I faced the same problem. The label of my input is a vector of size 8, ex [1,0.2,0.5,0.33,0.666,1,0.25,0.133], and each of my input has a label of size eight with different values,  I want to learn this vector for each of my input images, I tried to use CrossEntropy but I got this error RuntimeError: multi-target not supported.
bach_size = 3
target: torch.Size([3, 8])
predict: torch.Size([3, 8])
Do you have any suggestions on what type of loss function I should use to train my model?