paper

Recursive Sketching For Frequency Moments

arXiv:1011.2571

Abstract

In a ground-breaking paper, Indyk and Woodruff (STOC 05) showed how to compute (for ) in space complexity $O(\mbox{\em poly-log}(n,m)\cdot n^{1-\frac2k})$, which is optimal up to (large) poly-logarithmic factors in and , where is the length of the stream and is the upper bound on the number of distinct elements in a stream. The best known lower bound for large moments is . A follow-up work of Bhuvanagiri, Ganguly, Kesh and Saha (SODA 2006) reduced the poly-logarithmic factors of Indyk and Woodruff to . Further reduction of poly-log factors has been an elusive goal since 2006, when Indyk and Woodruff method seemed to hit a natural "barrier." Using our simple recursive sketch, we provide a different yet simple approach to obtain a algorithm for constant (our bound is, in fact, somewhat stronger, where the term can be replaced by any constant number of iterations instead of just two or three, thus approaching . Our bound also works for non-constant (for details see the body of the paper). Further, our algorithm requires only -wise independence, in contrast to existing methods that use pseudo-random generators for computing large frequency moments.

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