openAI-math-dataset / lean /OAI /Computability /VertexCover /Analysis /PowerValueRepetition.lean
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import Mathlib
import OAI.Computability.VertexCover.Analysis.BaseReductionCoherent
namespace OAI
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namespace VertexCover.LabelCover
open UniqueGames.Foundations.Games
noncomputable section
def occurrenceLaw (Φ : LabelCover) : FiniteDistribution (Fin Φ.M) := by
letI : Nonempty (Fin Φ.M) := ⟨⟨0, Φ.M_pos⟩⟩
exact FiniteDistribution.uniform (Fin Φ.M)
def questionProjection (Φ : LabelCover) (x : Fin Φ.u) (y : Fin Φ.v) (a : Fin Φ.qU) : Fin Φ.qV :=
if h : ∃ e, Φ.left e = x ∧ Φ.right e = y then Φ.projection h.choose a
else ⟨0, Φ.qV_pos⟩
theorem questionProjection_at (Φ : LabelCover) (hc : Φ.ParallelCoherent)
(e : Fin Φ.M) (a : Fin Φ.qU) :
Φ.questionProjection (Φ.left e) (Φ.right e) a = Φ.projection e a := by
unfold questionProjection
split
· rename_i h
exact congrFun (hc h.choose e h.choose_spec.1 h.choose_spec.2) a
· rename_i h
exact False.elim (h ⟨e, rfl, rfl⟩)
def asGame (Φ : LabelCover) : Game (Fin Φ.u) (Fin Φ.v) (Fin Φ.qU) (Fin Φ.qV) :=
{ questions := Φ.occurrenceLaw.pushforward (fun e => (Φ.left e, Φ.right e))
accepts := fun x y a b => decide (Φ.questionProjection x y a = b) }
theorem asGame_success (Φ : LabelCover) (hc : Φ.ParallelCoherent) (A : Φ.Labeling) :
Φ.asGame.success A = (Φ.satisfiedCount A : ℝ) / Φ.M := by
classical
change (Φ.occurrenceLaw.pushforward (fun e => (Φ.left e, Φ.right e))).probability _ = _
rw [FiniteDistribution.probability_pushforward]
simp only [FiniteDistribution.probability, Game.wins, asGame, questionProjection_at Φ hc,
decide_eq_true_eq]
simp only [occurrenceLaw, FiniteDistribution.uniform, Fintype.card_fin]
change (∑ e, if Φ.Satisfies A e then 1 / (Φ.M : ℝ) else 0) = _
calc
_ = (∑ e, (if Φ.Satisfies A e then 1 else 0 : ℝ)) / Φ.M := by
rw [Finset.sum_div]
apply Finset.sum_congr rfl
intro e he
split_ifs <;> simp
_ = _ := by rw [Finset.sum_boole]; rfl
def asGameValue (Φ : LabelCover) : ℝ := by
letI : Nonempty (Fin Φ.qU) := ⟨⟨0, Φ.qU_pos⟩⟩
letI : Nonempty (Fin Φ.qV) := ⟨⟨0, Φ.qV_pos⟩⟩
exact Φ.asGame.value
theorem asGameValue_eq (Φ : LabelCover) (hc : Φ.ParallelCoherent) : Φ.asGameValue = Φ.value := by
classical
let : Nonempty (Fin Φ.qU) := ⟨⟨0, Φ.qU_pos⟩⟩
let : Nonempty (Fin Φ.qV) := ⟨⟨0, Φ.qV_pos⟩⟩
change Φ.asGame.value = Φ.value
apply le_antisymm
· apply (Φ.asGame.value_le_iff _).mpr
intro A
rw [asGame_success Φ hc A]
