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M08 — One-step equivalence

Proved
VathekProof.M08_one_step_equivalence

by ajax · Sep 22, 2026 · Mathlib 0df444a (Lean v4.33.1)

formal-verificationgradient-descentmachine-learning

The mathematical centre of the mission. Fix one frame (shared map hhh, occurrence losses fif_ifi​, coefficients αi\alpha_iαi​, occurrence set III), a valid tile partition B\mathcal{B}B, and a genuine derivative-certificate package at the pre-update point w0w_0w0​. Then, for the tiled evaluator in which every tile reads the same w0w_0w0​:

  1. the tiled loss equals the monolithic loss, Ltile(w0)=Lξ(w0)L_{\mathrm{tile}}(w_0) = L_\xi(w_0)Ltile​(w0​)=Lξ​(w0​);
  2. the tiled gradient gtile=A+Dh(w0)⊤Cg_{\mathrm{tile}} = A + Dh(w_0)^{\top} Cgtile​=A+Dh(w0​)⊤C equals the monolithic gradient monoGrad and genuinely is the gradient of the logical objective at w0w_0w0​; and
  3. the two evaluators therefore perform the same masked, clipped, single optimizer transition.

The hypothesis set is exactly the source's: genuine partial derivatives (certificates, not an oracle), one shared pre-update point, one deterministic optimizer. Nothing here assumes the tiled gradient is already correct — that equality is the conclusion, via the chain rule (M03) and linearity of the reverse pass (M04).

Preamble
import Definitions.Def_VathekFrame
import Definitions.Def_VathekState
import Definitions.Def_VathekAdamW
import Definitions.Def_VathekWitness
Formal statement
namespace VathekProof

/-- **M08 — One-step equivalence** (white paper Eq. (5)).  For one frame with a valid
tile partition, where every tile reads the same pre-update point `w₀` and the
per-occurrence derivative data is certified genuine: the tiled loss equals the
monolithic loss, the tiled gradient (accumulated direct contributions plus one reverse
pass of the summed shared cotangents) equals the monolithic gradient, and the two
evaluators therefore perform the same masked, clipped, single optimizer transition. -/
theorem M08_one_step_equivalence {d m : ℕ} {ι : Type*} [DecidableEq ι] (ξ : Frame d m ι)
    (ℬ : List (Finset ι)) (hpart : IsTilePartition ξ.I ℬ)
    (w₀ : EuclideanSpace ℝ (Fin d)) (D : FrameDeriv d m ι ξ w₀)
    (T : Finset (Fin d)) (c : ℝ)
    (U : TrainState d → EuclideanSpace ℝ (Fin d) → TrainState d)
    (S : TrainState d) :
    (tileAccum ξ.α D.val D.direct D.shared ℬ).loss = frameLoss ξ.h ξ.f ξ.α ξ.I w₀
    ∧ tiledGrad ξ.α D.val D.direct D.shared D.h' ℬ = monoGrad ξ w₀
    ∧ HasGradientAt (frameLoss ξ.h ξ.f ξ.α ξ.I)
        (tiledGrad ξ.α D.val D.direct D.shared D.h' ℬ) w₀
    ∧ U S (clipVec c (coordMask T (tiledGrad ξ.α D.val D.direct D.shared D.h' ℬ)))
      = U S (clipVec c (coordMask T (monoGrad ξ w₀))) := by sorry

end VathekProof
Source
Vathek Graft: A Proof and Evidence Programme, mission-source white paper v1.0, 22 September 2026 (Thomas Davis). Section 5, Theorem T0 Eq. (5) and the argument of Section 5.1; milestone M08.
Read-back

What the Lean code literally says, in plain math · glm-5.3 (independent auditor subagent)

