Probabilistic losses
- Original Link : https://keras.io/api/losses/probabilistic_losses/
- Last Checked at : 2024-11-25
BinaryCrossentropy class
keras.losses.BinaryCrossentropy(
from_logits=False,
label_smoothing=0.0,
axis=-1,
reduction="sum_over_batch_size",
name="binary_crossentropy",
dtype=None,
)Computes the cross-entropy loss between true labels and predicted labels.
Use this cross-entropy loss for binary (0 or 1) classification applications. The loss function requires the following inputs:
y_true(true label): This is either 0 or 1.y_pred(predicted value): This is the model’s prediction, i.e, a single floating-point value which either represents a logit, (i.e, value in [-inf, inf] whenfrom_logits=True) or a probability (i.e, value in [0., 1.] whenfrom_logits=False).
Arguments
- from_logits: Whether to interpret
y_predas a tensor of logit values. By default, we assume thaty_predis probabilities (i.e., values in [0, 1]). - label_smoothing: Float in range [0, 1]. When 0, no smoothing occurs.
When > 0, we compute the loss between the predicted labels
and a smoothed version of the true labels, where the smoothing
squeezes the labels towards 0.5. Larger values of
label_smoothingcorrespond to heavier smoothing. - axis: The axis along which to compute crossentropy (the features axis).
Defaults to
-1. - reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
Examples
Recommended Usage: (set from_logits=True)
With compile() API:
model.compile(
loss=keras.losses.BinaryCrossentropy(from_logits=True),
...
)As a standalone function:
>>> # Example 1: (batch_size = 1, number of samples = 4)
>>> y_true = np.array([0, 1, 0, 0])
>>> y_pred = np.array([-18.6, 0.51, 2.94, -12.8])
>>> bce = keras.losses.BinaryCrossentropy(from_logits=True)
>>> bce(y_true, y_pred)
0.8654
>>> # Example 2: (batch_size = 2, number of samples = 4)
>>> y_true = np.array([[0, 1], [0, 0]])
>>> y_pred = np.array([[-18.6, 0.51], [2.94, -12.8]])
>>> # Using default 'auto'/'sum_over_batch_size' reduction type.
>>> bce = keras.losses.BinaryCrossentropy(from_logits=True)
>>> bce(y_true, y_pred)
0.8654
>>> # Using 'sample_weight' attribute
>>> bce(y_true, y_pred, sample_weight=[0.8, 0.2])
0.243
>>> # Using 'sum' reduction` type.
>>> bce = keras.losses.BinaryCrossentropy(from_logits=True,
... reduction="sum")
>>> bce(y_true, y_pred)
1.730
>>> # Using 'none' reduction type.
>>> bce = keras.losses.BinaryCrossentropy(from_logits=True,
... reduction=None)
>>> bce(y_true, y_pred)
array([0.235, 1.496], dtype=float32)
Default Usage: (set from_logits=False)
>>> # Make the following updates to the above "Recommended Usage" section
>>> # 1. Set `from_logits=False`
>>> keras.losses.BinaryCrossentropy() # OR ...('from_logits=False')
>>> # 2. Update `y_pred` to use probabilities instead of logits
>>> y_pred = [0.6, 0.3, 0.2, 0.8] # OR [[0.6, 0.3], [0.2, 0.8]]
BinaryFocalCrossentropy class
keras.losses.BinaryFocalCrossentropy(
apply_class_balancing=False,
alpha=0.25,
gamma=2.0,
from_logits=False,
label_smoothing=0.0,
axis=-1,
reduction="sum_over_batch_size",
name="binary_focal_crossentropy",
dtype=None,
)Computes focal cross-entropy loss between true labels and predictions.
Binary cross-entropy loss is often used for binary (0 or 1) classification tasks. The loss function requires the following inputs:
y_true(true label): This is either 0 or 1.y_pred(predicted value): This is the model’s prediction, i.e, a single floating-point value which either represents a logit, (i.e, value in [-inf, inf] whenfrom_logits=True) or a probability (i.e, value in[0., 1.]whenfrom_logits=False).
According to Lin et al., 2018, it helps to apply a “focal factor” to down-weight easy examples and focus more on hard examples. By default, the focal tensor is computed as follows:
focal_factor = (1 - output) ** gamma for class 1
focal_factor = output ** gamma for class 0
where gamma is a focusing parameter. When gamma=0, this function is
equivalent to the binary crossentropy loss.
Arguments
- apply_class_balancing: A bool, whether to apply weight balancing on the binary classes 0 and 1.
