torch.rsqrt
torch.rsqrt(input, *, out=None) -> Tensor
Returns a new tensor with the reciprocal of the square-root of each
   of the elements of "input".
  \text{out}_{i} = \frac{1}{\sqrt{\text{input}_{i}}}

Parameters:
      input (Tensor) -- the input tensor.
Keyword Arguments:
      out (Tensor, optional) -- the output tensor.
Example:
  >>> a = torch.randn(4)
  >>> a
  tensor([-0.0370,  0.2970,  1.5420, -0.9105])
  >>> torch.rsqrt(a)
  tensor([    nan,  1.8351,  0.8053,     nan])
