问题
Looking at the code of "Accuracy" layer, I see there is an option for a second output/"top" for this layer.
What does this second output produce?
回答1:
Looking at accuracy_layer.hpp, where the number of outputs for the layer are defined, there's this comment:
// If there are two top blobs, then the second blob will contain // accuracies per class.
So, the second "top" of the "Accuracy" layer simply reports per-class accuracies.
Just as a side note for layer Accuracy, the reported Accuracy is normalized by the number of "valid" predictions (same as using normalization: VALID for loss layers).
来源：https://stackoverflow.com/questions/45483604/caffes-second-top-of-accuracy-layer