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Information Retrieval 19 January 2019 Name: Surname: Matricola:

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Information Retrieval

19 January 2019

Name: Surname: Matricola:

Ex 1 [points 8+5+3]

 Define what is a Spectral Bloom filter, the operations supported, and show the formula of the error rate (as a function of the space and number of keys) and prove its correctness.

 Define what is a Permuterm index, the operations supported, comment on the occupied space with respect to the indexed set of keys.

 Define the formulas for Precision, Recall and F1

Ex 2 [points 4+5] You are given the two files: F_old = “abracadabra”, F_new =

“abracalabria”, and assume a block size B=3 chars.

 Show the execution of the algorithm rsync. (comment the various steps)

 Show the execution of the algorithm zsync. (comment the various steps)

Ex 3 [points 5] Given the two adjacency lists of a Web graph for the nodes 14 and 15, namely

14  3, 10, 12, 13, 14, 17, 19, 21, 25 15  5, 10, 11, 12, 14, 17, 19, 21, 24, 33

show how the list of “15” can be compressed given the list of “14” by means of the algorithm adopted in WebGraph via copy-lists and copy-blocks.

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