On Mon, 15 Jan 2007 10:46:37 George Warner <email@hidden> wrote:
Just for the record UpTime (and CFAbsoluteTimeGetCurrent and
mach_absolute_time) is still the lowest-overhead and highest
precision clock
on PPC or Intel. (IIRC UpTime & CFAbsoluteTimeGetCurrent both call
directly
thru to mach_absolute_time now.)
#import <mach/mach_time.h>
uint64_t t0 = mach_absolute_time();
// do your timed stuff here!
uint64_t t1 = mach_absolute_time();
// compute the delta
uint64_t t = t1 - t0;
// this is the timebase info
mach_timebase_info_data_t info;
mach_timebase_info(&info);
double nano = 1e-9 * ( (double) info.numer) / ((double)
info.denom);
For the record, how aggressively may we cache the result of
mach_timebase_info? Is it guaranteed to be a constant for a
program run or could it change with e.g. the change of
processor speed?
