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SIMD Compression and the Intersection of Sorted Integers [r-libre/601]

Lemire, Daniel; Boytsov, Leonid, & Kurz, Nathan (2016). SIMD Compression and the Intersection of Sorted Integers. Software: Practice and Experience, 46 (6).

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Content : Submitted Version
License : Creative Commons Attribution.
Item Type: Journal Articles
Refereed: Yes
Status: Published
Abstract: Sorted lists of integers are commonly used in inverted indexes and database systems. They are often compressed in memory. We can use the SIMD instructions available in common processors to boost the speed of integer compression schemes. Our S4-BP128-D4 scheme uses as little as 0.7 CPU cycles per decoded integer while still providing state-of-the-art compression. However, if the subsequent processing of the integers is slow, the effort spent on optimizing decoding speed can be wasted. To show that it does not have to be so, we (1) vectorize and optimize the intersection of posting lists; (2) introduce the SIMD Galloping algorithm. We exploit the fact that one SIMD instruction can compare 4 pairs of integers at once. We experiment with two TREC text collections, GOV2 and ClueWeb09 (Category B), using logs from the TREC million-query track. We show that using only the SIMD instructions ubiquitous in all modern CPUs, our techniques for conjunctive queries can double the speed of a state-of-the-art approach.
Depositor: Lemire, Daniel
Owner / Manager: Daniel Lemire
Deposited: 24 Mar 2015 19:42
Last Modified: 13 Dec 2017 15:08

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