Why is my variable undefined when using parsim?

I have a simulink model that runs when I'm not running it in parallel, but it will not run in parallel. In the function that invokes my model I create a class handle object and store it in the base workspace. From within the model I have a Matlab function that calls a function of the object by evaluating it in the base workspace. In parallel mode I get an error saying that this object handle is undefined. But it works fine if I don't run it in parallel mode. 

I've created a simple model that illustrates the problem (you will need to include the files TestClass.m and TestObjSim.slx in the same directory):

objH = TestClass(1);
assignin('base','objH',objH);

% This works:
simOut = sim('TestObjSim');

% Running in parallel doesn't work:
in = Simulink.SimulationInput('TestObjSim');
simout = parsim(in,'TransferBaseWorkspaceVariables','on');
disp(simout.ErrorMessage);

Answer 1

[MathWorks Support Team]

The reason the you see the error is because the base workspace is not shared among the workers, To make sure that each worker has access to everything, I would recommend create an initialization function that can be called by each worker to load the data including the class into the worker's base workspace. 

For example,

1) Define a function in loadObject.m.

function loadObject()
    objH = TestClass(1);
    assignin('base','objH',objH);

2) Load the function in all workers and run parsim:

% Load object in all workers
parfevalOnAll(@loadObject,0);

% Run parallel simulation
in = Simulink.SimulationInput('TestObjSim');
simout = parsim(in,'TransferBaseWorkspaceVariables','on');

For more information about the function parfevalOnAll, please refer to this page:

https://in.mathworks.com/help/parallel-computing/parallel.pool.parfevalonall.html

Although this documentation is talking about parfor, it has some useful discussions about workspace access issue that applies to your case:

https://in.mathworks.com/help/simulink/ug/running-parallel-simulations.html