What is pixel-wise softmax loss?
what is the pixel-wise softmax loss? In my understanding, it's just a cross-entropy loss, but I didn't find the formula. Can someone help me? It's better to have the pytorch code.

You can read here all about it (there's also a link to source code there).

As you already observed the "softmax loss" is basically a cross entropy loss which computation combines the softmax function and the loss for numerical stability and efficiency.
In your example, the loss is computed for a pixel-wise prediction so you have a per-pixel prediction, a per-pixel target and a per-pixel loss term.
