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Add lean source and binary files (part 59)
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import Mathlib.Algebra.BigOperators.Expect
import Mathlib.Algebra.BigOperators.Fin
import Mathlib.Algebra.BigOperators.Ring.Finset
import Mathlib.Algebra.Order.BigOperators.Expect
import Mathlib.Data.Finset.Max
import Mathlib.Data.Fintype.Pi
import Mathlib.Data.Fintype.Prod
import Mathlib.Basic.Real.Basic
import Mathlib.Logic.Equiv.Prod
import OAI.Computability.BinPacking.Information.GameDecoder
import OAI.Computability.BinPacking.PCP.AlphabetRetraction
namespace OAI
noncomputable section
namespace BinPackingGames.Foundations.PCP.UniformRestriction
open scoped BigOperators
variable {B : Type*} (p : B → Prop)
def restrict (f : B → Bool) : {b // p b} → Bool := fun b => f b.1
variable [DecidablePred p]
def extend (g : {b // p b} → Bool) : B → Bool :=
fun b => if hb : p b then g ⟨b, hb⟩ else false
def canonicalize (f : B → Bool) : B → Bool := extend p (restrict p f)
omit [DecidablePred p] in
@[simp] theorem restrict_apply (f : B → Bool) (b : {b // p b}) :
restrict p f b = f b.1 := rfl
@[simp] theorem extend_apply_of_mem (g : {b // p b} → Bool) (b : B) (hb : p b) :
extend p g b = g ⟨b, hb⟩ := by
simp [extend, hb]
@[simp] theorem extend_apply_of_not_mem (g : {b // p b} → Bool) (b : B)
(hb : ¬ p b) : extend p g b = false := by
simp [extend, hb]
@[simp] theorem restrict_extend (g : {b // p b} → Bool) :
restrict p (extend p g) = g := by
funext b
simp [restrict, extend, b.property]
@[simp] theorem canonicalize_apply_of_mem (f : B → Bool) (b : B) (hb : p b) :
canonicalize p f b = f b := by
simp [canonicalize, hb]
@[simp] theorem canonicalize_apply_of_not_mem (f : B → Bool) (b : B)
(hb : ¬ p b) : canonicalize p f b = false := by
simp [canonicalize, hb]
@[simp] theorem restrict_canonicalize (f : B → Bool) :
restrict p (canonicalize p f) = restrict p f := by
exact restrict_extend p (restrict p f)
@[simp] theorem canonicalize_idempotent (f : B → Bool) :
canonicalize p (canonicalize p f) = canonicalize p f := by
simp only [canonicalize, restrict_extend]
theorem canonicalize_eq_iff (f g : B → Bool) :
canonicalize p f = canonicalize p g ↔ restrict p f = restrict p g := by
constructor
· intro h
simpa only [restrict_canonicalize] using congrArg (restrict p) h
· intro h
exact congrArg (extend p) h
variable [Fintype B] [DecidableEq B]
theorem expect_restrict (h : ({b // p b} → Bool) → ℝ) :
(𝔼 f : B → Bool, h (restrict p f)) = 𝔼 g : {b // p b} → Bool, h g := by
calc
(𝔼 f : B → Bool, h (restrict p f)) =
𝔼 g : ({b // p b} → Bool) × ({b // ¬ p b} → Bool), h g.1 :=
Fintype.expect_equiv (Equiv.piEquivPiSubtypeProd p (fun _ => Bool))
_ _ (fun _ => rfl)
_ = 𝔼 g : {b // p b} → Bool, 𝔼 _k : {b // ¬ p b} → Bool, h g := by
simpa only [Finset.univ_product_univ] using
Finset.expect_product
(Finset.univ : Finset ({b // p b} → Bool))
(Finset.univ : Finset ({b // ¬ p b} → Bool))
(fun g : ({b // p b} → Bool) × ({b // ¬ p b} → Bool) => h g.1)
_ = 𝔼 g : {b // p b} → Bool, h g := by
simp only [Fintype.expect_const]
theorem expect_canonicalize (h : (B → Bool) → ℝ) :
(𝔼 f : B → Bool, h (canonicalize p f)) =
𝔼 g : {b // p b} → Bool, h (extend p g) :=
expect_restrict p (fun g => h (extend p g))
theorem expect_restrict_pair (h : ({b // p b} → Bool) → ({b // p b} → Bool) → ℝ) :
(𝔼 f : B → Bool, 𝔼 g : B → Bool, h (restrict p f) (restrict p g)) =
𝔼 f : {b // p b} → Bool, 𝔼 g : {b // p b} → Bool, h f g := by
calc
_ = 𝔼 f : B → Bool, 𝔼 g : {b // p b} → Bool, h (restrict p f) g := by
apply Finset.expect_congr rfl
intro f _
exact expect_restrict p (h (restrict p f))
_ = _ := expect_restrict p (fun f => 𝔼 g : {b // p b} → Bool, h f g)
end BinPackingGames.Foundations.PCP.UniformRestriction
namespace BinPackingGames.Foundations.PCP.CodeComposition
open scoped BigOperators
open BinPackingGames.Foundations.Hastad
def disagreement (a b : Bool) : ℝ := if a = b then 0 else 1
@[simp] theorem disagreement_self (a : Bool) : disagreement a a = 0 := by
simp [disagreement]
theorem disagreement_nonnegative (a b : Bool) : 0 ≤ disagreement a b := by
cases a <;> cases b <;> norm_num [disagreement]
theorem disagreement_le_one (a b : Bool) : disagreement a b ≤ 1 := by
cases a <;> cases b <;> norm_num [disagreement]
theorem disagreement_comm (a b : Bool) : disagreement a b = disagreement b a := by
simp [disagreement, eq_comm]
theorem disagreement_triangle (a b c : Bool) :
disagreement a c ≤ disagreement a b + disagreement b c := by
cases a <;> cases b <;> cases c <;> norm_num [disagreement]
theorem disagreement_eq_sign (a b : Bool) :
disagreement a b = (1 - bitSign a * bitSign b) / 2 := by
cases a <;> cases b <;> norm_num [disagreement, bitSign]
def relativeDistance {X : Type*} [Fintype X] (f g : X → Bool) : ℝ :=
𝔼 x, disagreement (f x) (g x)
@[simp] theorem relativeDistance_self {X : Type*} [Fintype X] (f : X → Bool) :
relativeDistance f f = 0 := by
simp [relativeDistance]
theorem relativeDistance_nonnegative {X : Type*} [Fintype X] (f g : X → Bool) :
0 ≤ relativeDistance f g :=
Finset.expect_nonneg (fun _ _ => disagreement_nonnegative _ _)
theorem relativeDistance_comm {X : Type*} [Fintype X] (f g : X → Bool) :
relativeDistance f g = relativeDistance g f := by
simp only [relativeDistance, disagreement_comm]
theorem relativeDistance_triangle {X : Type*} [Fintype X] (f g h : X → Bool) :
relativeDistance f h ≤ relativeDistance f g + relativeDistance g h := by
rw [relativeDistance, relativeDistance, relativeDistance,
← Finset.expect_add_distrib]
exact Finset.expect_le_expect (fun _ _ => disagreement_triangle _ _ _)
theorem relativeDistance_eq_sign {X : Type*} [Fintype X] [Nonempty X]
(f g : X → Bool) :
relativeDistance f g = (1 - 𝔼 x, bitSign (f x) * bitSign (g x)) / 2 := by
simp only [relativeDistance, disagreement_eq_sign]
rw [← Finset.expect_div, Finset.expect_sub_distrib]
simp
def codeword {A : Type*} (a : A) : Cube A → Bool := fun x => x a
private def singletonMask {A : Type*} [DecidableEq A] (a : A) : Cube A :=
fun i => decide (i = a)
private theorem walsh_singletonMask {A : Type*} [Fintype A] [DecidableEq A]
(a : A) (x : Cube A) : walsh (singletonMask a) x = bitSign (x a) := by
classical
unfold walsh singletonMask
rw [Finset.prod_eq_single a]
· simp
· intro b _ hba
simp [hba, bitSign]
· simp
private theorem singletonMask_ne {A : Type*} [DecidableEq A] {a b : A} (hab : a ≠ b) :
singletonMask a ≠ singletonMask b := by
intro h
