Does anyone know how to modify the error (Disciplined convex programming error: Illegal operation: pow_p( {convex}, {-1} ))

i write a cvx code by using matlab ,and the window show me a error ,but i don't know its meaning and how do i modify my code

The window show me as below

Error using cvx/pow_cvx (line 144)
Disciplined convex programming error:
    Illegal operation: pow_p( {convex}, {-1} )DO

Error in cvx/inv_pos (line 5)
y = pow_cvx( x, -1, 'pow_p' );

Error in f_kI (line 53)
       denominator=inv_pos(total+nois_var_ak_2pow(1) + nois_var_dk_2pow(1))

And my code is as below

bar_r=[10 10 10 10];
P_T=10;
h_1=sqrt(nois_var_hk_2pow/2)*(randn(N,1)+1i*randn(N,1));
h_2=sqrt(nois_var_hk_2pow/2)*(randn(N,1)+1i*randn(N,1));
h_3=sqrt(nois_var_hk_2pow/2)*(randn(N,1)+1i*randn(N,1));
h_4=sqrt(nois_var_hk_2pow/2)*(randn(N,1)+1i*randn(N,1));
h_kk=cat(2,h_1 ,h_2 ,h_3, h_4)
 for n=1:4
    h_k{n}=h_kk(1:4 , n);
    n=n+1;
 end
%===========================================================

cvx_begin
     variable f_kiii(N,1,K); 
     f_kii=cat(2, f_kiii)
   
   for o=1:4
      f_ki{o}=f_kii(1:4,o) 
   end

   op2=0;
   for k=1:K
      op2=op2+square_abs(f_ki{k});       
   end
%==========================================
%objected function
    minimize( op2 )
    subject to
%==========================================  
       %c8
        total = 0;
        for k = 1:K
            sub_denominator = 0;
            for j = 1:K
                if j ~= k  
                 sub_denominator = sub_denominator +  square_abs(h_k{k}' * f_ki{j});
                end
            end
            total = total + sub_denominator;
        end
   
       numerator=square_abs(h_k{k}' *f_ki{k}) 
       denominator=inv_pos(total+nois_var_ak_2pow(1) + nois_var_dk_2pow(1)) 
       numerator*denominator>=bar_r(1)
cvx_end

Does anyone know how to modify the error code?

denominator=inv_pos(total+nois_var_ak_2pow(1) + nois_var_dk_2pow(1)) 

[Adam]

What is inv_pos? It isn't a Matlab function that I am aware of.

[yang-En Hsiao]

that is the function that cvx can accept.

[Adam]

It still isn't defined anywhere. And what is cvx? If you don't give all the relevant information people can't provide useful help without just making guesses. You haven't added any tags other than Matlab to give an idea what domain it is related to. Are we supposed to all know what cvx is?

[yang-En Hsiao]

we don't need to define cvx,cvx is like a tool in matlab ,but you have to install it .

http://cvxr.com/cvx/doc/index.html