Section 11.2, part 2a: adaptive fits and staggered increments #
This file was automatically generated by Claude.
Formalization of blueprint Section 11, "The base reduction" (sec:base), subsection 2, "Adaptive
fits and the two earliest increments", part 2a: adaptive fits and staggered increments (lines
1569-1597) of blueprint/formalization_blueprint.tex.
Energy gain of one fresh column #
Adding a vector u to a closed range U increases the projection energy of z by at least
|⟨u, z - P_U z⟩|² / ‖u‖² (blueprint §11.2, line 1577: "squared energy gain").
Fit columns with private weight one #
The value (φ(y), e_v) of a fit column.
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- TrilinearHT.Auto.fitColumnValue φ v y = φ y • EuclideanSpace.single none 1 + EuclideanSpace.single (some v) 1
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The predicate on fit data: a measurable set of finite measure and a bounded measurable atom.
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- TrilinearHT.Auto.FitAdmissible s φ = (MeasurableSet s ∧ MeasureTheory.volume s < ⊤ ∧ Measurable φ ∧ ∀ (y : ℝ), ‖φ y‖ ≤ 1)
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The fit column 1_s (φ, e_v) in L²(ℝ; ℂ ⊕ ℓ²(V)).
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- TrilinearHT.Auto.fitColumn s φ v = if h : TrilinearHT.Auto.FitAdmissible s φ then MeasureTheory.MemLp.toLp (s.indicator (TrilinearHT.Auto.fitColumnValue φ v)) ⋯ else 0
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The range of the first n fit columns 1_s (a_i, e_i), i < n, over labels Fin M.
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- TrilinearHT.Auto.fitRange s a n = Submodule.span ℂ {x : ↥(TrilinearHT.Auto.ColumnL2 (Fin M)) | ∃ (i : Fin M), ↑i < n ∧ TrilinearHT.Auto.fitColumn s (a ↑i) i = x}
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Residual smallness and detection #
d_{j,I}(R) ≤ η (blueprint §11.2, line 1568): every local form at the cell [a₀, a₀ + r)
with R in slot j, one normalized L^q input and two normalized L² inputs in the other
slots (any choice of the L^q position) is at most η.
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Blueprint §11.2, line 1577 (detection step of the adaptive fit): a residual failing
d_{j,I} ≤ e^{-k} correlates with a bounded atom of complexity at most fitBudget by at least
fitBudget⁻¹ (Lemma lem:detection with C₁ = 2, δ = e^{-k}).
The greedy insertion at one cell #
One insertion step: while the residual is not small and the cap M is not reached, insert
the oracle's atom as the next label (blueprint §11.2, line 1577).
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Energy accumulates at least g per insertion along the greedy fit.
The fit projection at a cell with the first n atoms.
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- TrilinearHT.Auto.fitProj M s a n = (TrilinearHT.Auto.fitRange s a n).starProjection
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The fit residual f - (P F)_phys.
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- TrilinearHT.Auto.fitResid M s f a n y = ↑↑f y - (↑↑((TrilinearHT.Auto.fitProj M s a n) (TrilinearHT.Auto.physicalColumnInput f)) y).ofLp none
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Blueprint §11.2, line 1577: inserting an atom whose correlation with the residual is at least
ρ |I| increases the fit energy by at least ρ² |I| / 4.
A range inside the orthogonal sum of two ranges has at most their total projection energy.
The fit column on a disjoint union is the sum of the fit columns on the parts.
The fit energy on a cell is at most the sum of the fit energies on its two halves with the same atoms (refinement of the partition; nested subspaces).
One attempt of the adaptive fit on a dyadic tree #
The parent cell.
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- TrilinearHT.Auto.dyadicParent G c = (c.1 - 1, TrilinearHT.Auto.dyadicIndex G (c.1 - 1) (TrilinearHT.Auto.dyadicGridLeft G c.1 c.2))
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The states of one attempt: atoms and count at each cell of depth root + d.
