I'm having a problem with PAR in a pipeline of other components. If I
shut down the pipeline with a producerFinished() signal, the PAR
component does not exit. Using a shutdownMicroprocess() signal works OK
though.
By adding liberal quantities of print statements I've worked out that
PAR is hanging in the pause loop near the end of main():
# If there's nothing to do, then sleep
while not self.anyReady() and not shutdown:
self.pause()
yield 1
When each child component exits, PAR is woken up but, as there's no
input it instantly pauses again. A solution I've found is to put a
childrenDone() test in the loop:
# If there's nothing to do, then sleep
while not self.anyReady() and not shutdown:
if self.childrenDone():
shutdown = True
else:
self.pause()
yield 1
This appears to work, but there may be subtleties in PAR's design I
haven't considered.
A further simplification is to remove the shutdown variable entirely,
using break to exit the main loop wherever shutdown would have been set.
The sleeping inner loop then becomes:
# If there's nothing to do, then sleep
while not self.anyReady() and not self.childrenDone():
self.pause()
yield 1
This has the small disadvantage that childrenDone() is called once more
often than necessary before the main loop is exited.
(As an aside, I'm not a fan of having loops within loops like this. I
like my components to have a simple main loop with an if ... elif ...
elif ... else self.pause() chain.)
--
Jim Easterbrook
Senior Research Engineer
BBC Research & Development South Lab
BBC Centre House
56 Wood Lane
London W12 7SB
Phone: +44 303 040 9705
Mobile: +44 7590 307002
FAX: +44 20 8811 8815
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