How to express this concave function in cvx?

Function log( log( 1 + exp(x) )) is involved in my problem which is concave. However, the concavity is not recognized by cvx. So, how to express this function in cvx?

I doubt it is possible, I’m afraid. CVX cannot handle every function that is provably convex; it can only handle those whose convexity can be proven using its existing set of rules.

Thanks very much. I wonder whether it is possible to allow cvx in the future version to recognize the concavity of this function. :smile:

No, due to the particular way CVX works it is almost certain never to happen. See the FAQ…