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- TrilinearHT.Auto.fitState G M P O 0 x✝ = TrilinearHT.Auto.fitGreedy M (P x✝) (O x✝) (fun (x : ℕ) => 0, 0)
- TrilinearHT.Auto.fitState G M P O d.succ x✝ = TrilinearHT.Auto.fitGreedy M (P x✝) (O x✝) (TrilinearHT.Auto.fitState G M P O d (TrilinearHT.Auto.dyadicParent G x✝))
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The inherited count of a cell: the parent's final count (zero at the root).
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- TrilinearHT.Auto.fitInherited G M P O 0 x✝ = (fun (x : ℕ) => 0, 0)
- TrilinearHT.Auto.fitInherited G M P O d.succ x✝ = TrilinearHT.Auto.fitState G M P O d (TrilinearHT.Auto.dyadicParent G x✝)
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The number of atoms inserted at a cell.
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- TrilinearHT.Auto.fitNew G M P O d c = (TrilinearHT.Auto.fitState G M P O d c).2 - (TrilinearHT.Auto.fitInherited G M P O d c).2
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The oracle hypothesis: whenever the residual at a cell is not small and the cap is not
reached, the oracle's atom is admissible and correlates with the residual by ρ |I|.
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The fit energy at a cell for a state.
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- TrilinearHT.Auto.fitCellEnergy G M f c st = ‖(TrilinearHT.Auto.fitProj M (TrilinearHT.Auto.dyadicGridCell G c.1 c.2) st.1 st.2) (TrilinearHT.Auto.physicalColumnInput f)‖ ^ 2
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The two children of a cell carry at least the parent's fit energy with the same atoms.
Blueprint §11.2, line 1577 ("fits and refinements form nested subspaces"): the energy gains
of all insertions down to generation d are at most the fit energy of that generation.
The fit energy of a generation is at most the input energy on the root.
Coefficients of the fit projection #
The labels of the first n fit columns.
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- TrilinearHT.Auto.fitLabels M n = {i : Fin M | ↑i < n}
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The pointwise physical part of the fit projection: ∑ c_i a_i over admissible atoms.
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- TrilinearHT.Auto.fitPhys M s a n z y = ∑ i ∈ TrilinearHT.Auto.fitLabels M n, if TrilinearHT.Auto.FitAdmissible s (a ↑i) then TrilinearHT.Auto.fitCoeff M s a n z i * a (↑i) y else 0
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The squared coefficient norm over admissible atoms.
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- TrilinearHT.Auto.fitCoeffSq M s a n z = ∑ i ∈ TrilinearHT.Auto.fitLabels M n, if TrilinearHT.Auto.FitAdmissible s (a ↑i) then ‖TrilinearHT.Auto.fitCoeff M s a n z i‖ ^ 2 else 0
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Private weights one bound the coefficient ℓ² norm: |s| ∑ |c_i|² ≤ ∫_s ‖P z‖².
The physical fit is bounded in L²(s) by the fit energy.
The adaptive-fit oracle #
A detection chart: complexity and boundedness at budget B, and correlation B⁻¹.
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The kernel hull of a finite tree: cells containing a tree cell with a nonzero kernel (blueprint prop:normalized, line 2832: the normalization is only assumed on the rooted subtree of the used cells; the other cells carry the zero kernel).
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- TrilinearHT.Auto.kernelHull G J N w c = ∃ c' ∈ TrilinearHT.Auto.dyadicFiniteTree G J N, TrilinearHT.Auto.dyadicGridCell G c'.1 c'.2 ⊆ TrilinearHT.Auto.dyadicGridCell G c.1 c.2 ∧ w c' ≠ 0
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A failing residual test happens only at a cell of the kernel hull.
The data of one adaptive-fit construction.
- G : RealDyadicGrid
Dyadic grid used for the adaptive-fit construction.
