[kepler-dev] Sending multiple outputs through same output port

[Sivaramakrishnan, Chandrika]

Christopher, 

Thanks a lot for the pointers. I read the ICASSP paper and looks like I can have multirate actors provided I know what is the rate. In my case, ideally, there would be a single input and unknown number of outputs through a given output port and channel. I know the maximum number of output tokens though. For example, though I know what are the possible job statuses I going to poll for, I might have missed detecting a status during the sleep time between polling. The number of output tokens to be sent through the output port is not fixed - though only one would be sent at a time. So the SDF director is probably ruled out. I haven't referred to the ptolemy design document yet, I will go through it. If it can be done with a DDF director that would be perfect for my workflow. 

Thanks
Chandrika
-----Original Message-----
From: Christopher Brooks [mailto:cxh at eecs.berkeley.edu] 
Sent: Monday, May 03, 2010 8:35 AM
To: Sivaramakrishnan, Chandrika
Cc: kepler-dev at ecoinformatics.org
Subject: Re: [kepler-dev] Sending multiple outputs through same output port

Hi Chandrika,
The system you describe is known as a multirate system.
See
Buck, J. and Ha, S. and Lee, E. A. and Messerschmitt, D. G., "Multirate signal processing in Ptolemy". ICASSP 1991.

See also the Ptolemy Design document, try volume 1:
http://www.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-28.pdf
and volume 3:
http://www.eecs.berkeley.edu/Pubs/TechRpts/2008/EECS-2008-37.pdf
and search for multirate.

SDF and DDF can handle multirate systems.  With SDF, you need to know the rate of firing in advance.  A system that has a JobStatus actor that fires when the job status data changes would work in simple SDF systems.  What might not work in SDF would be to have one input to that actor and to have the actor produce an unknown number of outputs.  It is possible to construct such an SDF model, but it is also possible to construct models that are not scheduleable in SDF.  DDF is a good choice.

See also actors that have a trigger port.  The trigger is usually used the discrete event (DE) model of computation.

_Christopher


On 5/2/10 5:48 PM, Sivaramakrishnan, Chandrika wrote:
> Hi,
> Can an actor send multiple outputs through the same output port and 
> channel only when using a Continuous director? I am currently using 
> the JobStatus actor to get the status of a running job. I am 
> interested in modifying the actor such that it can send an output every time the job status changes. Essentially the actor should get input once but send multiple outputs. I was looking for examples and was able to find only those which work with Continuous director - ex Pulse, Clock. My workflow currently uses DDF director and has simple boolean switch and expression actors. Is multiple outputs possible with DDF director?
> Thought it would be better to ask here before I try to run my workflow 
> with any of the continuous directors or modify the actor similar to 
> ramp actor - to send next status on trigger input Thanks Chandrika
>
>
>
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-- 
Christopher Brooks, PMP                       University of California
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