loss-functions: Loss functions

Description

Loss functions

Usage

loss_binary_crossentropy(
  y_true,
  y_pred,
  from_logits = FALSE,
  label_smoothing = 0,
  axis = -1L,
  ...,
  reduction = "auto",
  name = "binary_crossentropy"
)
loss_categorical_crossentropy(
  y_true,
  y_pred,
  from_logits = FALSE,
  label_smoothing = 0L,
  axis = -1L,
  ...,
  reduction = "auto",
  name = "categorical_crossentropy"
)
loss_categorical_hinge(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "categorical_hinge"
)
loss_cosine_similarity(
  y_true,
  y_pred,
  axis = -1L,
  ...,
  reduction = "auto",
  name = "cosine_similarity"
)
loss_hinge(y_true, y_pred, ..., reduction = "auto", name = "hinge")
loss_huber(
  y_true,
  y_pred,
  delta = 1,
  ...,
  reduction = "auto",
  name = "huber_loss"
)
loss_kullback_leibler_divergence(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "kl_divergence"
)
loss_kl_divergence(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "kl_divergence"
)
loss_logcosh(y_true, y_pred, ..., reduction = "auto", name = "log_cosh")
loss_mean_absolute_error(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "mean_absolute_error"
)
loss_mean_absolute_percentage_error(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "mean_absolute_percentage_error"
)
loss_mean_squared_error(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "mean_squared_error"
)
loss_mean_squared_logarithmic_error(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "mean_squared_logarithmic_error"
)
loss_poisson(y_true, y_pred, ..., reduction = "auto", name = "poisson")
loss_sparse_categorical_crossentropy(
  y_true,
  y_pred,
  from_logits = FALSE,
  axis = -1L,
  ...,
  reduction = "auto",
  name = "sparse_categorical_crossentropy"
)
loss_squared_hinge(
  y_true,
  y_pred,
  ...,
  reduction = "auto",
  name = "squared_hinge"
)

Arguments

y_true

Ground truth values. shape = [batch_size, d1, .. dN].

y_pred

The predicted values. shape = [batch_size, d1, .. dN]. (Tensor of the same shape as y_true)

from_logits

Whether y_pred is expected to be a logits tensor. By default we assume that y_pred encodes a probability distribution.

label_smoothing

Float in [0, 1]. If > 0 then smooth the labels. For example, if 0.1, use 0.1 / num_classes for non-target labels and 0.9 + 0.1 / num_classes for target labels.

axis

The axis along which to compute crossentropy (the features axis). Axis is 1-based (e.g, first axis is axis=1). Defaults to -1 (the last axis).

...

Additional arguments passed on to the Python callable (for forward and backwards compatibility).

reduction

Only applicable if y_true and y_pred are missing. Type of keras$losses$Reduction to apply to loss. Default value is AUTO. AUTO indicates that the reduction option will be determined by the usage context. For almost all cases this defaults to SUM_OVER_BATCH_SIZE. When used with tf$distribute$Strategy, outside of built-in training loops such as compile and fit, using AUTO or SUM_OVER_BATCH_SIZE will raise an error. Please see this custom training tutorial for more details.

name

Only applicable if y_true and y_pred are missing. Optional name for the Loss instance.

delta

A float, the point where the Huber loss function changes from a quadratic to linear.

Value

If called with y_true and y_pred, then the corresponding loss is evaluated and the result returned (as a tensor). Alternatively, if y_true and y_pred are missing, then a callable is returned that will compute the loss function and, by default, reduce the loss to a scalar tensor; see the reduction parameter for details. (The callable is a typically a class instance that inherits from keras$losses$Loss).

binary_crossentropy

Computes the binary crossentropy loss.

label_smoothing details: Float in [0, 1]. If > 0 then smooth the labels by squeezing them towards 0.5 That is, using 1. - 0.5 * label_smoothing for the target class and 0.5 * label_smoothing for the non-target class.

categorical_crossentropy

Computes the categorical crossentropy loss.

When using the categorical_crossentropy loss, your targets should be in categorical format (e.g. if you have 10 classes, the target for each sample should be a 10-dimensional vector that is all-zeros except for a 1 at the index corresponding to the class of the sample). In order to convert integer targets into categorical targets, you can use the Keras utility function to_categorical():

categorical_labels <- to_categorical(int_labels, num_classes = NULL)

huber

Computes Huber loss value. For each value x in error = y_true - y_pred:

loss = 0.5 * x^2                  if |x| <= d
loss = d * |x| - 0.5 * d^2        if |x| > d

where d is delta. See: https://en.wikipedia.org/wiki/Huber_loss

log_cosh

Logarithm of the hyperbolic cosine of the prediction error.

log(cosh(x)) is approximately equal to (x ** 2) / 2 for small x and to abs(x) - log(2) for large x. This means that 'logcosh' works mostly like the mean squared error, but will not be so strongly affected by the occasional wildly incorrect prediction. However, it may return NaNs if the intermediate value cosh(y_pred - y_true) is too large to be represented in the chosen precision.

Details

Loss functions for model training. These are typically supplied in the loss parameter of the compile.keras.engine.training.Model() function.