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Round-six lemma `p2E_runs`

Proved
NLogN.KFUU.R6Crt.p2E_runs

by xuanji · Oct 20, 2026 · Mathlib 0df444a (Lean v4.33.1)

complexity-theoryinteger-multiplicationkappa-improvement

An auxiliary lemma of the round-six development, published as a separate node because its proof is long or shared.

The following holds (Lean statement, in the scope of module Solutions.R6CrtRev):

theorem NLogN.KFUU.R6Crt.p2E_runs {pM : Fin P} (hMul : MulOK I iprog pM MS) {pS : Fin HS} (hpS : LS pS)
    {eSw : Fin P} {dS : Fin HS} {K : ℝ} (hK : SwOKτ τ I iprog eSw dS K) (hdS : dS ≠ 0)
    {Dsc : Fin HS} (hD : Dsc = 18 ∨ Dsc = 19) (hDd : Dsc ≠ dS)
    (u w cz cr : ℕ) (bs : List Bool) (hu : 1 ≤ u) (hcz : cz = 2 * cr) (hcr : 1 ≤ cr)
    (hn2 : 2 ≤ bs.length)
    (xs0 : List ℤ) (hx : Bnd w xs0) (Z : ℕ) (hZ3 : 3 ≤ Z)
    (hVZ : zsz ((vol (shP u bs) * cz : ℕ) : ℤ) ≤ Z) (zw : zsz (w : ℤ) ≤ Z)
    (zU : zsz ((2 ^ u : ℕ) : ℤ) ≤ Z)
    (t : IState HS) (R : List Item)
    (h0 : t.G 0 = ints (Dl (mzB u bs.length cz) (bgB bs) (List.range bs.length ++ [bs.length])
      (lay1 (bgB bs) bs.length 0) xs0 0) ++ R)
    {RS LN LZ LW LU L2 : List Item}
    (hpS0 : t.G pS = ints (zl (shP u bs)) ++ RS) (hN : t.G nR = .int (bs.length : ℤ) :: LN)
    (hZ : t.G rCZ = .int (cz : ℤ) :: LZ)
    (hW : t.G rW = .int (w : ℤ) :: LW) (hUu : t.G rU = .int (u : ℤ) :: LU)
    (h2 : t.G rU2 = .int ((2 ^ u : ℕ) : ℤ) :: L2) :
    IRuns I iprog (p2E pM pS eSw dS Dsc) t
      (t.upd 0 (ints (Dl (mzB u bs.length cz) (bgB bs) (List.range bs.length ++ [bs.length])
        (((lay1 (bgB bs) bs.length 0).take bs.length).reverse ++
          (lay1 (bgB bs) bs.length 0).drop bs.length) xs0 0) ++ R))
      (cP2E τ K u bs.length w Z (vol (ctB u cz bs) * cr) (vol (shP u bs) * cz))

Context. CRT reversal §8: phase 2 by additive swaps (p2E) and the reversal revE = p1U; p2E; p3U

p2E replaces KFUU's p2U (⌊n/2⌋ single-digit swaps, cost n·h^τ) by the nine-phase word of mainU (three composite swaps of u·⌊n/2⌋-bit digits and six rotation sets). p2E_runs has the interface of p2U_runs (with SwOKτ τ and 2 ≤ n); revE_runs / revKE the interface of revU_runs / revK.

Formalization Note. Part of the Lean formalization of the round-six κ-improvement (integer-multiplication-kappa campaign, target IntMul.Kappa.jain_round6_framework). The statement is copied verbatim from the Lean development; the platform node carries the same declaration name. Definitions it mentions live in the IntMul_Kappa_R6_Defs* bundles (on top of the published κ bundles IntMul_Kappa_K_Defs*).

Preamble
-- Round-six κ development (integer-multiplication-kappa), generated by skeleton subtraction.

import Definitions.Def_IntMul_Kappa_R6_Defs14

set_option autoImplicit false
set_option relaxedAutoImplicit false
set_option maxHeartbeats 1000000

open NLogN NLogN.KFUU NLogN.KFUU.R6Crt
open IntMul NLogN.KIL NLogN.KFB NLogN.KFC NLogN.KFT NLogN.KFU AModel AModelL12 NLogN.KFUU
variable {P : ℕ} {I : List Sym} {iprog : Fin P → IStmt HS P} {τ : ℝ}
Formal statement
theorem NLogN.KFUU.R6Crt.p2E_runs {pM : Fin P} (hMul : MulOK I iprog pM MS) {pS : Fin HS} (hpS : LS pS)
    {eSw : Fin P} {dS : Fin HS} {K : ℝ} (hK : SwOKτ τ I iprog eSw dS K) (hdS : dS ≠ 0)
    {Dsc : Fin HS} (hD : Dsc = 18 ∨ Dsc = 19) (hDd : Dsc ≠ dS)
    (u w cz cr : ℕ) (bs : List Bool) (hu : 1 ≤ u) (hcz : cz = 2 * cr) (hcr : 1 ≤ cr)
    (hn2 : 2 ≤ bs.length)
    (xs0 : List ℤ) (hx : Bnd w xs0) (Z : ℕ) (hZ3 : 3 ≤ Z)
    (hVZ : zsz ((vol (shP u bs) * cz : ℕ) : ℤ) ≤ Z) (zw : zsz (w : ℤ) ≤ Z)
    (zU : zsz ((2 ^ u : ℕ) : ℤ) ≤ Z)
    (t : IState HS) (R : List Item)
    (h0 : t.G 0 = ints (Dl (mzB u bs.length cz) (bgB bs) (List.range bs.length ++ [bs.length])
      (lay1 (bgB bs) bs.length 0) xs0 0) ++ R)
    {RS LN LZ LW LU L2 : List Item}
    (hpS0 : t.G pS = ints (zl (shP u bs)) ++ RS) (hN : t.G nR = .int (bs.length : ℤ) :: LN)
    (hZ : t.G rCZ = .int (cz : ℤ) :: LZ)
    (hW : t.G rW = .int (w : ℤ) :: LW) (hUu : t.G rU = .int (u : ℤ) :: LU)
    (h2 : t.G rU2 = .int ((2 ^ u : ℕ) : ℤ) :: L2) :
    IRuns I iprog (p2E pM pS eSw dS Dsc) t
      (t.upd 0 (ints (Dl (mzB u bs.length cz) (bgB bs) (List.range bs.length ++ [bs.length])
        (((lay1 (bgB bs) bs.length 0).take bs.length).reverse ++
          (lay1 (bgB bs) bs.length 0).drop bs.length) xs0 0) ++ R))
      (cP2E τ K u bs.length w Z (vol (ctB u cz bs) * cr) (vol (shP u bs) * cz)) := by sorry
Source
S. Jain, round-six networks for the integer-multiplication κ-improvement campaign (https://github.com/Swapnil-jain/integer-mult-kappa, commit 5868dc7) and D. Colkitt, integer-mult-bounds (https://github.com/CrocSwap/integer-mult-bounds); target `IntMul.Kappa.jain_round6_framework`. Lean declaration `NLogN.KFUU.R6Crt.p2E_runs`, Solutions/R6CrtRev.lean (lines 219–333) of the round-six development.

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