- alpha: A weight balancing factor for class 1, default is
0.25as mentioned in reference Lin et al., 2018. The weight for class 0 is1.0 - alpha. - gamma: A focusing parameter used to compute the focal factor, default is
2.0as mentioned in the reference Lin et al., 2018. - from_logits: Whether to interpret
y_predas a tensor of logit values. By default, we assume thaty_predare probabilities (i.e., values in[0, 1]). - label_smoothing: Float in
[0, 1]. When0, no smoothing occurs. When >0, we compute the loss between the predicted labels and a smoothed version of the true labels, where the smoothing squeezes the labels towards0.5. Larger values oflabel_smoothingcorrespond to heavier smoothing. - axis: The axis along which to compute crossentropy (the features axis).
Defaults to
-1. - reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
Examples
With the compile() API:
model.compile(
loss=keras.losses.BinaryFocalCrossentropy(
gamma=2.0, from_logits=True),
...
)As a standalone function:
>>> # Example 1: (batch_size = 1, number of samples = 4)
>>> y_true = [0, 1, 0, 0]
>>> y_pred = [-18.6, 0.51, 2.94, -12.8]
>>> loss = keras.losses.BinaryFocalCrossentropy(
... gamma=2, from_logits=True)
>>> loss(y_true, y_pred)
0.691
>>> # Apply class weight
>>> loss = keras.losses.BinaryFocalCrossentropy(
... apply_class_balancing=True, gamma=2, from_logits=True)
>>> loss(y_true, y_pred)
0.51
>>> # Example 2: (batch_size = 2, number of samples = 4)
>>> y_true = [[0, 1], [0, 0]]
>>> y_pred = [[-18.6, 0.51], [2.94, -12.8]]
>>> # Using default 'auto'/'sum_over_batch_size' reduction type.
>>> loss = keras.losses.BinaryFocalCrossentropy(
... gamma=3, from_logits=True)
>>> loss(y_true, y_pred)
0.647
>>> # Apply class weight
>>> loss = keras.losses.BinaryFocalCrossentropy(
... apply_class_balancing=True, gamma=3, from_logits=True)
>>> loss(y_true, y_pred)
0.482
>>> # Using 'sample_weight' attribute with focal effect
>>> loss = keras.losses.BinaryFocalCrossentropy(
... gamma=3, from_logits=True)
>>> loss(y_true, y_pred, sample_weight=[0.8, 0.2])
0.133
>>> # Apply class weight
>>> loss = keras.losses.BinaryFocalCrossentropy(
... apply_class_balancing=True, gamma=3, from_logits=True)
>>> loss(y_true, y_pred, sample_weight=[0.8, 0.2])
0.097
>>> # Using 'sum' reduction` type.
>>> loss = keras.losses.BinaryFocalCrossentropy(
... gamma=4, from_logits=True,
... reduction="sum")
>>> loss(y_true, y_pred)
1.222
>>> # Apply class weight
>>> loss = keras.losses.BinaryFocalCrossentropy(
... apply_class_balancing=True, gamma=4, from_logits=True,
... reduction="sum")
>>> loss(y_true, y_pred)
0.914
>>> # Using 'none' reduction type.
>>> loss = keras.losses.BinaryFocalCrossentropy(
... gamma=5, from_logits=True,
... reduction=None)
>>> loss(y_true, y_pred)
array([0.0017 1.1561], dtype=float32)
>>> # Apply class weight
>>> loss = keras.losses.BinaryFocalCrossentropy(
... apply_class_balancing=True, gamma=5, from_logits=True,
... reduction=None)
>>> loss(y_true, y_pred)
array([0.0004 0.8670], dtype=float32)
CategoricalCrossentropy class
keras.losses.CategoricalCrossentropy(
from_logits=False,
label_smoothing=0.0,
axis=-1,
reduction="sum_over_batch_size",
name="categorical_crossentropy",
dtype=None,
)Computes the crossentropy loss between the labels and predictions.
Use this crossentropy loss function when there are two or more label
classes. We expect labels to be provided in a one_hot representation. If
you want to provide labels as integers, please use
SparseCategoricalCrossentropy loss. There should be num_classes floating
point values per feature, i.e., the shape of both y_pred and y_true are
[batch_size, num_classes].
