Check OpenMP Installed on Linux Systems,

openmp_test.cpp

// SOURCE : https://stackoverflow.com/questions/1304363/how-to-check-the-version-of-openmp-on-linux
// BUILD : g++ -std=c++11 -fopenmp openmp_test.cpp -o openmp_test
// RUN : ./openmp_test

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

int main(int argc, char *argv[])
{
  std::unordered_map<unsigned,std::string> map{
    {200505,"2.5"},{200805,"3.0"},{201107,"3.1"},{201307,"4.0"},{201511,"4.5"},{201811,"5.0"},{202011,"5.1"}};
  std::cout << "We have OpenMP " << map.at(_OPENMP) << ".\n";
  return 0;
}