Array of SimulationInput objects gets modified upon running with sim command

I am creating an array of SimulationInput objects, 'simIn'. If I try to run a single simulation, for example using simOut(1) = sim(simIn(1)) to run the first case, why does simIn lose all other array elementes. It changes to a 1x1 SimulationInput object, whereas before the sim command it was a 1x28 object

for casenumber = 1:NumFile
    if ~isempty(char(file{FileIdx(casenumber),1}))
        if exist(strrep(char(file{FileIdx(casenumber),1}), ';', ''), 'file')
            
            %% Setup parallel Simulation
            
            simIn(casenumber)=Simulink.SimulationInput('XWB_MSL_EEC');
            simIn(casenumber) = simIn(casenumber).setVariable('Experiment',Experiment);
            simIn(casenumber) = simIn(casenumber).setVariable('Enable_MSL_Validation_Logging',Enable_MSL_Validation_Logging);
            simIn(casenumber) = simIn(casenumber).setVariable('SimStartTime',0);
            simIn(casenumber) = simIn(casenumber).setVariable('TimeMode1',TimeMode1);
            simIn(casenumber) = simIn(casenumber).setVariable('TimeMode2',TimeMode2);
            simIn(casenumber) = simIn(casenumber).setVariable('parallel_casenumber',casenumber);
            simIn(casenumber) = simIn(casenumber).setVariable('ModelPath',ModelPath);
            simIn(casenumber) = simIn(casenumber).setVariable('toolGitStatus',toolGitStatus);
            simIn(casenumber) = simIn(casenumber).setVariable('configGitStatus',configGitStatus);
            simIn(casenumber) = simIn(casenumber).setVariable('toolConfigVersion',toolConfigVersion);
            simIn(casenumber) = simIn(casenumber).setVariable('configGitInfo',configGitInfo);
            simIn(casenumber) = simIn(casenumber).setVariable('switchBatchMode',switchBatchMode);
            simIn(casenumber) = simIn(casenumber).setVariable('resultsDir',resultsDir);
            simIn(casenumber) = simIn(casenumber).setVariable('switchExportDataToPhobos',switchExportDataToPhobos);
            if ~isempty(Suffix)
                simIn(casenumber) = simIn(casenumber).setVariable('CurveName',sprintf('%s_%s',file{FileIdx(casenumber),1},Suffix));
            else
                simIn(casenumber) = simIn(casenumber).setVariable('CurveName',file{FileIdx(casenumber),1});
            end
            
            % Use a temporary variable for the SimIn element to avoid runaway memory usage when using a preSimFcn with parsim
            tmpSimIn = simIn(casenumber);
            
            preSimFcnInputs = {file{FileIdx(casenumber)}, tmpSimIn};
            simIn(casenumber)=simIn(casenumber).setPreSimFcn(@(x) parsimMSLPreSimFcn(preSimFcnInputs));
            simIn(casenumber) = simIn(casenumber).setPostSimFcn(@(y) parsimMSLPostSimFcn(y, tmpSimIn));
        else
            error(['Could not find Case "',strrep(char(file{FileIdx(casenumber),1}), ';', ''),'"!'])
        end
    end
end

[Edric Ellis]

I can't reproduce that problem. Here's what I tried using an example model:

openExample("simulink_general/VanDerPolOscillatorExample")
mdl = "vdp";
simIn(1:10) = Simulink.SimulationInput(mdl);
out(1) = sim(simIn(1));

Warning: An error occurred while evaluating "loc_createToolchain" in "/MATLAB/toolbox/coder/autosar/rtwTargetInfo.p": Unrecognized function or variable 'autosarroot'.
This custom registration is not loaded.

size(simIn)

ans = 1x2

1 10

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[Afzal]

Could it be due to my PreSimFcn. I extract the simIn object from the PreSimFcnInputs created previously in the for loop. But I would have throught this simIn would be local to the PreSimFcn workspace

function parsimMSLPreSimFcn(PreSimFcnInputs)

try
    simIn = PreSimFcnInputs{2};
    runScript = PreSimFcnInputs{1};

[Swastik Sarkar]

Hi @Afzal,

Could you please attach your model, along with the complete code for the PreSim and PostSim functions?

From my understanding, the SimIn variable is local to the PreSimFcn function's workspace.

[Sahas]

Hi @Afzal,

As per my understanding, the "parsimMSLPreFcn" function takes "simIn" as an input but does not modify it.

I can offer better assistance if the model and code are shared.

Answer 1

[Githin George]

Hi Afzal,

Without looking at the implementation for the “PreSimFcn” and “PostSimFcn” it is difficult to predict how the “simIn” variable in base workspace is getting affected.

One thing you can try is to wrap this code in a MATLAB class and set a “PostSet” event listener to the property containing the “simIn” object. Then you can use breakpoints in the listener function and check the call stack every time it is being hit to root cause the issue. I’ve tested this out with an example below. I hope this debugging trick comes in handy.

classdef SimulationManager < handle
    properties (SetObservable)
        % Array of Simulink.SimulationInput objects
        SimulationInputs (1,:) Simulink.SimulationInput = Simulink.SimulationInput.empty
    end
    
    methods
        function obj = SimulationManager()
            % Constructor: Add listener for postset event
            addlistener(obj, 'SimulationInputs', 'PostSet', @(src, evt) obj.onSimulationInputsChanged());
        end
        
        function runSimulation(obj)
            % Run simulation with pre and post simulation functions
            for i = 1:length(obj.SimulationInputs)
                % Call the pre-simulation function
                obj.preSimulation(obj.SimulationInputs(i));
                
                % Here you would typically run the simulation
                % For example: simOut = sim(obj.SimulationInputs(i));
                fprintf('Running simulation for input %d...\n', i);
                
                % Call the post-simulation function
                obj.postSimulation(obj.SimulationInputs(i));
            end
        end
    end
    
    methods (Access = private)
        function onSimulationInputsChanged(obj)
            % Callback function for postset event
            fprintf('SimulationInputs property changed.\n');
            % You can add more debug information here
            disp(obj.SimulationInputs);
        end
        
        function preSimulation(obj, simIn)
            % Dummy pre-simulation function
            fprintf('Pre-simulation setup for model: %s\n', simIn.ModelName);
            % Insert pre-simulation logic here
        end
        
        function postSimulation(obj, simIn)
            % Dummy post-simulation function
            fprintf('Post-simulation cleanup for model: %s\n', simIn.ModelName);
            % Insert post-simulation logic here
        end
    end
end

For more information refer to the documentation below:

https://www.mathworks.com/help/matlab/matlab_oop/listening-for-changes-to-property-values.html

[Afzal]

I want to close this question. The issue was due to a assignin base command I was using in the PreSimFcn. This was also assigining the simIn from the inputs to the PreSimFcn (tmpSimIn)to the base workspace. This was used to assign variables required by the model to the base workspace. I just added a check to skip assigning simIn.

% Assign the variables to the parallel simulation instance base workspace
varList=whos;
for iVar=1:length(varList)
    if ~strcmp(varList(iVar).name,'simIn') % Do not overwrite base 'simIn'
        assignin('base',varList(iVar).name,eval(varList(iVar).name))
    end
end