text: #pragma once
  
  #include <iostream>
  #include <thread>
  
  #ifdef _OPENMP
  #include <omp.h>
  #endif
  
  #include <fmt/format.h>
  #include <fmt/ostream.h>
  
  namespace clt {
  void print_omp_diagnosis()
  {
      const auto ncpu = std::thread::hardware_concurrency();
      fmt::print(std::cerr, "# std::thread::hardware_concurrency() = {}\n", ncpu);
  #ifdef _OPENMP
      const auto omp_max_threads = omp_get_max_threads();
      fmt::print(std::cerr, "# omp_get_max_threads() = {} (OMP_NUM_THREADS)\n",
                 omp_max_threads);
      fmt::print(std::cerr,
                 "# NOTE: env. var. OMP_NUM_THREADS should be set manually.\n");
  #else
      fmt::print(std::cerr, "OpenMP is disabled.\n");
  #endif
  }
  } // namespace clt