How to programmatically determine if in headless mode..?

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

Answer 1

[Edric Ellis]

One option is to check:

java.lang.System.getProperty( 'java.awt.headless' )

[Bradley Stiritz]

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

[Edric Ellis]

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 ;)

[Bradley Stiritz]

Thanks for the deeper understanding, very appreciated. Sorry to have judged your suggestion too superficially. Accepting now..

[Seth Hillery]

unfortunately this only works for traditional desktop environments. Is there any way to also detect say a matlab online/matlab-proxy-app browser based environment?

Answer 2

[Bradley Stiritz]

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