Launching matlab remotely on windows via ssh? Impossible?

Question

Howdy, I am trying to run matlab remotely on windows via OpenSSH installed with Cygwin, but launching matlab in windows without the GUI seems to be impossible.

If i am logged in locally, I can launch matlab -nodesktop -nodisplay -r script, and matlab will launch up a stripped down GUI and do the command.

However, this is impossible to do remotely via ssh, as, matlab needs to display the GUI.

Does anyone have any suggestions or work arounds?

Thanks,

Bob

Answer 1

Short story: is your script calling exit()? Are you using "-wait"?

Long story: I think you're fundamentally out of luck if you want to interact with it, but this should work if you just want to batch jobs up. Matlab on Windows is a GUI application, not a console application, and won't interact with character-only remote connectivity. But you can still launch the process. Matlab will actually display the GUI - it will just be in a desktop session on the remote computer that you have no access to. But if you can get it to do your job without further input, this can be made to work, for some value of "work".

Your "-r script" switch is the right direction. But realize that on Windows, Matlab's "-r" behavior is to finish the script and then go back to the GUI, waiting for further input. You need to explicitly include an "exit()" call to get your job to finish, and add try/catches to make sure that exit() gets reached. Also, you should use a "-logfile" switch to capture a copy of all the command window output to a log file so you can see what it's doing (since you can't see the GUI) and have a record of prior runs.

Also, matlab.exe is asynchronous by default. Your ssh call will launch Matlab and return right away unless you add the "-wait" switch. Check the processes on the machine you're sshing to; Matlab may actually be running. Add -wait if you want it to block until finished.

One way to do this stuff just use -r to call to a standard job wrapper script that initializes your libraries and paths, runs a job, and does cleanup and exit. You'll also want to make a .bat wrapper that sets up the -logfile switch to point to a file with the job name, timestamp, and other info in it. Something like this at the M-code level.

function run_batch_job(jobname)
try
   init_my_matlab_library(); % By calling classpath(), javaclasspath(), etc
   feval(jobname); % assumes jobname is an M-file on the path
catch err
   warning('Error occurred while running job %s: %s', jobname, err.message)
end
try
   exit();
catch err
   % Yes, exit() can throw errors
   java.lang.System.exit(1); % Scuttle the process hard to make sure job finishes
end
% If your code makes it to here, your job will hang

I've set up batch job systems using this style in Windows Scheduler, Tidal, and TWS before. I think it should work the same way under ssh or other remote access.

A Matlab batch system on Windows like this is brittle and hard to manage. Matlab on Windows is fundamentally not built to be a headless batch execution system; assumptions about an interactive GUI are pervasive in it and hard to work around. Low-level errors or license errors will pop up modal dialog boxes and hang your job. The Matlab startup sequence seems to have race conditions. You can't set the exit status of MATLAB.exe. There's no way of getting at the Matlab GUI to debug errors the job throws. The log file may be buffered and you lose output near hangs and crashes. And so on.

Seriously consider porting to Linux. Matlab is much more suitable as a batch system there.

If you have the money or spare licenses, you could also use the Matlab Distributed Computing toolbox and server to run code on remote worker nodes. This can work for parallelization or for remote batch jobs.