In the backward pass, we compute each of these partials along each edge of the graph from right to left, using the chain rule just as we did above. Thus we begin by computing the downstream gradients from node L, which are ∂ L ∂ e and ∂ L ∂ c . For node e, we then multiply this upstream gradient ∂ L ∂ e by the local gradient (the gradient of the output with respect to the input), ∂ e ∂ d to get the output we send back to node d: