integral

int main(int argc, char** argv)
{
    float fTimeStart = clock() / (float)CLOCKS_PER_SEC;
    MPI_Init(&argc, &argv);
    int rank;
    int process_count;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &process_count);
    double a = 0;
    double b = PI/2;
    double length = b - a;
    int NUMBER_OF_INTERVALS = 1000000000;
    double dx = (b - a) / NUMBER_OF_INTERVALS;
    int intervals_per_one_rank = NUMBER_OF_INTERVALS / process_count;
    double length_per_rank = (b - a) / process_count;

    double my_a = a + rank * length_per_rank;
    double my_b = a + (rank + 1) * length_per_rank;
    double sum = 0;
    for (int i = 0; i < intervals_per_one_rank; ++i)
    {
        sum += F(my_a + i * dx) * dx;
    }
    double total;
    MPI_Reduce(&sum, &total, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
    if (rank == 0)
    {
        printf("%.10lf\n", total);
        float fTimeStop = clock() / (float)CLOCKS_PER_SEC;
        printf("Working time = %f", -fTimeStart + fTimeStop);
    }
    MPI_Finalize();
}