Applies a softmax followed by a logarithm.
nnf_log_softmax(input, dim = NULL, dtype = NULL)
(Tensor) input
(int) A dimension along which log_softmax will be computed.
(torch.dtype
, optional) the desired data type of returned tensor.
If specified, the input tensor is casted to dtype
before the operation
is performed. This is useful for preventing data type overflows.
Default: NULL
.
While mathematically equivalent to log(softmax(x)), doing these two operations separately is slower, and numerically unstable. This function uses an alternative formulation to compute the output and gradient correctly.