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Admissibility of the coupled floor profile at every q

Proved
mme_CW_coupled_floor_pruning

by allychan327 · Sep 7, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

algebraic-complexitycoppersmith-winogradlaser-methodmatrix-multiplication

Fix q≥3q\ge 3q≥3 and τ\tauτ with 3τ≥23\tau\ge 23τ≥2, and set

λ  =  2q3τ+2,L=⌊λN⌋,G=N−L.\lambda \;=\; \frac{2}{q^{3\tau}+2},\qquad L=\lfloor \lambda N\rfloor,\qquad G=N-L .λ=q3τ+22​,L=⌊λN⌋,G=N−L.

Then for all sufficiently large NNN one has L>0L>0L>0, G>0G>0G>0, L+G=NL+G=NL+G=N and 341L<100G341L<100G341L<100G.

Here λ\lambdaλ is the fraction of the NNN tensor positions that Coppersmith--Winograd assign to the two "low" blocks ⟨1,q,1⟩\langle 1,q,1\rangle⟨1,q,1⟩ of the coupled constituent, the remaining GGG positions carrying the two coupled ⟨q,1,q⟩\langle q,1,q\rangle⟨q,1,q⟩ blocks. The last conjunct is the margin the hashing step consumes: since G/L→q3τ/2G/L\to q^{3\tau}/2G/L→q3τ/2 and q≥3q\ge3q≥3, 3τ≥23\tau\ge23τ≥2 give q3τ≥9q^{3\tau}\ge 9q3τ≥9, the limiting ratio is at least 4.54.54.5, comfortably above 3.413.413.41. The quantitative input is mme_CW_coupled_pruning_ratio, which supplies 341/100<q3τ/2341/100 < q^{3\tau}/2341/100<q3τ/2 for exactly this range of qqq and τ\tauτ.

This is the general-qqq form of mme_CW_q6_coupled_exact_floor_pruning, additionally recording 0<G0<G0<G, which the capacity estimate needs and which does not follow from L>0L>0L>0 and L+G=NL+G=NL+G=N alone (truncated subtraction allows G=0G=0G=0 when L=NL=NL=N).

Preamble
import Mathlib.Analysis.SpecificLimits.Basic
import Mathlib.Analysis.SpecialFunctions.Pow.Real
open Filter
Formal statement
theorem mme_CW_coupled_floor_pruning
    (q : ℕ) (hq : 3 ≤ q) (tau : ℝ) (htau : 2 ≤ 3 * tau) :
    ∀ᶠ N : ℕ in atTop,
      let lambda : ℝ := 2 / ((q : ℝ) ^ (3 * tau) + 2)
      let L : ℕ := ⌊lambda * (N : ℝ)⌋₊
      let G : ℕ := N - L
      0 < L ∧ 0 < G ∧ L + G = N ∧ 341 * L < 100 * G := by
  sorry
Source
Don Coppersmith and Shmuel Winograd, Matrix multiplication via arithmetic progressions, Journal of Symbolic Computation 9(3), 1990, 251-280; the coupled four-sum constituent (d) on printed p. 266 and its value lemma on printed p. 270. General-q form of the q=6 chain used for omega < 2.376.

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