Keras Tensorflow二元交叉熵损失大于1

Question

Library: Keras, backend:Tensorflow

I am training a single class/binary classification problem, wherein my final layer has a single node, with activation of sigmoid type. I am compiling my model with a binary cross entropy loss. When I run the code to train my model, I notice that the loss is a value greater than 1. Is that right, or am I going wrong somewhere? I have checked the labels. They're all 0s and 1s.

Is it possible to have the binary cross entropy loss greater than 1?

Answer 1

Keras binary_crossentropy first convert your predicted probability to logits. Then it uses tf.nn.sigmoid_cross_entropy_with_logits to calculate cross entropy and return to you the mean of that. Mathematically speaking, if your label is 1 and your predicted probability is low (like 0.1), the cross entropy can be greater than 1, like losses.binary_crossentropy(tf.constant([1.]), tf.constant([0.1])) .

Answer 2

是的，它是正确的，交叉熵没有限制在任何特定范围内，只是正数（> 0）。