torch.numel
torch.numel(input) -> int
Returns the total number of elements in the "input" tensor.
Parameters:
      input (Tensor) -- the input tensor.
Example:
  >>> a = torch.randn(1, 2, 3, 4, 5)
  >>> torch.numel(a)
  120
  >>> a = torch.zeros(4,4)
  >>> torch.numel(a)
  16
