Provedsampleability-lawadaptive-exactnessunbiasedpitfall
Adaptive exactness is unbiased with an independent pilot: if the exact-or-sampled decision uses samples independent of the estimate, E[output] = θ whenever every branch is unbiased
For all , , , , and , if and (given and ), then
What the notation means · or point at any symbol
- Type
- Type: a definition from the library, not special notation. Its name is its meaning; open it in Lean to see how it is defined. (
Type) - x ∈ TVariables
- Ω₁, Ω₂, D range over Type: the statement must hold for every choice. (
(Ω₁ Ω₂ D : Type)) - Fintype
- Fintype: a definition from the library, not special notation. Its name is its meaning; open it in Lean to see how it is defined. (
Fintype) - f(x)Function application
- Fintype applied to Ω₁. Lean writes f x; papers write f(x). (
Fintype Ω₁) - ⟹Implies
- If Ω₁, then ℝ. (Between types, A → B is the type of functions from A to B.) (
Ω₁ → ℝ) - ∑Summation
- Add up w₁(x) for every x. (
∑ x, w₁ x) - =Equality
- ∑ x, w₁(x) and 1 are the same. (
∑ x, w₁ x = 1) - ∀For all
- The statement after the comma holds for every d. (
∀ d, ∑ y, w₂ y * X d y = θ) - RReal numbers
- The real numbers: every point on the number line. (
ℝ) - ·Multiplication
- w₂(y) times X(d, y). (
w₂ y * X d y)
theorem am-pilot-independence-unbiased {Ω₁ Ω₂ D : Type} [Fintype Ω₁] [Fintype Ω₂] (w₁ : Ω₁ → ℝ) (w₂ : Ω₂ → ℝ) (dec : Ω₁ → D) (X : D → Ω₂ → ℝ) (θ : ℝ) (hs1 : ∑ x, w₁ x = 1) (hX : ∀ d, ∑ y, w₂ y * X d y = θ) :
∑ x, ∑ y, w₁ x * w₂ y * X (dec x) y = θOn the product of a pilot space and an estimate space, any decision rule computed from the pilot leaves the output unbiased provided each branch (exact, or sampled and debiased) is unbiased. This licenses per-(head, step) exactness driven by the self-certificate, as long as the certificate is computed from pilot draws separate from the estimate's draws. Part of 'The Sampleability Law' (adaptive exactness: deciding per (head, step) between exact and sampled attention without bias).
How it was proved
- Proved
- 5 October 2026
- By
- Ajax, with the agent “Baguette math & proofs (Claude Code, 2026-10-03)”
- Checked by
- Lean's kernel (Lean 4.33.1, with Mathlib); the proof is signed and replays offline
- Axioms
- Classical.choice, Quot.sound, propext
- Proof
- 14 lines of Lean
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