exact div_le_div_of_nonneg_right (Nat.cast_le.mpr (Φ.satisfiedCount_le_max A)) (by positivity)
· apply value_le_of_counts
intro A
have hs := Φ.asGame.success_le_value A
rw [asGame_success Φ hc A] at hs
exact (div_le_iff₀ (Nat.cast_pos.mpr Φ.M_pos)).mp hs
def tupleEquiv (a n : ℕ) : (Fin n → Fin a) ≃ Fin (a ^ n) :=
Fintype.equivFinOfCardEq (by simp)
def parallelPower (Φ : LabelCover) (n : ℕ) : LabelCover where
u := Φ.u ^ n
v := Φ.v ^ n
qU := Φ.qU ^ n
qV := Φ.qV ^ n
M := Φ.M ^ n
qU_pos := pow_pos Φ.qU_pos _
qV_pos := pow_pos Φ.qV_pos _
M_pos := pow_pos Φ.M_pos _
left e := tupleEquiv Φ.u n (fun i => Φ.left ((tupleEquiv Φ.M n).symm e i))
right e := tupleEquiv Φ.v n (fun i => Φ.right ((tupleEquiv Φ.M n).symm e i))
projection e a := tupleEquiv Φ.qV n (fun i => Φ.projection ((tupleEquiv Φ.M n).symm e i)
((tupleEquiv Φ.qU n).symm a i))
def repeatLabeling (Φ : LabelCover) (n : ℕ) (A : Φ.Labeling) : (Φ.parallelPower n).Labeling :=
(fun x => tupleEquiv Φ.qU n (fun i => A.1 ((tupleEquiv Φ.u n).symm x i)),
fun y => tupleEquiv Φ.qV n (fun i => A.2 ((tupleEquiv Φ.v n).symm y i)))
theorem repeat_perfect (Φ : LabelCover) (n : ℕ) (A : Φ.Labeling) (hA : ∀ e, Φ.Satisfies A e) :
∀ e, (Φ.parallelPower n).Satisfies (Φ.repeatLabeling n A) e := by
intro e
change tupleEquiv Φ.qV n _ = tupleEquiv Φ.qV n _
apply congrArg (tupleEquiv Φ.qV n)
funext i
simpa only [Satisfies, repeatLabeling, parallelPower, Equiv.symm_apply_apply] using hA ((tupleEquiv Φ.M n).symm e i)
def repeatedStrategy (Φ : LabelCover) (n : ℕ) (A : (Φ.parallelPower n).Labeling) :
Strategy (Fin n → Fin Φ.u) (Fin n → Fin Φ.v) (Fin n → Fin Φ.qU) (Fin n → Fin Φ.qV) :=
(fun x => (tupleEquiv Φ.qU n).symm (A.1 (tupleEquiv Φ.u n x)),
fun y => (tupleEquiv Φ.qV n).symm (A.2 (tupleEquiv Φ.v n y)))
theorem repetition_success_probability (Φ : LabelCover) (hc : Φ.ParallelCoherent) (n : ℕ)
(B : Strategy (Fin n → Fin Φ.u) (Fin n → Fin Φ.v)
(Fin n → Fin Φ.qU) (Fin n → Fin Φ.qV)) :
(Φ.asGame.repetition n).success B = (Φ.occurrenceLaw.iid n).probability
(fun es => decide (∀ i, Φ.projection (es i)
(B.1 (fun j => Φ.left (es j)) i) = B.2 (fun j => Φ.right (es j)) i)) := by
classical
unfold Game.success
change (((Φ.occurrenceLaw.pushforward (fun e => (Φ.left e, Φ.right e))).iid n).transport
(Game.tupleQuestionEquiv n)).probability _ = _
rw [FiniteDistribution.probability_transport, FiniteDistribution.iid_pushforward,
FiniteDistribution.probability_pushforward]
congr 1
funext es
simp only [Game.wins, Game.repetition, Game.tupleQuestionEquiv, asGame,
Equiv.coe_fn_mk, questionProjection_at Φ hc, decide_eq_true_eq]
