pytorch

import torch
from torch.autograd import Variable
import torch.nn as nn


x = Variable(torch.ones(1, 2), requires_grad=True)
linear = nn.Linear(2, 2, bias=False)
linear.weight.data.copy_(torch.Tensor([[1, 2], [1, 2]]))

y = x
for i in range(2):
    y = linear(y)

loss = y.sum()
loss.backward()
print(linear.weight.grad)
print(x.grad)