Categorical crossentropy between an output tensor and a target tensor.
tf.keras.backend.categorical_crossentropy(
target, output, from_logits=False, axis=-1
)
Arguments |
target
|
A tensor of the same shape as output .
|
output
|
A tensor resulting from a softmax
(unless from_logits is True, in which
case output is expected to be the logits).
|
from_logits
|
Boolean, whether output is the
result of a softmax, or is a tensor of logits.
|
axis
|
Int specifying the channels axis. axis=-1 corresponds to data
format channels_last', and axis=1corresponds to data format channels_first`.
|
Raises |
ValueError
|
if axis is neither -1 nor one of the axes of output .
|
Example:
a = tf.constant([1., 0., 0., 0., 1., 0., 0., 0., 1.], shape=[3,3])
print(a)
tf.Tensor(
[[1. 0. 0.]
[0. 1. 0.]
[0. 0. 1.]], shape=(3, 3), dtype=float32)
b = tf.constant([.9, .05, .05, .5, .89, .6, .05, .01, .94], shape=[3,3])
print(b)
tf.Tensor(
[[0.9 0.05 0.05]
[0.5 0.89 0.6 ]
[0.05 0.01 0.94]], shape=(3, 3), dtype=float32)
loss = tf.keras.backend.categorical_crossentropy(a, b)
print(np.around(loss, 5))
[0.10536 0.80467 0.06188]
loss = tf.keras.backend.categorical_crossentropy(a, a)
print(np.around(loss, 5))
[0. 0. 0.]