Add on file for https://gist.github.com/2057852

stop_watch.inl

#include <sys/time.h>                // for gettimeofday()

class StopWatch {
  timeval     started;
  std::string msg;
  
public:
  StopWatch(const std::string& m): msg(m)
    { gettimeofday(&started, NULL); }

  ~StopWatch() {
    std::cerr << msg << " " << usecs() << " µsecs" << std::endl;
  }
  
  unsigned usecs() const {
    timeval t2;
    gettimeofday(&t2, NULL); 
    
    return (t2.tv_sec - started.tv_sec) * 1000000 + (t2.tv_usec - started.tv_usec);
  }
};