Prevent codegen from creating matrix copy for use as const* function parameter

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JM 2019-3-18

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https://ww2.mathworks.cn/matlabcentral/answers/450706-prevent-codegen-from-creating-matrix-copy-for-use-as-const-function-parameter

关闭： MATLAB Answer Bot 2021-8-20

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Using MATLAB R2018a with MEX code generation I have some troubling preventing from creating unnecessary copies of a value class present in the MATLAB code to be converted into C code.

The code pattern is as follows:

output = cell(P,1)
hugeblockoflogical = false(M,N)
% Fill all of output{:}
for i = 1:P
    
    (code that reads/writes to/from hugeblockoflogical)
    
    % ???
    hugeblockoflogical_copy = initheap(hugeblockoflogical)
    
    % Create class from matrix and store in output argument
    % ValueClass constructor does NOT modify input argument
    output{i} = ValueClass(hugeblockoflogical_copy)
end

At the assignment of output{i} Codegen decides to create a full copy of hugeblockoflogical before passing that copy into the constructor of ValueClass as a const pointer.

From inspecting the generated C code I see no reason why the huge copy should be generated.

Anyone have a suggestion as to why this is happening and how to prevent it?