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Moving a list of integers between stacks (expression-controlled count)

Proved
NLogN.FW.spec_mvList

by xuanji · Oct 13, 2026 · Mathlib 0df444a (Lean v4.33.1)

harvey-van-der-hoeven-tminteger-multiplicationturing-machines

Let i,j,ci,j,ci,j,c be distinct registers below 55 (ccc different from i,ji,ji,j), let stack iii start with the integer list lll, and let nnn be a clean linear expression, defined in sss, with value ∣l∣|l|∣l∣ and bit size bounded by BBB, where every entry of lll has bit length ≤B\le B≤B. Then the straight-line program mvList i j c n moves lll reversed onto stack jjj (using ccc as counter), with cost at most (size(n)+1)⋅2000(B+2)+∣l∣(14000(B+2)+30)+32(\mathrm{size}(n)+1)\cdot2000(B+2) + |l|(14000(B+2)+30) + 32(size(n)+1)⋅2000(B+2)+∣l∣(14000(B+2)+30)+32.

Formalization Note. The machine layer: IState HS is a state with 646464 stacks of items (Item = integer or mark), an input position and an output; RM programs (straight-line register code RS, loops rep, conditionals, calls of the multiplication procedure through a MulSpec MMM giving its domain and cost) have a functional semantics p.run s, a definedness predicate p.ok M s and a cost p.cost M s; Spec M p s s' c abbreviates p.ok M s ∧ p.run s = s' ∧ p.cost M s ≤ c. ints L / gints U push an integer list / a list of pairs as items (head = top); zsz z is the bit length of ∣z∣|z|∣z∣. MulBnd M m Φ says the multiplication procedure accepts all pairs of integers of bit length ≤m\le m≤m at cost ≤Φ\le Φ≤Φ. Register names (GU, CR, KB, XN, …) are fixed stack indices.

Preamble
-- Harvey–van der Hoeven multitape-TM development (NLogN), generated by skeleton subtraction.

import Definitions.Def_IntMul_HvdH_M_Defs4

set_option autoImplicit false
set_option relaxedAutoImplicit false
set_option maxHeartbeats 1000000

set_option linter.unusedSimpArgs false
set_option linter.unusedVariables false
open NLogN
open NLogN.FW
open IntMul NLogN
Formal statement
theorem NLogN.FW.spec_mvList (M : MulSpec) (i j c : Fin HS) (n : Ex HS) (s : IState HS) (l : List ℤ)
    (Ri : List Item) (hij : i ≠ j) (hci : c ≠ i) (hcj : c ≠ j) (hi : s.G i = ints l ++ Ri)
    (hn : n.eval s = l.length) (hi55 : i.val < 55) (hj55 : j.val < 55) (hc55 : c.val < 55)
    (hnc : n.Clean) (hno : n.ok s) (B : ℕ) (hl : n.Lin) (hnB : n.Bnd s B)
    (hB : ∀ x ∈ l, zsz x ≤ B) :
    Spec M (RM.rs (mvList i j c n)) s ((s.upd i Ri).upd j (ints l.reverse ++ s.G j))
      ((n.size + 1) * 2000 * (B + 2) + l.length * (14000 * (B + 2) + 30) + 32) := by sorry
Source
D. Harvey, J. van der Hoeven, Integer multiplication in time O(n log n), Ann. of Math. 193 (2021), 563–617 (Theorem 1.1: multitape Turing machine multiplication in O(n log n)). Lemma `NLogN.FW.spec_mvList` of the Lean development NLogN/HFW1.lean (lines 110–120), written for the prove2.me integer-multiplication campaign.

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