I have a function $f(x) = (\mathbf x ^ \top \mathbf x) ^ {p/2}$.
Its gradient is $\nabla f(x) = 2p (\mathbf x ^ \top \mathbf x) ^ {(p-2)/2} \mathbf x$
How do I compute its Hessian $\nabla^2f(x) $? Should I use product rule? Can someone show me how to do it or refer me to some resource?
Thanks