Hi All,

I want to write a code for label smoothing using **BCEWithLogitsLoss** .

Q1) Is BCEWithLogitLoss = BCELoss + sigmoid() ?

Q2) While checking the pytorch github docs I found following code in which sigmoid implementation is not there maybe I am looking at wrong Documents ?

Can someone tell me where they write proper BCEWithLogitLoss Code. ??

```
class BCEWithLogitsLoss(_Loss):
def __init__(self, weight: Optional[Tensor] = None, size_average=None, reduce=None, reduction: str = 'mean',
pos_weight: Optional[Tensor] = None) -> None:
super(BCEWithLogitsLoss, self).__init__(size_average, reduce, reduction)
self.register_buffer('weight', weight)
self.register_buffer('pos_weight', pos_weight)
def forward(self, input: Tensor, target: Tensor) -> Tensor:
return F.binary_cross_entropy_with_logits(input, target,
self.weight,
pos_weight=self.pos_weight)
def binary_cross_entropy_with_logits(input, target, weight=None, size_average=None,
reduce=None, reduction='mean', pos_weight=None):
# type: (Tensor, Tensor, Optional[Tensor], Optional[bool], Optional[bool], str, Optional[Tensor]) -> Tensor
r"""Function that measures Binary Cross Entropy between target and output
logits.
See :class:`~torch.nn.BCEWithLogitsLoss` for details.
Args:
input: Tensor of arbitrary shape
target: Tensor of the same shape as input
weight (Tensor, optional): a manual rescaling weight
if provided it's repeated to match input tensor shape
size_average (bool, optional): Deprecated (see :attr:`reduction`). By default,
the losses are averaged over each loss element in the batch. Note that for
some losses, there multiple elements per sample. If the field :attr:`size_average`
is set to ``False``, the losses are instead summed for each minibatch. Ignored
when reduce is ``False``. Default: ``True``
reduce (bool, optional): Deprecated (see :attr:`reduction`). By default, the
losses are averaged or summed over observations for each minibatch depending
on :attr:`size_average`. When :attr:`reduce` is ``False``, returns a loss per
batch element instead and ignores :attr:`size_average`. Default: ``True``
reduction (string, optional): Specifies the reduction to apply to the output:
``'none'`` | ``'mean'`` | ``'sum'``. ``'none'``: no reduction will be applied,
``'mean'``: the sum of the output will be divided by the number of
elements in the output, ``'sum'``: the output will be summed. Note: :attr:`size_average`
and :attr:`reduce` are in the process of being deprecated, and in the meantime,
specifying either of those two args will override :attr:`reduction`. Default: ``'mean'``
pos_weight (Tensor, optional): a weight of positive examples.
Must be a vector with length equal to the number of classes.
Examples::
>>> input = torch.randn(3, requires_grad=True)
>>> target = torch.empty(3).random_(2)
>>> loss = F.binary_cross_entropy_with_logits(input, target)
>>> loss.backward()
"""
if not torch.jit.is_scripting():
tens_ops = (input, target)
if any([type(t) is not Tensor for t in tens_ops]) and has_torch_function(tens_ops):
return handle_torch_function(
binary_cross_entropy_with_logits, tens_ops, input, target, weight=weight,
size_average=size_average, reduce=reduce, reduction=reduction,
pos_weight=pos_weight)
if size_average is not None or reduce is not None:
reduction_enum = _Reduction.legacy_get_enum(size_average, reduce)
else:
reduction_enum = _Reduction.get_enum(reduction)
if not (target.size() == input.size()):
raise ValueError("Target size ({}) must be the same as input size ({})".format(target.size(), input.size()))
return torch.binary_cross_entropy_with_logits(input, target, weight, pos_weight, reduction_enum)
```

Thanks !!!