openAI-math-dataset / lean /OAI /MeasureTheory /DyadicAvoidance /LocalPredicateFactor.lean
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import OAI.MeasureTheory.DyadicAvoidance.RoutingPath
import OAI.MeasureTheory.DyadicAvoidance.GridSeparation
namespace OAI
universe u_ι u_X u_K u_V u_J
noncomputable section
namespace Problem310.LocalPredicateFactor
open RoutingPath GridSeparation
variable {ι : Type u_ι} {X : Type u_X} {K : Type u_K} {V : Type u_V}
/-- Routing through a subtree only uses its strict-descendant choices.
If those choices factor through one key, the terminal leaf does too. -/
theorem route_eq_of_key_eq (choose : List ι → X → ι)
(key : X → K) (r : ℕ) (P : List ι)
(hchoice : ∀ Q : List ι, P.IsPrefix Q → Q.length < P.length + r →
∀ x y : X, key x = key y → choose Q x = choose Q y)
{x y : X} (hxy : key x = key y) :
routeFrom choose r P x = routeFrom choose r P y := by
apply routeFrom_eq_of_choices_eq choose r P y x
intro k hk
apply hchoice (routeFrom choose k P y) (prefix_routeFrom choose k P y)
· rw [length_routeFrom]
omega
· exact hxy
/-- A terminal output on a routed subtree factors through a common key
provided every choice and every possible terminal output does. -/
theorem terminal_eq_of_key_eq (choose : List ι → X → ι)
(terminal : List ι → X → V) (key : X → K) (r : ℕ) (P : List ι)
(hchoice : ∀ Q : List ι, P.IsPrefix Q → Q.length < P.length + r →
∀ x y : X, key x = key y → choose Q x = choose Q y)
(hterminal : ∀ Q : List ι, P.IsPrefix Q → Q.length = P.length + r →
∀ x y : X, key x = key y → terminal Q x = terminal Q y)
{x y : X} (hxy : key x = key y) :
terminal (routeFrom choose r P x) x = terminal (routeFrom choose r P y) y := by
have hroute := route_eq_of_key_eq choose key r P hchoice hxy
rw [hroute]
exact hterminal _ (prefix_routeFrom choose r P y)
(length_routeFrom choose r P y) x y hxy
/-- An incoming selector multiplied by a local terminal predicate also
factors through that key. This includes a child which is already a leaf. -/
theorem local_predicate_eq_of_key_eq (choose : List ι → X → ι)
(terminal : List ι → X → Bool) (incoming : X → Bool)
(key : X → K) (r : ℕ) (P : List ι)
(hchoice : ∀ Q : List ι, P.IsPrefix Q → Q.length < P.length + r →
∀ x y : X, key x = key y → choose Q x = choose Q y)
(hterminal : ∀ Q : List ι, P.IsPrefix Q → Q.length = P.length + r →
∀ x y : X, key x = key y → terminal Q x = terminal Q y)
(hincoming : ∀ x y : X, key x = key y → incoming x = incoming y)
{x y : X} (hxy : key x = key y) :
(incoming x && terminal (routeFrom choose r P x) x) =
(incoming y && terminal (routeFrom choose r P y) y) := by
rw [hincoming x y hxy,
terminal_eq_of_key_eq choose terminal key r P hchoice hterminal hxy]
/-- A single table evaluated at any coarser grid is a function of the finest key. -/
theorem table_eq_of_finest_key {b B : ℕ} (hb : b ≤ B)
(table : Fin (2 ^ (b + 2)) → V) {x y : ℝ}
(hxy : ⌊(2 : ℝ) ^ (B + 2) * Int.fract x⌋ =
⌊(2 : ℝ) ^ (B + 2) * Int.fract y⌋) :
table (dyadicKey b x) = table (dyadicKey b y) := by
apply congrArg table
apply (dyadicKey_eq_iff b x y).mpr
exact periodicKey_dyadic_eq_of_refine hb hxy
variable {J : Type u_J}
/-- An arbitrary deterministic rule applied to selector-table lookups depends
only on a common finer key. In particular this applies to first-success routing. -/
theorem choice_eq_of_finest_key (b : J → ℕ) (B : ℕ)
(tables : ∀ j, Fin (2 ^ (b j + 2)) → Bool)
(rule : (J → Bool) → ι) (hb : ∀ j, b j ≤ B) {x y : ℝ}
(hxy : ⌊(2 : ℝ) ^ (B + 2) * Int.fract x⌋ =
⌊(2 : ℝ) ^ (B + 2) * Int.fract y⌋) :
rule (fun j => tables j (dyadicKey (b j) x)) =
rule (fun j => tables j (dyadicKey (b j) y)) := by
apply congrArg rule
funext j
exact table_eq_of_finest_key (hb j) (tables j) hxy
/-- A table-based node rule, with no restriction on which deterministic
first-success/default convention the rule uses. -/
def gridChoice (b : List ι → J → ℕ)
(tables : ∀ Q j, Fin (2 ^ (b Q j + 2)) → Bool)
(rule : List ι → (J → Bool) → ι) (Q : List ι) (x : ℝ) : ι :=
rule Q (fun j => tables Q j (dyadicKey (b Q j) x))
def gridTerminal (c : List ι → ℕ)
(tables : ∀ Q, Fin (2 ^ (c Q + 2)) → Bool) (Q : List ι) (x : ℝ) : Bool :=
tables Q (dyadicKey (c Q) x)
/-- The incoming selector and every table in a child subtree may have different
resolutions. A bound on all those resolutions gives exactly the common-key
factorization needed for deterministic scale representatives. -/
theorem grid_local_predicate_factors
(b : List ι → J → ℕ) (c : List ι → ℕ) (bIn B : ℕ)
(selectors : ∀ Q j, Fin (2 ^ (b Q j + 2)) → Bool)
(terminals : ∀ Q, Fin (2 ^ (c Q + 2)) → Bool)
(incoming : Fin (2 ^ (bIn + 2)) → Bool)
(rule : List ι → (J → Bool) → ι) (r : ℕ) (P : List ι)
(hb : ∀ Q : List ι, P.IsPrefix Q → Q.length < P.length + r →
∀ j, b Q j ≤ B)
(hc : ∀ Q : List ι, P.IsPrefix Q → Q.length = P.length + r → c Q ≤ B)
(hIn : bIn ≤ B) {x y : ℝ}
(hxy : ⌊(2 : ℝ) ^ (B + 2) * Int.fract x⌋ =
⌊(2 : ℝ) ^ (B + 2) * Int.fract y⌋) :
(incoming (dyadicKey bIn x) &&
gridTerminal c terminals (routeFrom (gridChoice b selectors rule) r P x) x) =
(incoming (dyadicKey bIn y) &&
gridTerminal c terminals (routeFrom (gridChoice b selectors rule) r P y) y) := by
apply local_predicate_eq_of_key_eq
(gridChoice b selectors rule) (gridTerminal c terminals)
(fun z => incoming (dyadicKey bIn z))
(fun z => ⌊(2 : ℝ) ^ (B + 2) * Int.fract z⌋) r P
· intro Q hPQ hlen u v huv
exact choice_eq_of_finest_key (b Q) B (selectors Q) (rule Q)
(hb Q hPQ hlen) huv
· intro Q hPQ hlen u v huv
exact table_eq_of_finest_key (hc Q hPQ hlen) (terminals Q) huv
· intro u v huv
exact table_eq_of_finest_key hIn incoming huv
· exact hxy
end Problem310.LocalPredicateFactor
end
end OAI