Use a Monte-Carlo methodto calculate the value of the mathematical constant Ï. Pseudocode for this method of solving pie can be found in the book along with more insight on how the algorithm works. 
template:
#include
#include
#include
#include
#include

// Returns a random value between -1 and 1
double getRand(unsigned int *seed) {
   return (double) rand_r(seed) * 2 / (double) (RAND_MAX) – 1;
}

long double Calculate_Pi_Sequential(long long number_of_tosses) {
   unsigned int seed = (unsigned int) time(NULL);

   return 0;
}

long double Calculate_Pi_Parallel(long long number_of_tosses) {
#pragma omp parallel num_threads(omp_get_max_threads())
   {
       unsigned int seed = (unsigned int) time(NULL) + (unsigned int) omp_get_thread_num();

   }
   return 0;
}

int main() {
   struct timeval start, end;

   long long num_tosses = 10000000;

   printf(“Timing sequential…n”);
   gettimeofday(&start, NULL);
   long double sequential_pi = Calculate_Pi_Sequential(num_tosses);
   gettimeofday(&end, NULL);
   printf(“Took %f secondsnn”, end.tv_sec – start.tv_sec + (double) (end.tv_usec – start.tv_usec) / 1000000);

   printf(“Timing parallel…n”);
   gettimeofday(&start, NULL);
   long double parallel_pi = Calculate_Pi_Parallel(num_tosses);
   gettimeofday(&end, NULL);
   printf(“Took %f secondsnn”, end.tv_sec – start.tv_sec + (double) (end.tv_usec – start.tv_usec) / 1000000);

   // This will print the result to 10 decimal places
   printf(“Ï = %.10Lf (sequential)n”, sequential_pi);
   printf(“Ï = %.10Lf (parallel)”, parallel_pi);

   return 0;
}