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In the mathematical discipline of graph theory, the expander walk sampling theorem states that sampling vertices in an expander graph by doing a random walk is almost as good as sampling the vertices independently from a uniform distribution. The earliest version of this theorem is due to , and the more general version is typically attributed to . ==Statement== Let be an expander graph with normalized second-largest eigenvalue . Let denote the number of vertices in . Let be a function on the vertices of . Let denote the mean of , i.e. . Then, if we let denote the vertices encountered in a -step random walk on starting at a random vertex , we have the following for all : : Here the hides an absolute constant . An identical bound holds in the other direction: : 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Expander walk sampling」の詳細全文を読む スポンサード リンク
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