Root cell on which the adaptive-fit input is normalized.
- N : ℕ
Number of dyadic generations available below the root.
- M : ℕ
Maximum number of fit columns available to an attempt.
Scalar input to be approximated by the adaptive fit.
Local kernels assigned to the dyadic cells.
- j : Fin 4
Position of the input in the four-linear local form.
- q : ℝ
Integrability exponent used in the residual-smallness test.
- k : ℕ
Accuracy parameter giving the residual threshold
exp (-k). - c₂ : ℕ
Complexity exponent supplied to the fit oracle.
- B : ℝ
Complexity budget supplied to the fit oracle.
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The input 1_J f as an L² class.
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- S.input = if h : MeasureTheory.MemLp ((S.cell S.J).indicator S.f) 2 MeasureTheory.volume then MeasureTheory.MemLp.toLp ((S.cell S.J).indicator S.f) h else 0
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The column input.
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Hypotheses on the data.
- f_meas : Measurable S.f
- f_norm_root : MeasureTheory.eLpNorm S.f 2 (normalizedIntervalMeasure (dyadicGridLeft S.G S.J.1 S.J.2) (dyadicGridLength S.G S.J.1)) ≤ 1
- f_norm (c : ℤ × ℤ) : c ∈ dyadicFiniteTree S.G S.J S.N → kernelHull S.G S.J S.N S.w c → MeasureTheory.eLpNorm S.f 2 (normalizedIntervalMeasure (dyadicGridLeft S.G c.1 c.2) (dyadicGridLength S.G c.1)) ≤ 1
- detect (c : ℤ × ℤ) (a : ℕ → ℝ → ℂ) (n : ℕ) : c ∈ dyadicFiniteTree S.G S.J S.N → Measurable (S.res c a n) → MeasureTheory.eLpNorm (S.res c a n) 2 (normalizedIntervalMeasure (dyadicGridLeft S.G c.1 c.2) (dyadicGridLength S.G c.1)) ≤ ENNReal.ofReal 2 → ¬FormSmall (dyadicGridLeft S.G c.1 c.2) (dyadicGridLength S.G c.1) (S.w c) S.j S.q (S.res c a n) (Real.exp (-↑S.k)) → ∃ (p : (d : ℕ) × QuadraticChartData d), FitChartGood S.c₂ S.B (dyadicGridLeft S.G c.1 c.2) (dyadicGridLength S.G c.1) (S.res c a n) p
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The residual has normalized L² norm at most two.
Ancestor chains, inherited lists and counts #
A strict ancestor contains the parent.
Every atom of the greedy fit satisfies a property preserved by the oracle.
Along an ancestor chain, the deeper state extends the shallower one.
The count at a cell is the ancestor sum of the insertion counts within its attempt.
The weighted insertion mass of an attempt is at most 4/ρ² times the input energy.
Greedy attempts with restarts on a finite tree #
A greedy attempt structure: per-cell greedy insertion with predicate P and oracle O,
inherited along each attempt (fitState), with integrated insertion mass at most A |K| on every
attempt root K (blueprint sec:reduction, lines 429-451; §11.2, line 1577).
- G : RealDyadicGrid
Dyadic grid supporting the greedy attempts and restarts.
Initial root cell for the greedy construction.
- N : ℕ
Number of dyadic generations below the initial root.
- M : ℕ
Maximum number of insertions available in one greedy state.
Predicate deciding when an insertion attempt stops.
Oracle producing a new atom when the stopping predicate fails.
- A : ℝ
Integrated insertion-mass bound per unit length of an attempt root.
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The cell of an index.
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- S.cell c = TrilinearHT.Auto.dyadicGridCell S.G c.1 c.2
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The first-crossing threshold A / (1/4).
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The finite tree below K.
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- S.sub K = TrilinearHT.Auto.dyadicFiniteTree S.G K (TrilinearHT.Auto.dyadicRemainingDepth S.J S.N K)
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All attempt roots.
