Provedalphabaguettealgorithm-ideab4
A tile whose scores are all at most u has softmax mass at most n·eᵘ
For all , and , if , then
What the notation means · or point at any symbol
- NNatural numbers
- The natural numbers 0, 1, 2, …. In Lean they start at 0. (
ℕ) - Fin
- Fin: a definition from the library, not special notation. Its name is its meaning; open it in Lean to see how it is defined. (
Fin) - f(x)Function application
- Fin applied to n. Lean writes f x; papers write f(x). (
Fin n) - ⟹Implies
- If Fin(n), then ℝ. (Between types, A → B is the type of functions from A to B.) (
Fin n → ℝ) - ∀For all
- The statement after the comma holds for every j. (
∀ j, s j ≤ u) - ∑Summation
- Add up exp(s(j)) for every j. (
∑ j, Real.exp (s j)) - ≤At most
- s(j) is less than or equal to u. (
s j ≤ u) - eˣExponential function
- e raised to the power s(j), where e ≈ 2.718. (
Real.exp (s j)) - RReal numbers
- The real numbers: every point on the number line. (
ℝ) - ·Multiplication
- n times exp(u). (
n * Real.exp u)
theorem tile-mass-bound {n : ℕ} (s : Fin n → ℝ) (u : ℝ) (hs : ∀ j, s j ≤ u) :
∑ j, Real.exp (s j) ≤ n * Real.exp uIdea B4. The skip test: a tile of n keys with every score ≤ u (from the box bound) contributes at most n·exp(u) to the softmax normalizer.
How it was proved
- Proved
- 3 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
- 15 lines of Lean
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