gistfile1.txt

#include <stdio.h>
#include <omp.h>
static long num_steps = 1000;
double step,start = 0.0,stop = 0.0;
#define NUM_THREADS 1
int main ()
{
    double pi;
    step = 1.0/(double) num_steps;
    omp_set_num_threads(NUM_THREADS);
        #pragma omp parallel
        {
        int i, id,nthrds,nthreads = 0; double x, sum;
        id = omp_get_thread_num();
        nthrds = omp_get_num_threads();
        if (id == 0) nthreads = nthrds;
        start = omp_get_wtime();
           for (i=id, sum=0.0;i< num_steps; i=i+nthreads){
                x = (i+0.5)*step;
                sum += 4.0/(1.0+x*x);
                }
           sum = sum*step;
        #pragma omp atomic
        pi += sum ;
        }
    stop = omp_get_wtime();
    printf("pi = %f",pi);
    printf("time = %f",stop-start);
}