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Hypotheses: nonnegative mass constant, the mass bound, and trivial stopping off the tree.
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The restarted segments have total root length at most 4/3 |J|.
The root of the segment containing a tree cell: its deepest attempt root.
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- S.seg u = if h : u ∈ TrilinearHT.Auto.dyadicFiniteTree S.G S.J S.N ∧ S.Hyp then Classical.choose ⋯ else u
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Tuple-specific accurate high fits #
A cell between a tree cell and its segment root has the same segment root.
Restarts and segments of the adaptive fit #
Analytic fit hypotheses supply the three hypotheses of the general restart theorem.
Blueprint §11.2, line 1577: the restarted segments have total root length at most
4/3 |J|.
The inherited adaptive fit #
Within a segment, deeper cells inherit the list of their ancestors.
Every atom of every list is a bounded detection chart.
Packaging the adaptive fit as column tree data #
The column tree data of the attempt rooted at K, on the tree below a cell R of it
(blueprint §11.2, line 1574; renormalized at R as in sec:reduction, line 429): labels Fin M,
all born at R, private weight one, leaf-piecewise scalars.
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The inherited mask {m < count} of the attempt rooted at K.
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The attempt rooted at K as a column depth family on the tree below R.
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The projection of the packaged data is the fit projection.
Current projections: cellwise identification and depth energy #
On a row cell below the root, the current projection is a.e. the depth projection.
Current projection opponents have depth energy with constant one.
On tree cells below R, the current projection of the packaged attempt is the fit
(a.e. on the cell).
The fits as admissible opponents #
Admissibility is invariant under changes of the opponent on the cells below the root and of the input with the same energy on the root.
The conclusion of the adaptive fit (blueprint §11.2, lines 1567-1579) for an input f in
slot j at accuracy e^{-k} with chart budget B, on the complete finite tree of depth N below
J: restarted segments with total root length at most 4/3 |J|, inherited lists of at most
M ≤ 17 B² bounded chart atoms extending along each segment, and fitted combinations g_I
(coefficient ℓ² norm at most one, |g_I| ≤ √M, ‖g_I‖_{2,I} ≤ 1) with small residual
d_{j,I}(f - g_I) ≤ e^{-k} on every tree cell.
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The bilinear norm of the pair (X, Y) in slots p ≠ p' against normalized L² spectators is
at most η (blueprint §11.2, lines 1589-1596).
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Subtraction in one slot of the local form, for finite normalized L² inputs.
A function with finite normalized L² norm.
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- TrilinearHT.Auto.FinL2 a₀ r X = (Measurable X ∧ MeasureTheory.eLpNorm X 2 (TrilinearHT.Auto.normalizedIntervalMeasure a₀ r) ≠ ⊤)
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Apply residual smallness with the residual in slot p and an L^q input in slot p'.
The L^q slot may carry a function bounded by S, at the cost of the factor S.
Cyclic updates at one cell #
The position updated at level t (cyclic order).
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- TrilinearHT.Auto.stagPos t = ⟨t % 4, ⋯⟩
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The data of the cyclic updates at one cell: inputs normalized in L^q, and at each level
t ≥ 1 a bounded projection of the input in position t mod 4 with residual smallness
e^{-k_t}; the accuracies grow fast enough to dominate the supremum bounds.
- a₀ : ℝ
Left endpoint of the cell undergoing staggered updates.
- r : ℝ
Positive length of the cell undergoing staggered updates.
Admissible local kernel on the update cell.
- q : ℝ
Integrability exponent for the normalized input functions.
The four input functions before staggered projection updates.
Projected approximation selected at each update level.
Accuracy exponent controlling the residual at each update level.
Pointwise norm bound for each projected approximation.
