tf.keras.metrics.BinaryCrossentropy

TensorFlow 2 version View source on GitHub

Computes the crossentropy metric between the labels and predictions.

tf.keras.metrics.BinaryCrossentropy(
    name='binary_crossentropy', dtype=None, from_logits=False, label_smoothing=0
)

This is the crossentropy metric class to be used when there are only two label classes (0 and 1).

Usage:

m = tf.keras.metrics.BinaryCrossentropy()
m.update_state([1., 0., 1., 0.], [1., 1., 1., 0.])

# EPSILON = 1e-7, y = y_true, y` = y_pred, Y_MAX = 0.9999999
# y` = clip_ops.clip_by_value(output, EPSILON, 1. - EPSILON)
# y` = [Y_MAX, Y_MAX, Y_MAX, EPSILON]

# Metric = -(y log(y` + EPSILON) + (1 - y) log(1 - y` + EPSILON))
#        = [-log(Y_MAX + EPSILON), -log(1 - Y_MAX + EPSILON),
#           -log(Y_MAX + EPSILON), -log(1)]
#        = [(0 + 15.33) / 2, (0 + 0) / 2]
# Reduced metric = 7.665 / 2

print('Final result: ', m.result().numpy())  # Final result: 3.833

Usage with tf.keras API:

model = tf.keras.Model(inputs, outputs)
model.compile(
    'sgd',
    loss='mse',
    metrics=[tf.keras.metrics.BinaryCrossentropy()])

name (Optional) string name of the metric instance.
dtype (Optional) data type of the metric result.
from_logits (Optional )Whether output is expected to be a logits tensor. By default, we consider that output encodes a probability distribution.
label_smoothing (Optional) Float in [0, 1]. When > 0, label values are smoothed, meaning the confidence on label values are relaxed. e.g. label_smoothing=0.2 means that we will use a value of 0.1 for label 0 and 0.9 for label 1"

Methods

reset_states

View source

reset_states()

Resets all of the metric state variables.

This function is called between epochs/steps, when a metric is evaluated during training.

result

View source

result()

Computes and returns the metric value tensor.

Result computation is an idempotent operation that simply calculates the metric value using the state variables.

update_state

View source

update_state(
    y_true, y_pred, sample_weight=None
)

Accumulates metric statistics.

y_true and y_pred should have the same shape.

Args
y_true The ground truth values.
y_pred The predicted values.
sample_weight Optional weighting of each example. Defaults to 1. Can be a Tensor whose rank is either 0, or the same rank as y_true, and must be broadcastable to y_true.

Returns
Update op.