text: #ifndef TIMER_H
  #define TIMER_H
  
  #ifdef _WIN32
      #include <chrono>
      #define start_timer auto start = std::chrono::system_clock::now();
      #define stop_timer  auto stop = std::chrono::system_clock::now();
  #else
      #include <sys/time.h> //Linux/Unix systems with no C++11 support.
      struct timeval start, stop;
      #define start_timer gettimeofday(&start, NULL);
      #define stop_timer  gettimeofday(&stop, NULL);
  #endif
  #endif