Attempt to program parameter sweep on model in COMSOL, using OOP in MATLAB

Using COMSOL LiveLink and object-orientated programming (which I am new to) I am trying to develop a convenient way of passing vectorised parameters into a COMSOL model and running a parameter sweep efficiently without using the GUI on COMSOL.

I am aware that this code assumes that a is a 10-by-1 array, and that b, c and d are scalars.

After declaring this class, I try running:

Test = SimpleModel;
Test.a = 1:10;  Test.b = 2; Test.c = 3; Test.d = 4;
Test.solveAll

However, I keep getting Java errors, along the lines of "com.comsol.util.exceptions.FlException: Variable refers to an object which is no longer in the model"

classdef SimpleModel
    properties
        a {mustBeNumeric}
        b {mustBeNumeric}
        c {mustBeNumeric}
        d {mustBeNumeric}           
        model = mphopen('simpleModel')
    end
        
    methods
        
        function obj = paramSet(obj)
            obj.model.param.set("a",obj.a);
            obj.model.param.set("b",obj.b);
            obj.model.param.set("c",obj.c);
            obj.model.param.set("d",obj.d);
        end
        
        function obj = solve(obj)
            obj.model.study("std1").run()
            obj.model.result.dataset("dset1");
        end       
        
        function Solution = solution(obj)
            Solution = obj.model.result.dataset("dset1");
        end
            
        function Vertices = meshPoints(obj,show)
            [~ , data] = mphmeshstats(obj.model);
            Vertices = data.vertex';
            if show == true
                plot(Vertices(1,:),Vertices(2,:),'.')
            end
        end
        
        function Values = solValues(obj)
            Values = mpheval(obj.model,"u").d1';
        end
        
        function Value = meanValue(obj)
            Value = mphglobal(obj.model,"aveop1(u)");
        end
        
        % for parameter sweeps
              
        function Strings = paramNames(obj)
            Strings = ["a","b","c","d"];
        end
        
        function Values = paramValues(obj)
            Names = obj.paramNames;
            Values = cell(1,length(Names));
            for n = 1:length(Names)
                Values{n} = getfield(obj,Names(n));
            end
        end
            
        function Int = howManyParametersAreBeingSwept(obj)
            Int = 0;
            Values = obj.paramValues();
            for n = 1:length(Values)
                if length(Values{n}) > 1
                    Int = Int + 1;
                end
            end
        end
        
        function Strings = whichParametersAreBeingSwept(obj)
            Names = obj.paramNames;
            Values = obj.paramValues;
            Strings = [];
            for n = 1:length(Values)
               if length(Values{n}) > 1
                   Strings = [Names(n) Strings];
               end
            end
        end
        
        function Cell = paramIndices(obj)
            Cell = {1:10};            
        end
        
        function Cell = storageSpace(obj)
            Names = obj.paramNames;
            Values = obj.paramValues;
            Cell = cell(1,10);
            for idx = 1:10
                Cell{idx} = obj;
                Cell{idx}.a = obj.a(idx);
            end
        end
        
        function Solutions = solveAll(obj)
            Solutions = obj.storageSpace;
            for idx = 1:10
                % keyboard
                Temp = Solutions{idx};
                              
                Temp.model = mphopen('simpleModel');
                                
                ParamValues = Temp.paramValues;
                
                Temp.model.param.set("a",Temp.a);
                Temp.model.param.set("b",Temp.b);
                Temp.model.param.set("c",Temp.c);
                Temp.model.param.set("d",Temp.d);
                
                Temp.solve()
                Solutions{idx} = Temp;
            end
            clear Temp
        end
    end
end

As I am new to object-orientated programming, I am aware that the code above might have quite a few shortcomings. If anybody could provide guidance on these I would be very grateful.

Answer 1

[chrisw23]

I suggest to use the constructor to load the model like.

...

methods

function obj = SimpleModel(modelFilePath)

obj.model = mphopen(modelFilePath)

end

...

[Oliver Bond]

Thanks for this. I have implemented some similar code with a different model.

However, I don't really want to need to load the .mph file every single time a SimpleModel object is declared. This makes the code particularly slow when one of the parameters is vectorised (a in this case). I only need to open the .mph file once, and then cycle through each parameter and get a solution.

(Strictly speaking, it is only really the parameters that need to be part of the SimpleModel class - the Model part is probably better as a method than an attribute).

How can I modify the code to take this into account?

[chrisw23]

This suggestion was more in terms of having multiple objects (models) of the same class type. On the other hand you have path dependencies loading the model by file name and I would use the constructor to handle this by an argument or other options. I would also suggest to use the destructor (delete method) of your class to unload the model when the object lifetime ends. This could be importend for your comsol environment when a new model is to be loaded.