l = torch.tensor([2.0, 1.0, 0.1, -1.0])
p = torch.softmax(l, dim=0)
print(p)                    # tensor([0.6381, 0.2347, 0.0954, 0.0318])
print(p.sum())              # tensor(1.0000)
print(-torch.log(p[0]))     # tensor(0.4493)