set the task to write a pair of C++ algorithms using OpenMP.
Since I have MacBook, I had to install the IDE CLION and work with it.

Main.CPP code:

# include & lt; iostream & gt;
#Include "/usr/local/opt/libomp/include/omp.h"
#Define Thread_Num 4.
INT MAIN ()
{
  OMP_SET_NUM_THREADS (Thread_NUM);
  STD :: COUT & LT; & LT; OMP_GET_THREAD_LIMIT & LT; & LT; STD :: ENDL;
#Pragma Omp Parallel for Num_Threads (4)
  {
    STD :: COUT & LT; & LT; "Number of Available Threads:" & lt; & lt; OMP_GET_NUM_THREADS () & lt; & lt; STD :: ENDL;
    STD :: COUT & LT; & LT; "Current Thread Number:" & lt; & lt; OMP_GET_THREAD_NUM () & lt; & lt; STD :: ENDL;
    STD :: COUT & LT; & LT; "Hello, World!" & lt; & lt; STD :: ENDL;
  }
  Return 0;
}

Code CMakeLists.txt:

cmake_minimum_required (version 3.14)
Project (OpenMpTest)
set (cmake_cxx_standard 17)
Add_Executable (OpenMPTest main.cpp)
Find_Package (OpenMP Required)
target_link_librursees ($ {Project_name} $ {openmp_cxx_libraries})

When compiling, always the following:

1
Number of Available Threads: 1
Current Thread Number: 0
Hello, WORLD!

I can not understand the reason why the number of threads does not increase in accordance with the value that I try to ask him. Immediately I will say that before that I did not work with C++, nor with OpenMP.

OS: MacOS Catalina Beta version 10.15.6 (19G36E)

Answer 1, Authority 100%

You are using the OMP PARALLEL FOR directive, but you do not have a for cycle there. What do you expect to get it? Remove the word for and you will be happy.

# include & lt; iostream & gt;
#Include "/usr/local/opt/libomp/include/omp.h"
// #Include & lt; omp.h & gt;
#Define Thread_Num 4.
INT MAIN ()
{
  OMP_SET_NUM_THREADS (Thread_NUM);
  STD :: COUT & LT; & LT; OMP_GET_THREAD_LIMIT () & lt; & lt; STD :: ENDL;
#Pragma Omp Parallel Num_Threads (4)
  {
    STD :: COUT & LT; & LT; "Number of Available Threads:" & lt; & lt; OMP_GET_NUM_THREADS () & lt; & lt; STD :: ENDL;
    STD :: COUT & LT; & LT; "Current Thread Number:" & lt; & lt; OMP_GET_THREAD_NUM () & lt; & lt; STD :: ENDL;
    STD :: COUT & LT; & LT; "Hello, World!" & lt; & lt; STD :: ENDL;
  }
  Return 0;
}

An example was collected using Mingw-W64 under Win10; Command Line: G ++ test2.cpp -o test2 -o2 -fopenmp

PS: More, you did not write brackets from the OMP_GET_THREAD_LIMIT () function and because of this you did not receive the appropriate number.