Approximate Query Complexity

  • Authors:
  • Clifford Smyth

  • Affiliations:
  • University of North Carolina Greensboro

  • Venue:
  • ACM Transactions on Computation Theory (TOCT)
  • Year:
  • 2011

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Abstract

Let f : {0, 1}n → {0, 1}. Let μ be a product probability measure on {0, 1}n. For ε ≥ 0, we define Dε(f), the ε-approximate decision tree complexity of f, to be the minimum depth of a decision tree T with μ(T(x) ≠ f(x)) ≤ ε. For j = 0 or 1 and for δ ≥ 0, we define Cj,δ(f), the δ-approximate j-certificate complexity of f, to be the minimum certificate complexity of a set A ⊆ Ω with μ(AΔf−1(j)) ≤ ε. Note that if μ(x) 0 for all x then D0(f) = D(f) and Cj,0(f) = Cj(f) are the ordinary decision tree and j-certificate complexities of f, respectively. We extend the well-known result, D(f) ≤ C1(f)C0(f) [Blum and Impagliazzo 1987; Hartmanis and Hemachandra 1991; Tardos 1989], proving that for all ε 0 there exists a δ 0 and a constant K = K(ε, δ) 0 such that for all n, μ, f, Dε(f) ≤ K C1,δ(f)C0,δ (f). We also give a partial answer to a related question on query complexity raised by Tardos [1989]. We prove generalizations of these results to general product probability spaces.