Streaming algorithms for halo finders

Zaoxing Liu, Nikita Ivkin, Lin Yang, Mark Neyrinck, Gerard Lemson, Alexander Szalay, Vladimir Braverman, Tamas Budavari, Randal Burns, Xin Wang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Cosmological N-body simulations are essential for studies of the large-scale distribution of matter and galaxies in the Universe. This analysis often involves finding clusters of particles and retrieving their properties. Detecting such 'halos' among a very large set of particles is a computationally intensive problem, usually executed on the same super-computers that produced the simulations, requiring huge amounts of memory. Recently, a new area of computer science emerged. This area, called streaming algorithms, provides new theoretical methods to compute data analytics in a scalable way using only a single pass over a data sets and logarithmic memory. The main contribution of this paper is a novel connection between the N-body simulations and the streaming algorithms. In particular, we investigate a link between halo finders and the problem of finding frequent items (heavy hitters) in a data stream, that should greatly reduce the computational resource requirements, especially the memory needs. Based on this connection, we can build a new halo finder by running efficient heavy hitter algorithms as a black-box. We implement two representatives of the family of heavy hitter algorithms, the Count-Sketch algorithm (CS) and the Pick-and-Drop sampling (PD), and evaluate their accuracy and memory usage. Comparison with other halo-finding algorithms from [1] shows that our halo finder can locate the largest haloes using significantly smaller memory space and with comparable running time. This streaming approach makes it possible to run and analyze extremely large data sets from N-body simulations on a smaller machine, rather than on supercomputers. Our findings demonstrate the connection between the halo search problem and streaming algorithms as a promising initial direction of further research.

Original languageEnglish (US)
Title of host publicationProceedings - 11th IEEE International Conference on eScience, eScience 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages342-351
Number of pages10
ISBN (Electronic)9781467393256
DOIs
StatePublished - Oct 22 2015
Event11th IEEE International Conference on eScience, eScience 2015 - Munich, Germany
Duration: Aug 31 2015Sep 4 2015

Publication series

NameProceedings - 11th IEEE International Conference on eScience, eScience 2015

Conference

Conference11th IEEE International Conference on eScience, eScience 2015
Country/TerritoryGermany
CityMunich
Period8/31/159/4/15

Keywords

  • Cosmology
  • Halo finder
  • N-body simulation
  • Stream algorithm

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Management Science and Operations Research

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