in reply to Re^3: Waiting for Alarm
in thread Waiting for Alarm

Need more accurate still? Then sleep for 1/100th of a second. It will still consume very little cpu and be another order of magnitude more accurate.

One approach to achieve high accuracy while reducing the amount of calls to sleep and time is to sleep for long times initially and decrease them as you get closer to the time to "fire".

For example, if you want to call a routine every 10 seconds at a resolution of 1/100th of a second, then you could first sleep for 8 seconds, then for 0.2 seconds until within 0.2 sec, then for 0.01 seconds. (These are arbitrary values, of course.)

This could be premature optimization, though. :-)

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Re^5: Waiting for Alarm
by BrowserUk (Pope) on Feb 17, 2008 at 04:25 UTC

    Something along the lines of:

    print $target = time + 10; print $s and sleep $s while ( $s = ($target - time )/2 ) > 0; print time;; 1203221999.59375 5 2.49999403953552 1.24999451637268 0.624994039535522 0.312494516372681 0.15625 0.0781184434890747 0.0390595197677612 0.0155709981918335 0.00779902935028076 1203221999.59376

    would work quite well. If the "do something" might take longer than half the delay time, then use a larger divisor:

    print $target = time + 10; print $s and sleep $s while ( $s = ($target - time )/3 ) > 0; print time;; 1203222233.07813 3.33329796791077 2.21874562899272 1.47916666666667 0.984371026357015 0.656246026357015 0.437496026357015 0.29166833559672 0.192704677581787 0.125013987223307 0.0833380222320557 0.0520946979522705 0.0311883290608724 0.0208296775817871 0.010399341583252 0.0052033265431722 1.98682149251302e-006 1203222233.07822 print $target = time + 10; print $s and sleep $s while ( $s = ($target - time )/4 ) > 0; print time;; 1203222257.71875 2.4999732375145 1.87499701976776 1.40624725818634 1.05468475818634 0.78905975818634 0.58984100818634 0.44140350818634 0.328112483024597 0.246071517467499 0.183622241020203 0.136751472949982 0.10155975818634 0.0742244720458984 0.0546977519989014 0.0386837720870972 0.0273575186729431 0.0195417404174805 0.011723518371582 0.00780248641967773 0.00391250848770142 1.59740447998047e-005 1203222257.71881

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