Jure Leskovec, Stanford University - SNAP - Stanford University

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Filtering a stream: Select elements with property x from stream Bloom filters Counting distinct elements: Number of distinct elements in the last k elements of the stream Flajolet-Martin: Item hash func h 0010001011000 Drop the item For each item a, let r(a) be the # of trailing 0s in h(a) Record R = the maximum r(a) seen R = max a r(a), over all the items a seen so far Estimated number of distinct elements = 2 R Output the item since it may be in S; Bit array B 3/9/2011 Jure Leskovec, Stanford C246: Mining Massive Datasets 34
You get to see one input piece at a time, and need to make irrevocable decisions Competitive ratio = min all inputs I (|M my_alg|/|M opt|) Greedy online matching: competitive ratio= |M greedy|/|M opt| ≥ 1/2 Addwords problem: Query arrives to a search engine Several advertisers bid on the query query Pick a subset of advertisers whose ads are shown 3/9/2011 Jure Leskovec, Stanford C246: Mining Massive Datasets 35 1 2 3 4 a b c d Boys Girls
Page 1 and 2: CS246: Mining Massive Datasets Jure
Page 3 and 4: MapReduce Association Rules Findi
Page 5 and 6: The crew of the space shuttle Endea
Page 7 and 8: Many problems can be expressed as f
Page 9 and 10: Shingling: convert docs to sets of
Page 11 and 12: ands Hash cols of signature matrix
Page 13 and 14: SciFi Romnce A = U Σ V T - exampl
Page 15 and 16: SciFi Romnce A = U Σ V T - exampl
Page 17 and 18: Hierarchical: Agglomerative (botto
Page 19 and 20: LSH: Find somewhat similar pairs o
Page 21 and 22: Rank nodes using link structure Pa
Page 23 and 24: HITS (Hypertext-Induced Topic Selec
Page 25 and 26: High-dimensional data: Locality Sen
Page 27 and 28: Distance metric: Euclidean How ma
Page 29 and 30: Building decision trees using MapRe
Page 33: Can’t store the whole stream but
Page 39 and 40: Observation: Subsets of a frequent
Page 41 and 42: User-user collaborative filtering
Page 43 and 44: MapReduce Association Rules Aprio
Page 45 and 46: Seminars: InfoSeminar: http://i.st

Jure Leskovec, Stanford University - SNAP - Stanford University

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