Cvx real affine expression (1x2x2 array) Error using cvx_end (line 267) Your objective function is not a scalar

1

Hello All,
I have that error: “Your objectşve function is not scalar” But I could not find where I am wrong. This is my code can you look at it?
function G = TD_P_inv_Dual(P_exp,B,A_ax,B_by)

d = size(P_exp,1); %dimentions
m = size(P_exp,3); %number of operators
cvx_begin
variable S(1,m,m) %For the dual we have not dual variables instead of that we have variable and in this equation we have S
W_hat=zeros(d^2,d^2);
%variable sigma_e(d^2,d^2,d) hermitian semidefinite 
for a=1:d
    for b=1:d
        for x=1:m
            for y=1:m
                W_hat=W_hat+B(a,b,x,y).*(kron(A_ax(:,:,x,a),B_by(:,:,y,b)));  
            end
        end
    end
end
W=sum(sum(sum(sum(B.*P_exp))));


J=cvx(0);
J= (S*W);
J=real(J) 
minimize(J)

subject to

for e=1:d

(W_hat-kron(squeeze(A_ax(:,:,1,e)),eye(d)))==semidefinite(d^2,d^2);
end

cvx_end

G=double(J);

Bets!

2

You haven’t shown us the dimensions of W. If m > 1, I don’t think there are any dimensions of W which would make S*W a scalar. Therefore, J will not be a scalar, hence the error message. Based on " Cvx real affine expression (1x2x2 array)" appearing in the title of your question, I presume J evaluates to 1 by 2 by 2, which is not a scalar, which it needs to be in order to be used as the objective.

Also, you calculate W_hat but don’t use it, at least in the code that is shown.

3

Thanks

it needs to be in order to be used as the objective.
What does it mean? How can I use J as an objective? Can you please write me this code line?

Also, you calculate W_hat but don’t use it, at least in the code that is shown.
Later I saw and did a correction for this line

4

The objective must evaluate to a real scalar. It is your optimization problem, so hopefully you know what that real scalar objective function is supposed to be; it can’t be J, because it is not a scalar. I don’t know what objective function you are trying to minimize.

5

I got your mean thanks a lot I just forgat to thisnk for S