Hi Tom,
If I was limited to a yes or no answer to the question "Will using java
synchronization in an actor cause other problems with Kepler/Ptolemy
under PN?", I would have to say "yes", because threads rarely don't
cause problems :-)
That said, using Java synchronization within the actor should be
possible. At the worst, you could stall the execution of the actor. In
PN, you would probably probably have the actor some how signal to the
director that it was not ready to fire, but it could fire in the
future. Probably the way to do this is not read inputs or write
outputs, but I'm not sure...
In Ptolemy II, you might look at the DiningPhilosophers CSP demo. That
demo is very old, but it might help you. Unfortunately, those classes
are not built by Kepler, so you would probably need to download
PtolemyII separately. Or, you could try the applet at
http://ptolemy.eecs.berkeley.edu/ptolemyII/ptIIlatest/ptII8.0.1/ptolemy/domains/csp/doc/index.htm
The code is at
kepler/ptolemy/src/ptolemy/domains/csp/demo/DiningPhilosophers
We've seen this sort of pattern before where you have a model that has
asynchronous reads and writes to an external data source. I believe we
have some sample demos, but they are not coming to mind.
_Christopher
On 12/11/13 6:10 AM, Tom Parris wrote:
Dear kepler-users:
We have constructed some Java/JNI actors that make use of GDAL as an
external library for i/o. A recent change in computing platforms
exposed some thread-safety issues in GDAL that we are now struggling
to address.
*Nature of problem: *
We have two GDAL-based actors. One for reading raster imagery (ERDAS
IMG files) into a matrix, one for writing raster imagery into a matrix
(and, at some point, we would like to contribute these to Kepler).
These actors are used heavily in PN workflows. While GDAL is thread
safe for reading (multiple thread can read at the same time), it is
not thread safe for writing (problems occur if any thread is writing
while other threads are either reading or writing).
*Possible fix:*
The GDAL discussions suggest using Java synchronization to avoid
thread safety issues.
*Questions:*
1. Will using java synchronization in an actor cause other problems
with Kepler/Ptolemy under PN?
2. Does anybody have a model of an actor that uses java
synchronization to avoid thread safety issues in external libraries
that they would be willing to share?
3. Are there other solutions we should consider?
Many thanks,
Tom Parris
Thomas M. Parris
Vice President
ISciences, L.L.C.
61 Main Street, Suite 200
Burlington, VT 05401
(802) 864-2999; par...@isciences.com <mailto:par...@isciences.com>
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Christopher Brooks, PMP University of California
Academic Program Manager & Software Engineer US Mail: 337 Cory Hall
CHESS/iCyPhy/Ptolemy/TerraSwarm Berkeley, CA 94720-1774
c...@eecs.berkeley.edu, 707.332.0670 (Office: 545Q Cory)
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