Grant Edwards wrote:
On 2009-08-13, Dave Angel <da...@ieee.org> wrote:
I'm assuming you want to call it every time_interval seconds, on
average, with a little jitter allowed on each call, but keeping correct
long term. In other words, if one call is a little late, you want the
next one to still happen as close to on-time as possible.
The general outline is something like (untested):
times_called = 0 #number of times function has been called
start_time = now
while True:
elapsed = now - start_time
int_elapsed = int(elapsed/time_interval)
for times_called in range(times_called, int_elapsed):
call_the_function()
sleep(time_interval/10) #this might give us 10% jitter, which is
usually fine
I don't understand the reasoning behind the above loop --
specifically the sleeping of smaller intervals than needed.
Why not something like this:
interval = 5.0 # interval in seconds
next = time.time()
while True:
now = time.time()
if now < next:
time.sleep(now-next)
print "call_the_function()"
next += interval
That will be accurate over the long term with minimal jitter.
Two reasons I didn't take an approach like that one.
1) I frequently need to do something else while waiting, so I tend to do
multiple smaller sleeps. As long as each sleep is at least 100ms, the
overhead cost is pretty small.
2) If (occasionally) the function takes longer than the specified
interval time, my approach does catch-up calls so the average remains
the same.
My loop was only a rough outline, and if neither of these considerations
applies, yours is much nicer.
DaveA
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