Subexponential Size Hitting Sets for Bounded Depth Multilinear Formulas
Subexponential Size Hitting Sets for Bounded Depth Multilinear Formulas
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有界深度多线性公式的次指数大小命中集
DOI:
10.1007/s00037-016-0131-1
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发表时间:
2014
影响因子:
1.4
通讯作者:
Ben lee Volk
中科院分区:
文献类型:
--
作者:
R. Oliveira;Amir Shpilka;Ben lee Volk
In this paper, we give subexponential size hitting sets for bounded depth multilinear arithmetic formulas. Using the known relation between black-box PIT and lower bounds, we obtain lower bounds for these models. For depth-3 multilinear formulas, of size exp(nδ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${(n^\delta)}$$\end{document}, we give a hitting set of size expO~n2/3+2δ/3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\left(\tilde{O}\left(n^{2/3 + 2\delta/3}\right) \right)}$$\end{document}. This implies a lower bound of exp(Ω~(n1/2))\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${(\tilde{\Omega}(n^{1/2}))}$$\end{document} for depth-3 multilinear formulas, for some explicit polynomial. For depth-4 multilinear formulas, of size exp(nδ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${(n^\delta)}$$\end{document}, we give a hitting set of size expO~n2/3+4δ/3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\left(\tilde{O}\left(n^{2/3 + 4\delta/3}\right) \right)}$$\end{document}. This implies a lower bound of exp(Ω~(n1/4))\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${(\tilde{\Omega}(n^{1/4}))}$$\end{document} for depth-4 multilinear formulas, for some explicit polynomial. A regular formula consists of alternating layers of +,×\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${+,\times}$$\end{document} gates, where all gates at layer i have the same fan-in. We give a hitting set of size (roughly) expn1-δ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\left(n^{1- \delta}\right)}$$\end{document}, for regular depth-d multilinear formulas with formal degree at most n and size exp(nδ)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${(n^\delta)}$$\end{document}, where δ=O(1/5d)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\delta = O(1/{\sqrt{5}^d})}$$\end{document}. This result implies a lower bound of roughly exp(Ω~(n1/5d))\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${(\tilde{\Omega}(n^{1/{\sqrt{5}^d}}))}$$\end{document} for such formulas. We note that better lower bounds are known for these models, but also that none of these bounds was achieved via construction of a hitting set. Moreover, no lower bound that implies such PIT results, even in the white-box model, is currently known. Our results are combinatorial in nature and rely on reducing the underlying formula, first to a depth-4 formula, and then to a read-once algebraic branching program (from depth-3 formulas, we go straight to read-once algebraic branching programs).
影响因子:
1.4
作者:
Rohit Gurjar;Arpita Korwar;Nitin Saxena;Thomas Thierauf
通讯作者:
Thomas Thierauf