have he := congrFun h a
simp [singletonMask, hab] at he
theorem codeword_distance {A : Type*} [Fintype A] [DecidableEq A]
{a b : A} (hab : a ≠ b) :
relativeDistance (codeword a) (codeword b) = 1 / 2 := by
rw [relativeDistance_eq_sign]
have horth := walsh_orthogonality (singletonMask a) (singletonMask b)
rw [ite_eq_right (singletonMask_ne hab)] at horth
simp_rw [walsh_singletonMask] at horth
change (1 - 𝔼 x : Cube A, bitSign (x a) * bitSign (x b)) / 2 = 1 / 2
rw [horth]
norm_num
theorem exists_nearest {A : Type*} [Fintype A] [DecidableEq A] [Nonempty A]
(f : Cube A → Bool) :
∃ a : A, ∀ b : A, relativeDistance f (codeword a) ≤ relativeDistance f (codeword b) := by
classical
obtain ⟨a, _, ha⟩ := Finset.exists_min_image Finset.univ
(fun a : A => relativeDistance f (codeword a)) Finset.univ_nonempty
exact ⟨a, fun b => ha b (Finset.mem_univ b)⟩
def nearest {A : Type*} [Fintype A] [DecidableEq A] [Nonempty A] (f : Cube A → Bool) : A :=
Classical.choose (exists_nearest f)
theorem nearest_minimal {A : Type*} [Fintype A] [DecidableEq A] [Nonempty A]
(f : Cube A → Bool) (a : A) :
relativeDistance f (codeword (nearest f)) ≤ relativeDistance f (codeword a) :=
Classical.choose_spec (exists_nearest f) a
theorem distance_from_other_codeword {A : Type*} [Fintype A] [DecidableEq A]
[Nonempty A] (f : Cube A → Bool) {a : A} (ha : a ≠ nearest f) :
1 / 4 ≤ relativeDistance f (codeword a) := by
have htri := relativeDistance_triangle (codeword (nearest f)) f (codeword a)
rw [codeword_distance (Ne.symm ha), relativeDistance_comm (codeword (nearest f)) f] at htri
have hmin := nearest_minimal f a
linarith
def pairWord {X : Type*} (left right : X → Bool) : Bool × X → Bool :=
fun p => if p.1 then right p.2 else left p.2
theorem pairWord_distance {X : Type*} [Fintype X] [Nonempty X]
(left right left' right' : X → Bool) :
relativeDistance (pairWord left right) (pairWord left' right') =
(relativeDistance left left' + relativeDistance right right') / 2 := by
classical
simp [relativeDistance, Fintype.expect_eq_sum_div_card, Fintype.card_prod,
Fintype.sum_prod_type, pairWord]
ring
theorem rejected_pair_far {A : Type*} [Fintype A] [DecidableEq A] [Nonempty A]
(accepts : A → A → Bool) (left right : Cube A → Bool)
(hbad : accepts (nearest left) (nearest right) = false)
(a b : A) (hgood : accepts a b = true) :
1 / 8 ≤ relativeDistance (pairWord left right)
(pairWord (codeword a) (codeword b)) := by
rw [pairWord_distance]
have hleft := relativeDistance_nonnegative left (codeword a)
have hright := relativeDistance_nonnegative right (codeword b)
by_cases ha : a = nearest left
· have hb : b ≠ nearest right := by
intro hb
rw [ha, hb, hbad] at hgood
cases hgood
have hsep := distance_from_other_codeword right hb
linarith
· have hsep := distance_from_other_codeword left ha
linarith
end BinPackingGames.Foundations.PCP.CodeComposition
namespace BinPackingGames.Foundations.PCP.AssignmentTester
open BinPackingGames.Foundations.Hastad
open scoped BigOperators
open Finset
variable {A : Type*} [Fintype A] [DecidableEq A]
def truth (b : Bool) : ℝ := if b then 1 else 0
def disagree (a b : Bool) : ℝ := if a = b then 0 else 1
theorem truth_nonneg (b : Bool) : 0 ≤ truth b := by cases b <;> norm_num [truth]
theorem disagree_nonneg (a b : Bool) : 0 ≤ disagree a b := by
cases a <;> cases b <;> norm_num [disagree]
theorem disagree_eq (a b : Bool) :
disagree a b = (1 - bitSign a * bitSign b) / 2 := by
cases a <;> cases b <;> norm_num [disagree, bitSign]
theorem disagree_xor_le (a b c d : Bool) :
disagree (a ^^ b) (c ^^ d) ≤ disagree a c + disagree b d := by
cases a <;> cases b <;> cases c <;> cases d <;> norm_num [disagree]
def parity (s f : Cube A) : Bool :=
decide (Odd ((Finset.univ.filter fun a => s a && f a = true).card))
theorem bitSign_parity (s f : Cube A) : bitSign (parity s f) = walsh s f := by
have hw : walsh s f = (-1 : ℝ) ^
(Finset.univ.filter fun a => s a && f a = true).card := by
simp [walsh, bitSign, Finset.prod_ite]
rw [hw]
simpa [parity, bitSign] using
(sign_power_parity true (Finset.univ.filter fun a => s a && f a = true).card).symm
theorem bitSign_injective : Function.Injective bitSign := by
intro a b h
cases a <;> cases b <;> simp_all [bitSign] <;> linarith
theorem parity_xor (s f g : Cube A) :
parity s (cubeXor f g) = (parity s f ^^ parity s g) := by
apply bitSign_injective
rw [bitSign_parity, bitSign_xor, bitSign_parity, bitSign_parity, walsh_xor]
omit [Fintype A] [DecidableEq A] in
theorem cubeXor_comm (f g : Cube A) : cubeXor f g = cubeXor g f := by
funext a
simp [cubeXor, Bool.xor_comm]
omit [Fintype A] [DecidableEq A] in
@[simp] theorem cubeXor_right_twice (f g : Cube A) :
cubeXor (cubeXor f g) g = f := by
funext a
change ((f a ^^ g a) ^^ g a) = f a
cases f a <;> cases g a <;> rfl
theorem expect_cubeXor (F : Cube A → ℝ) (g : Cube A) :
(𝔼 f, F (cubeXor f g)) = 𝔼 f, F f := by
rw [Fintype.expect_eq_sum_div_card, Fintype.expect_eq_sum_div_card]
congr 1
refine Finset.sum_bij (fun f _ => cubeXor f g) ?_ ?_ ?_ ?_
· intro f _
exact Finset.mem_univ _
· intro f _ h _ heq
have hh := congrArg (fun x => cubeXor x g) heq
simpa only [cubeXor_right_twice] using hh
· intro f _
exact ⟨cubeXor f g, Finset.mem_univ _, cubeXor_right_twice f g⟩
· intro f _
rfl
def distance {K : Type*} [Fintype K] (f g : K → Bool) : ℝ :=
𝔼 k, disagree (f k) (g k)
theorem distance_nonneg {K : Type*} [Fintype K] (f g : K → Bool) :
0 ≤ distance f g := by
apply Finset.expect_nonneg
intro k _
exact disagree_nonneg _ _
theorem distance_parity (F : Cube A → Bool) (s : Cube A) :
distance F (parity s) = (1 - coefficient (fun f => bitSign (F f)) s) / 2 := by
unfold distance
simp_rw [disagree_eq, bitSign_parity, div_eq_mul_inv,
← Finset.expect_mul, Finset.expect_sub_distrib]
simp only [Fintype.expect_const]
rfl
def blrReject (F : Cube A → Bool) : ℝ :=
𝔼 f, 𝔼 g, disagree (F f ^^ F g) (F (cubeXor f g))
theorem blrReject_nonneg (F : Cube A → Bool) : 0 ≤ blrReject F := by
apply Finset.expect_nonneg
intro f _
apply Finset.expect_nonneg
intro g _
exact disagree_nonneg _ _
theorem blr_correlation (F : Cube A → Bool) :
(𝔼 f, 𝔼 g, bitSign (F f) * bitSign (F g) * bitSign (F (cubeXor f g))) =
∑ s, coefficient (fun f => bitSign (F f)) s ^ 3 := by
simp_rw [mul_assoc, ← Finset.mul_expect]
conv_lhs =>
enter [2, f, 2, 2, g, 2, 1]
rw [cubeXor_comm]
simp_rw [walsh_autocorrelation, Finset.mul_sum]
rw [Finset.expect_sum_comm]
apply Finset.sum_congr rfl
intro s _
have heq (f : Cube A) : bitSign (F f) *