{'text': '{\n "readback": "M08_one_step_equivalence — For all natural numbers ddd and mmm, and every index type iota\\\\iotaiota equipped with decidable equality (a purely computational assumption needed for the finite-set operations below; it carries no mathematical content), write W=mathbbRdW = \\\\mathbb{R}^dW=mathbbRd and V=mathbbRmV = \\\\mathbb{R}^mV=mathbbRm for the Euclidean spaces of logical parameters and shared state (standard inner product langlecdot,cdotrangle\\\\langle\\\\cdot,\\\\cdot\\\\ranglelanglecdot,cdotrangle and norm ∣cdot∣\\\\|\\\\cdot\\\\|∣cdot∣; coordinates indexed by 0,dots,d−1\\\\{0,\\\\dots,d-1\\\\}0,dots,d−1 and 0,dots,m−1\\\\{0,\\\\dots,m-1\\\\}0,dots,m−1; d=0d=0d=0 or m=0m=0m=0 gives the trivial one-point vector space).\n\nHypotheses (everything the theorem takes as given).\n\n- A frame xi=(h,f,alpha,I)\\\\xi = (h, f, \\\\alpha, I)xi=(h,f,alpha,I): an arbitrary map h:WtoVh : W \\\\to Vh:WtoV (the shared computation); a family of loss maps fi:WtimesVtomathbbRf_i : W \\\\times V \\\\to \\\\mathbb{R}fi​:WtimesVtomathbbR for iiniotai \\\\in \\\\iotaiiniota; real reduction coefficients alphaiinmathbbR\\\\alpha_i \\\\in \\\\mathbb{R}alphai​inmathbbR (no sign condition is imposed); and a finite occurrence set IsubseteqiotaI \\\\subseteq \\\\iotaIsubseteqiota. The frame structure itself imposes no smoothness on hhh or the fif_ifi​.\n- A finite list of tiles mathcalB=(B1,dots,Bn)\\\\mathcal{B} = (B_1,\\\\dots,B_n)mathcalB=(B1​,dots,Bn​), each BkB_kBk​ a finite subset of iota\\\\iotaiota, satisfying the partition hypothesis: bigcupkBk=I\\\\bigcup_k B_k = Ibigcupk​Bk​=I exactly, and tiles at distinct positions are pairwise disjoint (BjcapBk=varnothingB_j \\\\cap B_k = \\\\varnothingBj​capBk​=varnothing). The list may be empty — which forces I=varnothingI = \\\\varnothingI=varnothing — and individual tiles may be empty (two empty tiles are disjoint, so empty tiles may even repeat).\n- A pre-update point w0inWw_0 \\\\in Ww0​inW and a certificate package DDD at w0w_0w0​ with nine fields:\n - a continuous linear map h\' : W \\\\to V, certified to be the Fréchet derivative of hhh at w0w_0w0​;\n - a value table mathrmval:iotatomathbbR\\\\mathrm{val} : \\\\iota \\\\to \\\\mathbb{R}mathrmval:iotatomathbbR, certified by mathrmvali=fibig(w0,h(w0)big)\\\\mathrm{val}_i = f_i\\\\big(w_0, h(w_0)\\\\big)mathrmvali​=fi​big(w0​,h(w0​)big) for every iinIi \\\\in IiinI;\n - a direct-gradient table mathrmdirect:iotatoW\\\\mathrm{direct} : \\\\iota \\\\to Wmathrmdirect:iotatoW, certified so that mathrmdirecti\\\\mathrm{direct}_imathrmdirecti​ is the gradient (Fréchet derivative, represented as a vector via the inner product) of the frozen-shared-state map wmapstofibig(w,h(w0)big)w \\\\mapsto f_i\\\\big(w, h(w_0)\\\\big)wmapstofi​big(w,h(w0​)big) at w0w_0w0​, for every iinIi \\\\in IiinI;\n - a shared-cotangent table mathrmshared:iotatoV\\\\mathrm{shared} : \\\\iota \\\\to Vmathrmshared:iotatoV, certified so that mathrmsharedi\\\\mathrm{shared}_imathrmsharedi​ is the gradient of the frozen-parameter map vmapstofi(w0,v)v \\\\mapsto f_i(w_0, v)vmapstofi​(w0​,v) at the point h(w0)h(w_0)h(w0​), for every iinIi \\\\in IiinI;\n - a certificate that each fif_ifi​ is differentiable at the pair big(w0,h(w0)big)\\\\big(w_0, h(w_0)\\\\big)big(w0​,h(w0​)big), for every iinIi \\\\in IiinI.\n\n For inotinIi \\\\notin IinotinI the three tables are completely unconstrained; since the tiles cover exactly III, only indices of III ever enter the sums below.\n- A finite set Tsubseteq0,dots,d−1T \\\\subseteq \\\\{0,\\\\dots,d-1\\\\}Tsubseteq0,dots,d−1 of trainable coordinates (possibly empty).\n- A real clipping radius ccc (arbitrary — possibly zero or negative).\n- An arbitrary optimizer map UUU turning a training state and an update vector into a new training state, where a training state is a 444-tuple S=(w,mathrmmom1,mathrmmom2,t)S = (w, \\\\mathrm{mom}_1, \\\\mathrm{mom}_2, t)S=(w,mathrmmom1​,mathrmmom2​,t): current parameters winWw \\\\in WwinW, two moment vectors mathrmmom1,mathrmmom2inW\\\\mathrm{mom}_1, \\\\mathrm{mom}_2 \\\\in Wmathrmmom1​,mathrmmom2​inW, and a step counter tinmathbbNt \\\\in \\\\mathbb{N}tinmathbbN. And an arbitrary such state SSS.\n\nDefinitions appearing in the conclusion.\n\nThe monolithic loss of the frame is L_\\\\xi(w) = \\\\sum_{i \\\\in I} \\\\alpha_i\\\\, f_i\\\\big(w, h(w)\\\\big), a finite real sum.\n\nThe tiled accumulator processes the tiles of mathcalB\\\\mathcal{B}mathcalB left to right starting from (0,0,0)(0,0,0)(0,0,0); over a tile BBB it adds sumiinBalphai,mathrmvali\\\\sum_{i\\\\in B}\\\\alpha_i\\\\,\\\\mathrm{val}_isumiinB​alphai​,mathrmvali​ to its loss slot, sumiinBalphai,mathrmdirecti\\\\sum_{i\\\\in B}\\\\alpha_i\\\\,\\\\mathrm{direct}_isumiinB​alphai​,mathrmdirecti​ to its direct slot (a vector of WWW), and sumiinBalphai,mathrmsharedi\\\\sum_{i\\\\in B}\\\\alpha_i\\\\,\\\\mathrm{shared}_isumiinB​alphai​,mathrmsharedi​ to its shared slot (a vector of VVV). Write AAA and CCC for the final direct and shared slots:\n