Arguments
- from_logits: Whether
y_predis expected to be a logits tensor. By default, we assume thaty_predencodes a probability distribution. - label_smoothing: Float in [0, 1]. When > 0, label values are smoothed,
meaning the confidence on label values are relaxed. For example, if
0.1, use0.1 / num_classesfor non-target labels and0.9 + 0.1 / num_classesfor target labels. - axis: The axis along which to compute crossentropy (the features
axis). Defaults to
-1. - reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
Examples
Standalone usage:
>>> y_true = [[0, 1, 0], [0, 0, 1]]
>>> y_pred = [[0.05, 0.95, 0], [0.1, 0.8, 0.1]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> cce = keras.losses.CategoricalCrossentropy()
>>> cce(y_true, y_pred)
1.177
>>> # Calling with 'sample_weight'.
>>> cce(y_true, y_pred, sample_weight=np.array([0.3, 0.7]))
0.814
>>> # Using 'sum' reduction type.
>>> cce = keras.losses.CategoricalCrossentropy(
... reduction="sum")
>>> cce(y_true, y_pred)
2.354
>>> # Using 'none' reduction type.
>>> cce = keras.losses.CategoricalCrossentropy(
... reduction=None)
>>> cce(y_true, y_pred)
array([0.0513, 2.303], dtype=float32)
Usage with the compile() API:
model.compile(optimizer='sgd',
loss=keras.losses.CategoricalCrossentropy())CategoricalFocalCrossentropy class
keras.losses.CategoricalFocalCrossentropy(
alpha=0.25,
gamma=2.0,
from_logits=False,
label_smoothing=0.0,
axis=-1,
reduction="sum_over_batch_size",
name="categorical_focal_crossentropy",
dtype=None,
)Computes the alpha balanced focal crossentropy loss.
Use this crossentropy loss function when there are two or more label
classes and if you want to handle class imbalance without using
class_weights. We expect labels to be provided in a one_hot
representation.
According to Lin et al., 2018, it helps to apply a focal factor to down-weight easy examples and focus more on hard examples. The general formula for the focal loss (FL) is as follows:
FL(p_t) = (1 - p_t) ** gamma * log(p_t)
where p_t is defined as follows:
p_t = output if y_true == 1, else 1 - output
(1 - p_t) ** gamma is the modulating_factor, where gamma is a focusing
parameter. When gamma = 0, there is no focal effect on the cross entropy.
gamma reduces the importance given to simple examples in a smooth manner.
The authors use alpha-balanced variant of focal loss (FL) in the paper:
FL(p_t) = -alpha * (1 - p_t) ** gamma * log(p_t)
where alpha is the weight factor for the classes. If alpha = 1, the
loss won’t be able to handle class imbalance properly as all
classes will have the same weight. This can be a constant or a list of
constants. If alpha is a list, it must have the same length as the number
of classes.
The formula above can be generalized to:
FL(p_t) = alpha * (1 - p_t) ** gamma * CrossEntropy(y_true, y_pred)
where minus comes from CrossEntropy(y_true, y_pred) (CE).
Extending this to multi-class case is straightforward:
FL(p_t) = alpha * (1 - p_t) ** gamma * CategoricalCE(y_true, y_pred)
In the snippet below, there is num_classes floating pointing values per
example. The shape of both y_pred and y_true are
(batch_size, num_classes).
Arguments
- alpha: A weight balancing factor for all classes, default is
0.25as mentioned in the reference. It can be a list of floats or a scalar. In the multi-class case, alpha may be set by inverse class frequency by usingcompute_class_weightfromsklearn.utils. - gamma: A focusing parameter, default is
2.0as mentioned in the reference. It helps to gradually reduce the importance given to simple (easy) examples in a smooth manner. - from_logits: Whether
outputis expected to be a logits tensor. By default, we consider thatoutputencodes a probability distribution. - label_smoothing: Float in [0, 1]. When > 0, label values are smoothed,
meaning the confidence on label values are relaxed. For example, if
0.1, use0.1 / num_classesfor non-target labels and0.9 + 0.1 / num_classesfor target labels. - axis: The axis along which to compute crossentropy (the features
axis). Defaults to
-1. - reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
Examples
Standalone usage:
>>> y_true = [[0., 1., 0.], [0., 0., 1.]]
>>> y_pred = [[0.05, 0.95, 0], [0.1, 0.8, 0.1]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> cce = keras.losses.CategoricalFocalCrossentropy()
>>> cce(y_true, y_pred)
0.23315276
>>> # Calling with 'sample_weight'.
>>> cce(y_true, y_pred, sample_weight=np.array([0.3, 0.7]))
0.1632
>>> # Using 'sum' reduction type.