(coefficient (fun f => bitSign (F f)) s ^ 2 * walsh s f) =
coefficient (fun f => bitSign (F f)) s ^ 2 * (bitSign (F f) * walsh s f) := by ring
simp_rw [heq, ← Finset.mul_expect]
change coefficient (fun f => bitSign (F f)) s ^ 2 *
coefficient (fun f => bitSign (F f)) s = _
ring
theorem blrReject_fourier (F : Cube A → Bool) :
blrReject F = (1 - ∑ s, coefficient (fun f => bitSign (F f)) s ^ 3) / 2 := by
unfold blrReject
simp_rw [disagree_eq, bitSign_xor, div_eq_mul_inv,
← Finset.expect_mul, Finset.expect_sub_distrib]
simp only [Fintype.expect_const]
rw [blr_correlation]
theorem blr_near_parity (F : Cube A → Bool) :
∃ s : Cube A, distance F (parity s) ≤ blrReject F := by
classical
let c := coefficient (fun f => bitSign (F f))
have hmass : (∑ s, c s ^ 2) = 1 := sign_parseval F
have hlarge : ∃ s, (∑ t, c t ^ 3) ≤ c s := by
by_contra hn
push Not at hn
have hpos : ∃ s, 0 < c s ^ 2 := by
by_contra hh
push Not at hh
have hz := Finset.sum_nonpos (s := Finset.univ) (fun s _ => hh s)
linarith
obtain ⟨s₀, hs₀⟩ := hpos
have hle (s : Cube A) (_ : s ∈ Finset.univ) :
c s ^ 3 ≤ (∑ t, c t ^ 3) * c s ^ 2 := by
have h := mul_le_mul_of_nonneg_right (hn s).le (sq_nonneg (c s))
nlinarith
have hlt : c s₀ ^ 3 < (∑ t, c t ^ 3) * c s₀ ^ 2 := by
have h := mul_lt_mul_of_pos_right (hn s₀) hs₀
nlinarith
have hsum := Finset.sum_lt_sum hle ⟨s₀, Finset.mem_univ _, hlt⟩
rw [← Finset.mul_sum, hmass, mul_one] at hsum
exact (lt_irrefl _ hsum)
obtain ⟨s, hs⟩ := hlarge
refine ⟨s, ?_⟩
rw [distance_parity, blrReject_fourier]
dsimp [c] at hs
linarith
def selfCorrect (F : Cube A → Bool) (x r : Cube A) : Bool :=
F r ^^ F (cubeXor r x)
theorem parity_selfCorrect (s x r : Cube A) :
(parity s r ^^ parity s (cubeXor r x)) = parity s x := by
rw [parity_xor]
cases parity s r <;> cases parity s x <;> rfl
theorem selfCorrect_error (F : Cube A → Bool) (s x : Cube A) :
(𝔼 r, disagree (selfCorrect F x r) (parity s x)) ≤ 2 * distance F (parity s) := by
have hle (r : Cube A) :
disagree (selfCorrect F x r) (parity s x) ≤
disagree (F r) (parity s r) +
disagree (F (cubeXor r x)) (parity s (cubeXor r x)) := by
rw [← parity_selfCorrect s x r]
exact disagree_xor_le _ _ _ _
have h := Finset.expect_le_expect (s := Finset.univ) (fun r _ => hle r)
rw [Finset.expect_add_distrib,
expect_cubeXor (fun r => disagree (F r) (parity s r)) x] at h
change _ ≤ distance F (parity s) + distance F (parity s) at h
linarith
def singleMask (i : A) : Cube A := fun j => decide (j = i)
def flipAt (i : A) (f : Cube A) : Cube A :=
fun j => if j = i then !(f j) else f j
omit [Fintype A] in
@[simp] theorem flipAt_twice (i : A) (f : Cube A) : flipAt i (flipAt i f) = f := by
funext j
by_cases h : j = i <;> simp [flipAt, h]
omit [Fintype A] in
theorem flipAt_eq_xor (i : A) (f : Cube A) : flipAt i f = cubeXor f (singleMask i) := by
funext j
by_cases h : j = i <;> simp [flipAt, cubeXor, singleMask, h]
theorem expect_flipAt (F : Cube A → ℝ) (i : A) :
(𝔼 f, F (flipAt i f)) = 𝔼 f, F f := by
simp_rw [flipAt_eq_xor]
exact expect_cubeXor F _
theorem walsh_singleMask (s : Cube A) (i : A) :
walsh s (singleMask i) = bitSign (s i) := by
unfold walsh
rw [Finset.prod_eq_single i]
· simp [singleMask]
· intro j _ hj
simp [singleMask, hj, bitSign]
· intro h
exact False.elim (h (Finset.mem_univ _))
theorem parity_singleMask (s : Cube A) (i : A) : parity s (singleMask i) = s i := by
apply bitSign_injective
rw [bitSign_parity, walsh_singleMask]
theorem parity_flipAt (s : Cube A) (i : A) (f : Cube A) (hs : s i = true) :
parity s (flipAt i f) = !(parity s f) := by
rw [flipAt_eq_xor, parity_xor, parity_singleMask, hs]
cases parity s f <;> rfl
def cubeAnd (f g : Cube A) : Cube A := fun a => f a && g a
def andLawFailure (s f g : Cube A) : Bool :=
parity s (cubeAnd f g) ^^ (parity s f && parity s g)
theorem andLawFailure_flipAt_second (s : Cube A) (i : A) (f g : Cube A)
(hi : s i = true) :
andLawFailure s f (flipAt i g) =
(andLawFailure s f g ^^ (parity s f ^^ f i)) := by
have hAnd : cubeAnd f (flipAt i g) =
(if f i then flipAt i (cubeAnd f g) else cubeAnd f g) := by
funext a
by_cases ha : a = i
· subst a
cases hfi : f i <;> simp [cubeAnd, flipAt, hfi]
· cases f i <;> simp [cubeAnd, flipAt, ha]
have hg := parity_flipAt s i g hi
have hfg := parity_flipAt s i (cubeAnd f g) hi
cases hfi : f i <;> cases hf : parity s f <;>
cases hg₀ : parity s g <;> cases ha : parity s (cubeAnd f g) <;>
simp [andLawFailure, hAnd, hg, hfg, hfi, hf, hg₀, ha]
private theorem four_truth_lower (e₀ e₁ d : Bool) :
(1 : ℝ) ≤ truth e₀ + truth (e₀ ^^ d) + truth e₁ + truth (e₁ ^^ (!d)) := by
cases e₀ <;> cases e₁ <;> cases d <;> norm_num [truth]
theorem parity_and_rejection (s : Cube A) (i j : A)
(hi : s i = true) (hj : s j = true) (hij : i ≠ j) :
(1 : ℝ) / 4 ≤ 𝔼 f, 𝔼 g, truth (andLawFailure s f g) := by
have hpoint (f g : Cube A) : (1 : ℝ) ≤
truth (andLawFailure s f g) + truth (andLawFailure s f (flipAt i g)) +
truth (andLawFailure s (flipAt j f) g) +
truth (andLawFailure s (flipAt j f) (flipAt i g)) := by
rw [andLawFailure_flipAt_second s i f g hi,
andLawFailure_flipAt_second s i (flipAt j f) g hi]
have hD : (parity s (flipAt j f) ^^ (flipAt j f) i) =
!(parity s f ^^ f i) := by
rw [parity_flipAt s j f hj]
simp only [flipAt, ite_eq_right hij]
cases parity s f <;> cases f i <;> simp
rw [hD]
exact four_truth_lower _ _ _
have havg := Finset.expect_le_expect (s := Finset.univ) (fun f _ =>
Finset.expect_le_expect (s := Finset.univ) (fun g _ => hpoint f g))
simp only [Finset.expect_add_distrib, Fintype.expect_const] at havg
have hinner (f : Cube A) :
(𝔼 g, truth (andLawFailure s f (flipAt i g))) =
𝔼 g, truth (andLawFailure s f g) :=
expect_flipAt (fun g => truth (andLawFailure s f g)) i
have houter : (𝔼 f, 𝔼 g, truth (andLawFailure s (flipAt j f) g)) =
𝔼 f, 𝔼 g, truth (andLawFailure s f g) :=
expect_flipAt (fun f => 𝔼 g, truth (andLawFailure s f g)) j
simp only [hinner, houter] at havg
linarith
theorem truth_xor (a b : Bool) : truth (a ^^ b) = disagree a b := by
cases a <;> cases b <;> norm_num [truth, disagree]
theorem disagree_triangle (a b c : Bool) :
disagree a c ≤ disagree a b + disagree b c := by
cases a <;> cases b <;> cases c <;> norm_num [disagree]
theorem and_disagree_transfer (p₀ p₁ p₂ q₀ q₁ q₂ : Bool) :
disagree p₀ (p₁ && p₂) ≤ disagree q₀ (q₁ && q₂) +
disagree q₀ p₀ + disagree q₁ p₁ + disagree q₂ p₂ := by
cases p₀ <;> cases p₁ <;> cases p₂ <;>
cases q₀ <;> cases q₁ <;> cases q₂ <;> norm_num [disagree]
def andReject (F : Cube A → Bool) : ℝ :=
