pub fn cross_entropy(p: &[f64], q: &[f64]) -> Option<f64>
Cross-entropy H(p, q) = −Σ pᵢ·log₂ qᵢ (bits). None like kl_divergence.
H(p, q) = −Σ pᵢ·log₂ qᵢ
None
kl_divergence