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How to programmatically determine if in headless mode..?

Asked by Brad Stiritz on 14 Jan 2012
I'm working on an issue with the Parallel Computing Toolbox (PCT)..
As each MATLAB.exe worker thread process is initialized, startup.m is executed. All worker threads are "headless" (no output window). Certain graphics-related function calls that are fine-- when launched within the full MATLAB app with its output capability-- can cause problems in the headless context.
I have a graphics-related function that's very convenient to have in the full MATLAB app's startup.m, but mustn't execute in the PCT worker thread context. Is there a function call I can insert into startup.m to determine if its MATLAB.exe process is running in headless mode? I would like to use as follows:
% Is there an output window associated with this MATLAB.exe process?
if ~isInHeadlessMode()
% YES : render graphics window
someGraphicsFunction();
end
Any help appreciated, Thanks, Brad

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2 Answers

Edric Ellis 님의 답변 16 Jan 2012
 채택된 답변

One option is to check:
java.lang.System.getProperty( 'java.awt.headless' )

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Hi Edric, thanks for your suggestion. Your Java knowledge is very impressive! I would have accepted your answer, but someone at Mathworks suggested an even simpler function call..
Thank you again for posting,
Brad
FWIW, "usejava('desktop')" is fine for most purposes, but it's not quite the same thing - for example, if you run MATLAB in "-nodesktop" mode (as I do most of the time), then it will give you the wrong answer - you can still produce graphics in "-nodesktop" mode. Oh, and I'm a MathWorker too ;)
Thanks for the deeper understanding, very appreciated. Sorry to have judged your suggestion too superficially. Accepting now..

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Brad Stiritz 님의 답변 17 Jan 2012

Per Nathan Lloyd in Mathworks PCT support, the native MATLAB usejava() function can be used to determine whether the executing MATLAB.exe instance is in 'desktop' or 'headless' mode..
"[The following] code checks to see if a desktop exists before executing the sensitive block of code. For any worker, the desktop will never exist, so the code will be jumped over and the workers will persist; while the client MATLAB will execute the 'startup.m' file without issues."
if usejava('desktop')
% YES : render graphics window
someGraphicsFunction();
end

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