#include <iostream>
#include <omp.h>
#include <vector>
#include <cmath>
using namespace std;

const int N = 200000000;
const double step = 1 / N;
const double a = 0;
const double b = 4 * 3.14159265359;

double func(double x) {
    return sin(x);
}

double get_area(double left) {
    return (func(left + step) - func(left)) * step;
}

double get_integral(double a, double b, int points, int num_threads) {
    double integral = 0;
    #pragma omp parallel num_threads(num_threads) reduction(+:integral)
    {
    #pragma omp for
        for (long long j = 0; j < N; ++j)
            integral = get_area(a + (b - a) * j * 1. / N);
    }
    return integral;
}

double get_time(double start_time) {
    return omp_get_wtime() - start_time;
}

int main() {
    double integral = 0;

    cout << "Function f(x) = sin x, interval [0; 4*pi].\n\n";

    double time = 0;
    vector <double> diff(8);

    double start_time = omp_get_wtime();
    get_integral(a, b, N, 1);
    diff[0] = get_time(start_time);
    cout << 1 << " threads, integral = " << integral << ", time: " << get_time(start_time) <<
        ", speed up : " << diff[0] / get_time(start_time) << endl;

    for (int i = 2; i <= 8; ++i) {
        start_time = omp_get_wtime();
        integral = get_integral(a, b, N, i);
        cout << i << " threads, integral = " << integral << ", time: " << get_time(start_time) <<
            ", speed up : " << diff[0] / get_time(start_time) << endl;
    }

    return 0;
}