pub fn propensity(
pool: &[(f64, &Challenge)],
session: &str,
) -> HashMap<String, f64>Expand description
Each pooled lesson’s chance of a slot under the session’s posterior (budget, widen): the share of
P_DRAWS alternative draws in which in_scope_first, over the pool ordered by score × draw, keeps
it. A draw is the ratio explore is (memory.rs Memory::weight): (0.5 + x) / (0.5 + mean), x from
the lesson’s belief, seeded by (session#p<i>, id). Exactly 1 for every lesson when the pool fits the
slots, without a draw. Deterministic.