𝔼 f, 𝔼 g, 𝔼 r₀, 𝔼 r₁, 𝔼 r₂,
disagree (selfCorrect F (cubeAnd f g) r₀)
(selfCorrect F f r₁ && selfCorrect F g r₂)
def unitReject (F : Cube A → Bool) : ℝ :=
𝔼 r, disagree (selfCorrect F (fun _ => true) r) true
variable {K : Type*} [Fintype K] [Nonempty K]
def inputReject (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool) : ℝ :=
𝔼 k, 𝔼 r, disagree (σ k) (selfCorrect F (fun a => label a k) r)
def testerReject (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool) : ℝ :=
(blrReject F + andReject F + unitReject F + inputReject label σ F) / 4
theorem andReject_nonneg (F : Cube A → Bool) : 0 ≤ andReject F := by
apply Finset.expect_nonneg
intro f _
apply Finset.expect_nonneg
intro g _
apply Finset.expect_nonneg
intro r₀ _
apply Finset.expect_nonneg
intro r₁ _
apply Finset.expect_nonneg
intro r₂ _
exact disagree_nonneg _ _
theorem unitReject_nonneg (F : Cube A → Bool) : 0 ≤ unitReject F := by
apply Finset.expect_nonneg
intro r _
exact disagree_nonneg _ _
omit [Nonempty K] in
theorem inputReject_nonneg (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool) :
0 ≤ inputReject label σ F := by
apply Finset.expect_nonneg
intro k _
apply Finset.expect_nonneg
intro r _
exact disagree_nonneg _ _
theorem andReject_transfer (F : Cube A → Bool) (s : Cube A) :
(𝔼 f, 𝔼 g, truth (andLawFailure s f g)) ≤
andReject F + 6 * distance F (parity s) := by
have hlocal (f g : Cube A) : truth (andLawFailure s f g) ≤
(𝔼 r₀, 𝔼 r₁, 𝔼 r₂,
disagree (selfCorrect F (cubeAnd f g) r₀)
(selfCorrect F f r₁ && selfCorrect F g r₂)) +
6 * distance F (parity s) := by
have hp (r₀ r₁ r₂ : Cube A) := and_disagree_transfer
(parity s (cubeAnd f g)) (parity s f) (parity s g)
(selfCorrect F (cubeAnd f g) r₀) (selfCorrect F f r₁) (selfCorrect F g r₂)
have havg := Finset.expect_le_expect (s := Finset.univ) (fun r₀ _ =>
Finset.expect_le_expect (s := Finset.univ) (fun r₁ _ =>
Finset.expect_le_expect (s := Finset.univ) (fun r₂ _ => hp r₀ r₁ r₂)))
simp only [Finset.expect_add_distrib, Fintype.expect_const] at havg
have h₀ := selfCorrect_error F s (cubeAnd f g)
have h₁ := selfCorrect_error F s f
have h₂ := selfCorrect_error F s g
rw [andLawFailure, truth_xor]
linarith
have h := Finset.expect_le_expect (s := Finset.univ) (fun f _ =>
Finset.expect_le_expect (s := Finset.univ) (fun g _ => hlocal f g))
simpa only [Finset.expect_add_distrib, Fintype.expect_const, andReject] using h
theorem parity_zero (f : Cube A) : parity (fun _ => false) f = false := by
apply bitSign_injective
rw [bitSign_parity]
simp [walsh, bitSign]
theorem unitReject_zero_parity (F : Cube A → Bool) :
1 - 2 * distance F (parity (fun _ => false)) ≤ unitReject F := by
have herr := selfCorrect_error F (fun _ => false) (fun _ => true)
simp only [parity_zero] at herr
have heq : unitReject F +
(𝔼 r, disagree (selfCorrect F (fun _ => true) r) false) = 1 := by
unfold unitReject
rw [← Finset.expect_add_distrib]
have hp (b : Bool) : disagree b true + disagree b false = 1 := by
cases b <;> norm_num [disagree]
simp only [hp, Fintype.expect_const]
linarith
theorem parity_singleMask_eval (a : A) (f : Cube A) :
parity (singleMask a) f = f a := by
apply bitSign_injective
rw [bitSign_parity, walsh_symm, walsh_singleMask]
theorem inputReject_transfer (label : A → K → Bool) (σ : K → Bool)
(F : Cube A → Bool) (a : A) :
distance σ (label a) ≤ inputReject label σ F +
2 * distance F (parity (singleMask a)) := by
have hlocal (k : K) : disagree (σ k) (label a k) ≤
(𝔼 r, disagree (σ k) (selfCorrect F (fun a => label a k) r)) +
2 * distance F (parity (singleMask a)) := by
have hp (r : Cube A) := disagree_triangle (σ k)
(selfCorrect F (fun a => label a k) r) (label a k)
have havg := Finset.expect_le_expect (s := Finset.univ) (fun r _ => hp r)
simp only [Fintype.expect_const, Finset.expect_add_distrib] at havg
have herr := selfCorrect_error F (singleMask a) (fun a => label a k)
simp only [parity_singleMask_eval] at herr
linarith
have h := Finset.expect_le_expect (s := Finset.univ) (fun k _ => hlocal k)
simpa only [Finset.expect_add_distrib, Fintype.expect_const, inputReject, distance] using h
theorem tester_proximity_soundness (label : A → K → Bool) (σ : K → Bool)
(F : Cube A → Bool) {δ : ℝ} (hδ : 0 < δ) (hδ' : δ ≤ 1 / 4)
(hfar : ∀ a, δ ≤ distance σ (label a)) :
δ / 256 ≤ testerReject label σ F := by
have hblr := blrReject_nonneg F
have hand := andReject_nonneg F
have hunit := unitReject_nonneg F
have hin := inputReject_nonneg label σ F
by_cases hb : δ / 64 ≤ blrReject F
· unfold testerReject
linarith
obtain ⟨s, hs⟩ := blr_near_parity F
by_cases hz : s = fun _ => false
· subst s
have hu := unitReject_zero_parity F
unfold testerReject
linarith
have hsome : ∃ i, s i = true := by
by_contra hh
push Not at hh
apply hz
funext i
have h := hh i
cases hi : s i <;> simp_all
obtain ⟨i, hi⟩ := hsome
by_cases htwo : ∃ j, i ≠ j ∧ s j = true
· obtain ⟨j, hij, hj⟩ := htwo
have ha := parity_and_rejection s i j hi hj hij
have ht := andReject_transfer F s
unfold testerReject
linarith
· have heq : s = singleMask i := by
funext j
by_cases hji : j = i
· subst j
simp [singleMask, hi]
· have hj : s j = false := by
cases hv : s j
· rfl
· exact False.elim (htwo ⟨j, Ne.symm hji, hv⟩)
simp [singleMask, hji, hj]
subst s
have ht := inputReject_transfer label σ F i
have hf := hfar i
unfold testerReject
linarith
omit [Fintype A] [DecidableEq A] in
theorem selfCorrect_dictator (a : A) (x r : Cube A) :
selfCorrect (fun f => f a) x r = x a := by
change (r a ^^ (r a ^^ x a)) = x a
cases r a <;> cases x a <;> rfl
omit [Nonempty K] in
theorem tester_perfect_completeness (label : A → K → Bool) (a : A) :
testerReject label (label a) (fun f => f a) = 0 := by
have hb : blrReject (fun f : Cube A => f a) = 0 := by
simp [blrReject, cubeXor, disagree]
have ha : andReject (fun f : Cube A => f a) = 0 := by
simp [andReject, selfCorrect_dictator, cubeAnd, disagree]
have hu : unitReject (fun f : Cube A => f a) = 0 := by
simp [unitReject, selfCorrect_dictator, disagree]
have hi : inputReject label (label a) (fun f => f a) = 0 := by
simp [inputReject, selfCorrect_dictator, disagree]
simp [testerReject, hb, ha, hu, hi]
def eventQueries (label : A → K → Bool) (kind : Fin 4) (k : K)
(f g r₀ r₁ r₂ : Cube A) (slot : Fin 6) : K ⊕ Cube A :=
if kind = 0 then
if slot = 0 then .inr f else if slot = 1 then .inr g else .inr (cubeXor f g)
else if kind = 1 then
if slot = 0 then .inr r₀ else
if slot = 1 then .inr (cubeXor r₀ (cubeAnd f g)) else
if slot = 2 then .inr r₁ else
