label smoothing mixes the one-hot label with a uniform distribution:
y′=y(1−ϵ)+Kϵ, where
K is the number of classes and
ϵ is typically 0.1; the true class gets
1−ϵ+Kϵ and every other class gets
Kϵ. It is equivalent to adding a KL penalty toward the uniform distribution to the cross-entropy loss.