第一章基本操作-自动求导

使用目标对象的.backward()进行反向梯度求导 

import torch


x = torch.randn(3, 4, requires_grad=True)
print(x)

b = torch.randn(3, 4, requires_grad=True)

t = x + b
y = t.sum()

y.backward()

print(b.grad)

x = torch.rand(1)
b = torch.rand(1, requires_grad=True)
w = torch.rand(1, requires_grad=True)
y = x * w
z = y + b

z.backward(retain_graph=True)


print(w.grad)
print(b.grad)