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The uniform phase pass (round six, `cPhU_Y`)

Proved
NLogN.KFW.cPhU_Y

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

complexity-theoryinteger-multiplicationkappa-improvement

The uniform phase pass at a width in the window.

The following holds (Lean statement, in the scope of module Solutions.KFWCost1):

theorem NLogN.KFW.cPhU_Y {Bn t S0 r Z H x sz : ℕ} (hS : 1 ≤ S0) (hBn : 1 ≤ Bn) (hx : x ≤ 2 * H + 16)
    (εE : Ex HS) (hsz : εE.size ≤ sz) :
    cPhU x (Bn * (S0 * r * 2 ^ t)) t Bn Z (S0 * r) (xPh εE Z Z) ≤
      1000000000 * (sz + 2) * nN Bn t S0 * Yu r Z H

Context. KFW: cost units of the uniform level procedure

All costs of the level procedure are evaluated at widths in the window [0, H] (plus small offsets and the scale ES k ≤ H), so they are bounded by multiples of the cost unit

Yu r Z H = r (2H + 21) + (Z + 2)³

(per record). This file bounds the elementary cost pieces (cAtom, cPhU, push and move overheads, pow2Cost) by multiples of n · Yu.

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_K_Defs33
import Definitions.Def_IntMul_Kappa_R6_Defs1
import Mathlib
import Definitions.Def_IntMul_HvdH_M_Defs8
import Definitions.Def_IntMul_MultitapeModel

set_option autoImplicit false
set_option relaxedAutoImplicit false
set_option maxHeartbeats 1000000

open NLogN NLogN.KFW
open IntMul NLogN.KIL NLogN.KFD NLogN.KFB NLogN.KFG NLogN.KFH NLogN.KFN Complex Butterfly
Formal statement
theorem NLogN.KFW.cPhU_Y {Bn t S0 r Z H x sz : ℕ} (hS : 1 ≤ S0) (hBn : 1 ≤ Bn) (hx : x ≤ 2 * H + 16)
    (εE : Ex HS) (hsz : εE.size ≤ sz) :
    cPhU x (Bn * (S0 * r * 2 ^ t)) t Bn Z (S0 * r) (xPh εE Z Z) ≤
      1000000000 * (sz + 2) * nN Bn t S0 * Yu r Z H := 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.KFW.cPhU_Y`, Solutions/KFWCost1.lean (lines 111–208) of the round-six development.

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