Super-Cubic Lower Bound for Generalized Karchmer-Wigderson Games

Authors Artur Ignatiev , Ivan Mihajlin, Alexander Smal

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Artur Ignatiev
  • St.Petersburg State University, Russia
  • HSE University, St.Petersburg, Russia
Ivan Mihajlin
  • St.Petersburg Department of Steklov Mathematical Institute of Russian Academy of Sciences, Russia
Alexander Smal
  • St.Petersburg Department of Steklov Mathematical Institute of Russian Academy of Sciences, Russia
  • Technion, Haifa, Israel

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Artur Ignatiev, Ivan Mihajlin, and Alexander Smal. Super-Cubic Lower Bound for Generalized Karchmer-Wigderson Games. In 33rd International Symposium on Algorithms and Computation (ISAAC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 248, pp. 66:1-66:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


In this paper, we prove a super-cubic lower bound on the size of a communication protocol for generalized Karchmer-Wigderson game for an explicit function f: {0,1}ⁿ → {0,1}^{log n}. Lower bounds for original Karchmer-Wigderson games correspond to De Morgan formula lower bounds, thus the best known size lower bound is cubic. The generalized Karchmer-Wigderson games are similar to the original ones, so we hope that our approach can provide an insight for proving better lower bounds on the original Karchmer-Wigderson games, and hence for proving new lower bounds on De Morgan formula size. To achieve super-cubic lower bound we adapt several techniques used in formula complexity to communication protocols, prove communication complexity lower bound for a composition of several functions with a multiplexer relation, and use a technique from [Ivan Mihajlin and Alexander Smal, 2021] to extract the "hardest" function from it. As a result, in this setting we are able to show that there is a relatively small set of functions such that at least one of them does not have a small protocol. The resulting lower bound of Ω̃(n^3.156) is significantly better than the bound obtained from the counting argument.

Subject Classification

ACM Subject Classification
  • Theory of computation → Circuit complexity
  • communication complexity
  • circuit complexity
  • Karchmer-Wigderson games


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