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Preprocessing of the Theorem 30 data structure with pruned encodings meets its specification for all limits (preCore)

Proved
Light.Sec4.preCoreSpec_all

by xuanji · Oct 6, 2026 · Mathlib 0df444a (Lean v4.33.1)

apsp-299791apsp-exponentdata-structuresprogram-verification

Let PPP be a program of the light language that holds the fourteen routines of Section 4 at the numbers 40,…,5340,\dots,5340,…,53, holds the body of preCore at number 545454, and meets, for every limits lim\mathrm{lim}lim satisfying the standing assumptions, the specification of the shared stage with pruned encodings with constant ccc. Then for every limits lim\mathrm{lim}lim, preCore meets its specification:

for all parameters p=(L,m,N)p=(L,m,N)p=(L,m,N) with m≤Lm\le Lm≤L, t≤mt\le mt≤m, addresses aX,aY,b0a_X,a_Y,b_0aX​,aY​,b0​, matrices X∈ZN×4mX\in\mathbb Z^{N\times 4^m}X∈ZN×4m, Y∈Z4m×NY\in\mathbb Z^{4^m\times N}Y∈Z4m×N with entries of absolute value at most UUU, stored row by row at aXa_XaX​ and aYa_YaY​ below b0b_0b0​, limits satisfying Lim30(p,t,b0,U)\mathrm{Lim30}(p,t,b_0,U)Lim30(p,t,b0​,U), every memory μ\muμ and every depth ddd with d+L+6≤depthd+L+6\le\mathrm{depth}d+L+6≤depth, the call preCore(L,m,t,N,4m,aX,aY,b0)\mathrm{preCore}(L,m,t,N,4^m,a_X,a_Y,b_0)preCore(L,m,t,N,4m,aX​,aY​,b0​) ends within

c⋅sshared(p)+tallTiles(L,m,t,nB)+300c\cdot s_{\mathrm{shared}}(p)+t_{\mathrm{allTiles}}(L,m,t,n_B)+300c⋅sshared​(p)+tallTiles​(L,m,t,nB​)+300

steps, the final memory holds the data structure for X,YX,YX,Y at b0b_0b0​, and it differs from μ\muμ only in the block from b0b_0b0​ to its end. Nothing is assumed about the previous content of the block.

Setting. The data structure of Theorem 30 is built for parameters p=(L,m,N)p=(L,m,N)p=(L,m,N) with m≤Lm\le Lm≤L (LLL levels, mmm inner levels), integer matrices X∈ZN×4mX\in\mathbb Z^{N\times 4^m}X∈ZN×4m and Y∈Z4m×NY\in\mathbb Z^{4^m\times N}Y∈Z4m×N with entries of absolute value at most UUU, and a threshold t≤mt\le mt≤m. It lives in a block of memory starting at an address b0b_0b0​: the shared tables of Section 2 with the pruned encodings of the nBn_BnB​ row bands of XXX and column bands of YYY (only the leaves whose LLL decimal digits contain at most mmm nines are stored), the directory, the table of trie roots (one per tile) and the trie array (one trie per tile, holding the values of its boxes). The limits must satisfy the bounds Lim30\mathrm{Lim30}Lim30: the standing assumptions (an address fits in a word and 100≤word100\le\mathrm{word}100≤word), the block fits in memory, and 10m(7LU)210^m(7^LU)^210m(7LU)2, 7L+1U7^{L+1}U7L+1U and 10L+110^{L+1}10L+1 fit in a word.

Here sshared(p)s_{\mathrm{shared}}(p)sshared​(p) is the shape of the running time of the shared stage with pruned encodings, whose band term is nBn_BnB​ times the number ∑j≤m(Lj)9L−j\sum_{j\le m}\binom Lj9^{L-j}∑j≤m​(jL​)9L−j of leaves with at most mmm nines (instead of 10L10^L10L), and tallTilest_{\mathrm{allTiles}}tallTiles​ is the time of building the tries of all nB2n_B^2nB2​ tiles.

“Procedure ppp meets its specification within TTT steps” means: called at any depth ddd allowed by the hypothesis, with the given argument values and a memory μ\muμ satisfying the precondition, the body of ppp terminates within TTT steps without violating the limits, and the returned value and final memory satisfy the postcondition.

Formalization Note The statement is Has40 P → P[Proc.preCore]? = some preCoreBodyP → (∀ lim, Std lim → Sec2.SharedSpecP lim P c) → ∀ lim, PreCoreSpecP lim P c; the time is tPreCoreP c p t. The standing assumptions Std lim are part of Lim30.

Preamble
/-
Copyright (c) 2026 Anthropic, PBC. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
SPDX-License-Identifier: Apache-2.0
-/
-- Generated by skeleton subtraction from the ThreeSumApsp library at commit 27a2fa4bab32.

import Definitions.Def_APSP299791_Defs5

set_option autoImplicit false
set_option relaxedAutoImplicit false

open Light
open Light.Sec4
Formal statement
theorem Light.Sec4.preCoreSpec_all {P : Program} {c : ℕ} (h : Has40 P)
    (h54 : P[Proc.preCore]? = some preCoreBodyP)
    (hShared : ∀ lim, Std lim → Sec2.SharedSpecP lim P c) : ∀ lim, PreCoreSpecP lim P c := by sorry
Source
Developed for the prove2.me APSP exponent campaign (https://prove2.me/campaigns/apsp-exponent) on top of the Lean formalization anthropics/formal-math, folder 3sum-apsp, commit e1a4e65 (https://github.com/anthropics/formal-math/tree/e1a4e6508154ea59f030480661590a9fe3018011/3sum-apsp; Lean v4.33.1, Mathlib v4.33.1). The statement comes from the file 3sum-apsp/ThreeSumApsp/Programs/Sec4/Theorem30/Routines.lean of the campaign's modified copy of that library, which is not published; the new and modified definitions it uses are in the platform definition bundles APSP299791_Defs1 to APSP299791_Defs5. It builds on J. Alman and V. Vassilevska Williams, "Truly Subquadratic 3SUM and Truly Subcubic APSP via Triangles in Sparse Lopsided Graphs", arXiv:2610.06783v1 (https://arxiv.org/abs/2610.06783v1), Theorem 30 (pp. 46-47), "Preprocessing". This result belongs to an improvement of the paper's bounds developed for this campaign and is not stated in the paper.

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