Thanks for the tip. I have tried rel_entr() before, but I can only represent xlog(1+x/y), not ylog(1+x/y), can you provide a more detailed representation？Thank you！

ylog(1+x/y)=-ylog(y/(x+y))=-rel_entr(y,x+y). It can be written this way because (y,x+y) is a linear mapping of (x,y)，then the rule of composition of convex function applies.