if slot = 3 then .inr (cubeXor r₁ f) else
if slot = 4 then .inr r₂ else .inr (cubeXor r₂ g)
else if kind = 2 then
if slot = 0 then .inr r₀ else .inr (cubeXor r₀ (fun _ => true))
else
if slot = 0 then .inl k else
if slot = 1 then .inr r₀ else .inr (cubeXor r₀ (fun a => label a k))
def eventAccepts (kind : Fin 4) (b : Fin 6 → Bool) : Bool :=
if kind = 0 then decide ((b 0 ^^ b 1) = b 2)
else if kind = 1 then decide ((b 0 ^^ b 1) = ((b 2 ^^ b 3) && (b 4 ^^ b 5)))
else if kind = 2 then (b 0 ^^ b 1)
else decide (b 0 = (b 1 ^^ b 2))
def oracleAnswer (σ : K → Bool) (F : Cube A → Bool) : K ⊕ Cube A → Bool :=
Sum.elim σ F
def eventReject (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool)
(kind : Fin 4) (k : K) (f g r₀ r₁ r₂ : Cube A) : ℝ :=
truth (!(eventAccepts kind (fun slot =>
oracleAnswer σ F (eventQueries label kind k f g r₀ r₁ r₂ slot))))
theorem truth_not_decide_eq (a b : Bool) : truth (!(decide (a = b))) = disagree a b := by
cases a <;> cases b <;> norm_num [truth, disagree]
omit [Fintype A] [DecidableEq A] [Fintype K] [Nonempty K] in
theorem eventReject_blr (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool)
(k : K) (f g r₀ r₁ r₂ : Cube A) :
eventReject label σ F 0 k f g r₀ r₁ r₂ =
disagree (F f ^^ F g) (F (cubeXor f g)) := by
simp [eventReject, eventAccepts, eventQueries, oracleAnswer, truth_not_decide_eq]
omit [Fintype A] [DecidableEq A] [Fintype K] [Nonempty K] in
theorem eventReject_and (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool)
(k : K) (f g r₀ r₁ r₂ : Cube A) :
eventReject label σ F 1 k f g r₀ r₁ r₂ =
disagree (selfCorrect F (cubeAnd f g) r₀)
(selfCorrect F f r₁ && selfCorrect F g r₂) := by
simp [eventReject, eventAccepts, eventQueries, oracleAnswer,
truth_not_decide_eq, selfCorrect]
omit [Fintype A] [DecidableEq A] [Fintype K] [Nonempty K] in
theorem eventReject_unit (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool)
(k : K) (f g r₀ r₁ r₂ : Cube A) :
eventReject label σ F 2 k f g r₀ r₁ r₂ =
disagree (selfCorrect F (fun _ => true) r₀) true := by
simp only [eventReject, eventAccepts, eventQueries, oracleAnswer]
norm_num
change truth (!(selfCorrect F (fun _ => true) r₀)) =
disagree (selfCorrect F (fun _ => true) r₀) true
cases selfCorrect F (fun _ => true) r₀ <;> norm_num [truth, disagree]
omit [Fintype A] [DecidableEq A] [Fintype K] [Nonempty K] in
theorem eventReject_input (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool)
(k : K) (f g r₀ r₁ r₂ : Cube A) :
eventReject label σ F 3 k f g r₀ r₁ r₂ =
disagree (σ k) (selfCorrect F (fun a => label a k) r₀) := by
simp [eventReject, eventAccepts, eventQueries, oracleAnswer,
truth_not_decide_eq, selfCorrect]
omit [Fintype A] [DecidableEq A] [Fintype K] [Nonempty K] in
theorem event_perfect_completeness (label : A → K → Bool) (a : A)
(kind : Fin 4) (k : K) (f g r₀ r₁ r₂ : Cube A) :
eventAccepts kind (fun slot => oracleAnswer (label a) (fun x => x a)
(eventQueries label kind k f g r₀ r₁ r₂ slot)) = true := by
have hkind : kind = 0 ∨ kind = 1 ∨ kind = 2 ∨ kind = 3 := by omega
have hreject : eventReject label (label a) (fun x => x a) kind k f g r₀ r₁ r₂ = 0 := by
rcases hkind with h | h | h | h <;> subst kind
· simp [eventReject_blr, cubeXor, disagree]
· simp [eventReject_and, selfCorrect_dictator, cubeAnd, disagree]
· simp [eventReject_unit, selfCorrect_dictator, disagree]
· simp [eventReject_input, selfCorrect_dictator, disagree]
unfold eventReject at hreject
cases h : eventAccepts kind (fun slot => oracleAnswer (label a) (fun x => x a)
(eventQueries label kind k f g r₀ r₁ r₂ slot)) <;> simp_all [truth]
def explicitTesterReject (label : A → K → Bool) (σ : K → Bool) (F : Cube A → Bool) : ℝ :=
𝔼 kind : Fin 4, 𝔼 k, 𝔼 f, 𝔼 g, 𝔼 r₀, 𝔼 r₁, 𝔼 r₂,
eventReject label σ F kind k f g r₀ r₁ r₂
theorem explicitTesterReject_eq (label : A → K → Bool) (σ : K → Bool)
(F : Cube A → Bool) : explicitTesterReject label σ F = testerReject label σ F := by
unfold explicitTesterReject
rw [Fintype.expect_eq_sum_div_card]
simp [Fin.sum_univ_succ, eventReject_blr, eventReject_and, eventReject_unit,
eventReject_input, testerReject, blrReject, andReject, unitReject, inputReject, add_assoc]
theorem explicit_proximity_soundness (label : A → K → Bool) (σ : K → Bool)
(F : Cube A → Bool) {δ : ℝ} (hδ : 0 < δ) (hδ' : δ ≤ 1 / 4)
(hfar : ∀ a, δ ≤ distance σ (label a)) :
δ / 256 ≤ explicitTesterReject label σ F := by
rw [explicitTesterReject_eq]
exact tester_proximity_soundness label σ F hδ hδ' hfar
end BinPackingGames.Foundations.PCP.AssignmentTester
namespace BinPackingGames.Foundations.PCP.AlphabetReduction
open BinPackingGames.Foundations.Hastad
open CodeComposition
variable {A : Type*} [Fintype A] [DecidableEq A] [Nonempty A]
abbrev LegalPair (accepts : A → A → Bool) :=
{p : A × A // accepts p.1 p.2 = true}
abbrev InputCoordinate (A : Type*) := Bool × Cube A
def pairEncoding (accepts : A → A → Bool) (p : LegalPair accepts) :
InputCoordinate A → Bool :=
pairWord (codeword p.1.1) (codeword p.1.2)
def edgeTesterReject (accepts : A → A → Bool) (left right : Cube A → Bool)
(F : Cube (LegalPair accepts) → Bool) : ℝ :=
AssignmentTester.explicitTesterReject (pairEncoding accepts) (pairWord left right) F
theorem rejected_edge_tester_bound (accepts : A → A → Bool)
(left right : Cube A → Bool)
(F : Cube (LegalPair accepts) → Bool)
(hbad : accepts (nearest left) (nearest right) = false) :
1 / 2048 ≤ edgeTesterReject accepts left right F := by
have hfar (p : LegalPair accepts) :
(1 / 8 : ℝ) ≤ AssignmentTester.distance (pairWord left right) (pairEncoding accepts p) := by
have h := rejected_pair_far accepts left right hbad p.1.1 p.1.2 p.2
convert h using 1
rfl
have h := AssignmentTester.explicit_proximity_soundness (pairEncoding accepts)
(pairWord left right) F (δ := 1 / 8) (by norm_num) (by norm_num) hfar
norm_num at h
exact h
omit [Nonempty A] in
theorem honest_edge_tester (accepts : A → A → Bool) (a b : A)
(hab : accepts a b = true) :
edgeTesterReject accepts (codeword a) (codeword b)
(fun f => f ⟨(a, b), hab⟩) = 0 := by
unfold edgeTesterReject
rw [AssignmentTester.explicitTesterReject_eq]
exact AssignmentTester.tester_perfect_completeness
(pairEncoding accepts) ⟨(a, b), hab⟩
end BinPackingGames.Foundations.PCP.AlphabetReduction
namespace BinPackingGames.Foundations.PCP.AlphabetGraph
open BinPackingGames.Foundations.Hastad
open scoped BigOperators
abbrev Address (V E A : Type*) := (V × Cube A) ⊕ (E × Cube (A × A))
abbrev LocalEvent (A : Type*) := Fin 4 × AlphabetReduction.InputCoordinate A ×