A;=;sumBinmathcalB,sumiinBalphai,mathrmdirecti,qquadC;=;sumBinmathcalB,sumiinBalphai,mathrmsharedi.A \\\\;=\\\\; \\\\sum_{B \\\\in \\\\mathcal{B}}\\\\, \\\\sum_{i\\\\in B} \\\\alpha_i\\\\, \\\\mathrm{direct}_i, \\\\qquad C \\\\;=\\\\; \\\\sum_{B\\\\in\\\\mathcal{B}}\\\\,\\\\sum_{i\\\\in B}\\\\alpha_i\\\\, \\\\mathrm{shared}_i.A;=;sumBinmathcalB​,sumiinB​alphai​,mathrmdirecti​,qquadC;=;sumBinmathcalB​,sumiinB​alphai​,mathrmsharedi​.

\n\nThe tiled gradient is gmathrmtile=A+(h)ˊ∗[C]g_{\\\\mathrm{tile}} = A + (h\')^*[C]gmathrmtile​=A+(h)ˊ​∗[C], where (h)ˊ∗:VtoW(h\')^* : V \\\\to W(h)ˊ​∗:VtoW is the adjoint of the certified derivative h\', i.e. the unique continuous linear map with langlehuˊ,vrangle=langleu,(h)ˊ∗vrangle\\\\langle h\'u, v\\\\rangle = \\\\langle u, (h\')^* v\\\\ranglelanglehuˊ,vrangle=langleu,(h)ˊ​∗vrangle.\n\nThe monolithic gradient is\n

g_{\\\\mathrm{mono}} \\\\;=\\\\; \\\\big(D L_\\\\xi(w_0)\\\\big)^*[\\\\mathbf{1}],

\nthe inner-product representative of the Fréchet derivative of L_\\\\xi at w0w_0w0​: take that derivative (a continuous linear functional on WWW), form its adjoint (a map mathbbRtoW\\\\mathbb{R}\\\\to WmathbbRtoW), and evaluate at 1inmathbbR1 \\\\in \\\\mathbb{R}1inmathbbR. This is a total definition — where L_\\\\xi fails to be differentiable the derivative operator is defined to be the zero map, so gmathrmmonog_{\\\\mathrm{mono}}gmathrmmono​ always denotes some vector (then the junk value 000).\n\nThe coordinate mask and global clip are\n

