mindspore.nn.PoissonNLLLoss

class mindspore.nn.PoissonNLLLoss(log_input=True, full=False, eps=1e-08, reduction='mean')[source]

Poisson negative log likelihood loss.

The loss is:

\[\mathcal{L}_{D} = \sum_{i = 0}^{|D|}\left( x_{i} - y_{i}\ln x_{i} + \ln{y_{i}!} \right)\]

where \(\mathcal{L}_{D}\) is the loss, \(y_{i}\) is the target, \(x_{i}\) is the input.

If log_input is True, use \(e^{x_{i}} - y_{i} x_{i}\) instead of \(x_{i} - y_{i}\ln x_{i}\). When calculating logarithms, the lower bound of input is set to eps to avoid numerical errors.

If full is False, the last term \(\ln{y_{i}!}\) will be omitted, otherwise the last term will be approximated using Stirling formula:

\[n! \approx \sqrt{2\pi n}\left( \frac{n}{e} \right)^{n}\]

Note

Calculating the logarithm of a negative number or the exponent of a large positive number under Ascend will have a different range of return values and results different from those under GPU and CPU.

Parameters

  • log_input (bool, optional) – Whether use log input. Default: True.

  • full (bool, optional) – Whether include the Stirling approximation term in the loss calculation. Default: False.

  • eps (float, optional) – Lower bound of input when calculating logarithms. Default: 1e-08.

  • reduction (str, optional) – Apply specific reduction method to the output: ‘none’, ‘mean’, ‘sum’. Default: ‘mean’.

Inputs:

  • input (Tensor) - The input Tensor. The shape can be any number of dimensions.

  • target (Tensor) - The label Tensor which has the same shape as input.

Outputs:

Tensor or Scalar, if reduction is ‘none’, then output is a tensor and has the same shape as input. Otherwise it is a scalar.

Raises

  • TypeError – If reduction is not a str.

  • TypeError – If neither input nor target is a tensor.

  • TypeError – If dtype of input or target is not currently supported.

Supported Platforms:

Ascend GPU CPU

Examples

>>> x = Tensor([[0.3, 0.7], [0.5, 0.5]])
>>> target = Tensor([[1.0, 2.0], [3.0, 4.0]])
>>> loss = nn.PoissonNLLLoss()
>>> output = loss(x, target)
>>> print(output.asnumpy())
0.3652635