python - PyTorch: What is the difference between tensor.cuda() and tensor.to(torch.device("cuda:0"))?

Question

In PyTorch, what is the difference between the following two methods in sending a tensor (or model) to GPU:

Setup:

X = np.array([[1, 3, 2, 3], [2, 3, 5, 6], [1, 2, 3, 4]]) # X = model()
X = torch.DoubleTensor(X)

Method 1	Method 2
X.cuda()	device = torch.device("cuda:0") X = X.to(device)

Answer 1

There is no difference between the two.
Early versions of pytorch had .cuda() and .cpu() methods to move tensors and models from cpu to gpu and back. However, this made code writing a bit cumbersome:

if cuda_available:
  x = x.cuda()
  model.cuda()
else:
  x = x.cpu()
  model.cpu()

Later versions introduced .to() that basically takes care of everything in an elegant way:

device = torch.device('cuda') if cuda_available else torch.device('cpu')
x = x.to(device)
model = model.to(device)