pytorch: from tensors to variables

from_tensors_to_variables.py

import torch
from torch.autograd import Variable

# define an inputs
x_tensor = torch.randn(10, 20)
y_tensor = torch.randn(10, 5)
x = Variable(x_tensor, requires_grad=False)
y = Variable(y_tensor, requires_grad=False)
# define some weights
w = Variable(torch.randn(20, 5), requires_grad=True)

# get variable tensor
print(type(w.data))  # torch.FloatTensor
# get variable gradient
print(w.grad)  # None

loss = torch.mean((y - x @ w) ** 2)

# calculate the gradients
loss.backward()
print(w.grad)  # some gradients
# manually apply gradients
w.data -= 0.01 * w.grad.data
# manually zero gradients after update
w.grad.data.zero_()