Cube (A × A) × Cube (A × A) × Cube (A × A) × Cube (A × A) × Cube (A × A)
abbrev Event (E A : Type*) := E × LocalEvent A
variable {V E A : Type*} [Fintype A] [DecidableEq A] [Nonempty A]
abbrev legal (G : ConstraintGraph V E A) (e : E) (p : A × A) : Prop :=
G.accepts e p.1 p.2 = true
instance legalDecidable (G : ConstraintGraph V E A) (e : E) :
DecidablePred (legal G e) :=
fun p => inferInstanceAs (Decidable (G.accepts e p.1 p.2 = true))
def restrictTape (G : ConstraintGraph V E A) (e : E) (f : Cube (A × A)) :
Cube (AlphabetReduction.LegalPair (G.accepts e)) := UniformRestriction.restrict (legal G e) f
def extendTape (G : ConstraintGraph V E A) (e : E)
(f : Cube (AlphabetReduction.LegalPair (G.accepts e))) : Cube (A × A) :=
UniformRestriction.extend (legal G e) f
def globalizeQuery (G : ConstraintGraph V E A) (e : E) :
AlphabetReduction.InputCoordinate A ⊕ Cube (AlphabetReduction.LegalPair (G.accepts e)) → Address V E A
| .inl (side, tape) => .inl ((if side then G.head e else G.tail e), tape)
| .inr tape => .inr (e, extendTape G e tape)
def verifier (G : ConstraintGraph V E A) : QueryIncidence.Verifier (Event E A) (Address V E A) 6 where
query := fun (e, kind, k, f, g, r₀, r₁, r₂) slot =>
globalizeQuery G e (AssignmentTester.eventQueries (AlphabetReduction.pairEncoding (G.accepts e)) kind k
(restrictTape G e f) (restrictTape G e g) (restrictTape G e r₀)
(restrictTape G e r₁) (restrictTape G e r₂) slot)
accepts := fun (_, kind, _, _, _, _, _, _) b => AssignmentTester.eventAccepts kind b
def vertexBlock (assignment : Address V E A → Bool) (v : V) : Cube A → Bool :=
fun tape => assignment (.inl (v, tape))
def edgeOracle (G : ConstraintGraph V E A) (assignment : Address V E A → Bool) (e : E) :
Cube (AlphabetReduction.LegalPair (G.accepts e)) → Bool :=
fun tape => assignment (.inr (e, extendTape G e tape))
omit [Fintype A] [DecidableEq A] [Nonempty A] in
theorem oracleAnswer_globalize (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) (e : E)
(x : AlphabetReduction.InputCoordinate A ⊕ Cube (AlphabetReduction.LegalPair (G.accepts e))) :
assignment (globalizeQuery G e x) =
AssignmentTester.oracleAnswer
(CodeComposition.pairWord (vertexBlock assignment (G.tail e))
(vertexBlock assignment (G.head e))) (edgeOracle G assignment e) x := by
rcases x with ⟨side, tape⟩ | tape
· cases side <;> rfl
· rfl
omit [Fintype A] [DecidableEq A] [Nonempty A] in
theorem response_eq_local (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) (e : E) (kind : Fin 4)
(k : AlphabetReduction.InputCoordinate A) (f g r₀ r₁ r₂ : Cube (A × A)) :
QueryIncidence.response (verifier G) assignment (e, kind, k, f, g, r₀, r₁, r₂) =
fun slot => AssignmentTester.oracleAnswer
(CodeComposition.pairWord (vertexBlock assignment (G.tail e))
(vertexBlock assignment (G.head e))) (edgeOracle G assignment e)
(AssignmentTester.eventQueries (AlphabetReduction.pairEncoding (G.accepts e)) kind k
(restrictTape G e f) (restrictTape G e g) (restrictTape G e r₀)
(restrictTape G e r₁) (restrictTape G e r₂) slot) := by
funext slot
exact oracleAnswer_globalize G assignment e _
def eventReject (G : ConstraintGraph V E A) (assignment : Address V E A → Bool)
(event : Event E A) : ℝ :=
AssignmentTester.truth (!((verifier G).accepts event (QueryIncidence.response (verifier G) assignment event)))
omit [Fintype A] [DecidableEq A] [Nonempty A] in
theorem eventReject_eq_local (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) (e : E) (kind : Fin 4)
(k : AlphabetReduction.InputCoordinate A) (f g r₀ r₁ r₂ : Cube (A × A)) :
eventReject G assignment (e, kind, k, f, g, r₀, r₁, r₂) =
AssignmentTester.eventReject (AlphabetReduction.pairEncoding (G.accepts e))
(CodeComposition.pairWord (vertexBlock assignment (G.tail e))
(vertexBlock assignment (G.head e))) (edgeOracle G assignment e) kind k
(restrictTape G e f) (restrictTape G e g) (restrictTape G e r₀)
(restrictTape G e r₁) (restrictTape G e r₂) := by
unfold eventReject
rw [response_eq_local]
rfl
theorem expect_prod {I J : Type*} [Fintype I] [Fintype J] (f : I × J → ℝ) :
(𝔼 z : I × J, f z) = 𝔼 i : I, 𝔼 j : J, f (i, j) := by
simpa only [Finset.univ_product_univ] using
Finset.expect_product (Finset.univ : Finset I) (Finset.univ : Finset J) f
def localAverage (G : ConstraintGraph V E A) (assignment : Address V E A → Bool)
(e : E) : ℝ := 𝔼 sample : LocalEvent A, eventReject G assignment (e, sample)
theorem expect_restrict_five {B : Type*} [Fintype B] [DecidableEq B]
(p : B → Prop) [DecidablePred p]
(h : ({b // p b} → Bool) → ({b // p b} → Bool) → ({b // p b} → Bool) →
({b // p b} → Bool) → ({b // p b} → Bool) → ℝ) :
(𝔼 f : B → Bool, 𝔼 g : B → Bool, 𝔼 r₀ : B → Bool,
𝔼 r₁ : B → Bool, 𝔼 r₂ : B → Bool,
h (UniformRestriction.restrict p f) (UniformRestriction.restrict p g)
(UniformRestriction.restrict p r₀) (UniformRestriction.restrict p r₁)
(UniformRestriction.restrict p r₂)) =
𝔼 f : {b // p b} → Bool, 𝔼 g : {b // p b} → Bool,
𝔼 r₀ : {b // p b} → Bool, 𝔼 r₁ : {b // p b} → Bool,
𝔼 r₂ : {b // p b} → Bool, h f g r₀ r₁ r₂ := by
rw [UniformRestriction.expect_restrict p
(fun f => 𝔼 g : B → Bool, 𝔼 r₀ : B → Bool, 𝔼 r₁ : B → Bool,
𝔼 r₂ : B → Bool, h f (UniformRestriction.restrict p g)
(UniformRestriction.restrict p r₀) (UniformRestriction.restrict p r₁)
(UniformRestriction.restrict p r₂))]
apply Finset.expect_congr rfl
intro f _
rw [UniformRestriction.expect_restrict p
(fun g => 𝔼 r₀ : B → Bool, 𝔼 r₁ : B → Bool, 𝔼 r₂ : B → Bool,
h f g (UniformRestriction.restrict p r₀) (UniformRestriction.restrict p r₁)
(UniformRestriction.restrict p r₂))]
apply Finset.expect_congr rfl
intro g _
rw [UniformRestriction.expect_restrict p
(fun r₀ => 𝔼 r₁ : B → Bool, 𝔼 r₂ : B → Bool,
h f g r₀ (UniformRestriction.restrict p r₁) (UniformRestriction.restrict p r₂))]
apply Finset.expect_congr rfl
intro r₀ _
rw [UniformRestriction.expect_restrict p
(fun r₁ => 𝔼 r₂ : B → Bool, h f g r₀ r₁ (UniformRestriction.restrict p r₂))]
apply Finset.expect_congr rfl
intro r₁ _
exact UniformRestriction.expect_restrict p (h f g r₀ r₁)
omit [Nonempty A] in
theorem localAverage_eq_tester (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) (e : E) :
localAverage G assignment e = AlphabetReduction.edgeTesterReject (G.accepts e)
(vertexBlock assignment (G.tail e)) (vertexBlock assignment (G.head e))
(edgeOracle G assignment e) := by
unfold localAverage AlphabetReduction.edgeTesterReject AssignmentTester.explicitTesterReject