>>> cce = keras.losses.CategoricalFocalCrossentropy(
... reduction="sum")
>>> cce(y_true, y_pred)
0.46631
>>> # Using 'none' reduction type.
>>> cce = keras.losses.CategoricalFocalCrossentropy(
... reduction=None)
>>> cce(y_true, y_pred)
array([3.2058331e-05, 4.6627346e-01], dtype=float32)
Usage with the compile() API:
model.compile(optimizer='adam',
loss=keras.losses.CategoricalFocalCrossentropy())SparseCategoricalCrossentropy class
keras.losses.SparseCategoricalCrossentropy(
from_logits=False,
ignore_class=None,
reduction="sum_over_batch_size",
name="sparse_categorical_crossentropy",
dtype=None,
)Computes the crossentropy loss between the labels and predictions.
Use this crossentropy loss function when there are two or more label
classes. We expect labels to be provided as integers. If you want to
provide labels using one-hot representation, please use
CategoricalCrossentropy loss. There should be # classes floating point
values per feature for y_pred and a single floating point value per
feature for y_true.
In the snippet below, there is a single floating point value per example for
y_true and num_classes floating pointing values per example for
y_pred. The shape of y_true is [batch_size] and the shape of y_pred
is [batch_size, num_classes].
Arguments
- from_logits: Whether
y_predis expected to be a logits tensor. By default, we assume thaty_predencodes a probability distribution. - reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
Examples
>>> y_true = [1, 2]
>>> y_pred = [[0.05, 0.95, 0], [0.1, 0.8, 0.1]]
>>> # Using 'auto'/'sum_over_batch_size' reduction type.
>>> scce = keras.losses.SparseCategoricalCrossentropy()
>>> scce(y_true, y_pred)
1.177
>>> # Calling with 'sample_weight'.
>>> scce(y_true, y_pred, sample_weight=np.array([0.3, 0.7]))
0.814
>>> # Using 'sum' reduction type.
>>> scce = keras.losses.SparseCategoricalCrossentropy(
... reduction="sum")
>>> scce(y_true, y_pred)
2.354
>>> # Using 'none' reduction type.
>>> scce = keras.losses.SparseCategoricalCrossentropy(
... reduction=None)
>>> scce(y_true, y_pred)
array([0.0513, 2.303], dtype=float32)
Usage with the compile() API:
model.compile(optimizer='sgd',
loss=keras.losses.SparseCategoricalCrossentropy())Poisson class
keras.losses.Poisson(reduction="sum_over_batch_size", name="poisson", dtype=None)Computes the Poisson loss between y_true & y_pred.
Formula:
loss = y_pred - y_true * log(y_pred)Arguments
- reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
CTC class
keras.losses.CTC(reduction="sum_over_batch_size", name="ctc", dtype=None)CTC (Connectionist Temporal Classification) loss.
Arguments
- reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
KLDivergence class
keras.losses.KLDivergence(
reduction="sum_over_batch_size", name="kl_divergence", dtype=None
)Computes Kullback-Leibler divergence loss between y_true & y_pred.
Formula:
loss = y_true * log(y_true / y_pred)y_true and y_pred are expected to be probability
distributions, with values between 0 and 1. They will get
clipped to the [0, 1] range.
Arguments
- reduction: Type of reduction to apply to the loss. In almost all cases
this should be
"sum_over_batch_size". Supported options are"sum","sum_over_batch_size"orNone. - name: Optional name for the loss instance.
- dtype: The dtype of the loss’s computations. Defaults to
None, which means usingkeras.backend.floatx().keras.backend.floatx()is a"float32"unless set to different value (viakeras.backend.set_floatx()). If akeras.DTypePolicyis provided, then thecompute_dtypewill be utilized.
binary_crossentropy function
keras.losses.binary_crossentropy(
y_true, y_pred, from_logits=False, label_smoothing=0.0, axis=-1
)Computes the binary crossentropy loss.
Arguments
- y_true: Ground truth values. shape =
[batch_size, d0, .. dN]. - y_pred: The predicted values. shape =
[batch_size, d0, .. dN]. - from_logits: Whether
y_predis expected to be a logits tensor. By default, we assume thaty_predencodes a probability distribution. - label_smoothing: Float in
[0, 1]. If >0then smooth the labels by squeezing them towards 0.5, that is, using1. - 0.5 * label_smoothingfor the target class and0.5 * label_smoothingfor the non-target class. - axis: The axis along which the mean is computed. Defaults to
-1.
Returns
Binary crossentropy loss value. shape = [batch_size, d0, .. dN-1].
