sim command in try/catch, in parfor results in error

I'm using parfor to execute Monte Carlo runs of a Simulink diagram. It was working fine, but I added a try/catch statement to avoid aborting the loop if one of the Monte Carlo draws results in an error.

clear simout
parfor ii=1:2
    try
        simout(ii) = sim('sandbox');
    catch ME
        ME
        disp(ME.message)
    end
end

This code results in the following error every time (Sandbox is just a dummy diagram but it still results in an error):

MException with properties:

      identifier: 'MATLAB:UnableToConvert'
         message: 'The following error occurred converting from Simulink.Sim...'
           cause: {}
           stack: [2×1 struct]

The full error message is

The following error occurred converting from Simulink.SimulationOutput to double:
Conversion to double from Simulink.SimulationOutput is not possible.

If the parfor is changed to for or if the try/catch is removed from the parfor, the code runs without error. It's only when the try/catch is used with the parfor that I get this error. It could have something to do with the Single Simulation Output, but I believe using this data structure is necessary when using sim in a parfor. Any ideas on the root cause of the error and potential workarounds?

Thanks, Ryan

Answer 1

[Edric Ellis]

I'm not 100% sure what's going on there, but it might work simply to say:

simout = cell(1,2);
parfor ii=1:2
    try
        % note use of cell array indexing:
        simout{ii} = sim('sandbox');
    catch ME
        ME
        disp(ME.message)
    end
end