Simple
stopwatch objects with the following member functions:
void start() start timing
double stop() stop timing (return total time)
double stop_d() stop timing (return time since last start)
double reset() set elapsed time to 0.0 (return total)
double read() read elapsed time (total)
The following stopwatches are available:
stopwatch measures CPU time (userpace + system)
stopwatch_u measures CPU time in userspace incl. children
stopwatch_us measures CPU time userspace = system incl. children
stopwatch_e measures elapsed (wall clock) time