sigmoid_focal_loss

dragon.losses.sigmoid_focal_loss(
  inputs,
  axis=- 1,
  alpha=0.25,
  gamma=2.0,
  start_index=0,
  reduction='valid',
  **kwargs
)[source]

Compute the focal loss of sigmoid cross entropy. [Lin et.al, 2017].

Examples:

x = dragon.constant([[0.5, 0.5], [0.3, 0.7]])
y = dragon.constant([1, 0])
print(dragon.losses.sigmoid_focal_loss([x, y]))  # 0.3472295
Parameters:
  • inputs (Sequence[dragon.Tensor]) – The tensor input and target.
  • axis (int, optional, default=-1) – The reduce axis, can be negative.
  • alpha (float, optional, default=0.25) – The scale factor to the positive classes.
  • gamma (float, optional, default=2.0) – The exponential decay factor on the easy examples.
  • start_index (int, optional, default=0) – The start value of target.
  • reduction ({'none', 'sum', 'mean', 'valid'}, optional) – The reduction method.
Returns:

dragon.Tensor – The output tensor.