logits = torch.tensor([
    [2.0, 1.0, 0.1, -1.0],    # sample 0, correct class 0
    [0.5, 2.5, 0.3,  0.2],    # sample 1, correct class 1
    [0.1, 0.2, 3.0,  0.1],    # sample 2, correct class 2
])
labels = torch.tensor([0, 1, 2])

print(nn.CrossEntropyLoss()(logits, labels))    # tensor(0.3015)