OpenMP set_num_threads() is not working

Question

I am writing a parallel program using OpenMP in C++.

I want to control the number of threads in the program using omp_set_num_threads(), but it does not

Answer 1

According to the GCC manual for omp_get_num_threads:

In a sequential section of the program omp_get_num_threads returns 1

So this:

cout<<"sum="<#pragma omp parallel
{
    cout<<"sum="<