Re^4: 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. :-)

Comment on Re^4: Waiting for Alarm

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Re^5: Waiting for Alarm
by BrowserUk (Patriarch) 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
[download]

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
[download]

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