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Full Discussion: RDTSC use in C:
Top Forums Programming RDTSC use in C: Post 302241860 by calv on Tuesday 30th of September 2008 01:08:24 PM
Old 09-30-2008
rdtsc is not good for time measurement.

The problem is, that the CPU might throttle (with it does most of the time, when all processes are blocked), so a cpu clock might mean more time in that case. This is of course CPU and OS dependant.
 
SLEEP(3)								 1								  SLEEP(3)

sleep - Delay execution

SYNOPSIS
int sleep (int $seconds) DESCRIPTION
Delays the program execution for the given number of $seconds. PARAMETERS
o $seconds - Halt time in seconds. RETURN VALUES
Returns zero on success, or FALSE on error. If the call was interrupted by a signal, sleep(3) returns a non-zero value. On Windows, this value will always be 192 (the value of the WAIT_IO_COMPLETION constant within the Windows API). On other platforms, the return value will be the number of seconds left to sleep. ERRORS
/EXCEPTIONS If the specified number of $seconds is negative, this function will generate a E_WARNING. CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 5.3.4 | | | | | | | Before PHP 5.3.4, on Windows, sleep(3) always | | | returns NULL when sleep has occurred, regardless | | | of whether the sleep was interrupted or not. | | | | +--------+---------------------------------------------------+ EXAMPLES
Example #1 sleep(3) example <?php // current time echo date('h:i:s') . " "; // sleep for 10 seconds sleep(10); // wake up ! echo date('h:i:s') . " "; ?> This example will output (after 10 seconds) 05:31:23 05:31:33 SEE ALSO
usleep(3), time_nanosleep(3), time_sleep_until(3), set_time_limit(3). PHP Documentation Group SLEEP(3)
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