi using a Monte Carlo method */
double estimate_pi() {
    int number_in_circle = 0, toss;

    /* loop through each toss */
    for (toss = 0; toss < TOSSES; toss++) {
        double x = ((double) rand() / (double) RAND_MAX) * 2.0 - 1.0;
        double y = ((double) rand() / (double) RAND_MAX) * 2.0 - 1.0;
        double dist_squared = x*x + y*y;

        if (dist_squared <= 1) {
            number_in_circle++;
        }
    }

    /* calculater this thread's pi estimate */
    double pi_estimate = (4 * number_in_circle) / (double) TOSSES;
    return pi_estimate;
}

int main () {
    /* print result */
    double pi = estimate_pi();
    printf("Pi is roughly %lf\n", pi); 
    return 0;
}