Carrier-free analytic core of paper §5.4.3, (5.90)--(5.92).
Unskipped (5.91); Lemma 5.14's 1/4 gain implies the required 1/8.
theorem
Anderson4D.XYCluster.innerPi_parity_assembly
{ι : Type u_1}
[DecidableEq ι]
(blocks skipped : Finset ι)
(_hsub : skipped ⊆ blocks)
(_h20 : skipped.card ≤ 20)
(term base gain : ι → ℝ)
(hlocal0 : ∀ i ∈ blocks, 0 ≤ term i)
(hlocal : ∀ i ∈ blocks, term i ≤ base i * if i ∈ skipped then 1 else gain i)
:
One-parity product assembly with at most twenty discarded (5.87) gains.