[kepler-dev] Workflow for recursive algorithm?
cxh at eecs.berkeley.edu
Fri Jan 20 13:35:16 PST 2006
In Ptolemy II, you would use the Dynamic Dataflow (DDF) domain
I'm not sure if the DDFDirector is present in Kepler or not.
Does anybody have the experience of modeling recursive process using
Kepler workflow? Any comments/suggestions/ideas are appreciated.
Currently I am trying to model an algorithm which is similar to a tree
traversing process. Many algorithms involving tree data structrue use
recursion. Although theoretically any recursive function can be
transformed into an iterative function by using a stack, it is often
difficult to transform tree traversing algorithm because the tree may have
unknown length. So I prefer to explore Kepler's ability of describing
Here comes the pseudo code of the recursive algorithm:
IF tree is small enough THEN
subtrees = divideTree(tree)
FOR EACH subtree IN subtrees
recursiveDCM(subtree) // Recursive call
finaltree = mergeTree(subtrees)
The functions evaluateTree, divideTree, and mergeTree have been
implemented as actors. I would like to build the function recursiveDCM as
a workflow. I know it's pretty easy to wrap all the code into one actor
to implement the recursion since Java itself supports recursion. But I
would like see if Kepler can handle it.
The first method popped up in my mind is to use CompositeActors. I tested
my idea with a simple String Concatenate workflow. I firstly built up a
workflow which includes a StringConstant actor, a StringConcatenate actor,
and a TextDisplay actor. They are linked as the following:
StringConstant-->InputPort1 of StringConcatenate-->TextDisplay
Then I wrapped the StringConstant and StringConcatenate actors as a
CompositeActor. So the workflow now looks like:
Then I copied the CompositeActor, open the CompositeActor (look inside),
and pasted the CompositeActor into the CompositeActor editing interface.
Then within the CompositeActor editing interface, I connected the output
of CompositeActor to another input port of the StringConcatenate actor.
Now the inner structure of the CompositeActor looks like:
StringConcatenate -->Outgoing port
I hope including a CompositeActor into itself could let me model the
recursive process. But it does not work as I expected. I checked the
workflow XML file, this method only adds one more layer of CompositeActor
into workflow definition.
Does anybody have better solutions to this problem?
Thanks in advance!
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