TY - GEN

T1 - A randomized algorithm for finding frequent elements in streams using O(log log N) space

AU - Ogata, Masatora

AU - Yamauchi, Yukiko

AU - Kijima, Shuji

AU - Yamashita, Masafumi

PY - 2011

Y1 - 2011

N2 - Finding frequent items in a data stream is a fundamental problem; Given a threshold θ ε (0,1), find items appearing more than θ·N times in an input stream with length N. Karp, Shenker, Papadimiriou (2003) gave a simple deterministic online algorithm, which allows false positive outputs using memory of O(θ -1 log N) bits, while they also gave a lower bound. Motivated by the theoretical bound of the space complexity, this paper proposes a simple randomized online algorithm using memory of O(θ -2 log 2 θ -1+log log N) bits where parameters for approximation are hidden in the constant. Our algorithm is robust for memory overflow, compared with other naïve randomized algorithms, or deterministic algorithms using memory of O(logN) bits. We also give some randomized algorithms for approximate counting.

AB - Finding frequent items in a data stream is a fundamental problem; Given a threshold θ ε (0,1), find items appearing more than θ·N times in an input stream with length N. Karp, Shenker, Papadimiriou (2003) gave a simple deterministic online algorithm, which allows false positive outputs using memory of O(θ -1 log N) bits, while they also gave a lower bound. Motivated by the theoretical bound of the space complexity, this paper proposes a simple randomized online algorithm using memory of O(θ -2 log 2 θ -1+log log N) bits where parameters for approximation are hidden in the constant. Our algorithm is robust for memory overflow, compared with other naïve randomized algorithms, or deterministic algorithms using memory of O(logN) bits. We also give some randomized algorithms for approximate counting.

UR - http://www.scopus.com/inward/record.url?scp=84055190819&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84055190819&partnerID=8YFLogxK

U2 - 10.1007/978-3-642-25591-5_53

DO - 10.1007/978-3-642-25591-5_53

M3 - Conference contribution

AN - SCOPUS:84055190819

SN - 9783642255908

T3 - Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

SP - 514

EP - 523

BT - Algorithms and Computation - 22nd International Symposium, ISAAC 2011, Proceedings

T2 - 22nd International Symposium on Algorithms and Computation, ISAAC 2011

Y2 - 5 December 2011 through 8 December 2011

ER -