import torch

x  = torch.tensor(1.0)
w1 = torch.tensor(2.0, requires_grad=True)
b1 = torch.tensor(0.0, requires_grad=True)
w2 = torch.tensor(3.0, requires_grad=True)
b2 = torch.tensor(1.0, requires_grad=True)
y  = torch.tensor(2.0)

h1 = w1 * x + b1
a1 = torch.relu(h1)
h2 = w2 * a1 + b2
loss = (h2 - y) ** 2

loss.backward()

print(f"loss   = {loss.item()}")     # 25.0
print(f"dL/dw1 = {w1.grad.item()}")  # 30.0
print(f"dL/db1 = {b1.grad.item()}")  # 30.0
print(f"dL/dw2 = {w2.grad.item()}")  # 20.0
print(f"dL/db2 = {b2.grad.item()}")  # 10.0