Example
>>> y_true = [[0, 1], [0, 0]]
>>> y_pred = [[0.6, 0.4], [0.4, 0.6]]
>>> loss = keras.losses.binary_crossentropy(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> loss
array([0.916 , 0.714], dtype=float32)
categorical_crossentropy function
keras.losses.categorical_crossentropy(
y_true, y_pred, from_logits=False, label_smoothing=0.0, axis=-1
)Computes the categorical crossentropy loss.
Arguments
- y_true: Tensor of one-hot true targets.
- y_pred: Tensor of predicted targets.
- from_logits: Whether
y_predis expected to be a logits tensor. By default, we assume thaty_predencodes a probability distribution. - label_smoothing: Float in [0, 1]. If >
0then smooth the labels. For example, if0.1, use0.1 / num_classesfor non-target labels and0.9 + 0.1 / num_classesfor target labels. - axis: Defaults to
-1. The dimension along which the entropy is computed.
Returns
Categorical crossentropy loss value.
Example
>>> y_true = [[0, 1, 0], [0, 0, 1]]
>>> y_pred = [[0.05, 0.95, 0], [0.1, 0.8, 0.1]]
>>> loss = keras.losses.categorical_crossentropy(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> loss
array([0.0513, 2.303], dtype=float32)
sparse_categorical_crossentropy function
keras.losses.sparse_categorical_crossentropy(
y_true, y_pred, from_logits=False, ignore_class=None, axis=-1
)Computes the sparse categorical crossentropy loss.
Arguments
- y_true: Ground truth values.
- y_pred: The predicted values.
- from_logits: Whether
y_predis expected to be a logits tensor. By default, we assume thaty_predencodes a probability distribution. - ignore_class: Optional integer. The ID of a class to be ignored during
loss computation. This is useful, for example, in segmentation
problems featuring a “void” class (commonly -1 or 255) in
segmentation maps. By default (
ignore_class=None), all classes are considered. - axis: Defaults to
-1. The dimension along which the entropy is computed.
Returns
Sparse categorical crossentropy loss value.
Examples
>>> y_true = [1, 2]
>>> y_pred = [[0.05, 0.95, 0], [0.1, 0.8, 0.1]]
>>> loss = keras.losses.sparse_categorical_crossentropy(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> loss
array([0.0513, 2.303], dtype=float32)
poisson function
keras.losses.poisson(y_true, y_pred)Computes the Poisson loss between y_true and y_pred.
Formula:
loss = y_pred - y_true * log(y_pred)Arguments
- y_true: Ground truth values. shape =
[batch_size, d0, .. dN]. - y_pred: The predicted values. shape =
[batch_size, d0, .. dN].
Returns
Poisson loss values with shape = [batch_size, d0, .. dN-1].
Example
>>> y_true = np.random.randint(0, 2, size=(2, 3))
>>> y_pred = np.random.random(size=(2, 3))
>>> loss = keras.losses.poisson(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> y_pred = y_pred + 1e-7
>>> assert np.allclose(
... loss, np.mean(y_pred - y_true * np.log(y_pred), axis=-1),
... atol=1e-5)
ctc function
keras.losses.ctc(y_true, y_pred)CTC (Connectionist Temporal Classification) loss.
Arguments
- y_true: A tensor of shape
(batch_size, max_length)containing the true labels in integer format.0always represents the blank/mask index and should not be used for classes. - y_pred: A tensor of shape
(batch_size, max_length, num_classes)containing logits (the output of your model). They should not be normalized via softmax.
kl_divergence function
keras.losses.kl_divergence(y_true, y_pred)Computes Kullback-Leibler divergence loss between y_true & y_pred.
Formula:
loss = y_true * log(y_true / y_pred)y_true and y_pred are expected to be probability
distributions, with values between 0 and 1. They will get
clipped to the [0, 1] range.
Arguments
- y_true: Tensor of true targets.
- y_pred: Tensor of predicted targets.
Returns
KL Divergence loss values with shape = [batch_size, d0, .. dN-1].
Example
>>> y_true = np.random.randint(0, 2, size=(2, 3)).astype(np.float32)
>>> y_pred = np.random.random(size=(2, 3))
>>> loss = keras.losses.kl_divergence(y_true, y_pred)
>>> assert loss.shape == (2,)
>>> y_true = ops.clip(y_true, 1e-7, 1)
>>> y_pred = ops.clip(y_pred, 1e-7, 1)
>>> assert np.array_equal(
... loss, np.sum(y_true * np.log(y_true / y_pred), axis=-1))