Continuing the discussion from Status: Unbounded Optimal value (cvx_optval): -Inf:

help cvx/log

`Disciplined convex programming information: log(X) is concave and nondecreasing in X. When used in CVX expressions, X must be concave.`

Thang you!

my Log is log（(P*beta/(x+H))+a）,where P, beta ,H and a are 1*1 constant. how can i edit it with CVX.

Do you know the values or ranges of the constants? Have you proven it is convex?

Is y the only optimization (CVX) variable? if so, the sign of the 2nd derivative w.r.t y will show convexity or not.

when I rewirtten the program as

for n=1:1:N

for k=1:1:K

for m=1:1:M

if m==1

r(n,k,m)=log2((p2*beta/(y(n,k,m)+H^2))+delta);
% r(n,k,m)=rel_entr(p2*beta+(y(n,k,m)+H^2)

*delta,y(n,k,m))+rel_entr(y(n,k,m),p2*beta+(y(n,k,m)+H^2)

*delta);*

else

r(n,k,m)=log2((p1beta/(y(n,k,m)+H^2))+delta);

else

r(n,k,m)=log2((p1

% r(n,k,m)=rel_entr(p1*beta+(y(n,k,m)+H^2)

*delta,y(n,k,m))+rel_entr(y(n,k,m),p1*beta+(y(n,k,m)+H^2)*delta);

end

end

end

end

Disciplined convex programming error:

Invalid operation: {0.0001} / {real affine}.

However, when i written the program as follow

for n=1:1:N

for k=1:1:K

for m=1:1:M

if m==1

r(n,k,m)=log2((p2*beta*inv_pos(y(n,k,m)+H^2))+delta);

% r(n,k,m)=rel_entr(p2*beta+(y(n,k,m)+H^2) delta,y(n,k,m))+rel_entr(y(n,k,m),p2beta+(y(n,k,m)+H^2)delta);*inv_pos(y(n,k,m)+H^2))+delta);

else

r(n,k,m)=log2((p1beta

% r(n,k,m)=rel_entr(p1*beta+(y(n,k,m)+H^2)

*delta,y(n,k,m))+rel_entr(y(n,k,m),p1*beta+(y(n,k,m)+H^2)*delta);

end

end

end

end

Disciplined convex programming error:

Invalid operation: log( {positive convex} )

You haven’t answered my questions.

Please read what is expected for forum posters. Why isn't CVX accepting my model? READ THIS FIRST!

yes, the y is (cvx) veriable.