How to call protected functions in parfor?

This function is inside the common methods block of a class.

function GetWavelets(Me)
%Unrelated codes omitted…
    parfor c=1:ttpc
        %Me is the object itself, OnProgressReport is protectedly defined.
        Me.OnProgressReport(c,ttpc);
    %…
    end
%…
end

The protected function OnProgressReport is unaccessible in the parfor loop. I found two workarounds:

• Use for loop instead of parfor;
• Set the Access attribute of OnProgressReport to public.

If I want to preserve the parfor loop for performance reasons, is it unavoidable to expose the OnProgressReport to public? Any other solutions?

Update 20190728: The OnProgressReport function is inherited from the superclass.

Answer 1

[Edric Ellis]

EDIT: Changed my version to inherit protected method from parent class

Hm, I can't reproduce the problem - I tried in R2016b and R2019a. Here are my test classes:

%% Super.m:
classdef Super
    properties (Access = private)
        Value = 7
    end
    methods (Access = protected)
        function out = protectedMethod(obj, x)
            out = obj.Value + x;
        end
    end
end

%% Test.m:
classdef Test < Super
    methods
        function out = runInParfor(obj)
            parfor ii = 1:4
                out(ii) = obj.protectedMethod(ii);
            end
        end
    end
end

which I exercise like this:

>> runInParfor(Test)
ans =
     8     9    10    11

So, it appears to work for me. Could you elaborate on what you're doing differently?

[Tmfu Vh]

Sorry my description has some mistakes. That protected function is inherited from the superclass. Please try again thanks!

[Edric Ellis]

Ok, I updated my attempt to reproduce the problem, still works fine for me...

[Tmfu Vh]

Well I got it. The exception details showed in the commandline window is misleading - it said that the OnProgressReport function is undefined, but the real bug I found later has nothing to do with that function. So tricky! Whatever thank you for your patience.