theorem power_satisfies_iff (Φ : LabelCover) (n : ℕ) (A : (Φ.parallelPower n).Labeling)
(es : Fin n → Fin Φ.M) :
(Φ.parallelPower n).Satisfies A (tupleEquiv Φ.M n es) ↔
∀ i, Φ.projection (es i)
((Φ.repeatedStrategy n A).1 (fun j => Φ.left (es j)) i) =
(Φ.repeatedStrategy n A).2 (fun j => Φ.right (es j)) i := by
simp only [Satisfies, parallelPower, repeatedStrategy, Equiv.symm_apply_apply]
rw [← Equiv.eq_symm_apply]
exact funext_iff
theorem repetition_success (Φ : LabelCover) (hc : Φ.ParallelCoherent) (n : ℕ)
(A : (Φ.parallelPower n).Labeling) :
(Φ.asGame.repetition n).success (Φ.repeatedStrategy n A) =
((Φ.parallelPower n).satisfiedCount A : ℝ) / (Φ.M ^ n : ℕ) := by
classical
let : Nonempty (Fin Φ.M) := ⟨⟨0, Φ.M_pos⟩⟩
rw [repetition_success_probability Φ hc]
have hlaw : Φ.occurrenceLaw.iid n = FiniteDistribution.uniform (Fin n → Fin Φ.M) :=
FiniteDistribution.iid_uniform n
rw [hlaw]
simp only [← power_satisfies_iff Φ n A, FiniteDistribution.probability,
FiniteDistribution.uniform, Fintype.card_fun, Fintype.card_fin, decide_eq_true_eq]
calc
_ = ∑ e : Fin (Φ.M ^ n), if (Φ.parallelPower n).Satisfies A e then
1 / ((Φ.M ^ n : ℕ) : ℝ) else 0 :=
Fintype.sum_equiv (tupleEquiv Φ.M n) _ _ (fun _ => rfl)
_ = (∑ e : Fin (Φ.M ^ n), (if (Φ.parallelPower n).Satisfies A e then 1 else 0 : ℝ)) /
(Φ.M ^ n : ℕ) := by
rw [Finset.sum_div]
apply Finset.sum_congr rfl
intro e he
split_ifs <;> simp
_ = _ := by
have hsum : (∑ e : Fin (Φ.parallelPower n).M,
(@ite ℝ ((Φ.parallelPower n).Satisfies A e) (Classical.propDecidable _) 1 0)) =
((Φ.parallelPower n).satisfiedCount A : ℝ) := by
rw [satisfiedCount, Finset.card_filter, Nat.cast_sum]
apply Finset.sum_congr rfl
intro e he
by_cases h : (Φ.parallelPower n).Satisfies A e <;> simp only [h, ite_true, ite_false, Nat.cast_zero, Nat.cast_one]
exact congrArg (fun x : ℝ => x / ((Φ.M ^ n : ℕ) : ℝ)) hsum
theorem power_value_le_repetition (Φ : LabelCover) (hc : Φ.ParallelCoherent) (n : ℕ) :
(Φ.parallelPower n).value ≤
(letI : Nonempty (Fin Φ.qU) := ⟨⟨0, Φ.qU_pos⟩⟩;
letI : Nonempty (Fin Φ.qV) := ⟨⟨0, Φ.qV_pos⟩⟩;
(Φ.asGame.repetition n).value) := by
classical
let : Nonempty (Fin Φ.qU) := ⟨⟨0, Φ.qU_pos⟩⟩
let : Nonempty (Fin Φ.qV) := ⟨⟨0, Φ.qV_pos⟩⟩
apply value_le_of_counts
intro A
have hs := (Φ.asGame.repetition n).success_le_value (Φ.repeatedStrategy n A)
rw [repetition_success Φ hc] at hs
exact (div_le_iff₀ (Nat.cast_pos.mpr (pow_pos Φ.M_pos n))).mp hs
end
end VertexCover.LabelCover
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end OAI