Solved by KFrank in post #2 
              
              
                Hello Changrok! 

I’m not sure what you mean by “multitarget.” 
If you are working on a multi-label, multi-class classification problem, 
then you don’t want to be using NLLLoss (or CrossEntropyLoss). 
You should use BCEWithLogitsLoss. 
The key idea is that a multi-label, multi-class problem (say, n…