#include <iostream>
#include <omp.h>

using namespace std;

double IntegralPI = 0.0;
double func(double x1, double x2){
    return (4.0/(1+x1*x1)+4.0/(1+x2*x2))*(x1-x2)/2;
}
void  sum(double s){
    IntegralPI += s;
}

int main(){
    double a = 0.0;
    double b = 1.0;
    const int n = 1000000;
    double x[n];
    x[0] = a;
    //double IntegralPI = 0.0;
    //double integralBuffer = 0.0;
    for(int i = 0; i < n-1; i++){
	x[i+1] = x[i]+(b-a)/n;
    }
    double t1 = omp_get_wtime();
    #pragma omp parallel for reduction(+: IntegralPI)
    for(int i = 0; i < n-1; i++){
         IntegralPI += func(x[i+1],x[i]);
    }
    IntegralPI += func(x[n-1],x[n-2]);
    double t2 = omp_get_wtime();
    cout << IntegralPI << " Working time: " << t2-t1 << endl;
    IntegralPI = 0;
    double t3 = omp_get_wtime();
    for(int i = 0; i < n-1; i++){
        IntegralPI += func(x[i+1],x[i]);
    }
    IntegralPI += func(x[n-1],x[n-2]);
    double t4 = omp_get_wtime();
    cout<< IntegralPI << " Working time: " << t4-t3 << endl;
    return 0;
}