| - loss1
         | 

convs …fc3 - fc1 - fc2 - loss2
|
|  - loss3
I have three loss functions, I use torch.autogra.backward([l1,l2,l3]).
Firstly, Is it right, meaning different loss update different layers and layers before the leaf node?
Secondly, if I want to sum this three loss, how can I do? L = l1 + l2 + l3 , L.backward()?
If I do in this way, L update from which node?