(P_T g)_j = \\\\begin{cases} g_j & j \\\\in T,\\\\\\\\ 0 & j \\\\notin T,\\\\end{cases} \\\\qquad \\\\operatorname{clip}_c(g) = \\\\begin{cases} g & \\\\text{if } \\\\|g\\\\| \\\\le c,\\\\\\\\[2pt] \\\\dfrac{c}{\\\\|g\\\\|}\\\\, g & \\\\text{otherwise},\\\\end{cases}

\nwith ∣cdot∣\\\\|\\\\cdot\\\\|∣cdot∣ the Euclidean norm; real division is total with the convention tfracc0=0\\\\tfrac{c}{0}=0tfracc0=0.\n\nThe assertion is the conjunction of four statements.\n\n1. (Equal losses.) The tiled accumulator's final loss slot equals the monolithic loss at w0w_0w0​:\n

sumBinmathcalB,sumiinBalphai,mathrmvali;=;sumiinIalphai,fibig(w0,h(w0)big).\\\\sum_{B\\\\in\\\\mathcal{B}}\\\\,\\\\sum_{i\\\\in B}\\\\alpha_i\\\\, \\\\mathrm{val}_i \\\\;=\\\\; \\\\sum_{i\\\\in I} \\\\alpha_i\\\\, f_i\\\\big(w_0, h(w_0)\\\\big).sumBinmathcalB​,sumiinB​alphai​,mathrmvali​;=;sumiinI​alphai​,fi​big(w0​,h(w0​)big).

\nThe left side is built from the certified value table; the right side from the actual function values.\n\n2. (Equal gradients.) The tiled gradient equals the monolithic gradient:\n

A + (h\')^*[C] \\\\;=\\\\; \\\\big(D L_\\\\xi(w_0)\\\\big)^*[\\\\mathbf{1}].

\n\n3. (Genuine differentiability.) The monolithic loss map wmapstosumiinIalphai,fibig(w,h(w)big)w \\\\mapsto \\\\sum_{i\\\\in I}\\\\alpha_i\\\\, f_i\\\\big(w, h(w)\\\\big)wmapstosumiinI​alphai​,fi​big(w,h(w)big) is Fréchet-differentiable at w0w_0w0​ with gradient vector exactly gmathrmtileg_{\\\\mathrm{tile}}gmathrmtile​: its derivative at w0w_0w0​ exists and is the functional umapstolanglegmathrmtile,urangleu \\\\mapsto \\\\langle g_{\\\\mathrm{tile}}, u\\\\rangleumapstolanglegmathrmtile​,urangle.\n\n4. (Same optimizer transition.)\n

UBig(S,;operatornameclipcbig(PT,gmathrmtilebig)Big);=;UBig(S,;operatornameclipcbig(PT,gmathrmmonobig)Big),U\\\\Big(S,\\\\; \\\\operatorname{clip}_c\\\\big(P_T\\\\, g_{\\\\mathrm{tile}}\\\\big)\\\\Big) \\\\;=\\\\; U\\\\Big(S,\\\\; \\\\operatorname{clip}_c\\\\big(P_T\\\\, g_{\\\\mathrm{mono}}\\\\big)\\\\Big),UBig(S,;operatornameclipc​big(PT​,gmathrmtile​big)Big);=;UBig(S,;operatornameclipc​big(PT​,gmathrmmono​big)Big),

