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

int main(){

clock_t begin,end;

long int numSteps=1000000;
double step;

int i;
double x,pi,sum=0.0;

step=1/(double)numSteps;

begin=clock();

omp_set_num_threads(4); //I have set the number of threads =4, you can change this. 
#pragma omp parallel 
{
for(i=0;i<numSteps;i++){
   x=(i+0.5)*step;
   sum+=4.0/(1.0+x*x);
}
pi=sum*step;
end=clock();
printf("pi=%18.16f and time =%f\n",pi, (double)(end - begin) / CLOCKS_PER_SEC);
}
}