torch.lgamma
torch.lgamma(input, *, out=None) -> Tensor
Computes the natural logarithm of the absolute value of the gamma
   function on "input".
  \text{out}_{i} = \ln \Gamma(|\text{input}_{i}|)

Parameters:
      input (Tensor) -- the input tensor.
Keyword Arguments:
      out (Tensor, optional) -- the output tensor.
Example:
  >>> a = torch.arange(0.5, 2, 0.5)
  >>> torch.lgamma(a)
  tensor([ 0.5724,  0.0000, -0.1208])