simp only [LocalEvent, expect_prod, eventReject_eq_local, restrictTape]
apply Finset.expect_congr rfl
intro kind _
apply Finset.expect_congr rfl
intro side _
apply Finset.expect_congr rfl
intro tape _
exact expect_restrict_five (legal G e)
(AssignmentTester.eventReject (AlphabetReduction.pairEncoding (G.accepts e))
(CodeComposition.pairWord (vertexBlock assignment (G.tail e))
(vertexBlock assignment (G.head e))) (edgeOracle G assignment e) kind (side, tape))
def average [Fintype E] (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) : ℝ :=
𝔼 event : Event E A, eventReject G assignment event
omit [Nonempty A] in
theorem average_eq_testers [Fintype E] (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) :
average G assignment = 𝔼 e : E, AlphabetReduction.edgeTesterReject (G.accepts e)
(vertexBlock assignment (G.tail e)) (vertexBlock assignment (G.head e))
(edgeOracle G assignment e) := by
unfold average
rw [expect_prod]
exact Finset.expect_congr rfl (fun e _ => localAverage_eq_tester G assignment e)
def decodedLabeling (assignment : Address V E A → Bool) : V → A :=
fun v => CodeComposition.nearest (vertexBlock assignment v)
theorem local_gap (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) (e : E) :
AssignmentTester.truth (!(G.edgeSatisfied (decodedLabeling assignment) e)) / 2048 ≤
localAverage G assignment e := by
cases h : G.edgeSatisfied (decodedLabeling assignment) e with
| false =>
rw [localAverage_eq_tester]
simpa [AssignmentTester.truth] using
AlphabetReduction.rejected_edge_tester_bound (G.accepts e)
(vertexBlock assignment (G.tail e)) (vertexBlock assignment (G.head e))
(edgeOracle G assignment e) h
| true =>
simp only [Bool.not_true, AssignmentTester.truth, Bool.false_eq_true, ite_false, zero_div]
apply Finset.expect_nonneg
intro sample _
exact AssignmentTester.truth_nonneg _
theorem average_gap [Fintype E] (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) :
(𝔼 e : E, AssignmentTester.truth (!(G.edgeSatisfied (decodedLabeling assignment) e))) / 2048 ≤
average G assignment := by
unfold average
rw [expect_prod, Finset.expect_div]
exact Finset.expect_le_expect (fun e _ => local_gap G assignment e)
theorem expect_rejection_eq_count {I : Type*} [Fintype I] (b : I → Bool) :
(𝔼 i : I, AssignmentTester.truth (!(b i))) =
((Finset.univ.filter (fun i => b i = false)).card : ℝ) / Fintype.card I := by
rw [Fintype.expect_eq_sum_div_card]
congr 1
calc
(∑ i : I, AssignmentTester.truth (!(b i))) = ∑ i : I, if b i = false then (1 : ℝ) else 0 := by
apply Finset.sum_congr rfl
intro i _
cases b i <;> norm_num [AssignmentTester.truth]
_ = _ := Finset.sum_boole _ _
omit [Nonempty A] in
theorem average_eq_count [Fintype E] (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) :
average G assignment = (QueryIncidence.verifierRejectionCount (verifier G) assignment : ℝ) /
Fintype.card (Event E A) :=
expect_rejection_eq_count _
omit [Nonempty A] in
@[simp] theorem card_event [Fintype E] :
Fintype.card (Event E A) = Fintype.card E * Fintype.card (LocalEvent A) :=
Fintype.card_prod _ _
omit [Nonempty A] in
theorem card_localEvent :
Fintype.card (LocalEvent A) =
4 * (2 * 2 ^ Fintype.card A) * (2 ^ (Fintype.card A * Fintype.card A)) ^ 5 := by
simp [LocalEvent, AlphabetReduction.InputCoordinate, Cube, Fintype.card_prod,
pow_succ, Nat.mul_assoc, Nat.mul_comm, Nat.mul_left_comm]
omit [Nonempty A] in
theorem card_address [Fintype V] [Fintype E] :
Fintype.card (Address V E A) =
Fintype.card V * 2 ^ Fintype.card A +
Fintype.card E * 2 ^ (Fintype.card A * Fintype.card A) := by
simp [Address, Cube, Fintype.card_sum, Fintype.card_prod]
theorem rejection_count_bound [Fintype E] (G : ConstraintGraph V E A)
(assignment : Address V E A → Bool) :
Fintype.card (LocalEvent A) * G.rejectionCount (decodedLabeling assignment) ≤
2048 * QueryIncidence.verifierRejectionCount (verifier G) assignment := by
classical
cases isEmpty_or_nonempty E with
| inl empty =>
let := empty
simp [ConstraintGraph.rejectionCount, ConstraintGraph.rejectedDarts]
| inr inhabited =>
let := inhabited
have h := average_gap G assignment
rw [average_eq_count, expect_rejection_eq_count, card_event, Nat.cast_mul,
div_div] at h
have he : (0 : ℝ) < Fintype.card E := by exact_mod_cast Fintype.card_pos
have hl : (0 : ℝ) < Fintype.card (LocalEvent A) := by
exact_mod_cast Fintype.card_pos
have hc := (div_le_div_iff₀ (mul_pos he (by norm_num)) (mul_pos he hl)).mp h
have hc' :
((Fintype.card (LocalEvent A) : ℝ) *
(G.rejectionCount (decodedLabeling assignment) : ℝ)) * Fintype.card E ≤
(2048 * (QueryIncidence.verifierRejectionCount (verifier G) assignment : ℝ)) * Fintype.card E := by
simpa only [ConstraintGraph.rejectionCount, ConstraintGraph.rejectedDarts,
mul_assoc, mul_comm, mul_left_comm] using hc
have result := (mul_le_mul_iff_left₀ he).mp hc'
exact_mod_cast result
def honestAssignment (G : ConstraintGraph V E A) (labeling : V → A) : Address V E A → Bool
| .inl (v, tape) => tape (labeling v)
| .inr (e, tape) => tape (labeling (G.tail e), labeling (G.head e))
omit [Fintype A] [DecidableEq A] [Nonempty A] in
@[simp] theorem honest_vertexBlock (G : ConstraintGraph V E A) (labeling : V → A) (v : V) :
vertexBlock (honestAssignment G labeling) v = CodeComposition.codeword (labeling v) := rfl
omit [Fintype A] [DecidableEq A] [Nonempty A] in
theorem honest_edgeOracle (G : ConstraintGraph V E A) (labeling : V → A) (e : E)
(h : G.edgeSatisfied labeling e = true) :
edgeOracle G (honestAssignment G labeling) e =
fun tape => tape ⟨(labeling (G.tail e), labeling (G.head e)), h⟩ := by
funext tape
exact UniformRestriction.extend_apply_of_mem (legal G e) tape
(labeling (G.tail e), labeling (G.head e)) h
omit [Fintype A] [DecidableEq A] [Nonempty A] in
theorem honest_event (G : ConstraintGraph V E A) (labeling : V → A)
(satisfied : ∀ e, G.edgeSatisfied labeling e = true) (event : Event E A) :
(verifier G).accepts event (QueryIncidence.response (verifier G) (honestAssignment G labeling) event) =
true := by
rcases event with ⟨e, kind, k, f, g, r₀, r₁, r₂⟩
rw [response_eq_local, honest_edgeOracle G labeling e (satisfied e)]
simp only [honest_vertexBlock]
exact AssignmentTester.event_perfect_completeness (AlphabetReduction.pairEncoding (G.accepts e))
⟨(labeling (G.tail e), labeling (G.head e)), satisfied e⟩ kind k
(restrictTape G e f) (restrictTape G e g) (restrictTape G e r₀)
(restrictTape G e r₁) (restrictTape G e r₂)
def graph [DecidableEq V] [DecidableEq E] (G : ConstraintGraph V E A) :
