ChrisLiu2:

Does “tricky” in this scenario mean you can’t learn anything in the MLP?


You cannot define gradients for discrete quantities. So tricky here mean not possible 
A trick that can be used to get around this is to make these quantities continuous. But this is not always possible and can have very weird interpretation depending on the application. For the connectivity here for example, I’m not sure what it would mean to have an adjacency matrix with continuous values?