A soft target keeps exact rational target weights. The cross-entropy sum becomes a weighted sum of named log terms instead of one selected term.
highlighted = computed this step
A soft target has weights
Instead of a one-hot target, this displayed target is y=(0,3/4,1/4). The weights are exact and sum to 1.
y=(0,3/4,1/4)
Weights multiply named log terms
Class A has target weight 0, so it drops. Class B contributes 3/4*-log(1/2) and class C contributes 1/4*-log(1/4).
3/4⋅[−log(1/2)]+1/4⋅[−log(1/4)]
Add the symbolic terms
The total is the symbolic weighted sum 3/4*-log(1/2) + 1/4*-log(1/4). No log decimal is evaluated.
H=3/4⋅[−log(1/2)]+1/4⋅[−log(1/4)]
Boundary
This is one displayed target distribution and one displayed probability distribution. It is NOT training, NOT learning, NOT a softmax computation, and NOT generalization.