- adm : IsAdmissibleLocalKernel κ self.a₀ self.r self.w
- f_meas (p : Fin 4) : Measurable (self.f p)
- f_norm (p : Fin 4) : MeasureTheory.eLpNorm (self.f p) (ENNReal.ofReal self.q) (normalizedIntervalMeasure self.a₀ self.r) ≤ 1
- g_meas (t : ℕ) : Measurable (self.g t)
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The normalized measure of the cell.
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The local form.
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- C.H F = TrilinearHT.Auto.localProgressionForm C.r C.w F
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Normalized spectators for the slots p, p'.
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Replacing a projection by its input against an actual input: error e^{-k_ℓ}.
Replacing a projection by its input against a bounded function: error S e^{-k_ℓ}.
Blueprint eq:stagger (line 1589): replacing any two valid terms in distinct slots by the
actual inputs costs at most 2 e^{-k_m}.
Expansion of a pair of differences around a common reference value.
A difference of two valid terms.
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Two late differences in distinct slots have pair norm at most 8 e^{-k_m}.
A bounded old projection against a late term: replacing the late term costs
e^{-k_m/2}.
The tuple of the two earliest increments #
The previous value of the position updated at level t (zero before its first update).
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The increment at level t.
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The current projection of position l after the updates of levels ≤ t (zero before its
first update).
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- C.lastProj l t = if 1 ≤ TrilinearHT.Auto.StaggerCell.lastLevel l t then C.g (TrilinearHT.Auto.StaggerCell.lastLevel l t) else 0
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Blueprint eq:base-tuple (line 1583): X_i = g_u - g_{u-4}, X_j = g_t - g_{t-4} and
X_e = F_e - g_{e,prev} in the remaining slots.
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The early slot against a late difference (blueprint line 1596, case u < t - 4): each of
its two old projections is tested directly.
Blueprint §11.2, line 1596: for t ≥ 12 and the two earliest increment levels u < t in
distinct positions, every pair of full tuple arguments has bilinear norm at most
8 e^{-k_{t-7}}.
The expansion at a finite cutoff #
The terminal residuals F_p - (current projection) after the updates of levels ≤ τ.
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First increment decomposition: telescoping over the levels in time order.
The inputs after the first increment u has been fixed in its slot.
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- C.W u τ = Function.update (C.tail τ) (TrilinearHT.Auto.stagPos u) (C.incr u)
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Blueprint §11.2, line 1587: at a finite cutoff T the expansion of every input into its
increments and terminal residual groups exactly into the tuples eq:base-tuple of the two
earliest increments u < t (distinct positions), the terms with a single increment, and the
term with four terminal residuals.
Sizes and remainders #
Blueprint line 1596: all tuple factors have bounded normalized L² norm.
A pair estimate against spectators of normalized size at most c.
Blueprint line 1587: each term with a single increment and three terminal residuals tends to zero.
The accuracy schedule and the declaration stagger #
The accuracies k_t = k_1^{A^{t-1}}, so that k_{t+1} = k_t^A.
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- TrilinearHT.Auto.stagAcc k₁ A t = k₁ ^ A ^ (t - 1)
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The normalized L² norm of a fit is at most one.
On a tree cell, the leaf-read scalar is the cellwise scalar of an available label.
The column tree data rooted at a tree cell R, all labels born at R.
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The inherited mask of a rooted system.
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The system rooted at R as a column depth family down to the leaves.
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The column 1_c (φ_v, √ε_v e_v) of the system at the cell c.
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- P.column c v = MeasureTheory.MemLp.toLp ((TrilinearHT.Auto.dyadicGridCell G c.1 c.2).indicator (TrilinearHT.Auto.privateColumnValue (P.scalarAt c) P.weight v)) ⋯
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The range of the available columns at c.
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The rooted cell projections are the root-independent system projections.
The delayed opponent is the current projection plus a rolling square-energy sequence, hence admissible (blueprint lem:delay, line 1565; prop:base, line 1632).
An available label's rooted scalar is the cellwise scalar at the root, everywhere.