[kepler-users] PN Director Question

[Edward A. Lee]

Right... hasToken() always returns true in PN.
The semantics of the model of computation is explained here:

http://ptolemy.eecs.berkeley.edu/publications/papers/95/processNets/

Edward


Peter Reutemann wrote:
>> I am trying to implement an actor that has two input ports-input and window.
>> In the implementation, I want that the actor should execute different set of
>> lines depending on if the tokens are present or not present at the window
>> port. I am trying to do something like:
>> if(window.hasToken()){
>>   ArrayToken tokenD = (ArrayToken) input.get(0);
>> System.out.println("There is a token at the window port");
>> }
>> else
>>  System.out.println("There is no token at the window port");
>>
>> I observer that when I use a PN director, the value of  window.hasToken() is
>> true even if there is no token at the window port. I actually used an
>> arraytosequence actor to output the array tokens to my actor.So even if the
>> input to arraytosequence is { }, my actor returns true for window.hasToken()
>> and enters the "if" block. However after executing the first line of the
>> "if" block, it stops i.e it does not print the next line. Can someone tell
>> me why the PN director sets the value false when there is no token at the
>> window port?
> 
> Stumbled across that myself...
> 
>>From what I understand: the PN domain always assumes that there are
> tokens available in the queues, at one point or another (the
> ptolemy.domains.pn.kernel.PNQueueReceiver class always returns "true"
> in the "hasToken()" method). Only when using the "get(int)"-method of
> the port it is attempted to obtain a token. If none is present at the
> moment, then the method won't exit until a token shows up or the
> workflow terminates.
> 
> Cheers, Peter
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