Separation between Deterministic and Randomized Query Complexity

SIAM Journal on Computing (47:4)

Saks and Wigderson [FOCS 1986] conjectured that $R_0(f)=\Omega(D(f)^{0.753\ldots})$ for all Boolean functions $f$. We show that for the pointer function $GPW_{r \times s}$ defined by Goos, Pitassi, and Watson [FOCS 2015], the following hold:

  • $R_1(GPW_{r \times s})=\tilde\Theta(r + s)$ and

  • $R_1(\overline{GPW_{r \times s}})=\tilde \Theta(r + \sqrt{r}s)$,

where $R_1$ denotes the randomized one-sided error query complexity. These results imply that (i) $R_0(GPW_{s^2 \times s})=O(D(GPW_{s^2 \times s})^{2/3})$, thereby refuting the conjecture of Saks and Wigderson, and (ii) $R_1(GPW_{s \times s})=\tilde O(R_0(GPW_{s \times s})^{2/3})$, thereby providing a polynomial separation between the randomized zero-error and one sided error query complexity measures.

Sagnik Mukhopadhyay
Post-doctoral Researcher

My research interests include complexity theory and distributed graph algorithms.