\ni.e. running the optimizer once on the state SSS with the tile-accumulated gradient — first projected onto the trainable coordinates TTT (per-coordinate zeroing of jnotinTj \\\\notin TjnotinT), then clipped once globally by the single radius ccc — produces the same next training state (parameters, both moment slots, and step counter alike) as running it with the monolithic gradient treated identically.\n\nWhat the quantifiers silently include. No nonnegativity is assumed anywhere: the weights alphai\\\\alpha_ialphai​ may be negative or zero, and the radius ccc may be zero or negative. For c<0c < 0c<0 the test ∣g∣lec\\\\|g\\\\| \\\\le c∣g∣lec fails for every ggg (norms are ge0\\\\ge 0ge0), so the second clip branch is always taken: nonzero vectors are rescaled by the negative factor c/∣g∣c/\\\\|g\\\\|c/∣g∣ (length ∣c∣|c|∣c∣, direction reversed), and even g=0g = 0g=0 goes through that branch, giving tfracc0cdot0=0\\\\tfrac{c}{0}\\\\cdot 0 = 0tfracc0cdot0=0 under the division convention; for cge0c \\\\ge 0cge0 the clip is the usual radial projection onto the closed ball of radius ccc. Degenerate instances are all covered: d=0d = 0d=0 or m=0m = 0m=0 (trivial spaces), I=varnothingI = \\\\varnothingI=varnothing (then every tile is empty, all sums are empty, both losses are 000, and gmathrmtile=0+(h)ˊ∗[0]=0g_{\\\\mathrm{tile}} = 0 + (h\')^*[0] = 0gmathrmtile​=0+(h)ˊ​∗[0]=0), the empty tile list mathcalB=(,)\\\\mathcal{B} = (\\\\,)mathcalB=(,) (forcing I=varnothingI = \\\\varnothingI=varnothing), and T=varnothingT = \\\\varnothingT=varnothing (then PTg=0P_T g = 0PT​g=0 for every ggg, so both sides of clause 4 become Ubig(S,operatornameclipc(0)big)U\\\\big(S, \\\\operatorname{{clip}}_c(0)\\\\big)Ubig(S,operatornameclipc​(0)big)). The optimizer UUU is an arbitrary function of state and update vector, with no further assumptions. The hypotheses are jointly satisfiable in non-degenerate ways (e.g. smooth hhh and fif_ifi​ with mathcalB=(I)\\\\mathcal{B} = (I)mathcalB=(I) and the tables set to the genuine values), so nothing here is vacuous."\n}', 'details': {'resolvedPath': '/home/ajax/.omp/agent/sessions/-math/2026-09-22T19-31-08-510Z_01a0ca99-be5e-7000-93c6-dac7c74cc004/RB2-M08.md', 'contentType': 'text/markdown', 'totalLines': 3, 'displayContent': {'text': '{\n "readback": "M08_one_step_equivalence — For all natural numbers ddd and mmm, and every index type iota\\\\iotaiota equipped with decidable equality (a purely computational assumption needed for the finite-set operations below; it carries no mathematical content), write W=mathbbRdW = \\\\mathbb{R}^dW=mathbbRd and V=mathbbRmV = \\\\mathbb{R}^mV=mathbbRm for the Euclidean spaces of logical parameters and shared state (standard inner product langlecdot,cdotrangle\\\\langle\\\\cdot,\\\\cdot\\\\ranglelanglecdot,cdotrangle and norm ∣cdot∣\\\\|\\\\cdot\\\\|∣cdot∣; coordinates indexed by 0,dots,d−1\\\\{0,\\\\dots,d-1\\\\}0,dots,d−1 and 0,dots,m−1\\\\{0,\\\\dots,m-1\\\\}0,dots,m−1; d=0d=0d=0 or m=0m=0m=0 gives the trivial one-point vector space).\n\nHypotheses (everything the theorem takes as given).\n\n- A frame xi=(h,f,alpha,I)\\\\xi = (h, f, \\\\alpha, I)xi=(h,f,alpha,I): an arbitrary map h:WtoVh : W \\\\to Vh:WtoV (the shared computation); a family of loss maps fi:WtimesVtomathbbRf_i : W \\\\times V \\\\to \\\\mathbb{R}fi​:WtimesVtomathbbR for iiniotai \\\\in \\\\iotaiiniota; real reduction coefficients alphaiinmathbbR\\\\alpha_i \\\\in \\\\mathbb{R}alphai​inmathbbR (no sign condition is imposed); and a finite occurrence set IsubseteqiotaI \\\\subseteq \\\\iotaIsubseteqiota. The frame structure itself imposes no smoothness on hhh or the fif_ifi​.