Are x and y both CVX variables? If so, then log(1+x/y) is indefinite (neither convex not concave), and so will not be accepted by CVX. On the other hand, x*log(1+y/x) can be expressed in CVX, as shown in Perspective function .
Are x and y both CVX variables? If so, then log(1+x/y) is indefinite (neither convex not concave), and so will not be accepted by CVX. On the other hand, x*log(1+y/x) can be expressed in CVX, as shown in Perspective function .