Toward the KRW Composition Conjecture: Cubic Formula Lower Bounds via Communication Complexity
Toward the KRW Composition Conjecture: Cubic Formula Lower Bounds via Communication Complexity
复制标题
迈向 KRW 组成猜想:通过通信复杂性得出三次公式下界
DOI:
10.1007/s00037-017-0159-x
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发表时间:
2016
影响因子:
1.4
通讯作者:
Or Meir
中科院分区:
文献类型:
--
作者:
Irit Dinur;Or Meir
One of the major challenges of the research in circuit complexity is proving super-polynomial lower bounds for de Morgan formulas. Karchmer et al. (Comput Complex 5(3/4):191–204, 1995b) suggested to approach this problem by proving that formula complexity behaves “as expected” with respect to the composition of functions f⋄g\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${f\diamond g}$$\end{document} . They showed that this conjecture, if proved, would imply super-polynomial formula lower bounds. The first step toward proving the KRW conjecture was made by Edmonds et al. (Comput Complex 10(3):210–246, 2001), who proved an analogue of the conjecture for the composition of “universal relations.” In this work, we extend the argument of Edmonds et al. (2001) further to f⋄g\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${f\diamond g}$$\end{document} where f is an arbitrary function and g is the parity function. While this special case of the KRW conjecture was already proved implicitly in Håstad’s work on random restrictions (Håstad in SIAM J Comput 27(1):48–64, 1998), our proof seems more likely to be generalizable to other cases of the conjecture. In particular, our proof uses an entirely different approach, based on communication complexity technique of Karchmer & Wigderson in (SIAM J Discrete Math 3(2):255–265, 1990). In addition, our proof gives a new structural result, which roughly says that the naive way for computing f⋄g\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${f\diamond g}$$\end{document} is the only optimal way. Along the way, we obtain a new proof of the state-of-the-art formula lower bound of n3-o(1) due to Håstad (1998).