Log right inverse
Domain.CosetFftDomainClass.log_right_inverse'
Plain-language statement
Evaluating ω at the index found by log recovers x.
Exact Lean statement
@[simp]
lemma log_right_inverse' {ω : D} {x : ω} :
ω (log ω x) = xFormal artifact
Lean source
@[simp]lemma log_right_inverse' {ω : D} {x : ω} : ω (log ω x) = x := by have h_log : ∃ i : Fin (2 ^ n), ω i = x := by exact Finset.mem_image.mp x.2 |> fun ⟨i, _, hi⟩ ↦ ⟨i, hi⟩ obtain ⟨i, hi⟩ := h_log have h_log_aux : ∀ (fuel : ℕ) (i : Fin (2 ^ n)), i.val < fuel → ω i = x → ω (logAux ω x fuel) = x := by intro fuel i hi hx induction fuel generalizing i with | zero => simp_all | succ fuel ih => by_cases hfuel : fuel < 2 ^ n · by_cases hfound : ω (⟨fuel, hfuel⟩ : Fin (2 ^ n)) = x · simp [logAux, hfuel, hfound] · rw [show logAux ω x (fuel + 1) = logAux ω x fuel by simp [logAux, hfuel, hfound]] apply ih i · have hi_ne : i.val ≠ fuel := by intro hval apply hfound have hfin : i = (⟨fuel, hfuel⟩ : Fin (2 ^ n)) := Fin.ext hval rw [← hfin] exact hx omega · exact hx · rw [show logAux ω x (fuel + 1) = logAux ω x fuel by simp [logAux, hfuel]] apply ih i · exact lt_of_lt_of_le i.isLt (Nat.le_of_not_gt hfuel) · exact hx exact h_log_aux _ _ (Fin.is_lt i) hi- Project
- ArkLib
- License
- Apache-2.0
- Commit
- fad5cbf80877
- Source
- ArkLib/Data/Domain/CosetFftDomain/Log.lean:61-91
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affine_gaps_lifted_to_interleaved_codes
Project documentation
This lemma proves the final algebraic step in the DG25 Theorem 3.1 proof. It shows that if R > e + 1, then e * (R / (R - 1)) < e + 1. The intuition is that the fraction R / (R - 1) is always greater than 1, but as R gets larger, it gets closer to 1. The hypothesis R > e + 1 provides a strong enough bound to ensure the product e * (fraction) do...
Source project: ArkLib
Person-level attribution pending.
Gadget Decompose coeff
ArkLib.Lattices.Ajtai.gadgetDecompose_coeff
Plain-language statement
The k-th coefficient (k < deg φ) of a gadget-decomposition block is exactly the corresponding digit of the corresponding input coefficient.
Source project: ArkLib
Person-level attribution pending.
Gadget Decompose lawful
ArkLib.Lattices.Ajtai.gadgetDecompose_lawful
Plain-language statement
The base-b gadget decomposition is a lawful gadget decomposition.
Source project: ArkLib
Person-level attribution pending.