benchmark/bench.cpp
double start_time() {
  struct timespec tp;
  clock_gettime(CLOCK_REALTIME, &tp);
  return 1e9*tp.tv_sec + tp.tv_nsec;
}
// start timer and return start time
start timer and return start time
start timer and return start time
double start_time() {
  struct timespec tp;
  clock_gettime(CLOCK_REALTIME, &tp);
  return 1e9*tp.tv_sec + tp.tv_nsec;
}
double start_time ( ) { struct timespec tp ; clock_gettime ( CLOCK_REALTIME , & tp ) ; return 1e9 * tp . tv_sec + tp . tv_nsec ; }
start timer and return start time
start timer and return start time