??? Dimension 1 is fixed on the left-hand side but varies on the right ([256 x 256] ~= [:? x :?]) when running codegen command

I ran into a weird issue when running codegen in matlab. I am aware that codegen requires you to predefine all the variables used. In this case, I predefined Dec as a cell array of cell arrays with each index corresponding to a m x n matrix.

nD = length(D);

kDec = A;
[m,n] = size(A);
Dec = cell(1,L);
for c = 1:L
   Dec{c} = cell(nD-1);
    for i = 1:nD-1
        for j  = 1:nD-1
            Dec{c}{i,j} = zeros(m,n);
        end
    end
end

for k = 1:L
    Dec{k} = FraDec(kDec,D,k);
    kDec = Dec{k}{1,1};
end

kDec is predefined as a Matrix and therefore by equating kDec to Dec{k}{1,1}, there shouldn't be any issues in the matrix size allocation since both kDec and Dec have been predefined and each entry to Dec has been instantiated to a matrix of the same size. However when running codegen, I get the error ??? Dimension 1 is fixed on the left-hand side but varies on the right ([256 x 256] ~= [:? x :?]) for line:

kDec = Dec{k}{1,1};

After spending a very long time on this error, I have no idea how I can resolve this issue.

[Darshan Ramakant Bhat]

Can you please attach the full sample code along with the full reproduction steps. This will help us to reproduce the issue at our end.

[Kanha Srivastav]

I have attached my project files in a zip file. I first run the 'test_SplitBregDebP.m' file to generate variables needed in the 'SplitBregDebP.m' function. From there I run

codegen SplitBregDebP.m -args {g,ker,mu,lambda,tol,frame,Level,wLevel,maxit,img}

in the command window.

Doing this, I get the error. If I run

A = zeros(256,256);
D = cell(1,4);
L = 5;
codegen FraDecMultiLevel.m -args {A,D,L}

In the command window, in order to test the function by itself, I run into a different issue in 'FraDec.m' function:

??? Index expression out of bounds. Attempted to access element 1. The valid range is 1-0

This issue is taking a lot of time to debug and the documentation is quite convoluted.

Answer 1

[Darshan Ramakant Bhat]

I have modified the sample code attached and made it work.

Please use "codes_modified" file and run below command :

codegen SplitBregDebP.m -args {g,ker,mu,lambda,tol,frame,Level,wLevel,maxit,img} -report

The "-report" option will generate a codegen report and that will help you to debug the issue. Please refer below doc :

https://www.mathworks.com/help/coder/ug/code-generation-reports.html

I have made use of coder.varsize() to make the code work. You can read below doc for more information :

https://www.mathworks.com/help/fixedpoint/ref/coder.varsize.html

There are some limitations when you are using cell arrays for codegeneration :

https://www.mathworks.com/help/simulink/ug/unable-to-determine-that-every-element-of-cell-array-is-assigned.html

Hope this will be helpful for you.

[Kanha Srivastav]

Thank you for this update. The changes you made have fixed the issue with variable size error when running codegen. I gave you a heavily modified code that broke the initial functionality of the code and by reverting to the original code I ran into new errors:

??? Unable to determine that every element of 'd{:}' is assigned before this line.

in the uncommented line 68 in the SplitBregDebP.m file.

[Darshan Ramakant Bhat]

As I mentioned in my answer, you would have run into the cell array problem as mentioned in the doc :

https://www.mathworks.com/help/simulink/ug/unable-to-determine-that-every-element-of-cell-array-is-assigned.html

Please try the methods suggested in the doc.

Please take a look at line 31 and 32 of "FraDecMultiLevel.m" file. Compare the code, before and after the modification that I did. You may follow the same approach for your code.

[Kanha Srivastav]

I followed the same approach you had done in "FraDecMultiLevel.m" in my "SplitBregDebP.m" but still run into the same error. I even tried the approach in the given doc regarding the nullcopy approach but still get similar issues.

C1 = coder.nullcopy(C);
coder.varsize('C1');
b1 = coder.nullcopy(b);
d1 = coder.nullcopy(d);
error = 0.0;
deltab = zeros(m,n);
for nstep=1:maxit 
    for innerstep=1:1
        % solve u.
        for ki=1:Level
            for ji=1:nD-1
                for jj=1:nD-1
                    C1{ki}{ji,jj}=d1{ki}{ji,jj}-b1{ki}{ji,jj};
                end
            end
        end
        u=abs(ifft2(fft2(lambda*FraRecMultiLevel(C1,R,Level)+BTg)./eigenP)); %converted to non-complex %new error Codegen requires that every cell-array element contained in 'C' be assigned a value before being passed into 'FraRecMultiLevel'. Check assignments to element(s):
        %u = zeros(m,n);
        % solve d
        % size(FraDecMultiLevel(u,D,Level))
        C1=FraDecMultiLevel(u,D,Level); %changed name of variable %same LHS size != RHS error
        for ki=1:Level
            for ji=1:nD-1
                for jj=1:nD-1
                    d1{ki}{ji,jj}=wthresh(C1{ki}{ji,jj}+b1{ki}{ji,jj},'s',muLevel{ki}{ji,jj}/lambda); %Unable to determine that every element of 'C{:}' is assigned before this line.
                end
            end
        end

Could this issue be related to the fact that C1, d1 and b1 are changing in different loops?