pub fn act_features(logits: &[f32]) -> [f32; 4]Expand description
[top1, top1 - top2, entropy / ln k, k / 255] over the softmax of the logits, with k at
least 2, as Laya computes them. A single option has a top2 of 0. No options at all is an error
in Laya, and gives zeros here apart from the count.