Hi Kevin,
The short answer is that the Generic Director is a hack. As you've
found, it depends on the order of the entities in MoML file.
To be honest, I think it was a fluke that using a Generic Director
works at all. As I remember it, Professor Lee and I think Jorn
Janneck (probably with others), discovered that the Generic Director
could be made to work without much effort. The Generic Director
does have its role for small models though.
For more complex models, you probably want to use SDF.
Ptolemy II 5.0-beta, due out in May, will include DDF and HDF:
"The Dynamic Dataflow (DDF) domain, created by Gang Zhou, is a
superset of the Synchronous Dataflow (SDF) and Boolean dataflow (BDF)
domains. In the SDF domain, an actor consumes and produces a fixed
number of tokens per firing. This static information makes possible
compile-time scheduling. In the DDF domain, an actor could change the
production and consumption rates after each firing. The scheduler
makes no attempt to construct a compile-time schedule, neither does it
attempt to statically answer questions about deadlock and boundedness,
which are fundamentally undecidable. Instead, each actor has a set of
sequential firing rules (patterns) and can be fired if one of them is
satisfied, i.e., one particular firing pattern forms a prefix of
sequences of unconsumed tokens at input ports. The scheduler
dynamically schedules the firing of actors according to some criteria.
The canonical actors in the DDF domain include Select and Switch,
which consume or produce tokens on different channels based on the
token received from the control port."
"The Heterochronous Dataflow (HDF) Domain, created by Ye Zhou is an
optimization of the SDFDirector and implements the HDF model of
computation. The HDF model of computation is a generalization of
Synchronous Dataflow (SDF). In SDF, the set of port rates of an actor
(called rate signatures) are constant. In HDF, however, rate
signatures are allowed to change between iterations of the HDF
schedule. Within each state, the HDF model behaves like an SDF model."
It would be nice if someone would create a Boolean Dataflow (BDF)
domain.
_Christopher
--------
Hi Hackers,
I've encountered an inconsistency in the way MoML written by Vergil gets
executed by the generic Director.
At the end of this message are two simple Ptolemy layouts that are
functionally and structurally identical in Vergil. However, running the
first layout produces a "full mailbox" exception. Is this a bug?
Reordering entities in the xml file will solve the problem. However, in
more complex layouts more connected entities, the proper order is not
clear. What is the correct ordering of entities in MoML to get the
generic Director to run layout without full mailbox execeptions?
I can send the xml files as email attachments as requested. I also have
examples of slightly more complex MoML reproducing the bad behavior and
the fix, and can send those as well.
Thank you very much,
Kevin
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