when I use loss.backward(), I meet the error of “RuntimeError: Function SubBackward0 returned an invalid gradient at index 0 - expected type torch.cuda.FloatTensor but got torch.cuda.DoubleTensor”
, I 'm sure that the type of  variable “loss” is torch.cuda.FloatTensor . Because
isinstance(loss, torch.cuda.FloatTensor)

it show True.
Can you help me what’s wrong with the loss.backward().