\n- A finite list of tiles mathcalB=(B1,dots,Bn)\\\\mathcal{B} = (B_1,\\\\dots,B_n)mathcalB=(B1​,dots,Bn​), each BkB_kBk​ a finite subset of iota\\\\iotaiota, satisfying the partition hypothesis: bigcupkBk=I\\\\bigcup_k B_k = Ibigcupk​Bk​=I exactly, and tiles at distinct positions are pairwise disjoint (BjcapBk=varnothingB_j \\\\cap B_k = \\\\varnothingBj​capBk​=varnothing). The list may be empty — which forces I=varnothingI = \\\\varnothingI=varnothing — and individual tiles may be empty (two empty tiles are disjoint, so empty tiles may even repeat).\n- A pre-update point w0inWw_0 \\\\in Ww0​inW and a certificate package DDD at w0w_0w0​ with nine fields:\n - a continuous linear map h\' : W \\\\to V, certified to be the Fréchet derivative of hhh at w0w_0w0​;\n - a value table mathrmval:iotatomathbbR\\\\mathrm{val} : \\\\iota \\\\to \\\\mathbb{R}mathrmval:iotatomathbbR, certified by mathrmvali=fibig(w0,h(w0)big)\\\\mathrm{val}_i = f_i\\\\big(w_0, h(w_0)\\\\big)mathrmvali​=fi​big(w0​,h(w0​)big) for every iinIi \\\\in IiinI;\n - a direct-gradient table mathrmdirect:iotatoW\\\\mathrm{direct} : \\\\iota \\\\to Wmathrmdirect:iotatoW, certified so that mathrmdirecti\\\\mathrm{direct}_imathrmdirecti​ is the gradient (Fréchet derivative, represented as a vector via the inner product) of the frozen-shared-state map wmapstofibig(w,h(w0)big)w \\\\mapsto f_i\\\\big(w, h(w_0)\\\\big)wmapstofi​big(w,h(w0​)big) at w0w_0w0​, for every iinIi \\\\in IiinI;\n - a shared-cotangent table mathrmshared:iotatoV\\\\mathrm{shared} : \\\\iota \\\\to Vmathrmshared:iotatoV, certified so that mathrmsharedi\\\\mathrm{shared}_imathrmsharedi​ is the gradient of the frozen-parameter map vmapstofi(w0,v)v \\\\mapsto f_i(w_0, v)vmapstofi​(w0​,v) at the point h(w0)h(w_0)h(w0​), for every iinIi \\\\in IiinI;\n - a certificate that each fif_ifi​ is differentiable at the pair big(w0,h(w0)big)\\\\big(w_0, h(w_0)\\\\big)big(w0​,h(w0​)big), for every iinIi \\\\in IiinI.\n\n For inotinIi \\\\notin IinotinI the three tables are completely unconstrained; since the tiles cover exactly III, only indices of III ever enter the sums below.\n- A finite set Tsubseteq0,dots,d−1T \\\\subseteq \\\\{0,\\\\dots,d-1\\\\}Tsubseteq0,dots,d−1 of trainable coordinates (possibly empty).\n- A real clipping radius ccc (arbitrary — possibly zero or negative).\n- An arbitrary optimizer map UUU turning a training state and an update vector into a new training state, where a training state is a 444-tuple S=(w,mathrmmom1,mathrmmom2,t)S = (w, \\\\mathrm{mom}_1, \\\\mathrm{mom}_2, t)S=(w,mathrmmom1​,mathrmmom2​,t): current parameters winWw \\\\in WwinW, two moment vectors mathrmmom1,mathrmmom2inW\\\\mathrm{mom}_1, \\\\mathrm{mom}_2 \\\\in Wmathrmmom1​,mathrmmom2​inW, and a step counter tinmathbbNt \\\\in \\\\mathbb{N}tinmathbbN. And an arbitrary such state SSS.\n\nDefinitions appearing in the conclusion.\n\nThe monolithic loss of the frame is L_\\\\xi(w) = \\\\sum_{i \\\\in I} \\\\alpha_i\\\\, f_i\\\\big(w, h(w)\\\\big), a finite real sum.\n\nThe tiled accumulator processes the tiles of mathcalB\\\\mathcal{B}mathcalB left to right starting from (0,0,0)(0,0,0)(0,0,0); over a tile BBB it adds sumiinBalphai,mathrmvali\\\\sum_{i\\\\in B}\\\\alpha_i\\\\,\\\\mathrm{val}_isumiinB​alphai​,mathrmvali​ to its loss slot, sumiinBalphai,mathrmdirecti\\\\sum_{i\\\\in B}\\\\alpha_i\\\\,\\\\mathrm{direct}_isumiinB​alphai​,mathrmdirecti​ to its direct slot (a vector of WWW), and sumiinBalphai,mathrmsharedi\\\\sum_{i\\\\in B}\\\\alpha_i\\\\,\\\\mathrm{shared}_isumiinB​alphai​,mathrmsharedi​ to its shared slot (a vector of VVV). Write AAA and CCC for the final direct and shared slots:\n

