L1Loss

class L1Loss

Bases: Loss

This class computes the L1 loss (i.e. absolute error) for each sample as:

\[\text{L1Loss}(predict, target) = \sum_{i=0}^{N_{\text{elements}}} \left| predict_i - target_i \right|.\]

Methods

evaluate(predict, target)

An abstract method for evaluating the loss function. Inputs are expected in a shape of (N, *). Where N is a number of samples. Loss is computed for each sample individually.

Parameters:

• predict (ndarray) -- an array of predicted values using the model.

• target (ndarray) -- an array of the true values.

Returns:

An array with values of the loss function of the shape (N, 1).

Raises:

QiskitMachineLearningError -- shapes of predict and target do not match

Return type:

ndarray

gradient(predict, target)

An abstract method for computing the gradient. Inputs are expected in a shape of (N, *). Where N is a number of samples. Gradient is computed for each sample individually.

Parameters:

• predict (ndarray) -- an array of predicted values using the model.

• target (ndarray) -- an array of the true values.

Returns:

An array with gradient values of the shape (N, *). The output shape depends on the loss function.

Raises:

QiskitMachineLearningError -- shapes of predict and target do not match.

Return type:

ndarray