<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Hi Tom,<br>
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 :-)<br>
<br>
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...<br>
<br>
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
<a class="moz-txt-link-freetext" href="http://ptolemy.eecs.berkeley.edu/ptolemyII/ptIIlatest/ptII8.0.1/ptolemy/domains/csp/doc/index.htm">http://ptolemy.eecs.berkeley.edu/ptolemyII/ptIIlatest/ptII8.0.1/ptolemy/domains/csp/doc/index.htm</a><br>
<br>
The code is at
kepler/ptolemy/src/ptolemy/domains/csp/demo/DiningPhilosophers<br>
<br>
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.<br>
<br>
_Christopher<br>
<br>
<br>
On 12/11/13 6:10 AM, Tom Parris wrote:<br>
</div>
<blockquote
cite="mid:CAJiB5bXFmSwYoziGzawnpp++mjVUwe6UX6rF0od8os4T28WvzQ@mail.gmail.com"
type="cite">
<div dir="ltr">Dear kepler-users:
<div><br>
</div>
<div>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. </div>
<div><br>
</div>
<div><b>Nature of problem: </b></div>
<div>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).</div>
<div><br>
</div>
<div><b>Possible fix:</b> </div>
<div>The GDAL discussions suggest using Java synchronization to
avoid thread safety issues. </div>
<div><br>
</div>
<div><b>Questions:</b></div>
<div>1. Will using java synchronization in an actor cause other
problems with Kepler/Ptolemy under PN?</div>
<div>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? </div>
<div>3. Are there other solutions we should consider?</div>
<div><br>
</div>
<div>Many thanks,</div>
<div>Tom Parris</div>
<div><br>
</div>
<div><br>
</div>
<div>Thomas M. Parris</div>
<div>Vice President</div>
<div>ISciences, L.L.C.</div>
<div>61 Main Street, Suite 200</div>
<div>Burlington, VT 05401</div>
<div>(802) 864-2999; <a moz-do-not-send="true"
href="mailto:parris@isciences.com">parris@isciences.com</a></div>
<div><br>
</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Kepler-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Kepler-users@kepler-project.org">Kepler-users@kepler-project.org</a>
<a class="moz-txt-link-freetext" href="http://lists.nceas.ucsb.edu/kepler/mailman/listinfo/kepler-users">http://lists.nceas.ucsb.edu/kepler/mailman/listinfo/kepler-users</a>
</pre>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Christopher Brooks, PMP University of California
Academic Program Manager & Software Engineer US Mail: 337 Cory Hall
CHESS/iCyPhy/Ptolemy/TerraSwarm Berkeley, CA 94720-1774
<a class="moz-txt-link-abbreviated" href="mailto:cxh@eecs.berkeley.edu">cxh@eecs.berkeley.edu</a>, 707.332.0670 (Office: 545Q Cory)
</pre>
</body>
</html>