A;=;sumBinmathcalB,sumiinBalphai,mathrmdirecti,qquadC;=;sumBinmathcalB,sumiinBalphai,mathrmsharedi.A \\\\;=\\\\; \\\\sum_{B \\\\in \\\\mathcal{B}}\\\\, \\\\sum_{i\\\\in B} \\\\alpha_i\\\\, \\\\mathrm{direct}_i, \\\\qquad C \\\\;=\\\\; \\\\sum_{B\\\\in\\\\mathcal{B}}\\\\,\\\\sum_{i\\\\in B}\\\\alpha_i\\\\, \\\\mathrm{shared}_i.A;=;sumBinmathcalB​,sumiinB​alphai​,mathrmdirecti​,qquadC;=;sumBinmathcalB​,sumiinB​alphai​,mathrmsharedi​.

\n\nThe tiled gradient is gmathrmtile=A+(h)ˊ∗[C]g_{\\\\mathrm{tile}} = A + (h\')^*[C]gmathrmtile​=A+(h)ˊ​∗[C], where (h)ˊ∗:VtoW(h\')^* : V \\\\to W(h)ˊ​∗:VtoW is the adjoint of the certified derivative h\', i.e. the unique continuous linear map with langlehuˊ,vrangle=langleu,(h)ˊ∗vrangle\\\\langle h\'u, v\\\\rangle = \\\\langle u, (h\')^* v\\\\ranglelanglehuˊ,vrangle=langleu,(h)ˊ​∗vrangle.\n\nThe monolithic gradient is\n

g_{\\\\mathrm{mono}} \\\\;=\\\\; \\\\big(D L_\\\\xi(w_0)\\\\big)^*[\\\\mathbf{1}],

\nthe inner-product representative of the Fréchet derivative of L_\\\\xi at w0w_0w0​: take that derivative (a continuous linear functional on WWW), form its adjoint (a map mathbbRtoW\\\\mathbb{R}\\\\to WmathbbRtoW), and evaluate at 1inmathbbR1 \\\\in \\\\mathbb{R}1inmathbbR. This is a total definition — where L_\\\\xi fails to be differentiable the derivative operator is defined to be the zero map, so gmathrmmonog_{\\\\mathrm{mono}}gmathrmmono​ always denotes some vector (then the junk value 000).\n\nThe coordinate mask and global clip are\n

(P_T g)_j = \\\\begin{cases} g_j & j \\\\in T,\\\\\\\\ 0 & j \\\\notin T,\\\\end{cases} \\\\qquad \\\\operatorname{clip}_c(g) = \\\\begin{cases} g & \\\\text{if } \\\\|g\\\\| \\\\le c,\\\\\\\\[2pt] \\\\dfrac{c}{\\\\|g\\\\|}\\\\, g & \\\\text{otherwise},\\\\end{cases}

\nwith ∣cdot∣\\\\|\\\\cdot\\\\|∣cdot∣ the Euclidean norm; real division is total with the convention tfracc0=0\\\\tfrac{c}{0}=0tfracc0=0.\n\nThe assertion is the conjunction of four statements.\n\n1. (Equal losses.) The tiled accumulator's final loss slot equals the monolithic loss at w0w_0w0​:\n

sumBinmathcalB,sumiinBalphai,mathrmvali;=;sumiinIalphai,fibig(w0,h(w0)big).\\\\sum_{B\\\\in\\\\mathcal{B}}\\\\,\\\\sum_{i\\\\in B}\\\\alpha_i\\\\, \\\\mathrm{val}_i \\\\;=\\\\; \\\\sum_{i\\\\in I} \\\\alpha_i\\\\, f_i\\\\big(w_0, h(w_0)\\\\big).sumBinmathcalB​,sumiinB​alphai​,mathrmvali​;=;sumiinI​alphai​,fi​big(w0​,h(w0​)big).

\nThe left side is built from the certified value table; the right side from the actual function values.\n\n2. (Equal gradients.) The tiled gradient equals the monolithic gradient:\n

A + (h\')^*[C] \\\\;=\\\\; \\\\big(D L_\\\\xi(w_0)\\\\big)^*[\\\\mathbf{1}].