ConstraintGraph (QueryIncidence.Vertex (Event E A) (Address V E A))
(QueryIncidence.Dart (Event E A) 6) (QueryIncidence.Label 6) := QueryIncidence.graph (verifier G) (by omega)
omit [DecidableEq A] [Nonempty A] in
theorem perfect_completeness [DecidableEq V] [DecidableEq E] (G : ConstraintGraph V E A)
(satisfied : G.Satisfiable) : (graph G).Satisfiable := by
obtain ⟨labeling, h⟩ := satisfied
exact QueryIncidence.satisfiable_of_verifier_satisfiable (verifier G) (by omega)
⟨honestAssignment G labeling, honest_event G labeling h⟩
theorem gap_transfer [Fintype E] [DecidableEq V] [DecidableEq E]
(G : ConstraintGraph V E A) (a b : Nat)
(source : ∀ labeling : V → A,
a * Fintype.card E ≤ b * G.rejectionCount labeling)
(labeling : QueryIncidence.Vertex (Event E A) (Address V E A) → QueryIncidence.Label 6) :
a * Fintype.card (QueryIncidence.Dart (Event E A) 6) ≤
(b * 12288) * (graph G).rejectionCount labeling := by
have verifierGap (assignment : Address V E A → Bool) :
a * Fintype.card (Event E A) ≤
(b * 2048) * QueryIncidence.verifierRejectionCount (verifier G) assignment := by
rw [card_event]
calc
a * (Fintype.card E * Fintype.card (LocalEvent A)) =
Fintype.card (LocalEvent A) * (a * Fintype.card E) := by ac_rfl
_ ≤ Fintype.card (LocalEvent A) * (b * G.rejectionCount (decodedLabeling assignment)) :=
Nat.mul_le_mul_left _ (source (decodedLabeling assignment))
_ = b * (Fintype.card (LocalEvent A) * G.rejectionCount (decodedLabeling assignment)) := by
ac_rfl
_ ≤ b * (2048 * QueryIncidence.verifierRejectionCount (verifier G) assignment) :=
Nat.mul_le_mul_left _ (rejection_count_bound G assignment)
_ = (b * 2048) * QueryIncidence.verifierRejectionCount (verifier G) assignment := by ac_rfl
have h := QueryIncidence.gap_transfer (verifier G) (by omega) a (b * 2048) verifierGap labeling
have hcoef : b * 2048 * 6 = b * 12288 := by omega
rw [hcoef] at h
exact h
theorem alphabet_card : Fintype.card (QueryIncidence.Label 6) = 64 := QueryIncidence.six_query_alphabet
end BinPackingGames.Foundations.PCP.AlphabetGraph
namespace BinPackingGames.Foundations.PCP.AlphabetTable.Queries
open BinPackingGames.Foundations.Hastad
abbrev RawQuery (q : Nat) :=
(Bool × Cube (Fin q)) ⊕ Cube (Fin q × Fin q)
abbrev LocalEvent (q : Nat) := AlphabetGraph.LocalEvent (Fin q)
def mask {q : Nat} (P : Fin q → Fin q → Bool) (f : Cube (Fin q × Fin q)) :
Cube (Fin q × Fin q) := fun p => if P p.1 p.2 then f p else false
def xorTape {A : Type*} (f g : Cube A) : Cube A := fun a => f a ^^ g a
def andTape {A : Type*} (f g : Cube A) : Cube A := fun a => f a && g a
def inputPairTape {q : Nat} (k : Bool × Cube (Fin q)) : Cube (Fin q × Fin q) :=
fun p => if k.1 then k.2 p.2 else k.2 p.1
def query {q : Nat} (P : Fin q → Fin q → Bool) (event : LocalEvent q)
(slot : Fin 6) : RawQuery q :=
match event with
| (kind, k, f, g, r₀, r₁, r₂) =>
if kind = 0 then
if slot = 0 then .inr (mask P f) else
if slot = 1 then .inr (mask P g) else .inr (mask P (xorTape f g))
else if kind = 1 then
if slot = 0 then .inr (mask P r₀) else
if slot = 1 then .inr (mask P (xorTape r₀ (andTape f g))) else
if slot = 2 then .inr (mask P r₁) else
if slot = 3 then .inr (mask P (xorTape r₁ f)) else
if slot = 4 then .inr (mask P r₂) else .inr (mask P (xorTape r₂ g))
else if kind = 2 then
if slot = 0 then .inr (mask P r₀) else
.inr (mask P (xorTape r₀ (fun _ => true)))
else
if slot = 0 then .inl k else
if slot = 1 then .inr (mask P r₀) else
.inr (mask P (xorTape r₀ (inputPairTape k)))
def globalize {q : Nat} {V E : Type*} (tail head : V) (edge : E) :
RawQuery q → AlphabetGraph.Address V E (Fin q)
| .inl (side, tape) => .inl ((if side then head else tail), tape)
| .inr tape => .inr (edge, tape)
@[simp] theorem mask_idempotent {q : Nat} (P : Fin q → Fin q → Bool)
(f : Cube (Fin q × Fin q)) : mask P (mask P f) = mask P f := by
funext p
cases hp : P p.1 p.2 <;> simp [mask, hp]
theorem mask_of_empty {q : Nat} (P : Fin q → Fin q → Bool)
(empty : ∀ a b, P a b = false) (f : Cube (Fin q × Fin q)) :
mask P f = fun _ => false := by
funext p
simp [mask, empty]
theorem query_is_masked {q : Nat} (P : Fin q → Fin q → Bool)
(event : LocalEvent q) (slot : Fin 6) :
match query P event slot with
| .inl _ => True
| .inr tape => mask P tape = tape := by
rcases event with ⟨kind, k, f, g, r₀, r₁, r₂⟩
by_cases hk₀ : kind = 0 <;> by_cases hk₁ : kind = 1 <;> by_cases hk₂ : kind = 2 <;>
simp only [query, hk₀, hk₁, hk₂, ite_true, ite_false] <;>
split_ifs <;> simp
def extendQuery {q : Nat} (P : Fin q → Fin q → Bool) :
AlphabetReduction.InputCoordinate (Fin q) ⊕ Cube (AlphabetReduction.LegalPair P) →
RawQuery q
| .inl k => .inl k
| .inr tape => .inr (UniformRestriction.extend (fun p : Fin q × Fin q => P p.1 p.2 = true) tape)
theorem query_eq_extend_eventQueries {q : Nat} (P : Fin q → Fin q → Bool)
(kind : Fin 4) (k : AlphabetReduction.InputCoordinate (Fin q))
(f g r₀ r₁ r₂ : Cube (Fin q × Fin q)) (slot : Fin 6) :
query P (kind, k, f, g, r₀, r₁, r₂) slot =
extendQuery P (AssignmentTester.eventQueries (AlphabetReduction.pairEncoding P) kind k
(UniformRestriction.restrict (fun p : Fin q × Fin q => P p.1 p.2 = true) f)
(UniformRestriction.restrict (fun p : Fin q × Fin q => P p.1 p.2 = true) g)
(UniformRestriction.restrict (fun p : Fin q × Fin q => P p.1 p.2 = true) r₀)
(UniformRestriction.restrict (fun p : Fin q × Fin q => P p.1 p.2 = true) r₁)
(UniformRestriction.restrict (fun p : Fin q × Fin q => P p.1 p.2 = true) r₂) slot) := by
by_cases hk₀ : kind = 0 <;> by_cases hk₁ : kind = 1 <;> by_cases hk₂ : kind = 2 <;>
simp only [query, AssignmentTester.eventQueries, hk₀, hk₁, hk₂, ite_true, ite_false]
all_goals split_ifs <;> simp_all only [extendQuery]
all_goals rfl
theorem globalize_extendQuery {q : Nat} {V E : Type*}
(G : ConstraintGraph V E (Fin q)) (e : E)
(x : AlphabetReduction.InputCoordinate (Fin q) ⊕
Cube (AlphabetReduction.LegalPair (G.accepts e))) :
globalize (G.tail e) (G.head e) e (extendQuery (G.accepts e) x) =
AlphabetGraph.globalizeQuery G e x := by
cases x with
| inl k => cases k; rfl
| inr tape => rfl
theorem globalize_query {q : Nat} {V E : Type*}
(G : ConstraintGraph V E (Fin q)) (e : E) (event : LocalEvent q) (slot : Fin 6) :
globalize (G.tail e) (G.head e) e (query (G.accepts e) event slot) =
(AlphabetGraph.verifier G).query (e, event) slot := by
rcases event with ⟨kind, k, f, g, r₀, r₁, r₂⟩
rw [query_eq_extend_eventQueries]
exact globalize_extendQuery G e _
end BinPackingGames.Foundations.PCP.AlphabetTable.Queries
end
end OAI