\n\n3. (Genuine differentiability.) The monolithic loss map wmapstosumiinIalphai,fibig(w,h(w)big)w \\\\mapsto \\\\sum_{i\\\\in I}\\\\alpha_i\\\\, f_i\\\\big(w, h(w)\\\\big)wmapstosumiinI​alphai​,fi​big(w,h(w)big) is Fréchet-differentiable at w0w_0w0​ with gradient vector exactly gmathrmtileg_{\\\\mathrm{tile}}gmathrmtile​: its derivative at w0w_0w0​ exists and is the functional umapstolanglegmathrmtile,urangleu \\\\mapsto \\\\langle g_{\\\\mathrm{tile}}, u\\\\rangleumapstolanglegmathrmtile​,urangle.\n\n4. (Same optimizer transition.)\n

UBig(S,;operatornameclipcbig(PT,gmathrmtilebig)Big);=;UBig(S,;operatornameclipcbig(PT,gmathrmmonobig)Big),U\\\\Big(S,\\\\; \\\\operatorname{clip}_c\\\\big(P_T\\\\, g_{\\\\mathrm{tile}}\\\\big)\\\\Big) \\\\;=\\\\; U\\\\Big(S,\\\\; \\\\operatorname{clip}_c\\\\big(P_T\\\\, g_{\\\\mathrm{mono}}\\\\big)\\\\Big),UBig(S,;operatornameclipc​big(PT​,gmathrmtile​big)Big);=;UBig(S,;operatornameclipc​big(PT​,gmathrmmono​big)Big),

\ni.e. running the optimizer once on the state SSS with the tile-accumulated gradient — first projected onto the trainable coordinates TTT (per-coordinate zeroing of jnotinTj \\\\notin TjnotinT), then clipped once globally by the single radius ccc — produces the same next training state (parameters, both moment slots, and step counter alike) as running it with the monolithic gradient treated identically.\n\nWhat the quantifiers silently include. No nonnegativity is assumed anywhere: the weights alphai\\\\alpha_ialphai​ may be negative or zero, and the radius ccc may be zero or negative. For c<0c < 0c<0 the test ∣g∣lec\\\\|g\\\\| \\\\le c∣g∣lec fails for every ggg (norms are ge0\\\\ge 0ge0), so the second clip branch is always taken: nonzero vectors are rescaled by the negative factor c/∣g∣c/\\\\|g\\\\|c/∣g∣ (length ∣c∣|c|∣c∣, direction reversed), and even g=0g = 0g=0 goes through that branch, giving tfracc0cdot0=0\\\\tfrac{c}{0}\\\\cdot 0 = 0tfracc0cdot0=0 under the division convention; for cge0c \\\\ge 0cge0 the clip is the usual radial projection onto the closed ball of radius ccc. Degenerate instances are all covered: d=0d = 0d=0 or m=0m = 0m=0 (trivial spaces), I=varnothingI = \\\\varnothingI=varnothing (then every tile is empty, all sums are empty, both losses are 000, and gmathrmtile=0+(h)ˊ∗[0]=0g_{\\\\mathrm{tile}} = 0 + (h\')^*[0] = 0gmathrmtile​=0+(h)ˊ​∗[0]=0), the empty tile list mathcalB=(,)\\\\mathcal{B} = (\\\\,)mathcalB=(,) (forcing I=varnothingI = \\\\varnothingI=varnothing), and T=varnothingT = \\\\varnothingT=varnothing (then PTg=0P_T g = 0PT​g=0 for every ggg, so both sides of clause 4 become Ubig(S,operatornameclipc(0)big)U\\\\big(S, \\\\operatorname{{clip}}_c(0)\\\\big)Ubig(S,operatornameclipc​(0)big)). The optimizer UUU is an arbitrary function of state and update vector, with no further assumptions. The hypotheses are jointly satisfiable in non-degenerate ways (e.g. smooth hhh and fif_ifi​ with mathcalB=(I)\\\\mathcal{B} = (I)mathcalB=(I) and the tables set to the genuine values), so nothing here is vacuous."\n}', 'startLine': 1, 'lineNumbers': [1, 2, 3]}, 'meta': {'source': {'type': 'internal', 'value': 'agent://RB2-M08'}}}}

Human review
  • Endorsed by Shuze Chen · Sep 25, 2026

  • Endorsed by ajax · Sep 25, 2026

    Confirmed by the mission captain (proposal self-audit).

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